| File: | src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Transforms/Scalar/SimpleLoopUnswitch.cpp |
| Warning: | line 2966, column 3 Forming reference to null pointer |
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| 1 | ///===- SimpleLoopUnswitch.cpp - Hoist loop-invariant control flow ---------===// | ||||||||
| 2 | // | ||||||||
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||||||||
| 4 | // See https://llvm.org/LICENSE.txt for license information. | ||||||||
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||||||||
| 6 | // | ||||||||
| 7 | //===----------------------------------------------------------------------===// | ||||||||
| 8 | |||||||||
| 9 | #include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h" | ||||||||
| 10 | #include "llvm/ADT/DenseMap.h" | ||||||||
| 11 | #include "llvm/ADT/STLExtras.h" | ||||||||
| 12 | #include "llvm/ADT/Sequence.h" | ||||||||
| 13 | #include "llvm/ADT/SetVector.h" | ||||||||
| 14 | #include "llvm/ADT/SmallPtrSet.h" | ||||||||
| 15 | #include "llvm/ADT/SmallVector.h" | ||||||||
| 16 | #include "llvm/ADT/Statistic.h" | ||||||||
| 17 | #include "llvm/ADT/Twine.h" | ||||||||
| 18 | #include "llvm/Analysis/AssumptionCache.h" | ||||||||
| 19 | #include "llvm/Analysis/CFG.h" | ||||||||
| 20 | #include "llvm/Analysis/CodeMetrics.h" | ||||||||
| 21 | #include "llvm/Analysis/GuardUtils.h" | ||||||||
| 22 | #include "llvm/Analysis/InstructionSimplify.h" | ||||||||
| 23 | #include "llvm/Analysis/LoopAnalysisManager.h" | ||||||||
| 24 | #include "llvm/Analysis/LoopInfo.h" | ||||||||
| 25 | #include "llvm/Analysis/LoopIterator.h" | ||||||||
| 26 | #include "llvm/Analysis/LoopPass.h" | ||||||||
| 27 | #include "llvm/Analysis/MemorySSA.h" | ||||||||
| 28 | #include "llvm/Analysis/MemorySSAUpdater.h" | ||||||||
| 29 | #include "llvm/Analysis/MustExecute.h" | ||||||||
| 30 | #include "llvm/Analysis/ScalarEvolution.h" | ||||||||
| 31 | #include "llvm/IR/BasicBlock.h" | ||||||||
| 32 | #include "llvm/IR/Constant.h" | ||||||||
| 33 | #include "llvm/IR/Constants.h" | ||||||||
| 34 | #include "llvm/IR/Dominators.h" | ||||||||
| 35 | #include "llvm/IR/Function.h" | ||||||||
| 36 | #include "llvm/IR/IRBuilder.h" | ||||||||
| 37 | #include "llvm/IR/InstrTypes.h" | ||||||||
| 38 | #include "llvm/IR/Instruction.h" | ||||||||
| 39 | #include "llvm/IR/Instructions.h" | ||||||||
| 40 | #include "llvm/IR/IntrinsicInst.h" | ||||||||
| 41 | #include "llvm/IR/PatternMatch.h" | ||||||||
| 42 | #include "llvm/IR/Use.h" | ||||||||
| 43 | #include "llvm/IR/Value.h" | ||||||||
| 44 | #include "llvm/InitializePasses.h" | ||||||||
| 45 | #include "llvm/Pass.h" | ||||||||
| 46 | #include "llvm/Support/Casting.h" | ||||||||
| 47 | #include "llvm/Support/CommandLine.h" | ||||||||
| 48 | #include "llvm/Support/Debug.h" | ||||||||
| 49 | #include "llvm/Support/ErrorHandling.h" | ||||||||
| 50 | #include "llvm/Support/GenericDomTree.h" | ||||||||
| 51 | #include "llvm/Support/raw_ostream.h" | ||||||||
| 52 | #include "llvm/Transforms/Scalar/SimpleLoopUnswitch.h" | ||||||||
| 53 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" | ||||||||
| 54 | #include "llvm/Transforms/Utils/Cloning.h" | ||||||||
| 55 | #include "llvm/Transforms/Utils/Local.h" | ||||||||
| 56 | #include "llvm/Transforms/Utils/LoopUtils.h" | ||||||||
| 57 | #include "llvm/Transforms/Utils/ValueMapper.h" | ||||||||
| 58 | #include <algorithm> | ||||||||
| 59 | #include <cassert> | ||||||||
| 60 | #include <iterator> | ||||||||
| 61 | #include <numeric> | ||||||||
| 62 | #include <utility> | ||||||||
| 63 | |||||||||
| 64 | #define DEBUG_TYPE"simple-loop-unswitch" "simple-loop-unswitch" | ||||||||
| 65 | |||||||||
| 66 | using namespace llvm; | ||||||||
| 67 | using namespace llvm::PatternMatch; | ||||||||
| 68 | |||||||||
| 69 | STATISTIC(NumBranches, "Number of branches unswitched")static llvm::Statistic NumBranches = {"simple-loop-unswitch", "NumBranches", "Number of branches unswitched"}; | ||||||||
| 70 | STATISTIC(NumSwitches, "Number of switches unswitched")static llvm::Statistic NumSwitches = {"simple-loop-unswitch", "NumSwitches", "Number of switches unswitched"}; | ||||||||
| 71 | STATISTIC(NumGuards, "Number of guards turned into branches for unswitching")static llvm::Statistic NumGuards = {"simple-loop-unswitch", "NumGuards" , "Number of guards turned into branches for unswitching"}; | ||||||||
| 72 | STATISTIC(NumTrivial, "Number of unswitches that are trivial")static llvm::Statistic NumTrivial = {"simple-loop-unswitch", "NumTrivial" , "Number of unswitches that are trivial"}; | ||||||||
| 73 | STATISTIC(static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch" , "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped" } | ||||||||
| 74 | NumCostMultiplierSkipped,static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch" , "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped" } | ||||||||
| 75 | "Number of unswitch candidates that had their cost multiplier skipped")static llvm::Statistic NumCostMultiplierSkipped = {"simple-loop-unswitch" , "NumCostMultiplierSkipped", "Number of unswitch candidates that had their cost multiplier skipped" }; | ||||||||
| 76 | |||||||||
| 77 | static cl::opt<bool> EnableNonTrivialUnswitch( | ||||||||
| 78 | "enable-nontrivial-unswitch", cl::init(false), cl::Hidden, | ||||||||
| 79 | cl::desc("Forcibly enables non-trivial loop unswitching rather than " | ||||||||
| 80 | "following the configuration passed into the pass.")); | ||||||||
| 81 | |||||||||
| 82 | static cl::opt<int> | ||||||||
| 83 | UnswitchThreshold("unswitch-threshold", cl::init(50), cl::Hidden, | ||||||||
| 84 | cl::desc("The cost threshold for unswitching a loop.")); | ||||||||
| 85 | |||||||||
| 86 | static cl::opt<bool> EnableUnswitchCostMultiplier( | ||||||||
| 87 | "enable-unswitch-cost-multiplier", cl::init(true), cl::Hidden, | ||||||||
| 88 | cl::desc("Enable unswitch cost multiplier that prohibits exponential " | ||||||||
| 89 | "explosion in nontrivial unswitch.")); | ||||||||
| 90 | static cl::opt<int> UnswitchSiblingsToplevelDiv( | ||||||||
| 91 | "unswitch-siblings-toplevel-div", cl::init(2), cl::Hidden, | ||||||||
| 92 | cl::desc("Toplevel siblings divisor for cost multiplier.")); | ||||||||
| 93 | static cl::opt<int> UnswitchNumInitialUnscaledCandidates( | ||||||||
| 94 | "unswitch-num-initial-unscaled-candidates", cl::init(8), cl::Hidden, | ||||||||
| 95 | cl::desc("Number of unswitch candidates that are ignored when calculating " | ||||||||
| 96 | "cost multiplier.")); | ||||||||
| 97 | static cl::opt<bool> UnswitchGuards( | ||||||||
| 98 | "simple-loop-unswitch-guards", cl::init(true), cl::Hidden, | ||||||||
| 99 | cl::desc("If enabled, simple loop unswitching will also consider " | ||||||||
| 100 | "llvm.experimental.guard intrinsics as unswitch candidates.")); | ||||||||
| 101 | static cl::opt<bool> DropNonTrivialImplicitNullChecks( | ||||||||
| 102 | "simple-loop-unswitch-drop-non-trivial-implicit-null-checks", | ||||||||
| 103 | cl::init(false), cl::Hidden, | ||||||||
| 104 | cl::desc("If enabled, drop make.implicit metadata in unswitched implicit " | ||||||||
| 105 | "null checks to save time analyzing if we can keep it.")); | ||||||||
| 106 | static cl::opt<unsigned> | ||||||||
| 107 | MSSAThreshold("simple-loop-unswitch-memoryssa-threshold", | ||||||||
| 108 | cl::desc("Max number of memory uses to explore during " | ||||||||
| 109 | "partial unswitching analysis"), | ||||||||
| 110 | cl::init(100), cl::Hidden); | ||||||||
| 111 | |||||||||
| 112 | /// Collect all of the loop invariant input values transitively used by the | ||||||||
| 113 | /// homogeneous instruction graph from a given root. | ||||||||
| 114 | /// | ||||||||
| 115 | /// This essentially walks from a root recursively through loop variant operands | ||||||||
| 116 | /// which have the exact same opcode and finds all inputs which are loop | ||||||||
| 117 | /// invariant. For some operations these can be re-associated and unswitched out | ||||||||
| 118 | /// of the loop entirely. | ||||||||
| 119 | static TinyPtrVector<Value *> | ||||||||
| 120 | collectHomogenousInstGraphLoopInvariants(Loop &L, Instruction &Root, | ||||||||
| 121 | LoopInfo &LI) { | ||||||||
| 122 | assert(!L.isLoopInvariant(&Root) &&((void)0) | ||||||||
| 123 | "Only need to walk the graph if root itself is not invariant.")((void)0); | ||||||||
| 124 | TinyPtrVector<Value *> Invariants; | ||||||||
| 125 | |||||||||
| 126 | bool IsRootAnd = match(&Root, m_LogicalAnd()); | ||||||||
| 127 | bool IsRootOr = match(&Root, m_LogicalOr()); | ||||||||
| 128 | |||||||||
| 129 | // Build a worklist and recurse through operators collecting invariants. | ||||||||
| 130 | SmallVector<Instruction *, 4> Worklist; | ||||||||
| 131 | SmallPtrSet<Instruction *, 8> Visited; | ||||||||
| 132 | Worklist.push_back(&Root); | ||||||||
| 133 | Visited.insert(&Root); | ||||||||
| 134 | do { | ||||||||
| 135 | Instruction &I = *Worklist.pop_back_val(); | ||||||||
| 136 | for (Value *OpV : I.operand_values()) { | ||||||||
| 137 | // Skip constants as unswitching isn't interesting for them. | ||||||||
| 138 | if (isa<Constant>(OpV)) | ||||||||
| 139 | continue; | ||||||||
| 140 | |||||||||
| 141 | // Add it to our result if loop invariant. | ||||||||
| 142 | if (L.isLoopInvariant(OpV)) { | ||||||||
| 143 | Invariants.push_back(OpV); | ||||||||
| 144 | continue; | ||||||||
| 145 | } | ||||||||
| 146 | |||||||||
| 147 | // If not an instruction with the same opcode, nothing we can do. | ||||||||
| 148 | Instruction *OpI = dyn_cast<Instruction>(OpV); | ||||||||
| 149 | |||||||||
| 150 | if (OpI && ((IsRootAnd && match(OpI, m_LogicalAnd())) || | ||||||||
| 151 | (IsRootOr && match(OpI, m_LogicalOr())))) { | ||||||||
| 152 | // Visit this operand. | ||||||||
| 153 | if (Visited.insert(OpI).second) | ||||||||
| 154 | Worklist.push_back(OpI); | ||||||||
| 155 | } | ||||||||
| 156 | } | ||||||||
| 157 | } while (!Worklist.empty()); | ||||||||
| 158 | |||||||||
| 159 | return Invariants; | ||||||||
| 160 | } | ||||||||
| 161 | |||||||||
| 162 | static void replaceLoopInvariantUses(Loop &L, Value *Invariant, | ||||||||
| 163 | Constant &Replacement) { | ||||||||
| 164 | assert(!isa<Constant>(Invariant) && "Why are we unswitching on a constant?")((void)0); | ||||||||
| 165 | |||||||||
| 166 | // Replace uses of LIC in the loop with the given constant. | ||||||||
| 167 | // We use make_early_inc_range as set invalidates the iterator. | ||||||||
| 168 | for (Use &U : llvm::make_early_inc_range(Invariant->uses())) { | ||||||||
| 169 | Instruction *UserI = dyn_cast<Instruction>(U.getUser()); | ||||||||
| 170 | |||||||||
| 171 | // Replace this use within the loop body. | ||||||||
| 172 | if (UserI && L.contains(UserI)) | ||||||||
| 173 | U.set(&Replacement); | ||||||||
| 174 | } | ||||||||
| 175 | } | ||||||||
| 176 | |||||||||
| 177 | /// Check that all the LCSSA PHI nodes in the loop exit block have trivial | ||||||||
| 178 | /// incoming values along this edge. | ||||||||
| 179 | static bool areLoopExitPHIsLoopInvariant(Loop &L, BasicBlock &ExitingBB, | ||||||||
| 180 | BasicBlock &ExitBB) { | ||||||||
| 181 | for (Instruction &I : ExitBB) { | ||||||||
| 182 | auto *PN = dyn_cast<PHINode>(&I); | ||||||||
| 183 | if (!PN) | ||||||||
| 184 | // No more PHIs to check. | ||||||||
| 185 | return true; | ||||||||
| 186 | |||||||||
| 187 | // If the incoming value for this edge isn't loop invariant the unswitch | ||||||||
| 188 | // won't be trivial. | ||||||||
| 189 | if (!L.isLoopInvariant(PN->getIncomingValueForBlock(&ExitingBB))) | ||||||||
| 190 | return false; | ||||||||
| 191 | } | ||||||||
| 192 | llvm_unreachable("Basic blocks should never be empty!")__builtin_unreachable(); | ||||||||
| 193 | } | ||||||||
| 194 | |||||||||
| 195 | /// Copy a set of loop invariant values \p ToDuplicate and insert them at the | ||||||||
| 196 | /// end of \p BB and conditionally branch on the copied condition. We only | ||||||||
| 197 | /// branch on a single value. | ||||||||
| 198 | static void buildPartialUnswitchConditionalBranch(BasicBlock &BB, | ||||||||
| 199 | ArrayRef<Value *> Invariants, | ||||||||
| 200 | bool Direction, | ||||||||
| 201 | BasicBlock &UnswitchedSucc, | ||||||||
| 202 | BasicBlock &NormalSucc) { | ||||||||
| 203 | IRBuilder<> IRB(&BB); | ||||||||
| 204 | |||||||||
| 205 | Value *Cond = Direction ? IRB.CreateOr(Invariants) : | ||||||||
| 206 | IRB.CreateAnd(Invariants); | ||||||||
| 207 | IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc, | ||||||||
| 208 | Direction ? &NormalSucc : &UnswitchedSucc); | ||||||||
| 209 | } | ||||||||
| 210 | |||||||||
| 211 | /// Copy a set of loop invariant values, and conditionally branch on them. | ||||||||
| 212 | static void buildPartialInvariantUnswitchConditionalBranch( | ||||||||
| 213 | BasicBlock &BB, ArrayRef<Value *> ToDuplicate, bool Direction, | ||||||||
| 214 | BasicBlock &UnswitchedSucc, BasicBlock &NormalSucc, Loop &L, | ||||||||
| 215 | MemorySSAUpdater *MSSAU) { | ||||||||
| 216 | ValueToValueMapTy VMap; | ||||||||
| 217 | for (auto *Val : reverse(ToDuplicate)) { | ||||||||
| 218 | Instruction *Inst = cast<Instruction>(Val); | ||||||||
| 219 | Instruction *NewInst = Inst->clone(); | ||||||||
| 220 | BB.getInstList().insert(BB.end(), NewInst); | ||||||||
| 221 | RemapInstruction(NewInst, VMap, | ||||||||
| 222 | RF_NoModuleLevelChanges | RF_IgnoreMissingLocals); | ||||||||
| 223 | VMap[Val] = NewInst; | ||||||||
| 224 | |||||||||
| 225 | if (!MSSAU) | ||||||||
| 226 | continue; | ||||||||
| 227 | |||||||||
| 228 | MemorySSA *MSSA = MSSAU->getMemorySSA(); | ||||||||
| 229 | if (auto *MemUse = | ||||||||
| 230 | dyn_cast_or_null<MemoryUse>(MSSA->getMemoryAccess(Inst))) { | ||||||||
| 231 | auto *DefiningAccess = MemUse->getDefiningAccess(); | ||||||||
| 232 | // Get the first defining access before the loop. | ||||||||
| 233 | while (L.contains(DefiningAccess->getBlock())) { | ||||||||
| 234 | // If the defining access is a MemoryPhi, get the incoming | ||||||||
| 235 | // value for the pre-header as defining access. | ||||||||
| 236 | if (auto *MemPhi = dyn_cast<MemoryPhi>(DefiningAccess)) | ||||||||
| 237 | DefiningAccess = | ||||||||
| 238 | MemPhi->getIncomingValueForBlock(L.getLoopPreheader()); | ||||||||
| 239 | else | ||||||||
| 240 | DefiningAccess = cast<MemoryDef>(DefiningAccess)->getDefiningAccess(); | ||||||||
| 241 | } | ||||||||
| 242 | MSSAU->createMemoryAccessInBB(NewInst, DefiningAccess, | ||||||||
| 243 | NewInst->getParent(), | ||||||||
| 244 | MemorySSA::BeforeTerminator); | ||||||||
| 245 | } | ||||||||
| 246 | } | ||||||||
| 247 | |||||||||
| 248 | IRBuilder<> IRB(&BB); | ||||||||
| 249 | Value *Cond = VMap[ToDuplicate[0]]; | ||||||||
| 250 | IRB.CreateCondBr(Cond, Direction ? &UnswitchedSucc : &NormalSucc, | ||||||||
| 251 | Direction ? &NormalSucc : &UnswitchedSucc); | ||||||||
| 252 | } | ||||||||
| 253 | |||||||||
| 254 | /// Rewrite the PHI nodes in an unswitched loop exit basic block. | ||||||||
| 255 | /// | ||||||||
| 256 | /// Requires that the loop exit and unswitched basic block are the same, and | ||||||||
| 257 | /// that the exiting block was a unique predecessor of that block. Rewrites the | ||||||||
| 258 | /// PHI nodes in that block such that what were LCSSA PHI nodes become trivial | ||||||||
| 259 | /// PHI nodes from the old preheader that now contains the unswitched | ||||||||
| 260 | /// terminator. | ||||||||
| 261 | static void rewritePHINodesForUnswitchedExitBlock(BasicBlock &UnswitchedBB, | ||||||||
| 262 | BasicBlock &OldExitingBB, | ||||||||
| 263 | BasicBlock &OldPH) { | ||||||||
| 264 | for (PHINode &PN : UnswitchedBB.phis()) { | ||||||||
| 265 | // When the loop exit is directly unswitched we just need to update the | ||||||||
| 266 | // incoming basic block. We loop to handle weird cases with repeated | ||||||||
| 267 | // incoming blocks, but expect to typically only have one operand here. | ||||||||
| 268 | for (auto i : seq<int>(0, PN.getNumOperands())) { | ||||||||
| 269 | assert(PN.getIncomingBlock(i) == &OldExitingBB &&((void)0) | ||||||||
| 270 | "Found incoming block different from unique predecessor!")((void)0); | ||||||||
| 271 | PN.setIncomingBlock(i, &OldPH); | ||||||||
| 272 | } | ||||||||
| 273 | } | ||||||||
| 274 | } | ||||||||
| 275 | |||||||||
| 276 | /// Rewrite the PHI nodes in the loop exit basic block and the split off | ||||||||
| 277 | /// unswitched block. | ||||||||
| 278 | /// | ||||||||
| 279 | /// Because the exit block remains an exit from the loop, this rewrites the | ||||||||
| 280 | /// LCSSA PHI nodes in it to remove the unswitched edge and introduces PHI | ||||||||
| 281 | /// nodes into the unswitched basic block to select between the value in the | ||||||||
| 282 | /// old preheader and the loop exit. | ||||||||
| 283 | static void rewritePHINodesForExitAndUnswitchedBlocks(BasicBlock &ExitBB, | ||||||||
| 284 | BasicBlock &UnswitchedBB, | ||||||||
| 285 | BasicBlock &OldExitingBB, | ||||||||
| 286 | BasicBlock &OldPH, | ||||||||
| 287 | bool FullUnswitch) { | ||||||||
| 288 | assert(&ExitBB != &UnswitchedBB &&((void)0) | ||||||||
| 289 | "Must have different loop exit and unswitched blocks!")((void)0); | ||||||||
| 290 | Instruction *InsertPt = &*UnswitchedBB.begin(); | ||||||||
| 291 | for (PHINode &PN : ExitBB.phis()) { | ||||||||
| 292 | auto *NewPN = PHINode::Create(PN.getType(), /*NumReservedValues*/ 2, | ||||||||
| 293 | PN.getName() + ".split", InsertPt); | ||||||||
| 294 | |||||||||
| 295 | // Walk backwards over the old PHI node's inputs to minimize the cost of | ||||||||
| 296 | // removing each one. We have to do this weird loop manually so that we | ||||||||
| 297 | // create the same number of new incoming edges in the new PHI as we expect | ||||||||
| 298 | // each case-based edge to be included in the unswitched switch in some | ||||||||
| 299 | // cases. | ||||||||
| 300 | // FIXME: This is really, really gross. It would be much cleaner if LLVM | ||||||||
| 301 | // allowed us to create a single entry for a predecessor block without | ||||||||
| 302 | // having separate entries for each "edge" even though these edges are | ||||||||
| 303 | // required to produce identical results. | ||||||||
| 304 | for (int i = PN.getNumIncomingValues() - 1; i >= 0; --i) { | ||||||||
| 305 | if (PN.getIncomingBlock(i) != &OldExitingBB) | ||||||||
| 306 | continue; | ||||||||
| 307 | |||||||||
| 308 | Value *Incoming = PN.getIncomingValue(i); | ||||||||
| 309 | if (FullUnswitch) | ||||||||
| 310 | // No more edge from the old exiting block to the exit block. | ||||||||
| 311 | PN.removeIncomingValue(i); | ||||||||
| 312 | |||||||||
| 313 | NewPN->addIncoming(Incoming, &OldPH); | ||||||||
| 314 | } | ||||||||
| 315 | |||||||||
| 316 | // Now replace the old PHI with the new one and wire the old one in as an | ||||||||
| 317 | // input to the new one. | ||||||||
| 318 | PN.replaceAllUsesWith(NewPN); | ||||||||
| 319 | NewPN->addIncoming(&PN, &ExitBB); | ||||||||
| 320 | } | ||||||||
| 321 | } | ||||||||
| 322 | |||||||||
| 323 | /// Hoist the current loop up to the innermost loop containing a remaining exit. | ||||||||
| 324 | /// | ||||||||
| 325 | /// Because we've removed an exit from the loop, we may have changed the set of | ||||||||
| 326 | /// loops reachable and need to move the current loop up the loop nest or even | ||||||||
| 327 | /// to an entirely separate nest. | ||||||||
| 328 | static void hoistLoopToNewParent(Loop &L, BasicBlock &Preheader, | ||||||||
| 329 | DominatorTree &DT, LoopInfo &LI, | ||||||||
| 330 | MemorySSAUpdater *MSSAU, ScalarEvolution *SE) { | ||||||||
| 331 | // If the loop is already at the top level, we can't hoist it anywhere. | ||||||||
| 332 | Loop *OldParentL = L.getParentLoop(); | ||||||||
| 333 | if (!OldParentL) | ||||||||
| 334 | return; | ||||||||
| 335 | |||||||||
| 336 | SmallVector<BasicBlock *, 4> Exits; | ||||||||
| 337 | L.getExitBlocks(Exits); | ||||||||
| 338 | Loop *NewParentL = nullptr; | ||||||||
| 339 | for (auto *ExitBB : Exits) | ||||||||
| 340 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) | ||||||||
| 341 | if (!NewParentL || NewParentL->contains(ExitL)) | ||||||||
| 342 | NewParentL = ExitL; | ||||||||
| 343 | |||||||||
| 344 | if (NewParentL == OldParentL) | ||||||||
| 345 | return; | ||||||||
| 346 | |||||||||
| 347 | // The new parent loop (if different) should always contain the old one. | ||||||||
| 348 | if (NewParentL) | ||||||||
| 349 | assert(NewParentL->contains(OldParentL) &&((void)0) | ||||||||
| 350 | "Can only hoist this loop up the nest!")((void)0); | ||||||||
| 351 | |||||||||
| 352 | // The preheader will need to move with the body of this loop. However, | ||||||||
| 353 | // because it isn't in this loop we also need to update the primary loop map. | ||||||||
| 354 | assert(OldParentL == LI.getLoopFor(&Preheader) &&((void)0) | ||||||||
| 355 | "Parent loop of this loop should contain this loop's preheader!")((void)0); | ||||||||
| 356 | LI.changeLoopFor(&Preheader, NewParentL); | ||||||||
| 357 | |||||||||
| 358 | // Remove this loop from its old parent. | ||||||||
| 359 | OldParentL->removeChildLoop(&L); | ||||||||
| 360 | |||||||||
| 361 | // Add the loop either to the new parent or as a top-level loop. | ||||||||
| 362 | if (NewParentL) | ||||||||
| 363 | NewParentL->addChildLoop(&L); | ||||||||
| 364 | else | ||||||||
| 365 | LI.addTopLevelLoop(&L); | ||||||||
| 366 | |||||||||
| 367 | // Remove this loops blocks from the old parent and every other loop up the | ||||||||
| 368 | // nest until reaching the new parent. Also update all of these | ||||||||
| 369 | // no-longer-containing loops to reflect the nesting change. | ||||||||
| 370 | for (Loop *OldContainingL = OldParentL; OldContainingL != NewParentL; | ||||||||
| 371 | OldContainingL = OldContainingL->getParentLoop()) { | ||||||||
| 372 | llvm::erase_if(OldContainingL->getBlocksVector(), | ||||||||
| 373 | [&](const BasicBlock *BB) { | ||||||||
| 374 | return BB == &Preheader || L.contains(BB); | ||||||||
| 375 | }); | ||||||||
| 376 | |||||||||
| 377 | OldContainingL->getBlocksSet().erase(&Preheader); | ||||||||
| 378 | for (BasicBlock *BB : L.blocks()) | ||||||||
| 379 | OldContainingL->getBlocksSet().erase(BB); | ||||||||
| 380 | |||||||||
| 381 | // Because we just hoisted a loop out of this one, we have essentially | ||||||||
| 382 | // created new exit paths from it. That means we need to form LCSSA PHI | ||||||||
| 383 | // nodes for values used in the no-longer-nested loop. | ||||||||
| 384 | formLCSSA(*OldContainingL, DT, &LI, SE); | ||||||||
| 385 | |||||||||
| 386 | // We shouldn't need to form dedicated exits because the exit introduced | ||||||||
| 387 | // here is the (just split by unswitching) preheader. However, after trivial | ||||||||
| 388 | // unswitching it is possible to get new non-dedicated exits out of parent | ||||||||
| 389 | // loop so let's conservatively form dedicated exit blocks and figure out | ||||||||
| 390 | // if we can optimize later. | ||||||||
| 391 | formDedicatedExitBlocks(OldContainingL, &DT, &LI, MSSAU, | ||||||||
| 392 | /*PreserveLCSSA*/ true); | ||||||||
| 393 | } | ||||||||
| 394 | } | ||||||||
| 395 | |||||||||
| 396 | // Return the top-most loop containing ExitBB and having ExitBB as exiting block | ||||||||
| 397 | // or the loop containing ExitBB, if there is no parent loop containing ExitBB | ||||||||
| 398 | // as exiting block. | ||||||||
| 399 | static Loop *getTopMostExitingLoop(BasicBlock *ExitBB, LoopInfo &LI) { | ||||||||
| 400 | Loop *TopMost = LI.getLoopFor(ExitBB); | ||||||||
| 401 | Loop *Current = TopMost; | ||||||||
| 402 | while (Current) { | ||||||||
| 403 | if (Current->isLoopExiting(ExitBB)) | ||||||||
| 404 | TopMost = Current; | ||||||||
| 405 | Current = Current->getParentLoop(); | ||||||||
| 406 | } | ||||||||
| 407 | return TopMost; | ||||||||
| 408 | } | ||||||||
| 409 | |||||||||
| 410 | /// Unswitch a trivial branch if the condition is loop invariant. | ||||||||
| 411 | /// | ||||||||
| 412 | /// This routine should only be called when loop code leading to the branch has | ||||||||
| 413 | /// been validated as trivial (no side effects). This routine checks if the | ||||||||
| 414 | /// condition is invariant and one of the successors is a loop exit. This | ||||||||
| 415 | /// allows us to unswitch without duplicating the loop, making it trivial. | ||||||||
| 416 | /// | ||||||||
| 417 | /// If this routine fails to unswitch the branch it returns false. | ||||||||
| 418 | /// | ||||||||
| 419 | /// If the branch can be unswitched, this routine splits the preheader and | ||||||||
| 420 | /// hoists the branch above that split. Preserves loop simplified form | ||||||||
| 421 | /// (splitting the exit block as necessary). It simplifies the branch within | ||||||||
| 422 | /// the loop to an unconditional branch but doesn't remove it entirely. Further | ||||||||
| 423 | /// cleanup can be done with some simplifycfg like pass. | ||||||||
| 424 | /// | ||||||||
| 425 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | ||||||||
| 426 | /// invalidated by this. | ||||||||
| 427 | static bool unswitchTrivialBranch(Loop &L, BranchInst &BI, DominatorTree &DT, | ||||||||
| 428 | LoopInfo &LI, ScalarEvolution *SE, | ||||||||
| 429 | MemorySSAUpdater *MSSAU) { | ||||||||
| 430 | assert(BI.isConditional() && "Can only unswitch a conditional branch!")((void)0); | ||||||||
| 431 | LLVM_DEBUG(dbgs() << " Trying to unswitch branch: " << BI << "\n")do { } while (false); | ||||||||
| 432 | |||||||||
| 433 | // The loop invariant values that we want to unswitch. | ||||||||
| 434 | TinyPtrVector<Value *> Invariants; | ||||||||
| 435 | |||||||||
| 436 | // When true, we're fully unswitching the branch rather than just unswitching | ||||||||
| 437 | // some input conditions to the branch. | ||||||||
| 438 | bool FullUnswitch = false; | ||||||||
| 439 | |||||||||
| 440 | if (L.isLoopInvariant(BI.getCondition())) { | ||||||||
| 441 | Invariants.push_back(BI.getCondition()); | ||||||||
| 442 | FullUnswitch = true; | ||||||||
| 443 | } else { | ||||||||
| 444 | if (auto *CondInst = dyn_cast<Instruction>(BI.getCondition())) | ||||||||
| 445 | Invariants = collectHomogenousInstGraphLoopInvariants(L, *CondInst, LI); | ||||||||
| 446 | if (Invariants.empty()) { | ||||||||
| 447 | LLVM_DEBUG(dbgs() << " Couldn't find invariant inputs!\n")do { } while (false); | ||||||||
| 448 | return false; | ||||||||
| 449 | } | ||||||||
| 450 | } | ||||||||
| 451 | |||||||||
| 452 | // Check that one of the branch's successors exits, and which one. | ||||||||
| 453 | bool ExitDirection = true; | ||||||||
| 454 | int LoopExitSuccIdx = 0; | ||||||||
| 455 | auto *LoopExitBB = BI.getSuccessor(0); | ||||||||
| 456 | if (L.contains(LoopExitBB)) { | ||||||||
| 457 | ExitDirection = false; | ||||||||
| 458 | LoopExitSuccIdx = 1; | ||||||||
| 459 | LoopExitBB = BI.getSuccessor(1); | ||||||||
| 460 | if (L.contains(LoopExitBB)) { | ||||||||
| 461 | LLVM_DEBUG(dbgs() << " Branch doesn't exit the loop!\n")do { } while (false); | ||||||||
| 462 | return false; | ||||||||
| 463 | } | ||||||||
| 464 | } | ||||||||
| 465 | auto *ContinueBB = BI.getSuccessor(1 - LoopExitSuccIdx); | ||||||||
| 466 | auto *ParentBB = BI.getParent(); | ||||||||
| 467 | if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, *LoopExitBB)) { | ||||||||
| 468 | LLVM_DEBUG(dbgs() << " Loop exit PHI's aren't loop-invariant!\n")do { } while (false); | ||||||||
| 469 | return false; | ||||||||
| 470 | } | ||||||||
| 471 | |||||||||
| 472 | // When unswitching only part of the branch's condition, we need the exit | ||||||||
| 473 | // block to be reached directly from the partially unswitched input. This can | ||||||||
| 474 | // be done when the exit block is along the true edge and the branch condition | ||||||||
| 475 | // is a graph of `or` operations, or the exit block is along the false edge | ||||||||
| 476 | // and the condition is a graph of `and` operations. | ||||||||
| 477 | if (!FullUnswitch) { | ||||||||
| 478 | if (ExitDirection ? !match(BI.getCondition(), m_LogicalOr()) | ||||||||
| 479 | : !match(BI.getCondition(), m_LogicalAnd())) { | ||||||||
| 480 | LLVM_DEBUG(dbgs() << " Branch condition is in improper form for "do { } while (false) | ||||||||
| 481 | "non-full unswitch!\n")do { } while (false); | ||||||||
| 482 | return false; | ||||||||
| 483 | } | ||||||||
| 484 | } | ||||||||
| 485 | |||||||||
| 486 | LLVM_DEBUG({do { } while (false) | ||||||||
| 487 | dbgs() << " unswitching trivial invariant conditions for: " << BIdo { } while (false) | ||||||||
| 488 | << "\n";do { } while (false) | ||||||||
| 489 | for (Value *Invariant : Invariants) {do { } while (false) | ||||||||
| 490 | dbgs() << " " << *Invariant << " == true";do { } while (false) | ||||||||
| 491 | if (Invariant != Invariants.back())do { } while (false) | ||||||||
| 492 | dbgs() << " ||";do { } while (false) | ||||||||
| 493 | dbgs() << "\n";do { } while (false) | ||||||||
| 494 | }do { } while (false) | ||||||||
| 495 | })do { } while (false); | ||||||||
| 496 | |||||||||
| 497 | // If we have scalar evolutions, we need to invalidate them including this | ||||||||
| 498 | // loop, the loop containing the exit block and the topmost parent loop | ||||||||
| 499 | // exiting via LoopExitBB. | ||||||||
| 500 | if (SE) { | ||||||||
| 501 | if (Loop *ExitL = getTopMostExitingLoop(LoopExitBB, LI)) | ||||||||
| 502 | SE->forgetLoop(ExitL); | ||||||||
| 503 | else | ||||||||
| 504 | // Forget the entire nest as this exits the entire nest. | ||||||||
| 505 | SE->forgetTopmostLoop(&L); | ||||||||
| 506 | } | ||||||||
| 507 | |||||||||
| 508 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 509 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 510 | |||||||||
| 511 | // Split the preheader, so that we know that there is a safe place to insert | ||||||||
| 512 | // the conditional branch. We will change the preheader to have a conditional | ||||||||
| 513 | // branch on LoopCond. | ||||||||
| 514 | BasicBlock *OldPH = L.getLoopPreheader(); | ||||||||
| 515 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI, MSSAU); | ||||||||
| 516 | |||||||||
| 517 | // Now that we have a place to insert the conditional branch, create a place | ||||||||
| 518 | // to branch to: this is the exit block out of the loop that we are | ||||||||
| 519 | // unswitching. We need to split this if there are other loop predecessors. | ||||||||
| 520 | // Because the loop is in simplified form, *any* other predecessor is enough. | ||||||||
| 521 | BasicBlock *UnswitchedBB; | ||||||||
| 522 | if (FullUnswitch && LoopExitBB->getUniquePredecessor()) { | ||||||||
| 523 | assert(LoopExitBB->getUniquePredecessor() == BI.getParent() &&((void)0) | ||||||||
| 524 | "A branch's parent isn't a predecessor!")((void)0); | ||||||||
| 525 | UnswitchedBB = LoopExitBB; | ||||||||
| 526 | } else { | ||||||||
| 527 | UnswitchedBB = | ||||||||
| 528 | SplitBlock(LoopExitBB, &LoopExitBB->front(), &DT, &LI, MSSAU); | ||||||||
| 529 | } | ||||||||
| 530 | |||||||||
| 531 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 532 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 533 | |||||||||
| 534 | // Actually move the invariant uses into the unswitched position. If possible, | ||||||||
| 535 | // we do this by moving the instructions, but when doing partial unswitching | ||||||||
| 536 | // we do it by building a new merge of the values in the unswitched position. | ||||||||
| 537 | OldPH->getTerminator()->eraseFromParent(); | ||||||||
| 538 | if (FullUnswitch) { | ||||||||
| 539 | // If fully unswitching, we can use the existing branch instruction. | ||||||||
| 540 | // Splice it into the old PH to gate reaching the new preheader and re-point | ||||||||
| 541 | // its successors. | ||||||||
| 542 | OldPH->getInstList().splice(OldPH->end(), BI.getParent()->getInstList(), | ||||||||
| 543 | BI); | ||||||||
| 544 | if (MSSAU) { | ||||||||
| 545 | // Temporarily clone the terminator, to make MSSA update cheaper by | ||||||||
| 546 | // separating "insert edge" updates from "remove edge" ones. | ||||||||
| 547 | ParentBB->getInstList().push_back(BI.clone()); | ||||||||
| 548 | } else { | ||||||||
| 549 | // Create a new unconditional branch that will continue the loop as a new | ||||||||
| 550 | // terminator. | ||||||||
| 551 | BranchInst::Create(ContinueBB, ParentBB); | ||||||||
| 552 | } | ||||||||
| 553 | BI.setSuccessor(LoopExitSuccIdx, UnswitchedBB); | ||||||||
| 554 | BI.setSuccessor(1 - LoopExitSuccIdx, NewPH); | ||||||||
| 555 | } else { | ||||||||
| 556 | // Only unswitching a subset of inputs to the condition, so we will need to | ||||||||
| 557 | // build a new branch that merges the invariant inputs. | ||||||||
| 558 | if (ExitDirection) | ||||||||
| 559 | assert(match(BI.getCondition(), m_LogicalOr()) &&((void)0) | ||||||||
| 560 | "Must have an `or` of `i1`s or `select i1 X, true, Y`s for the "((void)0) | ||||||||
| 561 | "condition!")((void)0); | ||||||||
| 562 | else | ||||||||
| 563 | assert(match(BI.getCondition(), m_LogicalAnd()) &&((void)0) | ||||||||
| 564 | "Must have an `and` of `i1`s or `select i1 X, Y, false`s for the"((void)0) | ||||||||
| 565 | " condition!")((void)0); | ||||||||
| 566 | buildPartialUnswitchConditionalBranch(*OldPH, Invariants, ExitDirection, | ||||||||
| 567 | *UnswitchedBB, *NewPH); | ||||||||
| 568 | } | ||||||||
| 569 | |||||||||
| 570 | // Update the dominator tree with the added edge. | ||||||||
| 571 | DT.insertEdge(OldPH, UnswitchedBB); | ||||||||
| 572 | |||||||||
| 573 | // After the dominator tree was updated with the added edge, update MemorySSA | ||||||||
| 574 | // if available. | ||||||||
| 575 | if (MSSAU) { | ||||||||
| 576 | SmallVector<CFGUpdate, 1> Updates; | ||||||||
| 577 | Updates.push_back({cfg::UpdateKind::Insert, OldPH, UnswitchedBB}); | ||||||||
| 578 | MSSAU->applyInsertUpdates(Updates, DT); | ||||||||
| 579 | } | ||||||||
| 580 | |||||||||
| 581 | // Finish updating dominator tree and memory ssa for full unswitch. | ||||||||
| 582 | if (FullUnswitch) { | ||||||||
| 583 | if (MSSAU) { | ||||||||
| 584 | // Remove the cloned branch instruction. | ||||||||
| 585 | ParentBB->getTerminator()->eraseFromParent(); | ||||||||
| 586 | // Create unconditional branch now. | ||||||||
| 587 | BranchInst::Create(ContinueBB, ParentBB); | ||||||||
| 588 | MSSAU->removeEdge(ParentBB, LoopExitBB); | ||||||||
| 589 | } | ||||||||
| 590 | DT.deleteEdge(ParentBB, LoopExitBB); | ||||||||
| 591 | } | ||||||||
| 592 | |||||||||
| 593 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 594 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 595 | |||||||||
| 596 | // Rewrite the relevant PHI nodes. | ||||||||
| 597 | if (UnswitchedBB == LoopExitBB) | ||||||||
| 598 | rewritePHINodesForUnswitchedExitBlock(*UnswitchedBB, *ParentBB, *OldPH); | ||||||||
| 599 | else | ||||||||
| 600 | rewritePHINodesForExitAndUnswitchedBlocks(*LoopExitBB, *UnswitchedBB, | ||||||||
| 601 | *ParentBB, *OldPH, FullUnswitch); | ||||||||
| 602 | |||||||||
| 603 | // The constant we can replace all of our invariants with inside the loop | ||||||||
| 604 | // body. If any of the invariants have a value other than this the loop won't | ||||||||
| 605 | // be entered. | ||||||||
| 606 | ConstantInt *Replacement = ExitDirection | ||||||||
| 607 | ? ConstantInt::getFalse(BI.getContext()) | ||||||||
| 608 | : ConstantInt::getTrue(BI.getContext()); | ||||||||
| 609 | |||||||||
| 610 | // Since this is an i1 condition we can also trivially replace uses of it | ||||||||
| 611 | // within the loop with a constant. | ||||||||
| 612 | for (Value *Invariant : Invariants) | ||||||||
| 613 | replaceLoopInvariantUses(L, Invariant, *Replacement); | ||||||||
| 614 | |||||||||
| 615 | // If this was full unswitching, we may have changed the nesting relationship | ||||||||
| 616 | // for this loop so hoist it to its correct parent if needed. | ||||||||
| 617 | if (FullUnswitch) | ||||||||
| 618 | hoistLoopToNewParent(L, *NewPH, DT, LI, MSSAU, SE); | ||||||||
| 619 | |||||||||
| 620 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 621 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 622 | |||||||||
| 623 | LLVM_DEBUG(dbgs() << " done: unswitching trivial branch...\n")do { } while (false); | ||||||||
| 624 | ++NumTrivial; | ||||||||
| 625 | ++NumBranches; | ||||||||
| 626 | return true; | ||||||||
| 627 | } | ||||||||
| 628 | |||||||||
| 629 | /// Unswitch a trivial switch if the condition is loop invariant. | ||||||||
| 630 | /// | ||||||||
| 631 | /// This routine should only be called when loop code leading to the switch has | ||||||||
| 632 | /// been validated as trivial (no side effects). This routine checks if the | ||||||||
| 633 | /// condition is invariant and that at least one of the successors is a loop | ||||||||
| 634 | /// exit. This allows us to unswitch without duplicating the loop, making it | ||||||||
| 635 | /// trivial. | ||||||||
| 636 | /// | ||||||||
| 637 | /// If this routine fails to unswitch the switch it returns false. | ||||||||
| 638 | /// | ||||||||
| 639 | /// If the switch can be unswitched, this routine splits the preheader and | ||||||||
| 640 | /// copies the switch above that split. If the default case is one of the | ||||||||
| 641 | /// exiting cases, it copies the non-exiting cases and points them at the new | ||||||||
| 642 | /// preheader. If the default case is not exiting, it copies the exiting cases | ||||||||
| 643 | /// and points the default at the preheader. It preserves loop simplified form | ||||||||
| 644 | /// (splitting the exit blocks as necessary). It simplifies the switch within | ||||||||
| 645 | /// the loop by removing now-dead cases. If the default case is one of those | ||||||||
| 646 | /// unswitched, it replaces its destination with a new basic block containing | ||||||||
| 647 | /// only unreachable. Such basic blocks, while technically loop exits, are not | ||||||||
| 648 | /// considered for unswitching so this is a stable transform and the same | ||||||||
| 649 | /// switch will not be revisited. If after unswitching there is only a single | ||||||||
| 650 | /// in-loop successor, the switch is further simplified to an unconditional | ||||||||
| 651 | /// branch. Still more cleanup can be done with some simplifycfg like pass. | ||||||||
| 652 | /// | ||||||||
| 653 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | ||||||||
| 654 | /// invalidated by this. | ||||||||
| 655 | static bool unswitchTrivialSwitch(Loop &L, SwitchInst &SI, DominatorTree &DT, | ||||||||
| 656 | LoopInfo &LI, ScalarEvolution *SE, | ||||||||
| 657 | MemorySSAUpdater *MSSAU) { | ||||||||
| 658 | LLVM_DEBUG(dbgs() << " Trying to unswitch switch: " << SI << "\n")do { } while (false); | ||||||||
| 659 | Value *LoopCond = SI.getCondition(); | ||||||||
| 660 | |||||||||
| 661 | // If this isn't switching on an invariant condition, we can't unswitch it. | ||||||||
| 662 | if (!L.isLoopInvariant(LoopCond)) | ||||||||
| 663 | return false; | ||||||||
| 664 | |||||||||
| 665 | auto *ParentBB = SI.getParent(); | ||||||||
| 666 | |||||||||
| 667 | // The same check must be used both for the default and the exit cases. We | ||||||||
| 668 | // should never leave edges from the switch instruction to a basic block that | ||||||||
| 669 | // we are unswitching, hence the condition used to determine the default case | ||||||||
| 670 | // needs to also be used to populate ExitCaseIndices, which is then used to | ||||||||
| 671 | // remove cases from the switch. | ||||||||
| 672 | auto IsTriviallyUnswitchableExitBlock = [&](BasicBlock &BBToCheck) { | ||||||||
| 673 | // BBToCheck is not an exit block if it is inside loop L. | ||||||||
| 674 | if (L.contains(&BBToCheck)) | ||||||||
| 675 | return false; | ||||||||
| 676 | // BBToCheck is not trivial to unswitch if its phis aren't loop invariant. | ||||||||
| 677 | if (!areLoopExitPHIsLoopInvariant(L, *ParentBB, BBToCheck)) | ||||||||
| 678 | return false; | ||||||||
| 679 | // We do not unswitch a block that only has an unreachable statement, as | ||||||||
| 680 | // it's possible this is a previously unswitched block. Only unswitch if | ||||||||
| 681 | // either the terminator is not unreachable, or, if it is, it's not the only | ||||||||
| 682 | // instruction in the block. | ||||||||
| 683 | auto *TI = BBToCheck.getTerminator(); | ||||||||
| 684 | bool isUnreachable = isa<UnreachableInst>(TI); | ||||||||
| 685 | return !isUnreachable || | ||||||||
| 686 | (isUnreachable && (BBToCheck.getFirstNonPHIOrDbg() != TI)); | ||||||||
| 687 | }; | ||||||||
| 688 | |||||||||
| 689 | SmallVector<int, 4> ExitCaseIndices; | ||||||||
| 690 | for (auto Case : SI.cases()) | ||||||||
| 691 | if (IsTriviallyUnswitchableExitBlock(*Case.getCaseSuccessor())) | ||||||||
| 692 | ExitCaseIndices.push_back(Case.getCaseIndex()); | ||||||||
| 693 | BasicBlock *DefaultExitBB = nullptr; | ||||||||
| 694 | SwitchInstProfUpdateWrapper::CaseWeightOpt DefaultCaseWeight = | ||||||||
| 695 | SwitchInstProfUpdateWrapper::getSuccessorWeight(SI, 0); | ||||||||
| 696 | if (IsTriviallyUnswitchableExitBlock(*SI.getDefaultDest())) { | ||||||||
| 697 | DefaultExitBB = SI.getDefaultDest(); | ||||||||
| 698 | } else if (ExitCaseIndices.empty()) | ||||||||
| 699 | return false; | ||||||||
| 700 | |||||||||
| 701 | LLVM_DEBUG(dbgs() << " unswitching trivial switch...\n")do { } while (false); | ||||||||
| 702 | |||||||||
| 703 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 704 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 705 | |||||||||
| 706 | // We may need to invalidate SCEVs for the outermost loop reached by any of | ||||||||
| 707 | // the exits. | ||||||||
| 708 | Loop *OuterL = &L; | ||||||||
| 709 | |||||||||
| 710 | if (DefaultExitBB) { | ||||||||
| 711 | // Clear out the default destination temporarily to allow accurate | ||||||||
| 712 | // predecessor lists to be examined below. | ||||||||
| 713 | SI.setDefaultDest(nullptr); | ||||||||
| 714 | // Check the loop containing this exit. | ||||||||
| 715 | Loop *ExitL = LI.getLoopFor(DefaultExitBB); | ||||||||
| 716 | if (!ExitL || ExitL->contains(OuterL)) | ||||||||
| 717 | OuterL = ExitL; | ||||||||
| 718 | } | ||||||||
| 719 | |||||||||
| 720 | // Store the exit cases into a separate data structure and remove them from | ||||||||
| 721 | // the switch. | ||||||||
| 722 | SmallVector<std::tuple<ConstantInt *, BasicBlock *, | ||||||||
| 723 | SwitchInstProfUpdateWrapper::CaseWeightOpt>, | ||||||||
| 724 | 4> ExitCases; | ||||||||
| 725 | ExitCases.reserve(ExitCaseIndices.size()); | ||||||||
| 726 | SwitchInstProfUpdateWrapper SIW(SI); | ||||||||
| 727 | // We walk the case indices backwards so that we remove the last case first | ||||||||
| 728 | // and don't disrupt the earlier indices. | ||||||||
| 729 | for (unsigned Index : reverse(ExitCaseIndices)) { | ||||||||
| 730 | auto CaseI = SI.case_begin() + Index; | ||||||||
| 731 | // Compute the outer loop from this exit. | ||||||||
| 732 | Loop *ExitL = LI.getLoopFor(CaseI->getCaseSuccessor()); | ||||||||
| 733 | if (!ExitL || ExitL->contains(OuterL)) | ||||||||
| 734 | OuterL = ExitL; | ||||||||
| 735 | // Save the value of this case. | ||||||||
| 736 | auto W = SIW.getSuccessorWeight(CaseI->getSuccessorIndex()); | ||||||||
| 737 | ExitCases.emplace_back(CaseI->getCaseValue(), CaseI->getCaseSuccessor(), W); | ||||||||
| 738 | // Delete the unswitched cases. | ||||||||
| 739 | SIW.removeCase(CaseI); | ||||||||
| 740 | } | ||||||||
| 741 | |||||||||
| 742 | if (SE) { | ||||||||
| 743 | if (OuterL) | ||||||||
| 744 | SE->forgetLoop(OuterL); | ||||||||
| 745 | else | ||||||||
| 746 | SE->forgetTopmostLoop(&L); | ||||||||
| 747 | } | ||||||||
| 748 | |||||||||
| 749 | // Check if after this all of the remaining cases point at the same | ||||||||
| 750 | // successor. | ||||||||
| 751 | BasicBlock *CommonSuccBB = nullptr; | ||||||||
| 752 | if (SI.getNumCases() > 0 && | ||||||||
| 753 | all_of(drop_begin(SI.cases()), [&SI](const SwitchInst::CaseHandle &Case) { | ||||||||
| 754 | return Case.getCaseSuccessor() == SI.case_begin()->getCaseSuccessor(); | ||||||||
| 755 | })) | ||||||||
| 756 | CommonSuccBB = SI.case_begin()->getCaseSuccessor(); | ||||||||
| 757 | if (!DefaultExitBB) { | ||||||||
| 758 | // If we're not unswitching the default, we need it to match any cases to | ||||||||
| 759 | // have a common successor or if we have no cases it is the common | ||||||||
| 760 | // successor. | ||||||||
| 761 | if (SI.getNumCases() == 0) | ||||||||
| 762 | CommonSuccBB = SI.getDefaultDest(); | ||||||||
| 763 | else if (SI.getDefaultDest() != CommonSuccBB) | ||||||||
| 764 | CommonSuccBB = nullptr; | ||||||||
| 765 | } | ||||||||
| 766 | |||||||||
| 767 | // Split the preheader, so that we know that there is a safe place to insert | ||||||||
| 768 | // the switch. | ||||||||
| 769 | BasicBlock *OldPH = L.getLoopPreheader(); | ||||||||
| 770 | BasicBlock *NewPH = SplitEdge(OldPH, L.getHeader(), &DT, &LI, MSSAU); | ||||||||
| 771 | OldPH->getTerminator()->eraseFromParent(); | ||||||||
| 772 | |||||||||
| 773 | // Now add the unswitched switch. | ||||||||
| 774 | auto *NewSI = SwitchInst::Create(LoopCond, NewPH, ExitCases.size(), OldPH); | ||||||||
| 775 | SwitchInstProfUpdateWrapper NewSIW(*NewSI); | ||||||||
| 776 | |||||||||
| 777 | // Rewrite the IR for the unswitched basic blocks. This requires two steps. | ||||||||
| 778 | // First, we split any exit blocks with remaining in-loop predecessors. Then | ||||||||
| 779 | // we update the PHIs in one of two ways depending on if there was a split. | ||||||||
| 780 | // We walk in reverse so that we split in the same order as the cases | ||||||||
| 781 | // appeared. This is purely for convenience of reading the resulting IR, but | ||||||||
| 782 | // it doesn't cost anything really. | ||||||||
| 783 | SmallPtrSet<BasicBlock *, 2> UnswitchedExitBBs; | ||||||||
| 784 | SmallDenseMap<BasicBlock *, BasicBlock *, 2> SplitExitBBMap; | ||||||||
| 785 | // Handle the default exit if necessary. | ||||||||
| 786 | // FIXME: It'd be great if we could merge this with the loop below but LLVM's | ||||||||
| 787 | // ranges aren't quite powerful enough yet. | ||||||||
| 788 | if (DefaultExitBB) { | ||||||||
| 789 | if (pred_empty(DefaultExitBB)) { | ||||||||
| 790 | UnswitchedExitBBs.insert(DefaultExitBB); | ||||||||
| 791 | rewritePHINodesForUnswitchedExitBlock(*DefaultExitBB, *ParentBB, *OldPH); | ||||||||
| 792 | } else { | ||||||||
| 793 | auto *SplitBB = | ||||||||
| 794 | SplitBlock(DefaultExitBB, &DefaultExitBB->front(), &DT, &LI, MSSAU); | ||||||||
| 795 | rewritePHINodesForExitAndUnswitchedBlocks(*DefaultExitBB, *SplitBB, | ||||||||
| 796 | *ParentBB, *OldPH, | ||||||||
| 797 | /*FullUnswitch*/ true); | ||||||||
| 798 | DefaultExitBB = SplitExitBBMap[DefaultExitBB] = SplitBB; | ||||||||
| 799 | } | ||||||||
| 800 | } | ||||||||
| 801 | // Note that we must use a reference in the for loop so that we update the | ||||||||
| 802 | // container. | ||||||||
| 803 | for (auto &ExitCase : reverse(ExitCases)) { | ||||||||
| 804 | // Grab a reference to the exit block in the pair so that we can update it. | ||||||||
| 805 | BasicBlock *ExitBB = std::get<1>(ExitCase); | ||||||||
| 806 | |||||||||
| 807 | // If this case is the last edge into the exit block, we can simply reuse it | ||||||||
| 808 | // as it will no longer be a loop exit. No mapping necessary. | ||||||||
| 809 | if (pred_empty(ExitBB)) { | ||||||||
| 810 | // Only rewrite once. | ||||||||
| 811 | if (UnswitchedExitBBs.insert(ExitBB).second) | ||||||||
| 812 | rewritePHINodesForUnswitchedExitBlock(*ExitBB, *ParentBB, *OldPH); | ||||||||
| 813 | continue; | ||||||||
| 814 | } | ||||||||
| 815 | |||||||||
| 816 | // Otherwise we need to split the exit block so that we retain an exit | ||||||||
| 817 | // block from the loop and a target for the unswitched condition. | ||||||||
| 818 | BasicBlock *&SplitExitBB = SplitExitBBMap[ExitBB]; | ||||||||
| 819 | if (!SplitExitBB) { | ||||||||
| 820 | // If this is the first time we see this, do the split and remember it. | ||||||||
| 821 | SplitExitBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI, MSSAU); | ||||||||
| 822 | rewritePHINodesForExitAndUnswitchedBlocks(*ExitBB, *SplitExitBB, | ||||||||
| 823 | *ParentBB, *OldPH, | ||||||||
| 824 | /*FullUnswitch*/ true); | ||||||||
| 825 | } | ||||||||
| 826 | // Update the case pair to point to the split block. | ||||||||
| 827 | std::get<1>(ExitCase) = SplitExitBB; | ||||||||
| 828 | } | ||||||||
| 829 | |||||||||
| 830 | // Now add the unswitched cases. We do this in reverse order as we built them | ||||||||
| 831 | // in reverse order. | ||||||||
| 832 | for (auto &ExitCase : reverse(ExitCases)) { | ||||||||
| 833 | ConstantInt *CaseVal = std::get<0>(ExitCase); | ||||||||
| 834 | BasicBlock *UnswitchedBB = std::get<1>(ExitCase); | ||||||||
| 835 | |||||||||
| 836 | NewSIW.addCase(CaseVal, UnswitchedBB, std::get<2>(ExitCase)); | ||||||||
| 837 | } | ||||||||
| 838 | |||||||||
| 839 | // If the default was unswitched, re-point it and add explicit cases for | ||||||||
| 840 | // entering the loop. | ||||||||
| 841 | if (DefaultExitBB) { | ||||||||
| 842 | NewSIW->setDefaultDest(DefaultExitBB); | ||||||||
| 843 | NewSIW.setSuccessorWeight(0, DefaultCaseWeight); | ||||||||
| 844 | |||||||||
| 845 | // We removed all the exit cases, so we just copy the cases to the | ||||||||
| 846 | // unswitched switch. | ||||||||
| 847 | for (const auto &Case : SI.cases()) | ||||||||
| 848 | NewSIW.addCase(Case.getCaseValue(), NewPH, | ||||||||
| 849 | SIW.getSuccessorWeight(Case.getSuccessorIndex())); | ||||||||
| 850 | } else if (DefaultCaseWeight) { | ||||||||
| 851 | // We have to set branch weight of the default case. | ||||||||
| 852 | uint64_t SW = *DefaultCaseWeight; | ||||||||
| 853 | for (const auto &Case : SI.cases()) { | ||||||||
| 854 | auto W = SIW.getSuccessorWeight(Case.getSuccessorIndex()); | ||||||||
| 855 | assert(W &&((void)0) | ||||||||
| 856 | "case weight must be defined as default case weight is defined")((void)0); | ||||||||
| 857 | SW += *W; | ||||||||
| 858 | } | ||||||||
| 859 | NewSIW.setSuccessorWeight(0, SW); | ||||||||
| 860 | } | ||||||||
| 861 | |||||||||
| 862 | // If we ended up with a common successor for every path through the switch | ||||||||
| 863 | // after unswitching, rewrite it to an unconditional branch to make it easy | ||||||||
| 864 | // to recognize. Otherwise we potentially have to recognize the default case | ||||||||
| 865 | // pointing at unreachable and other complexity. | ||||||||
| 866 | if (CommonSuccBB) { | ||||||||
| 867 | BasicBlock *BB = SI.getParent(); | ||||||||
| 868 | // We may have had multiple edges to this common successor block, so remove | ||||||||
| 869 | // them as predecessors. We skip the first one, either the default or the | ||||||||
| 870 | // actual first case. | ||||||||
| 871 | bool SkippedFirst = DefaultExitBB == nullptr; | ||||||||
| 872 | for (auto Case : SI.cases()) { | ||||||||
| 873 | assert(Case.getCaseSuccessor() == CommonSuccBB &&((void)0) | ||||||||
| 874 | "Non-common successor!")((void)0); | ||||||||
| 875 | (void)Case; | ||||||||
| 876 | if (!SkippedFirst) { | ||||||||
| 877 | SkippedFirst = true; | ||||||||
| 878 | continue; | ||||||||
| 879 | } | ||||||||
| 880 | CommonSuccBB->removePredecessor(BB, | ||||||||
| 881 | /*KeepOneInputPHIs*/ true); | ||||||||
| 882 | } | ||||||||
| 883 | // Now nuke the switch and replace it with a direct branch. | ||||||||
| 884 | SIW.eraseFromParent(); | ||||||||
| 885 | BranchInst::Create(CommonSuccBB, BB); | ||||||||
| 886 | } else if (DefaultExitBB) { | ||||||||
| 887 | assert(SI.getNumCases() > 0 &&((void)0) | ||||||||
| 888 | "If we had no cases we'd have a common successor!")((void)0); | ||||||||
| 889 | // Move the last case to the default successor. This is valid as if the | ||||||||
| 890 | // default got unswitched it cannot be reached. This has the advantage of | ||||||||
| 891 | // being simple and keeping the number of edges from this switch to | ||||||||
| 892 | // successors the same, and avoiding any PHI update complexity. | ||||||||
| 893 | auto LastCaseI = std::prev(SI.case_end()); | ||||||||
| 894 | |||||||||
| 895 | SI.setDefaultDest(LastCaseI->getCaseSuccessor()); | ||||||||
| 896 | SIW.setSuccessorWeight( | ||||||||
| 897 | 0, SIW.getSuccessorWeight(LastCaseI->getSuccessorIndex())); | ||||||||
| 898 | SIW.removeCase(LastCaseI); | ||||||||
| 899 | } | ||||||||
| 900 | |||||||||
| 901 | // Walk the unswitched exit blocks and the unswitched split blocks and update | ||||||||
| 902 | // the dominator tree based on the CFG edits. While we are walking unordered | ||||||||
| 903 | // containers here, the API for applyUpdates takes an unordered list of | ||||||||
| 904 | // updates and requires them to not contain duplicates. | ||||||||
| 905 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | ||||||||
| 906 | for (auto *UnswitchedExitBB : UnswitchedExitBBs) { | ||||||||
| 907 | DTUpdates.push_back({DT.Delete, ParentBB, UnswitchedExitBB}); | ||||||||
| 908 | DTUpdates.push_back({DT.Insert, OldPH, UnswitchedExitBB}); | ||||||||
| 909 | } | ||||||||
| 910 | for (auto SplitUnswitchedPair : SplitExitBBMap) { | ||||||||
| 911 | DTUpdates.push_back({DT.Delete, ParentBB, SplitUnswitchedPair.first}); | ||||||||
| 912 | DTUpdates.push_back({DT.Insert, OldPH, SplitUnswitchedPair.second}); | ||||||||
| 913 | } | ||||||||
| 914 | |||||||||
| 915 | if (MSSAU) { | ||||||||
| 916 | MSSAU->applyUpdates(DTUpdates, DT, /*UpdateDT=*/true); | ||||||||
| 917 | if (VerifyMemorySSA) | ||||||||
| 918 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 919 | } else { | ||||||||
| 920 | DT.applyUpdates(DTUpdates); | ||||||||
| 921 | } | ||||||||
| 922 | |||||||||
| 923 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))((void)0); | ||||||||
| 924 | |||||||||
| 925 | // We may have changed the nesting relationship for this loop so hoist it to | ||||||||
| 926 | // its correct parent if needed. | ||||||||
| 927 | hoistLoopToNewParent(L, *NewPH, DT, LI, MSSAU, SE); | ||||||||
| 928 | |||||||||
| 929 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 930 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 931 | |||||||||
| 932 | ++NumTrivial; | ||||||||
| 933 | ++NumSwitches; | ||||||||
| 934 | LLVM_DEBUG(dbgs() << " done: unswitching trivial switch...\n")do { } while (false); | ||||||||
| 935 | return true; | ||||||||
| 936 | } | ||||||||
| 937 | |||||||||
| 938 | /// This routine scans the loop to find a branch or switch which occurs before | ||||||||
| 939 | /// any side effects occur. These can potentially be unswitched without | ||||||||
| 940 | /// duplicating the loop. If a branch or switch is successfully unswitched the | ||||||||
| 941 | /// scanning continues to see if subsequent branches or switches have become | ||||||||
| 942 | /// trivial. Once all trivial candidates have been unswitched, this routine | ||||||||
| 943 | /// returns. | ||||||||
| 944 | /// | ||||||||
| 945 | /// The return value indicates whether anything was unswitched (and therefore | ||||||||
| 946 | /// changed). | ||||||||
| 947 | /// | ||||||||
| 948 | /// If `SE` is not null, it will be updated based on the potential loop SCEVs | ||||||||
| 949 | /// invalidated by this. | ||||||||
| 950 | static bool unswitchAllTrivialConditions(Loop &L, DominatorTree &DT, | ||||||||
| 951 | LoopInfo &LI, ScalarEvolution *SE, | ||||||||
| 952 | MemorySSAUpdater *MSSAU) { | ||||||||
| 953 | bool Changed = false; | ||||||||
| 954 | |||||||||
| 955 | // If loop header has only one reachable successor we should keep looking for | ||||||||
| 956 | // trivial condition candidates in the successor as well. An alternative is | ||||||||
| 957 | // to constant fold conditions and merge successors into loop header (then we | ||||||||
| 958 | // only need to check header's terminator). The reason for not doing this in | ||||||||
| 959 | // LoopUnswitch pass is that it could potentially break LoopPassManager's | ||||||||
| 960 | // invariants. Folding dead branches could either eliminate the current loop | ||||||||
| 961 | // or make other loops unreachable. LCSSA form might also not be preserved | ||||||||
| 962 | // after deleting branches. The following code keeps traversing loop header's | ||||||||
| 963 | // successors until it finds the trivial condition candidate (condition that | ||||||||
| 964 | // is not a constant). Since unswitching generates branches with constant | ||||||||
| 965 | // conditions, this scenario could be very common in practice. | ||||||||
| 966 | BasicBlock *CurrentBB = L.getHeader(); | ||||||||
| 967 | SmallPtrSet<BasicBlock *, 8> Visited; | ||||||||
| 968 | Visited.insert(CurrentBB); | ||||||||
| 969 | do { | ||||||||
| 970 | // Check if there are any side-effecting instructions (e.g. stores, calls, | ||||||||
| 971 | // volatile loads) in the part of the loop that the code *would* execute | ||||||||
| 972 | // without unswitching. | ||||||||
| 973 | if (MSSAU) // Possible early exit with MSSA | ||||||||
| 974 | if (auto *Defs = MSSAU->getMemorySSA()->getBlockDefs(CurrentBB)) | ||||||||
| 975 | if (!isa<MemoryPhi>(*Defs->begin()) || (++Defs->begin() != Defs->end())) | ||||||||
| 976 | return Changed; | ||||||||
| 977 | if (llvm::any_of(*CurrentBB, | ||||||||
| 978 | [](Instruction &I) { return I.mayHaveSideEffects(); })) | ||||||||
| 979 | return Changed; | ||||||||
| 980 | |||||||||
| 981 | Instruction *CurrentTerm = CurrentBB->getTerminator(); | ||||||||
| 982 | |||||||||
| 983 | if (auto *SI = dyn_cast<SwitchInst>(CurrentTerm)) { | ||||||||
| 984 | // Don't bother trying to unswitch past a switch with a constant | ||||||||
| 985 | // condition. This should be removed prior to running this pass by | ||||||||
| 986 | // simplifycfg. | ||||||||
| 987 | if (isa<Constant>(SI->getCondition())) | ||||||||
| 988 | return Changed; | ||||||||
| 989 | |||||||||
| 990 | if (!unswitchTrivialSwitch(L, *SI, DT, LI, SE, MSSAU)) | ||||||||
| 991 | // Couldn't unswitch this one so we're done. | ||||||||
| 992 | return Changed; | ||||||||
| 993 | |||||||||
| 994 | // Mark that we managed to unswitch something. | ||||||||
| 995 | Changed = true; | ||||||||
| 996 | |||||||||
| 997 | // If unswitching turned the terminator into an unconditional branch then | ||||||||
| 998 | // we can continue. The unswitching logic specifically works to fold any | ||||||||
| 999 | // cases it can into an unconditional branch to make it easier to | ||||||||
| 1000 | // recognize here. | ||||||||
| 1001 | auto *BI = dyn_cast<BranchInst>(CurrentBB->getTerminator()); | ||||||||
| 1002 | if (!BI || BI->isConditional()) | ||||||||
| 1003 | return Changed; | ||||||||
| 1004 | |||||||||
| 1005 | CurrentBB = BI->getSuccessor(0); | ||||||||
| 1006 | continue; | ||||||||
| 1007 | } | ||||||||
| 1008 | |||||||||
| 1009 | auto *BI = dyn_cast<BranchInst>(CurrentTerm); | ||||||||
| 1010 | if (!BI) | ||||||||
| 1011 | // We do not understand other terminator instructions. | ||||||||
| 1012 | return Changed; | ||||||||
| 1013 | |||||||||
| 1014 | // Don't bother trying to unswitch past an unconditional branch or a branch | ||||||||
| 1015 | // with a constant value. These should be removed by simplifycfg prior to | ||||||||
| 1016 | // running this pass. | ||||||||
| 1017 | if (!BI->isConditional() || isa<Constant>(BI->getCondition())) | ||||||||
| 1018 | return Changed; | ||||||||
| 1019 | |||||||||
| 1020 | // Found a trivial condition candidate: non-foldable conditional branch. If | ||||||||
| 1021 | // we fail to unswitch this, we can't do anything else that is trivial. | ||||||||
| 1022 | if (!unswitchTrivialBranch(L, *BI, DT, LI, SE, MSSAU)) | ||||||||
| 1023 | return Changed; | ||||||||
| 1024 | |||||||||
| 1025 | // Mark that we managed to unswitch something. | ||||||||
| 1026 | Changed = true; | ||||||||
| 1027 | |||||||||
| 1028 | // If we only unswitched some of the conditions feeding the branch, we won't | ||||||||
| 1029 | // have collapsed it to a single successor. | ||||||||
| 1030 | BI = cast<BranchInst>(CurrentBB->getTerminator()); | ||||||||
| 1031 | if (BI->isConditional()) | ||||||||
| 1032 | return Changed; | ||||||||
| 1033 | |||||||||
| 1034 | // Follow the newly unconditional branch into its successor. | ||||||||
| 1035 | CurrentBB = BI->getSuccessor(0); | ||||||||
| 1036 | |||||||||
| 1037 | // When continuing, if we exit the loop or reach a previous visited block, | ||||||||
| 1038 | // then we can not reach any trivial condition candidates (unfoldable | ||||||||
| 1039 | // branch instructions or switch instructions) and no unswitch can happen. | ||||||||
| 1040 | } while (L.contains(CurrentBB) && Visited.insert(CurrentBB).second); | ||||||||
| 1041 | |||||||||
| 1042 | return Changed; | ||||||||
| 1043 | } | ||||||||
| 1044 | |||||||||
| 1045 | /// Build the cloned blocks for an unswitched copy of the given loop. | ||||||||
| 1046 | /// | ||||||||
| 1047 | /// The cloned blocks are inserted before the loop preheader (`LoopPH`) and | ||||||||
| 1048 | /// after the split block (`SplitBB`) that will be used to select between the | ||||||||
| 1049 | /// cloned and original loop. | ||||||||
| 1050 | /// | ||||||||
| 1051 | /// This routine handles cloning all of the necessary loop blocks and exit | ||||||||
| 1052 | /// blocks including rewriting their instructions and the relevant PHI nodes. | ||||||||
| 1053 | /// Any loop blocks or exit blocks which are dominated by a different successor | ||||||||
| 1054 | /// than the one for this clone of the loop blocks can be trivially skipped. We | ||||||||
| 1055 | /// use the `DominatingSucc` map to determine whether a block satisfies that | ||||||||
| 1056 | /// property with a simple map lookup. | ||||||||
| 1057 | /// | ||||||||
| 1058 | /// It also correctly creates the unconditional branch in the cloned | ||||||||
| 1059 | /// unswitched parent block to only point at the unswitched successor. | ||||||||
| 1060 | /// | ||||||||
| 1061 | /// This does not handle most of the necessary updates to `LoopInfo`. Only exit | ||||||||
| 1062 | /// block splitting is correctly reflected in `LoopInfo`, essentially all of | ||||||||
| 1063 | /// the cloned blocks (and their loops) are left without full `LoopInfo` | ||||||||
| 1064 | /// updates. This also doesn't fully update `DominatorTree`. It adds the cloned | ||||||||
| 1065 | /// blocks to them but doesn't create the cloned `DominatorTree` structure and | ||||||||
| 1066 | /// instead the caller must recompute an accurate DT. It *does* correctly | ||||||||
| 1067 | /// update the `AssumptionCache` provided in `AC`. | ||||||||
| 1068 | static BasicBlock *buildClonedLoopBlocks( | ||||||||
| 1069 | Loop &L, BasicBlock *LoopPH, BasicBlock *SplitBB, | ||||||||
| 1070 | ArrayRef<BasicBlock *> ExitBlocks, BasicBlock *ParentBB, | ||||||||
| 1071 | BasicBlock *UnswitchedSuccBB, BasicBlock *ContinueSuccBB, | ||||||||
| 1072 | const SmallDenseMap<BasicBlock *, BasicBlock *, 16> &DominatingSucc, | ||||||||
| 1073 | ValueToValueMapTy &VMap, | ||||||||
| 1074 | SmallVectorImpl<DominatorTree::UpdateType> &DTUpdates, AssumptionCache &AC, | ||||||||
| 1075 | DominatorTree &DT, LoopInfo &LI, MemorySSAUpdater *MSSAU) { | ||||||||
| 1076 | SmallVector<BasicBlock *, 4> NewBlocks; | ||||||||
| 1077 | NewBlocks.reserve(L.getNumBlocks() + ExitBlocks.size()); | ||||||||
| 1078 | |||||||||
| 1079 | // We will need to clone a bunch of blocks, wrap up the clone operation in | ||||||||
| 1080 | // a helper. | ||||||||
| 1081 | auto CloneBlock = [&](BasicBlock *OldBB) { | ||||||||
| 1082 | // Clone the basic block and insert it before the new preheader. | ||||||||
| 1083 | BasicBlock *NewBB = CloneBasicBlock(OldBB, VMap, ".us", OldBB->getParent()); | ||||||||
| 1084 | NewBB->moveBefore(LoopPH); | ||||||||
| 1085 | |||||||||
| 1086 | // Record this block and the mapping. | ||||||||
| 1087 | NewBlocks.push_back(NewBB); | ||||||||
| 1088 | VMap[OldBB] = NewBB; | ||||||||
| 1089 | |||||||||
| 1090 | return NewBB; | ||||||||
| 1091 | }; | ||||||||
| 1092 | |||||||||
| 1093 | // We skip cloning blocks when they have a dominating succ that is not the | ||||||||
| 1094 | // succ we are cloning for. | ||||||||
| 1095 | auto SkipBlock = [&](BasicBlock *BB) { | ||||||||
| 1096 | auto It = DominatingSucc.find(BB); | ||||||||
| 1097 | return It != DominatingSucc.end() && It->second != UnswitchedSuccBB; | ||||||||
| 1098 | }; | ||||||||
| 1099 | |||||||||
| 1100 | // First, clone the preheader. | ||||||||
| 1101 | auto *ClonedPH = CloneBlock(LoopPH); | ||||||||
| 1102 | |||||||||
| 1103 | // Then clone all the loop blocks, skipping the ones that aren't necessary. | ||||||||
| 1104 | for (auto *LoopBB : L.blocks()) | ||||||||
| 1105 | if (!SkipBlock(LoopBB)) | ||||||||
| 1106 | CloneBlock(LoopBB); | ||||||||
| 1107 | |||||||||
| 1108 | // Split all the loop exit edges so that when we clone the exit blocks, if | ||||||||
| 1109 | // any of the exit blocks are *also* a preheader for some other loop, we | ||||||||
| 1110 | // don't create multiple predecessors entering the loop header. | ||||||||
| 1111 | for (auto *ExitBB : ExitBlocks) { | ||||||||
| 1112 | if (SkipBlock(ExitBB)) | ||||||||
| 1113 | continue; | ||||||||
| 1114 | |||||||||
| 1115 | // When we are going to clone an exit, we don't need to clone all the | ||||||||
| 1116 | // instructions in the exit block and we want to ensure we have an easy | ||||||||
| 1117 | // place to merge the CFG, so split the exit first. This is always safe to | ||||||||
| 1118 | // do because there cannot be any non-loop predecessors of a loop exit in | ||||||||
| 1119 | // loop simplified form. | ||||||||
| 1120 | auto *MergeBB = SplitBlock(ExitBB, &ExitBB->front(), &DT, &LI, MSSAU); | ||||||||
| 1121 | |||||||||
| 1122 | // Rearrange the names to make it easier to write test cases by having the | ||||||||
| 1123 | // exit block carry the suffix rather than the merge block carrying the | ||||||||
| 1124 | // suffix. | ||||||||
| 1125 | MergeBB->takeName(ExitBB); | ||||||||
| 1126 | ExitBB->setName(Twine(MergeBB->getName()) + ".split"); | ||||||||
| 1127 | |||||||||
| 1128 | // Now clone the original exit block. | ||||||||
| 1129 | auto *ClonedExitBB = CloneBlock(ExitBB); | ||||||||
| 1130 | assert(ClonedExitBB->getTerminator()->getNumSuccessors() == 1 &&((void)0) | ||||||||
| 1131 | "Exit block should have been split to have one successor!")((void)0); | ||||||||
| 1132 | assert(ClonedExitBB->getTerminator()->getSuccessor(0) == MergeBB &&((void)0) | ||||||||
| 1133 | "Cloned exit block has the wrong successor!")((void)0); | ||||||||
| 1134 | |||||||||
| 1135 | // Remap any cloned instructions and create a merge phi node for them. | ||||||||
| 1136 | for (auto ZippedInsts : llvm::zip_first( | ||||||||
| 1137 | llvm::make_range(ExitBB->begin(), std::prev(ExitBB->end())), | ||||||||
| 1138 | llvm::make_range(ClonedExitBB->begin(), | ||||||||
| 1139 | std::prev(ClonedExitBB->end())))) { | ||||||||
| 1140 | Instruction &I = std::get<0>(ZippedInsts); | ||||||||
| 1141 | Instruction &ClonedI = std::get<1>(ZippedInsts); | ||||||||
| 1142 | |||||||||
| 1143 | // The only instructions in the exit block should be PHI nodes and | ||||||||
| 1144 | // potentially a landing pad. | ||||||||
| 1145 | assert(((void)0) | ||||||||
| 1146 | (isa<PHINode>(I) || isa<LandingPadInst>(I) || isa<CatchPadInst>(I)) &&((void)0) | ||||||||
| 1147 | "Bad instruction in exit block!")((void)0); | ||||||||
| 1148 | // We should have a value map between the instruction and its clone. | ||||||||
| 1149 | assert(VMap.lookup(&I) == &ClonedI && "Mismatch in the value map!")((void)0); | ||||||||
| 1150 | |||||||||
| 1151 | auto *MergePN = | ||||||||
| 1152 | PHINode::Create(I.getType(), /*NumReservedValues*/ 2, ".us-phi", | ||||||||
| 1153 | &*MergeBB->getFirstInsertionPt()); | ||||||||
| 1154 | I.replaceAllUsesWith(MergePN); | ||||||||
| 1155 | MergePN->addIncoming(&I, ExitBB); | ||||||||
| 1156 | MergePN->addIncoming(&ClonedI, ClonedExitBB); | ||||||||
| 1157 | } | ||||||||
| 1158 | } | ||||||||
| 1159 | |||||||||
| 1160 | // Rewrite the instructions in the cloned blocks to refer to the instructions | ||||||||
| 1161 | // in the cloned blocks. We have to do this as a second pass so that we have | ||||||||
| 1162 | // everything available. Also, we have inserted new instructions which may | ||||||||
| 1163 | // include assume intrinsics, so we update the assumption cache while | ||||||||
| 1164 | // processing this. | ||||||||
| 1165 | for (auto *ClonedBB : NewBlocks) | ||||||||
| 1166 | for (Instruction &I : *ClonedBB) { | ||||||||
| 1167 | RemapInstruction(&I, VMap, | ||||||||
| 1168 | RF_NoModuleLevelChanges | RF_IgnoreMissingLocals); | ||||||||
| 1169 | if (auto *II = dyn_cast<AssumeInst>(&I)) | ||||||||
| 1170 | AC.registerAssumption(II); | ||||||||
| 1171 | } | ||||||||
| 1172 | |||||||||
| 1173 | // Update any PHI nodes in the cloned successors of the skipped blocks to not | ||||||||
| 1174 | // have spurious incoming values. | ||||||||
| 1175 | for (auto *LoopBB : L.blocks()) | ||||||||
| 1176 | if (SkipBlock(LoopBB)) | ||||||||
| 1177 | for (auto *SuccBB : successors(LoopBB)) | ||||||||
| 1178 | if (auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB))) | ||||||||
| 1179 | for (PHINode &PN : ClonedSuccBB->phis()) | ||||||||
| 1180 | PN.removeIncomingValue(LoopBB, /*DeletePHIIfEmpty*/ false); | ||||||||
| 1181 | |||||||||
| 1182 | // Remove the cloned parent as a predecessor of any successor we ended up | ||||||||
| 1183 | // cloning other than the unswitched one. | ||||||||
| 1184 | auto *ClonedParentBB = cast<BasicBlock>(VMap.lookup(ParentBB)); | ||||||||
| 1185 | for (auto *SuccBB : successors(ParentBB)) { | ||||||||
| 1186 | if (SuccBB == UnswitchedSuccBB) | ||||||||
| 1187 | continue; | ||||||||
| 1188 | |||||||||
| 1189 | auto *ClonedSuccBB = cast_or_null<BasicBlock>(VMap.lookup(SuccBB)); | ||||||||
| 1190 | if (!ClonedSuccBB) | ||||||||
| 1191 | continue; | ||||||||
| 1192 | |||||||||
| 1193 | ClonedSuccBB->removePredecessor(ClonedParentBB, | ||||||||
| 1194 | /*KeepOneInputPHIs*/ true); | ||||||||
| 1195 | } | ||||||||
| 1196 | |||||||||
| 1197 | // Replace the cloned branch with an unconditional branch to the cloned | ||||||||
| 1198 | // unswitched successor. | ||||||||
| 1199 | auto *ClonedSuccBB = cast<BasicBlock>(VMap.lookup(UnswitchedSuccBB)); | ||||||||
| 1200 | Instruction *ClonedTerminator = ClonedParentBB->getTerminator(); | ||||||||
| 1201 | // Trivial Simplification. If Terminator is a conditional branch and | ||||||||
| 1202 | // condition becomes dead - erase it. | ||||||||
| 1203 | Value *ClonedConditionToErase = nullptr; | ||||||||
| 1204 | if (auto *BI = dyn_cast<BranchInst>(ClonedTerminator)) | ||||||||
| 1205 | ClonedConditionToErase = BI->getCondition(); | ||||||||
| 1206 | else if (auto *SI = dyn_cast<SwitchInst>(ClonedTerminator)) | ||||||||
| 1207 | ClonedConditionToErase = SI->getCondition(); | ||||||||
| 1208 | |||||||||
| 1209 | ClonedTerminator->eraseFromParent(); | ||||||||
| 1210 | BranchInst::Create(ClonedSuccBB, ClonedParentBB); | ||||||||
| 1211 | |||||||||
| 1212 | if (ClonedConditionToErase) | ||||||||
| 1213 | RecursivelyDeleteTriviallyDeadInstructions(ClonedConditionToErase, nullptr, | ||||||||
| 1214 | MSSAU); | ||||||||
| 1215 | |||||||||
| 1216 | // If there are duplicate entries in the PHI nodes because of multiple edges | ||||||||
| 1217 | // to the unswitched successor, we need to nuke all but one as we replaced it | ||||||||
| 1218 | // with a direct branch. | ||||||||
| 1219 | for (PHINode &PN : ClonedSuccBB->phis()) { | ||||||||
| 1220 | bool Found = false; | ||||||||
| 1221 | // Loop over the incoming operands backwards so we can easily delete as we | ||||||||
| 1222 | // go without invalidating the index. | ||||||||
| 1223 | for (int i = PN.getNumOperands() - 1; i >= 0; --i) { | ||||||||
| 1224 | if (PN.getIncomingBlock(i) != ClonedParentBB) | ||||||||
| 1225 | continue; | ||||||||
| 1226 | if (!Found) { | ||||||||
| 1227 | Found = true; | ||||||||
| 1228 | continue; | ||||||||
| 1229 | } | ||||||||
| 1230 | PN.removeIncomingValue(i, /*DeletePHIIfEmpty*/ false); | ||||||||
| 1231 | } | ||||||||
| 1232 | } | ||||||||
| 1233 | |||||||||
| 1234 | // Record the domtree updates for the new blocks. | ||||||||
| 1235 | SmallPtrSet<BasicBlock *, 4> SuccSet; | ||||||||
| 1236 | for (auto *ClonedBB : NewBlocks) { | ||||||||
| 1237 | for (auto *SuccBB : successors(ClonedBB)) | ||||||||
| 1238 | if (SuccSet.insert(SuccBB).second) | ||||||||
| 1239 | DTUpdates.push_back({DominatorTree::Insert, ClonedBB, SuccBB}); | ||||||||
| 1240 | SuccSet.clear(); | ||||||||
| 1241 | } | ||||||||
| 1242 | |||||||||
| 1243 | return ClonedPH; | ||||||||
| 1244 | } | ||||||||
| 1245 | |||||||||
| 1246 | /// Recursively clone the specified loop and all of its children. | ||||||||
| 1247 | /// | ||||||||
| 1248 | /// The target parent loop for the clone should be provided, or can be null if | ||||||||
| 1249 | /// the clone is a top-level loop. While cloning, all the blocks are mapped | ||||||||
| 1250 | /// with the provided value map. The entire original loop must be present in | ||||||||
| 1251 | /// the value map. The cloned loop is returned. | ||||||||
| 1252 | static Loop *cloneLoopNest(Loop &OrigRootL, Loop *RootParentL, | ||||||||
| 1253 | const ValueToValueMapTy &VMap, LoopInfo &LI) { | ||||||||
| 1254 | auto AddClonedBlocksToLoop = [&](Loop &OrigL, Loop &ClonedL) { | ||||||||
| 1255 | assert(ClonedL.getBlocks().empty() && "Must start with an empty loop!")((void)0); | ||||||||
| 1256 | ClonedL.reserveBlocks(OrigL.getNumBlocks()); | ||||||||
| 1257 | for (auto *BB : OrigL.blocks()) { | ||||||||
| 1258 | auto *ClonedBB = cast<BasicBlock>(VMap.lookup(BB)); | ||||||||
| 1259 | ClonedL.addBlockEntry(ClonedBB); | ||||||||
| 1260 | if (LI.getLoopFor(BB) == &OrigL) | ||||||||
| 1261 | LI.changeLoopFor(ClonedBB, &ClonedL); | ||||||||
| 1262 | } | ||||||||
| 1263 | }; | ||||||||
| 1264 | |||||||||
| 1265 | // We specially handle the first loop because it may get cloned into | ||||||||
| 1266 | // a different parent and because we most commonly are cloning leaf loops. | ||||||||
| 1267 | Loop *ClonedRootL = LI.AllocateLoop(); | ||||||||
| 1268 | if (RootParentL) | ||||||||
| 1269 | RootParentL->addChildLoop(ClonedRootL); | ||||||||
| 1270 | else | ||||||||
| 1271 | LI.addTopLevelLoop(ClonedRootL); | ||||||||
| 1272 | AddClonedBlocksToLoop(OrigRootL, *ClonedRootL); | ||||||||
| 1273 | |||||||||
| 1274 | if (OrigRootL.isInnermost()) | ||||||||
| 1275 | return ClonedRootL; | ||||||||
| 1276 | |||||||||
| 1277 | // If we have a nest, we can quickly clone the entire loop nest using an | ||||||||
| 1278 | // iterative approach because it is a tree. We keep the cloned parent in the | ||||||||
| 1279 | // data structure to avoid repeatedly querying through a map to find it. | ||||||||
| 1280 | SmallVector<std::pair<Loop *, Loop *>, 16> LoopsToClone; | ||||||||
| 1281 | // Build up the loops to clone in reverse order as we'll clone them from the | ||||||||
| 1282 | // back. | ||||||||
| 1283 | for (Loop *ChildL : llvm::reverse(OrigRootL)) | ||||||||
| 1284 | LoopsToClone.push_back({ClonedRootL, ChildL}); | ||||||||
| 1285 | do { | ||||||||
| 1286 | Loop *ClonedParentL, *L; | ||||||||
| 1287 | std::tie(ClonedParentL, L) = LoopsToClone.pop_back_val(); | ||||||||
| 1288 | Loop *ClonedL = LI.AllocateLoop(); | ||||||||
| 1289 | ClonedParentL->addChildLoop(ClonedL); | ||||||||
| 1290 | AddClonedBlocksToLoop(*L, *ClonedL); | ||||||||
| 1291 | for (Loop *ChildL : llvm::reverse(*L)) | ||||||||
| 1292 | LoopsToClone.push_back({ClonedL, ChildL}); | ||||||||
| 1293 | } while (!LoopsToClone.empty()); | ||||||||
| 1294 | |||||||||
| 1295 | return ClonedRootL; | ||||||||
| 1296 | } | ||||||||
| 1297 | |||||||||
| 1298 | /// Build the cloned loops of an original loop from unswitching. | ||||||||
| 1299 | /// | ||||||||
| 1300 | /// Because unswitching simplifies the CFG of the loop, this isn't a trivial | ||||||||
| 1301 | /// operation. We need to re-verify that there even is a loop (as the backedge | ||||||||
| 1302 | /// may not have been cloned), and even if there are remaining backedges the | ||||||||
| 1303 | /// backedge set may be different. However, we know that each child loop is | ||||||||
| 1304 | /// undisturbed, we only need to find where to place each child loop within | ||||||||
| 1305 | /// either any parent loop or within a cloned version of the original loop. | ||||||||
| 1306 | /// | ||||||||
| 1307 | /// Because child loops may end up cloned outside of any cloned version of the | ||||||||
| 1308 | /// original loop, multiple cloned sibling loops may be created. All of them | ||||||||
| 1309 | /// are returned so that the newly introduced loop nest roots can be | ||||||||
| 1310 | /// identified. | ||||||||
| 1311 | static void buildClonedLoops(Loop &OrigL, ArrayRef<BasicBlock *> ExitBlocks, | ||||||||
| 1312 | const ValueToValueMapTy &VMap, LoopInfo &LI, | ||||||||
| 1313 | SmallVectorImpl<Loop *> &NonChildClonedLoops) { | ||||||||
| 1314 | Loop *ClonedL = nullptr; | ||||||||
| 1315 | |||||||||
| 1316 | auto *OrigPH = OrigL.getLoopPreheader(); | ||||||||
| 1317 | auto *OrigHeader = OrigL.getHeader(); | ||||||||
| 1318 | |||||||||
| 1319 | auto *ClonedPH = cast<BasicBlock>(VMap.lookup(OrigPH)); | ||||||||
| 1320 | auto *ClonedHeader = cast<BasicBlock>(VMap.lookup(OrigHeader)); | ||||||||
| 1321 | |||||||||
| 1322 | // We need to know the loops of the cloned exit blocks to even compute the | ||||||||
| 1323 | // accurate parent loop. If we only clone exits to some parent of the | ||||||||
| 1324 | // original parent, we want to clone into that outer loop. We also keep track | ||||||||
| 1325 | // of the loops that our cloned exit blocks participate in. | ||||||||
| 1326 | Loop *ParentL = nullptr; | ||||||||
| 1327 | SmallVector<BasicBlock *, 4> ClonedExitsInLoops; | ||||||||
| 1328 | SmallDenseMap<BasicBlock *, Loop *, 16> ExitLoopMap; | ||||||||
| 1329 | ClonedExitsInLoops.reserve(ExitBlocks.size()); | ||||||||
| 1330 | for (auto *ExitBB : ExitBlocks) | ||||||||
| 1331 | if (auto *ClonedExitBB = cast_or_null<BasicBlock>(VMap.lookup(ExitBB))) | ||||||||
| 1332 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | ||||||||
| 1333 | ExitLoopMap[ClonedExitBB] = ExitL; | ||||||||
| 1334 | ClonedExitsInLoops.push_back(ClonedExitBB); | ||||||||
| 1335 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | ||||||||
| 1336 | ParentL = ExitL; | ||||||||
| 1337 | } | ||||||||
| 1338 | assert((!ParentL || ParentL == OrigL.getParentLoop() ||((void)0) | ||||||||
| 1339 | ParentL->contains(OrigL.getParentLoop())) &&((void)0) | ||||||||
| 1340 | "The computed parent loop should always contain (or be) the parent of "((void)0) | ||||||||
| 1341 | "the original loop.")((void)0); | ||||||||
| 1342 | |||||||||
| 1343 | // We build the set of blocks dominated by the cloned header from the set of | ||||||||
| 1344 | // cloned blocks out of the original loop. While not all of these will | ||||||||
| 1345 | // necessarily be in the cloned loop, it is enough to establish that they | ||||||||
| 1346 | // aren't in unreachable cycles, etc. | ||||||||
| 1347 | SmallSetVector<BasicBlock *, 16> ClonedLoopBlocks; | ||||||||
| 1348 | for (auto *BB : OrigL.blocks()) | ||||||||
| 1349 | if (auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB))) | ||||||||
| 1350 | ClonedLoopBlocks.insert(ClonedBB); | ||||||||
| 1351 | |||||||||
| 1352 | // Rebuild the set of blocks that will end up in the cloned loop. We may have | ||||||||
| 1353 | // skipped cloning some region of this loop which can in turn skip some of | ||||||||
| 1354 | // the backedges so we have to rebuild the blocks in the loop based on the | ||||||||
| 1355 | // backedges that remain after cloning. | ||||||||
| 1356 | SmallVector<BasicBlock *, 16> Worklist; | ||||||||
| 1357 | SmallPtrSet<BasicBlock *, 16> BlocksInClonedLoop; | ||||||||
| 1358 | for (auto *Pred : predecessors(ClonedHeader)) { | ||||||||
| 1359 | // The only possible non-loop header predecessor is the preheader because | ||||||||
| 1360 | // we know we cloned the loop in simplified form. | ||||||||
| 1361 | if (Pred == ClonedPH) | ||||||||
| 1362 | continue; | ||||||||
| 1363 | |||||||||
| 1364 | // Because the loop was in simplified form, the only non-loop predecessor | ||||||||
| 1365 | // should be the preheader. | ||||||||
| 1366 | assert(ClonedLoopBlocks.count(Pred) && "Found a predecessor of the loop "((void)0) | ||||||||
| 1367 | "header other than the preheader "((void)0) | ||||||||
| 1368 | "that is not part of the loop!")((void)0); | ||||||||
| 1369 | |||||||||
| 1370 | // Insert this block into the loop set and on the first visit (and if it | ||||||||
| 1371 | // isn't the header we're currently walking) put it into the worklist to | ||||||||
| 1372 | // recurse through. | ||||||||
| 1373 | if (BlocksInClonedLoop.insert(Pred).second && Pred != ClonedHeader) | ||||||||
| 1374 | Worklist.push_back(Pred); | ||||||||
| 1375 | } | ||||||||
| 1376 | |||||||||
| 1377 | // If we had any backedges then there *is* a cloned loop. Put the header into | ||||||||
| 1378 | // the loop set and then walk the worklist backwards to find all the blocks | ||||||||
| 1379 | // that remain within the loop after cloning. | ||||||||
| 1380 | if (!BlocksInClonedLoop.empty()) { | ||||||||
| 1381 | BlocksInClonedLoop.insert(ClonedHeader); | ||||||||
| 1382 | |||||||||
| 1383 | while (!Worklist.empty()) { | ||||||||
| 1384 | BasicBlock *BB = Worklist.pop_back_val(); | ||||||||
| 1385 | assert(BlocksInClonedLoop.count(BB) &&((void)0) | ||||||||
| 1386 | "Didn't put block into the loop set!")((void)0); | ||||||||
| 1387 | |||||||||
| 1388 | // Insert any predecessors that are in the possible set into the cloned | ||||||||
| 1389 | // set, and if the insert is successful, add them to the worklist. Note | ||||||||
| 1390 | // that we filter on the blocks that are definitely reachable via the | ||||||||
| 1391 | // backedge to the loop header so we may prune out dead code within the | ||||||||
| 1392 | // cloned loop. | ||||||||
| 1393 | for (auto *Pred : predecessors(BB)) | ||||||||
| 1394 | if (ClonedLoopBlocks.count(Pred) && | ||||||||
| 1395 | BlocksInClonedLoop.insert(Pred).second) | ||||||||
| 1396 | Worklist.push_back(Pred); | ||||||||
| 1397 | } | ||||||||
| 1398 | |||||||||
| 1399 | ClonedL = LI.AllocateLoop(); | ||||||||
| 1400 | if (ParentL) { | ||||||||
| 1401 | ParentL->addBasicBlockToLoop(ClonedPH, LI); | ||||||||
| 1402 | ParentL->addChildLoop(ClonedL); | ||||||||
| 1403 | } else { | ||||||||
| 1404 | LI.addTopLevelLoop(ClonedL); | ||||||||
| 1405 | } | ||||||||
| 1406 | NonChildClonedLoops.push_back(ClonedL); | ||||||||
| 1407 | |||||||||
| 1408 | ClonedL->reserveBlocks(BlocksInClonedLoop.size()); | ||||||||
| 1409 | // We don't want to just add the cloned loop blocks based on how we | ||||||||
| 1410 | // discovered them. The original order of blocks was carefully built in | ||||||||
| 1411 | // a way that doesn't rely on predecessor ordering. Rather than re-invent | ||||||||
| 1412 | // that logic, we just re-walk the original blocks (and those of the child | ||||||||
| 1413 | // loops) and filter them as we add them into the cloned loop. | ||||||||
| 1414 | for (auto *BB : OrigL.blocks()) { | ||||||||
| 1415 | auto *ClonedBB = cast_or_null<BasicBlock>(VMap.lookup(BB)); | ||||||||
| 1416 | if (!ClonedBB || !BlocksInClonedLoop.count(ClonedBB)) | ||||||||
| 1417 | continue; | ||||||||
| 1418 | |||||||||
| 1419 | // Directly add the blocks that are only in this loop. | ||||||||
| 1420 | if (LI.getLoopFor(BB) == &OrigL) { | ||||||||
| 1421 | ClonedL->addBasicBlockToLoop(ClonedBB, LI); | ||||||||
| 1422 | continue; | ||||||||
| 1423 | } | ||||||||
| 1424 | |||||||||
| 1425 | // We want to manually add it to this loop and parents. | ||||||||
| 1426 | // Registering it with LoopInfo will happen when we clone the top | ||||||||
| 1427 | // loop for this block. | ||||||||
| 1428 | for (Loop *PL = ClonedL; PL; PL = PL->getParentLoop()) | ||||||||
| 1429 | PL->addBlockEntry(ClonedBB); | ||||||||
| 1430 | } | ||||||||
| 1431 | |||||||||
| 1432 | // Now add each child loop whose header remains within the cloned loop. All | ||||||||
| 1433 | // of the blocks within the loop must satisfy the same constraints as the | ||||||||
| 1434 | // header so once we pass the header checks we can just clone the entire | ||||||||
| 1435 | // child loop nest. | ||||||||
| 1436 | for (Loop *ChildL : OrigL) { | ||||||||
| 1437 | auto *ClonedChildHeader = | ||||||||
| 1438 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | ||||||||
| 1439 | if (!ClonedChildHeader || !BlocksInClonedLoop.count(ClonedChildHeader)) | ||||||||
| 1440 | continue; | ||||||||
| 1441 | |||||||||
| 1442 | #ifndef NDEBUG1 | ||||||||
| 1443 | // We should never have a cloned child loop header but fail to have | ||||||||
| 1444 | // all of the blocks for that child loop. | ||||||||
| 1445 | for (auto *ChildLoopBB : ChildL->blocks()) | ||||||||
| 1446 | assert(BlocksInClonedLoop.count(((void)0) | ||||||||
| 1447 | cast<BasicBlock>(VMap.lookup(ChildLoopBB))) &&((void)0) | ||||||||
| 1448 | "Child cloned loop has a header within the cloned outer "((void)0) | ||||||||
| 1449 | "loop but not all of its blocks!")((void)0); | ||||||||
| 1450 | #endif | ||||||||
| 1451 | |||||||||
| 1452 | cloneLoopNest(*ChildL, ClonedL, VMap, LI); | ||||||||
| 1453 | } | ||||||||
| 1454 | } | ||||||||
| 1455 | |||||||||
| 1456 | // Now that we've handled all the components of the original loop that were | ||||||||
| 1457 | // cloned into a new loop, we still need to handle anything from the original | ||||||||
| 1458 | // loop that wasn't in a cloned loop. | ||||||||
| 1459 | |||||||||
| 1460 | // Figure out what blocks are left to place within any loop nest containing | ||||||||
| 1461 | // the unswitched loop. If we never formed a loop, the cloned PH is one of | ||||||||
| 1462 | // them. | ||||||||
| 1463 | SmallPtrSet<BasicBlock *, 16> UnloopedBlockSet; | ||||||||
| 1464 | if (BlocksInClonedLoop.empty()) | ||||||||
| 1465 | UnloopedBlockSet.insert(ClonedPH); | ||||||||
| 1466 | for (auto *ClonedBB : ClonedLoopBlocks) | ||||||||
| 1467 | if (!BlocksInClonedLoop.count(ClonedBB)) | ||||||||
| 1468 | UnloopedBlockSet.insert(ClonedBB); | ||||||||
| 1469 | |||||||||
| 1470 | // Copy the cloned exits and sort them in ascending loop depth, we'll work | ||||||||
| 1471 | // backwards across these to process them inside out. The order shouldn't | ||||||||
| 1472 | // matter as we're just trying to build up the map from inside-out; we use | ||||||||
| 1473 | // the map in a more stably ordered way below. | ||||||||
| 1474 | auto OrderedClonedExitsInLoops = ClonedExitsInLoops; | ||||||||
| 1475 | llvm::sort(OrderedClonedExitsInLoops, [&](BasicBlock *LHS, BasicBlock *RHS) { | ||||||||
| 1476 | return ExitLoopMap.lookup(LHS)->getLoopDepth() < | ||||||||
| 1477 | ExitLoopMap.lookup(RHS)->getLoopDepth(); | ||||||||
| 1478 | }); | ||||||||
| 1479 | |||||||||
| 1480 | // Populate the existing ExitLoopMap with everything reachable from each | ||||||||
| 1481 | // exit, starting from the inner most exit. | ||||||||
| 1482 | while (!UnloopedBlockSet.empty() && !OrderedClonedExitsInLoops.empty()) { | ||||||||
| 1483 | assert(Worklist.empty() && "Didn't clear worklist!")((void)0); | ||||||||
| 1484 | |||||||||
| 1485 | BasicBlock *ExitBB = OrderedClonedExitsInLoops.pop_back_val(); | ||||||||
| 1486 | Loop *ExitL = ExitLoopMap.lookup(ExitBB); | ||||||||
| 1487 | |||||||||
| 1488 | // Walk the CFG back until we hit the cloned PH adding everything reachable | ||||||||
| 1489 | // and in the unlooped set to this exit block's loop. | ||||||||
| 1490 | Worklist.push_back(ExitBB); | ||||||||
| 1491 | do { | ||||||||
| 1492 | BasicBlock *BB = Worklist.pop_back_val(); | ||||||||
| 1493 | // We can stop recursing at the cloned preheader (if we get there). | ||||||||
| 1494 | if (BB == ClonedPH) | ||||||||
| 1495 | continue; | ||||||||
| 1496 | |||||||||
| 1497 | for (BasicBlock *PredBB : predecessors(BB)) { | ||||||||
| 1498 | // If this pred has already been moved to our set or is part of some | ||||||||
| 1499 | // (inner) loop, no update needed. | ||||||||
| 1500 | if (!UnloopedBlockSet.erase(PredBB)) { | ||||||||
| 1501 | assert(((void)0) | ||||||||
| 1502 | (BlocksInClonedLoop.count(PredBB) || ExitLoopMap.count(PredBB)) &&((void)0) | ||||||||
| 1503 | "Predecessor not mapped to a loop!")((void)0); | ||||||||
| 1504 | continue; | ||||||||
| 1505 | } | ||||||||
| 1506 | |||||||||
| 1507 | // We just insert into the loop set here. We'll add these blocks to the | ||||||||
| 1508 | // exit loop after we build up the set in an order that doesn't rely on | ||||||||
| 1509 | // predecessor order (which in turn relies on use list order). | ||||||||
| 1510 | bool Inserted = ExitLoopMap.insert({PredBB, ExitL}).second; | ||||||||
| 1511 | (void)Inserted; | ||||||||
| 1512 | assert(Inserted && "Should only visit an unlooped block once!")((void)0); | ||||||||
| 1513 | |||||||||
| 1514 | // And recurse through to its predecessors. | ||||||||
| 1515 | Worklist.push_back(PredBB); | ||||||||
| 1516 | } | ||||||||
| 1517 | } while (!Worklist.empty()); | ||||||||
| 1518 | } | ||||||||
| 1519 | |||||||||
| 1520 | // Now that the ExitLoopMap gives as mapping for all the non-looping cloned | ||||||||
| 1521 | // blocks to their outer loops, walk the cloned blocks and the cloned exits | ||||||||
| 1522 | // in their original order adding them to the correct loop. | ||||||||
| 1523 | |||||||||
| 1524 | // We need a stable insertion order. We use the order of the original loop | ||||||||
| 1525 | // order and map into the correct parent loop. | ||||||||
| 1526 | for (auto *BB : llvm::concat<BasicBlock *const>( | ||||||||
| 1527 | makeArrayRef(ClonedPH), ClonedLoopBlocks, ClonedExitsInLoops)) | ||||||||
| 1528 | if (Loop *OuterL = ExitLoopMap.lookup(BB)) | ||||||||
| 1529 | OuterL->addBasicBlockToLoop(BB, LI); | ||||||||
| 1530 | |||||||||
| 1531 | #ifndef NDEBUG1 | ||||||||
| 1532 | for (auto &BBAndL : ExitLoopMap) { | ||||||||
| 1533 | auto *BB = BBAndL.first; | ||||||||
| 1534 | auto *OuterL = BBAndL.second; | ||||||||
| 1535 | assert(LI.getLoopFor(BB) == OuterL &&((void)0) | ||||||||
| 1536 | "Failed to put all blocks into outer loops!")((void)0); | ||||||||
| 1537 | } | ||||||||
| 1538 | #endif | ||||||||
| 1539 | |||||||||
| 1540 | // Now that all the blocks are placed into the correct containing loop in the | ||||||||
| 1541 | // absence of child loops, find all the potentially cloned child loops and | ||||||||
| 1542 | // clone them into whatever outer loop we placed their header into. | ||||||||
| 1543 | for (Loop *ChildL : OrigL) { | ||||||||
| 1544 | auto *ClonedChildHeader = | ||||||||
| 1545 | cast_or_null<BasicBlock>(VMap.lookup(ChildL->getHeader())); | ||||||||
| 1546 | if (!ClonedChildHeader || BlocksInClonedLoop.count(ClonedChildHeader)) | ||||||||
| 1547 | continue; | ||||||||
| 1548 | |||||||||
| 1549 | #ifndef NDEBUG1 | ||||||||
| 1550 | for (auto *ChildLoopBB : ChildL->blocks()) | ||||||||
| 1551 | assert(VMap.count(ChildLoopBB) &&((void)0) | ||||||||
| 1552 | "Cloned a child loop header but not all of that loops blocks!")((void)0); | ||||||||
| 1553 | #endif | ||||||||
| 1554 | |||||||||
| 1555 | NonChildClonedLoops.push_back(cloneLoopNest( | ||||||||
| 1556 | *ChildL, ExitLoopMap.lookup(ClonedChildHeader), VMap, LI)); | ||||||||
| 1557 | } | ||||||||
| 1558 | } | ||||||||
| 1559 | |||||||||
| 1560 | static void | ||||||||
| 1561 | deleteDeadClonedBlocks(Loop &L, ArrayRef<BasicBlock *> ExitBlocks, | ||||||||
| 1562 | ArrayRef<std::unique_ptr<ValueToValueMapTy>> VMaps, | ||||||||
| 1563 | DominatorTree &DT, MemorySSAUpdater *MSSAU) { | ||||||||
| 1564 | // Find all the dead clones, and remove them from their successors. | ||||||||
| 1565 | SmallVector<BasicBlock *, 16> DeadBlocks; | ||||||||
| 1566 | for (BasicBlock *BB : llvm::concat<BasicBlock *const>(L.blocks(), ExitBlocks)) | ||||||||
| 1567 | for (auto &VMap : VMaps) | ||||||||
| 1568 | if (BasicBlock *ClonedBB = cast_or_null<BasicBlock>(VMap->lookup(BB))) | ||||||||
| 1569 | if (!DT.isReachableFromEntry(ClonedBB)) { | ||||||||
| 1570 | for (BasicBlock *SuccBB : successors(ClonedBB)) | ||||||||
| 1571 | SuccBB->removePredecessor(ClonedBB); | ||||||||
| 1572 | DeadBlocks.push_back(ClonedBB); | ||||||||
| 1573 | } | ||||||||
| 1574 | |||||||||
| 1575 | // Remove all MemorySSA in the dead blocks | ||||||||
| 1576 | if (MSSAU) { | ||||||||
| 1577 | SmallSetVector<BasicBlock *, 8> DeadBlockSet(DeadBlocks.begin(), | ||||||||
| 1578 | DeadBlocks.end()); | ||||||||
| 1579 | MSSAU->removeBlocks(DeadBlockSet); | ||||||||
| 1580 | } | ||||||||
| 1581 | |||||||||
| 1582 | // Drop any remaining references to break cycles. | ||||||||
| 1583 | for (BasicBlock *BB : DeadBlocks) | ||||||||
| 1584 | BB->dropAllReferences(); | ||||||||
| 1585 | // Erase them from the IR. | ||||||||
| 1586 | for (BasicBlock *BB : DeadBlocks) | ||||||||
| 1587 | BB->eraseFromParent(); | ||||||||
| 1588 | } | ||||||||
| 1589 | |||||||||
| 1590 | static void | ||||||||
| 1591 | deleteDeadBlocksFromLoop(Loop &L, | ||||||||
| 1592 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | ||||||||
| 1593 | DominatorTree &DT, LoopInfo &LI, | ||||||||
| 1594 | MemorySSAUpdater *MSSAU, | ||||||||
| 1595 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||||||
| 1596 | // Find all the dead blocks tied to this loop, and remove them from their | ||||||||
| 1597 | // successors. | ||||||||
| 1598 | SmallSetVector<BasicBlock *, 8> DeadBlockSet; | ||||||||
| 1599 | |||||||||
| 1600 | // Start with loop/exit blocks and get a transitive closure of reachable dead | ||||||||
| 1601 | // blocks. | ||||||||
| 1602 | SmallVector<BasicBlock *, 16> DeathCandidates(ExitBlocks.begin(), | ||||||||
| 1603 | ExitBlocks.end()); | ||||||||
| 1604 | DeathCandidates.append(L.blocks().begin(), L.blocks().end()); | ||||||||
| 1605 | while (!DeathCandidates.empty()) { | ||||||||
| 1606 | auto *BB = DeathCandidates.pop_back_val(); | ||||||||
| 1607 | if (!DeadBlockSet.count(BB) && !DT.isReachableFromEntry(BB)) { | ||||||||
| 1608 | for (BasicBlock *SuccBB : successors(BB)) { | ||||||||
| 1609 | SuccBB->removePredecessor(BB); | ||||||||
| 1610 | DeathCandidates.push_back(SuccBB); | ||||||||
| 1611 | } | ||||||||
| 1612 | DeadBlockSet.insert(BB); | ||||||||
| 1613 | } | ||||||||
| 1614 | } | ||||||||
| 1615 | |||||||||
| 1616 | // Remove all MemorySSA in the dead blocks | ||||||||
| 1617 | if (MSSAU) | ||||||||
| 1618 | MSSAU->removeBlocks(DeadBlockSet); | ||||||||
| 1619 | |||||||||
| 1620 | // Filter out the dead blocks from the exit blocks list so that it can be | ||||||||
| 1621 | // used in the caller. | ||||||||
| 1622 | llvm::erase_if(ExitBlocks, | ||||||||
| 1623 | [&](BasicBlock *BB) { return DeadBlockSet.count(BB); }); | ||||||||
| 1624 | |||||||||
| 1625 | // Walk from this loop up through its parents removing all of the dead blocks. | ||||||||
| 1626 | for (Loop *ParentL = &L; ParentL; ParentL = ParentL->getParentLoop()) { | ||||||||
| 1627 | for (auto *BB : DeadBlockSet) | ||||||||
| 1628 | ParentL->getBlocksSet().erase(BB); | ||||||||
| 1629 | llvm::erase_if(ParentL->getBlocksVector(), | ||||||||
| 1630 | [&](BasicBlock *BB) { return DeadBlockSet.count(BB); }); | ||||||||
| 1631 | } | ||||||||
| 1632 | |||||||||
| 1633 | // Now delete the dead child loops. This raw delete will clear them | ||||||||
| 1634 | // recursively. | ||||||||
| 1635 | llvm::erase_if(L.getSubLoopsVector(), [&](Loop *ChildL) { | ||||||||
| 1636 | if (!DeadBlockSet.count(ChildL->getHeader())) | ||||||||
| 1637 | return false; | ||||||||
| 1638 | |||||||||
| 1639 | assert(llvm::all_of(ChildL->blocks(),((void)0) | ||||||||
| 1640 | [&](BasicBlock *ChildBB) {((void)0) | ||||||||
| 1641 | return DeadBlockSet.count(ChildBB);((void)0) | ||||||||
| 1642 | }) &&((void)0) | ||||||||
| 1643 | "If the child loop header is dead all blocks in the child loop must "((void)0) | ||||||||
| 1644 | "be dead as well!")((void)0); | ||||||||
| 1645 | DestroyLoopCB(*ChildL, ChildL->getName()); | ||||||||
| 1646 | LI.destroy(ChildL); | ||||||||
| 1647 | return true; | ||||||||
| 1648 | }); | ||||||||
| 1649 | |||||||||
| 1650 | // Remove the loop mappings for the dead blocks and drop all the references | ||||||||
| 1651 | // from these blocks to others to handle cyclic references as we start | ||||||||
| 1652 | // deleting the blocks themselves. | ||||||||
| 1653 | for (auto *BB : DeadBlockSet) { | ||||||||
| 1654 | // Check that the dominator tree has already been updated. | ||||||||
| 1655 | assert(!DT.getNode(BB) && "Should already have cleared domtree!")((void)0); | ||||||||
| 1656 | LI.changeLoopFor(BB, nullptr); | ||||||||
| 1657 | // Drop all uses of the instructions to make sure we won't have dangling | ||||||||
| 1658 | // uses in other blocks. | ||||||||
| 1659 | for (auto &I : *BB) | ||||||||
| 1660 | if (!I.use_empty()) | ||||||||
| 1661 | I.replaceAllUsesWith(UndefValue::get(I.getType())); | ||||||||
| 1662 | BB->dropAllReferences(); | ||||||||
| 1663 | } | ||||||||
| 1664 | |||||||||
| 1665 | // Actually delete the blocks now that they've been fully unhooked from the | ||||||||
| 1666 | // IR. | ||||||||
| 1667 | for (auto *BB : DeadBlockSet) | ||||||||
| 1668 | BB->eraseFromParent(); | ||||||||
| 1669 | } | ||||||||
| 1670 | |||||||||
| 1671 | /// Recompute the set of blocks in a loop after unswitching. | ||||||||
| 1672 | /// | ||||||||
| 1673 | /// This walks from the original headers predecessors to rebuild the loop. We | ||||||||
| 1674 | /// take advantage of the fact that new blocks can't have been added, and so we | ||||||||
| 1675 | /// filter by the original loop's blocks. This also handles potentially | ||||||||
| 1676 | /// unreachable code that we don't want to explore but might be found examining | ||||||||
| 1677 | /// the predecessors of the header. | ||||||||
| 1678 | /// | ||||||||
| 1679 | /// If the original loop is no longer a loop, this will return an empty set. If | ||||||||
| 1680 | /// it remains a loop, all the blocks within it will be added to the set | ||||||||
| 1681 | /// (including those blocks in inner loops). | ||||||||
| 1682 | static SmallPtrSet<const BasicBlock *, 16> recomputeLoopBlockSet(Loop &L, | ||||||||
| 1683 | LoopInfo &LI) { | ||||||||
| 1684 | SmallPtrSet<const BasicBlock *, 16> LoopBlockSet; | ||||||||
| 1685 | |||||||||
| 1686 | auto *PH = L.getLoopPreheader(); | ||||||||
| 1687 | auto *Header = L.getHeader(); | ||||||||
| 1688 | |||||||||
| 1689 | // A worklist to use while walking backwards from the header. | ||||||||
| 1690 | SmallVector<BasicBlock *, 16> Worklist; | ||||||||
| 1691 | |||||||||
| 1692 | // First walk the predecessors of the header to find the backedges. This will | ||||||||
| 1693 | // form the basis of our walk. | ||||||||
| 1694 | for (auto *Pred : predecessors(Header)) { | ||||||||
| 1695 | // Skip the preheader. | ||||||||
| 1696 | if (Pred == PH) | ||||||||
| 1697 | continue; | ||||||||
| 1698 | |||||||||
| 1699 | // Because the loop was in simplified form, the only non-loop predecessor | ||||||||
| 1700 | // is the preheader. | ||||||||
| 1701 | assert(L.contains(Pred) && "Found a predecessor of the loop header other "((void)0) | ||||||||
| 1702 | "than the preheader that is not part of the "((void)0) | ||||||||
| 1703 | "loop!")((void)0); | ||||||||
| 1704 | |||||||||
| 1705 | // Insert this block into the loop set and on the first visit and, if it | ||||||||
| 1706 | // isn't the header we're currently walking, put it into the worklist to | ||||||||
| 1707 | // recurse through. | ||||||||
| 1708 | if (LoopBlockSet.insert(Pred).second && Pred != Header) | ||||||||
| 1709 | Worklist.push_back(Pred); | ||||||||
| 1710 | } | ||||||||
| 1711 | |||||||||
| 1712 | // If no backedges were found, we're done. | ||||||||
| 1713 | if (LoopBlockSet.empty()) | ||||||||
| 1714 | return LoopBlockSet; | ||||||||
| 1715 | |||||||||
| 1716 | // We found backedges, recurse through them to identify the loop blocks. | ||||||||
| 1717 | while (!Worklist.empty()) { | ||||||||
| 1718 | BasicBlock *BB = Worklist.pop_back_val(); | ||||||||
| 1719 | assert(LoopBlockSet.count(BB) && "Didn't put block into the loop set!")((void)0); | ||||||||
| 1720 | |||||||||
| 1721 | // No need to walk past the header. | ||||||||
| 1722 | if (BB == Header) | ||||||||
| 1723 | continue; | ||||||||
| 1724 | |||||||||
| 1725 | // Because we know the inner loop structure remains valid we can use the | ||||||||
| 1726 | // loop structure to jump immediately across the entire nested loop. | ||||||||
| 1727 | // Further, because it is in loop simplified form, we can directly jump | ||||||||
| 1728 | // to its preheader afterward. | ||||||||
| 1729 | if (Loop *InnerL = LI.getLoopFor(BB)) | ||||||||
| 1730 | if (InnerL != &L) { | ||||||||
| 1731 | assert(L.contains(InnerL) &&((void)0) | ||||||||
| 1732 | "Should not reach a loop *outside* this loop!")((void)0); | ||||||||
| 1733 | // The preheader is the only possible predecessor of the loop so | ||||||||
| 1734 | // insert it into the set and check whether it was already handled. | ||||||||
| 1735 | auto *InnerPH = InnerL->getLoopPreheader(); | ||||||||
| 1736 | assert(L.contains(InnerPH) && "Cannot contain an inner loop block "((void)0) | ||||||||
| 1737 | "but not contain the inner loop "((void)0) | ||||||||
| 1738 | "preheader!")((void)0); | ||||||||
| 1739 | if (!LoopBlockSet.insert(InnerPH).second) | ||||||||
| 1740 | // The only way to reach the preheader is through the loop body | ||||||||
| 1741 | // itself so if it has been visited the loop is already handled. | ||||||||
| 1742 | continue; | ||||||||
| 1743 | |||||||||
| 1744 | // Insert all of the blocks (other than those already present) into | ||||||||
| 1745 | // the loop set. We expect at least the block that led us to find the | ||||||||
| 1746 | // inner loop to be in the block set, but we may also have other loop | ||||||||
| 1747 | // blocks if they were already enqueued as predecessors of some other | ||||||||
| 1748 | // outer loop block. | ||||||||
| 1749 | for (auto *InnerBB : InnerL->blocks()) { | ||||||||
| 1750 | if (InnerBB == BB) { | ||||||||
| 1751 | assert(LoopBlockSet.count(InnerBB) &&((void)0) | ||||||||
| 1752 | "Block should already be in the set!")((void)0); | ||||||||
| 1753 | continue; | ||||||||
| 1754 | } | ||||||||
| 1755 | |||||||||
| 1756 | LoopBlockSet.insert(InnerBB); | ||||||||
| 1757 | } | ||||||||
| 1758 | |||||||||
| 1759 | // Add the preheader to the worklist so we will continue past the | ||||||||
| 1760 | // loop body. | ||||||||
| 1761 | Worklist.push_back(InnerPH); | ||||||||
| 1762 | continue; | ||||||||
| 1763 | } | ||||||||
| 1764 | |||||||||
| 1765 | // Insert any predecessors that were in the original loop into the new | ||||||||
| 1766 | // set, and if the insert is successful, add them to the worklist. | ||||||||
| 1767 | for (auto *Pred : predecessors(BB)) | ||||||||
| 1768 | if (L.contains(Pred) && LoopBlockSet.insert(Pred).second) | ||||||||
| 1769 | Worklist.push_back(Pred); | ||||||||
| 1770 | } | ||||||||
| 1771 | |||||||||
| 1772 | assert(LoopBlockSet.count(Header) && "Cannot fail to add the header!")((void)0); | ||||||||
| 1773 | |||||||||
| 1774 | // We've found all the blocks participating in the loop, return our completed | ||||||||
| 1775 | // set. | ||||||||
| 1776 | return LoopBlockSet; | ||||||||
| 1777 | } | ||||||||
| 1778 | |||||||||
| 1779 | /// Rebuild a loop after unswitching removes some subset of blocks and edges. | ||||||||
| 1780 | /// | ||||||||
| 1781 | /// The removal may have removed some child loops entirely but cannot have | ||||||||
| 1782 | /// disturbed any remaining child loops. However, they may need to be hoisted | ||||||||
| 1783 | /// to the parent loop (or to be top-level loops). The original loop may be | ||||||||
| 1784 | /// completely removed. | ||||||||
| 1785 | /// | ||||||||
| 1786 | /// The sibling loops resulting from this update are returned. If the original | ||||||||
| 1787 | /// loop remains a valid loop, it will be the first entry in this list with all | ||||||||
| 1788 | /// of the newly sibling loops following it. | ||||||||
| 1789 | /// | ||||||||
| 1790 | /// Returns true if the loop remains a loop after unswitching, and false if it | ||||||||
| 1791 | /// is no longer a loop after unswitching (and should not continue to be | ||||||||
| 1792 | /// referenced). | ||||||||
| 1793 | static bool rebuildLoopAfterUnswitch(Loop &L, ArrayRef<BasicBlock *> ExitBlocks, | ||||||||
| 1794 | LoopInfo &LI, | ||||||||
| 1795 | SmallVectorImpl<Loop *> &HoistedLoops) { | ||||||||
| 1796 | auto *PH = L.getLoopPreheader(); | ||||||||
| 1797 | |||||||||
| 1798 | // Compute the actual parent loop from the exit blocks. Because we may have | ||||||||
| 1799 | // pruned some exits the loop may be different from the original parent. | ||||||||
| 1800 | Loop *ParentL = nullptr; | ||||||||
| 1801 | SmallVector<Loop *, 4> ExitLoops; | ||||||||
| 1802 | SmallVector<BasicBlock *, 4> ExitsInLoops; | ||||||||
| 1803 | ExitsInLoops.reserve(ExitBlocks.size()); | ||||||||
| 1804 | for (auto *ExitBB : ExitBlocks) | ||||||||
| 1805 | if (Loop *ExitL = LI.getLoopFor(ExitBB)) { | ||||||||
| 1806 | ExitLoops.push_back(ExitL); | ||||||||
| 1807 | ExitsInLoops.push_back(ExitBB); | ||||||||
| 1808 | if (!ParentL || (ParentL != ExitL && ParentL->contains(ExitL))) | ||||||||
| 1809 | ParentL = ExitL; | ||||||||
| 1810 | } | ||||||||
| 1811 | |||||||||
| 1812 | // Recompute the blocks participating in this loop. This may be empty if it | ||||||||
| 1813 | // is no longer a loop. | ||||||||
| 1814 | auto LoopBlockSet = recomputeLoopBlockSet(L, LI); | ||||||||
| 1815 | |||||||||
| 1816 | // If we still have a loop, we need to re-set the loop's parent as the exit | ||||||||
| 1817 | // block set changing may have moved it within the loop nest. Note that this | ||||||||
| 1818 | // can only happen when this loop has a parent as it can only hoist the loop | ||||||||
| 1819 | // *up* the nest. | ||||||||
| 1820 | if (!LoopBlockSet.empty() && L.getParentLoop() != ParentL) { | ||||||||
| 1821 | // Remove this loop's (original) blocks from all of the intervening loops. | ||||||||
| 1822 | for (Loop *IL = L.getParentLoop(); IL != ParentL; | ||||||||
| 1823 | IL = IL->getParentLoop()) { | ||||||||
| 1824 | IL->getBlocksSet().erase(PH); | ||||||||
| 1825 | for (auto *BB : L.blocks()) | ||||||||
| 1826 | IL->getBlocksSet().erase(BB); | ||||||||
| 1827 | llvm::erase_if(IL->getBlocksVector(), [&](BasicBlock *BB) { | ||||||||
| 1828 | return BB == PH || L.contains(BB); | ||||||||
| 1829 | }); | ||||||||
| 1830 | } | ||||||||
| 1831 | |||||||||
| 1832 | LI.changeLoopFor(PH, ParentL); | ||||||||
| 1833 | L.getParentLoop()->removeChildLoop(&L); | ||||||||
| 1834 | if (ParentL) | ||||||||
| 1835 | ParentL->addChildLoop(&L); | ||||||||
| 1836 | else | ||||||||
| 1837 | LI.addTopLevelLoop(&L); | ||||||||
| 1838 | } | ||||||||
| 1839 | |||||||||
| 1840 | // Now we update all the blocks which are no longer within the loop. | ||||||||
| 1841 | auto &Blocks = L.getBlocksVector(); | ||||||||
| 1842 | auto BlocksSplitI = | ||||||||
| 1843 | LoopBlockSet.empty() | ||||||||
| 1844 | ? Blocks.begin() | ||||||||
| 1845 | : std::stable_partition( | ||||||||
| 1846 | Blocks.begin(), Blocks.end(), | ||||||||
| 1847 | [&](BasicBlock *BB) { return LoopBlockSet.count(BB); }); | ||||||||
| 1848 | |||||||||
| 1849 | // Before we erase the list of unlooped blocks, build a set of them. | ||||||||
| 1850 | SmallPtrSet<BasicBlock *, 16> UnloopedBlocks(BlocksSplitI, Blocks.end()); | ||||||||
| 1851 | if (LoopBlockSet.empty()) | ||||||||
| 1852 | UnloopedBlocks.insert(PH); | ||||||||
| 1853 | |||||||||
| 1854 | // Now erase these blocks from the loop. | ||||||||
| 1855 | for (auto *BB : make_range(BlocksSplitI, Blocks.end())) | ||||||||
| 1856 | L.getBlocksSet().erase(BB); | ||||||||
| 1857 | Blocks.erase(BlocksSplitI, Blocks.end()); | ||||||||
| 1858 | |||||||||
| 1859 | // Sort the exits in ascending loop depth, we'll work backwards across these | ||||||||
| 1860 | // to process them inside out. | ||||||||
| 1861 | llvm::stable_sort(ExitsInLoops, [&](BasicBlock *LHS, BasicBlock *RHS) { | ||||||||
| 1862 | return LI.getLoopDepth(LHS) < LI.getLoopDepth(RHS); | ||||||||
| 1863 | }); | ||||||||
| 1864 | |||||||||
| 1865 | // We'll build up a set for each exit loop. | ||||||||
| 1866 | SmallPtrSet<BasicBlock *, 16> NewExitLoopBlocks; | ||||||||
| 1867 | Loop *PrevExitL = L.getParentLoop(); // The deepest possible exit loop. | ||||||||
| 1868 | |||||||||
| 1869 | auto RemoveUnloopedBlocksFromLoop = | ||||||||
| 1870 | [](Loop &L, SmallPtrSetImpl<BasicBlock *> &UnloopedBlocks) { | ||||||||
| 1871 | for (auto *BB : UnloopedBlocks) | ||||||||
| 1872 | L.getBlocksSet().erase(BB); | ||||||||
| 1873 | llvm::erase_if(L.getBlocksVector(), [&](BasicBlock *BB) { | ||||||||
| 1874 | return UnloopedBlocks.count(BB); | ||||||||
| 1875 | }); | ||||||||
| 1876 | }; | ||||||||
| 1877 | |||||||||
| 1878 | SmallVector<BasicBlock *, 16> Worklist; | ||||||||
| 1879 | while (!UnloopedBlocks.empty() && !ExitsInLoops.empty()) { | ||||||||
| 1880 | assert(Worklist.empty() && "Didn't clear worklist!")((void)0); | ||||||||
| 1881 | assert(NewExitLoopBlocks.empty() && "Didn't clear loop set!")((void)0); | ||||||||
| 1882 | |||||||||
| 1883 | // Grab the next exit block, in decreasing loop depth order. | ||||||||
| 1884 | BasicBlock *ExitBB = ExitsInLoops.pop_back_val(); | ||||||||
| 1885 | Loop &ExitL = *LI.getLoopFor(ExitBB); | ||||||||
| 1886 | assert(ExitL.contains(&L) && "Exit loop must contain the inner loop!")((void)0); | ||||||||
| 1887 | |||||||||
| 1888 | // Erase all of the unlooped blocks from the loops between the previous | ||||||||
| 1889 | // exit loop and this exit loop. This works because the ExitInLoops list is | ||||||||
| 1890 | // sorted in increasing order of loop depth and thus we visit loops in | ||||||||
| 1891 | // decreasing order of loop depth. | ||||||||
| 1892 | for (; PrevExitL != &ExitL; PrevExitL = PrevExitL->getParentLoop()) | ||||||||
| 1893 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | ||||||||
| 1894 | |||||||||
| 1895 | // Walk the CFG back until we hit the cloned PH adding everything reachable | ||||||||
| 1896 | // and in the unlooped set to this exit block's loop. | ||||||||
| 1897 | Worklist.push_back(ExitBB); | ||||||||
| 1898 | do { | ||||||||
| 1899 | BasicBlock *BB = Worklist.pop_back_val(); | ||||||||
| 1900 | // We can stop recursing at the cloned preheader (if we get there). | ||||||||
| 1901 | if (BB == PH) | ||||||||
| 1902 | continue; | ||||||||
| 1903 | |||||||||
| 1904 | for (BasicBlock *PredBB : predecessors(BB)) { | ||||||||
| 1905 | // If this pred has already been moved to our set or is part of some | ||||||||
| 1906 | // (inner) loop, no update needed. | ||||||||
| 1907 | if (!UnloopedBlocks.erase(PredBB)) { | ||||||||
| 1908 | assert((NewExitLoopBlocks.count(PredBB) ||((void)0) | ||||||||
| 1909 | ExitL.contains(LI.getLoopFor(PredBB))) &&((void)0) | ||||||||
| 1910 | "Predecessor not in a nested loop (or already visited)!")((void)0); | ||||||||
| 1911 | continue; | ||||||||
| 1912 | } | ||||||||
| 1913 | |||||||||
| 1914 | // We just insert into the loop set here. We'll add these blocks to the | ||||||||
| 1915 | // exit loop after we build up the set in a deterministic order rather | ||||||||
| 1916 | // than the predecessor-influenced visit order. | ||||||||
| 1917 | bool Inserted = NewExitLoopBlocks.insert(PredBB).second; | ||||||||
| 1918 | (void)Inserted; | ||||||||
| 1919 | assert(Inserted && "Should only visit an unlooped block once!")((void)0); | ||||||||
| 1920 | |||||||||
| 1921 | // And recurse through to its predecessors. | ||||||||
| 1922 | Worklist.push_back(PredBB); | ||||||||
| 1923 | } | ||||||||
| 1924 | } while (!Worklist.empty()); | ||||||||
| 1925 | |||||||||
| 1926 | // If blocks in this exit loop were directly part of the original loop (as | ||||||||
| 1927 | // opposed to a child loop) update the map to point to this exit loop. This | ||||||||
| 1928 | // just updates a map and so the fact that the order is unstable is fine. | ||||||||
| 1929 | for (auto *BB : NewExitLoopBlocks) | ||||||||
| 1930 | if (Loop *BBL = LI.getLoopFor(BB)) | ||||||||
| 1931 | if (BBL == &L || !L.contains(BBL)) | ||||||||
| 1932 | LI.changeLoopFor(BB, &ExitL); | ||||||||
| 1933 | |||||||||
| 1934 | // We will remove the remaining unlooped blocks from this loop in the next | ||||||||
| 1935 | // iteration or below. | ||||||||
| 1936 | NewExitLoopBlocks.clear(); | ||||||||
| 1937 | } | ||||||||
| 1938 | |||||||||
| 1939 | // Any remaining unlooped blocks are no longer part of any loop unless they | ||||||||
| 1940 | // are part of some child loop. | ||||||||
| 1941 | for (; PrevExitL; PrevExitL = PrevExitL->getParentLoop()) | ||||||||
| 1942 | RemoveUnloopedBlocksFromLoop(*PrevExitL, UnloopedBlocks); | ||||||||
| 1943 | for (auto *BB : UnloopedBlocks) | ||||||||
| 1944 | if (Loop *BBL = LI.getLoopFor(BB)) | ||||||||
| 1945 | if (BBL == &L || !L.contains(BBL)) | ||||||||
| 1946 | LI.changeLoopFor(BB, nullptr); | ||||||||
| 1947 | |||||||||
| 1948 | // Sink all the child loops whose headers are no longer in the loop set to | ||||||||
| 1949 | // the parent (or to be top level loops). We reach into the loop and directly | ||||||||
| 1950 | // update its subloop vector to make this batch update efficient. | ||||||||
| 1951 | auto &SubLoops = L.getSubLoopsVector(); | ||||||||
| 1952 | auto SubLoopsSplitI = | ||||||||
| 1953 | LoopBlockSet.empty() | ||||||||
| 1954 | ? SubLoops.begin() | ||||||||
| 1955 | : std::stable_partition( | ||||||||
| 1956 | SubLoops.begin(), SubLoops.end(), [&](Loop *SubL) { | ||||||||
| 1957 | return LoopBlockSet.count(SubL->getHeader()); | ||||||||
| 1958 | }); | ||||||||
| 1959 | for (auto *HoistedL : make_range(SubLoopsSplitI, SubLoops.end())) { | ||||||||
| 1960 | HoistedLoops.push_back(HoistedL); | ||||||||
| 1961 | HoistedL->setParentLoop(nullptr); | ||||||||
| 1962 | |||||||||
| 1963 | // To compute the new parent of this hoisted loop we look at where we | ||||||||
| 1964 | // placed the preheader above. We can't lookup the header itself because we | ||||||||
| 1965 | // retained the mapping from the header to the hoisted loop. But the | ||||||||
| 1966 | // preheader and header should have the exact same new parent computed | ||||||||
| 1967 | // based on the set of exit blocks from the original loop as the preheader | ||||||||
| 1968 | // is a predecessor of the header and so reached in the reverse walk. And | ||||||||
| 1969 | // because the loops were all in simplified form the preheader of the | ||||||||
| 1970 | // hoisted loop can't be part of some *other* loop. | ||||||||
| 1971 | if (auto *NewParentL = LI.getLoopFor(HoistedL->getLoopPreheader())) | ||||||||
| 1972 | NewParentL->addChildLoop(HoistedL); | ||||||||
| 1973 | else | ||||||||
| 1974 | LI.addTopLevelLoop(HoistedL); | ||||||||
| 1975 | } | ||||||||
| 1976 | SubLoops.erase(SubLoopsSplitI, SubLoops.end()); | ||||||||
| 1977 | |||||||||
| 1978 | // Actually delete the loop if nothing remained within it. | ||||||||
| 1979 | if (Blocks.empty()) { | ||||||||
| 1980 | assert(SubLoops.empty() &&((void)0) | ||||||||
| 1981 | "Failed to remove all subloops from the original loop!")((void)0); | ||||||||
| 1982 | if (Loop *ParentL = L.getParentLoop()) | ||||||||
| 1983 | ParentL->removeChildLoop(llvm::find(*ParentL, &L)); | ||||||||
| 1984 | else | ||||||||
| 1985 | LI.removeLoop(llvm::find(LI, &L)); | ||||||||
| 1986 | // markLoopAsDeleted for L should be triggered by the caller (it is typically | ||||||||
| 1987 | // done by using the UnswitchCB callback). | ||||||||
| 1988 | LI.destroy(&L); | ||||||||
| 1989 | return false; | ||||||||
| 1990 | } | ||||||||
| 1991 | |||||||||
| 1992 | return true; | ||||||||
| 1993 | } | ||||||||
| 1994 | |||||||||
| 1995 | /// Helper to visit a dominator subtree, invoking a callable on each node. | ||||||||
| 1996 | /// | ||||||||
| 1997 | /// Returning false at any point will stop walking past that node of the tree. | ||||||||
| 1998 | template <typename CallableT> | ||||||||
| 1999 | void visitDomSubTree(DominatorTree &DT, BasicBlock *BB, CallableT Callable) { | ||||||||
| 2000 | SmallVector<DomTreeNode *, 4> DomWorklist; | ||||||||
| 2001 | DomWorklist.push_back(DT[BB]); | ||||||||
| 2002 | #ifndef NDEBUG1 | ||||||||
| 2003 | SmallPtrSet<DomTreeNode *, 4> Visited; | ||||||||
| 2004 | Visited.insert(DT[BB]); | ||||||||
| 2005 | #endif | ||||||||
| 2006 | do { | ||||||||
| 2007 | DomTreeNode *N = DomWorklist.pop_back_val(); | ||||||||
| 2008 | |||||||||
| 2009 | // Visit this node. | ||||||||
| 2010 | if (!Callable(N->getBlock())) | ||||||||
| 2011 | continue; | ||||||||
| 2012 | |||||||||
| 2013 | // Accumulate the child nodes. | ||||||||
| 2014 | for (DomTreeNode *ChildN : *N) { | ||||||||
| 2015 | assert(Visited.insert(ChildN).second &&((void)0) | ||||||||
| 2016 | "Cannot visit a node twice when walking a tree!")((void)0); | ||||||||
| 2017 | DomWorklist.push_back(ChildN); | ||||||||
| 2018 | } | ||||||||
| 2019 | } while (!DomWorklist.empty()); | ||||||||
| 2020 | } | ||||||||
| 2021 | |||||||||
| 2022 | static void unswitchNontrivialInvariants( | ||||||||
| 2023 | Loop &L, Instruction &TI, ArrayRef<Value *> Invariants, | ||||||||
| 2024 | SmallVectorImpl<BasicBlock *> &ExitBlocks, IVConditionInfo &PartialIVInfo, | ||||||||
| 2025 | DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | ||||||||
| 2026 | function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB, | ||||||||
| 2027 | ScalarEvolution *SE, MemorySSAUpdater *MSSAU, | ||||||||
| 2028 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||||||
| 2029 | auto *ParentBB = TI.getParent(); | ||||||||
| 2030 | BranchInst *BI = dyn_cast<BranchInst>(&TI); | ||||||||
| 2031 | SwitchInst *SI = BI ? nullptr : cast<SwitchInst>(&TI); | ||||||||
| 2032 | |||||||||
| 2033 | // We can only unswitch switches, conditional branches with an invariant | ||||||||
| 2034 | // condition, or combining invariant conditions with an instruction or | ||||||||
| 2035 | // partially invariant instructions. | ||||||||
| 2036 | assert((SI || (BI && BI->isConditional())) &&((void)0) | ||||||||
| 2037 | "Can only unswitch switches and conditional branch!")((void)0); | ||||||||
| 2038 | bool PartiallyInvariant = !PartialIVInfo.InstToDuplicate.empty(); | ||||||||
| 2039 | bool FullUnswitch = | ||||||||
| 2040 | SI || (BI->getCondition() == Invariants[0] && !PartiallyInvariant); | ||||||||
| 2041 | if (FullUnswitch) | ||||||||
| 2042 | assert(Invariants.size() == 1 &&((void)0) | ||||||||
| 2043 | "Cannot have other invariants with full unswitching!")((void)0); | ||||||||
| 2044 | else | ||||||||
| 2045 | assert(isa<Instruction>(BI->getCondition()) &&((void)0) | ||||||||
| 2046 | "Partial unswitching requires an instruction as the condition!")((void)0); | ||||||||
| 2047 | |||||||||
| 2048 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 2049 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 2050 | |||||||||
| 2051 | // Constant and BBs tracking the cloned and continuing successor. When we are | ||||||||
| 2052 | // unswitching the entire condition, this can just be trivially chosen to | ||||||||
| 2053 | // unswitch towards `true`. However, when we are unswitching a set of | ||||||||
| 2054 | // invariants combined with `and` or `or` or partially invariant instructions, | ||||||||
| 2055 | // the combining operation determines the best direction to unswitch: we want | ||||||||
| 2056 | // to unswitch the direction that will collapse the branch. | ||||||||
| 2057 | bool Direction = true; | ||||||||
| 2058 | int ClonedSucc = 0; | ||||||||
| 2059 | if (!FullUnswitch) { | ||||||||
| 2060 | Value *Cond = BI->getCondition(); | ||||||||
| 2061 | (void)Cond; | ||||||||
| 2062 | assert(((match(Cond, m_LogicalAnd()) ^ match(Cond, m_LogicalOr())) ||((void)0) | ||||||||
| 2063 | PartiallyInvariant) &&((void)0) | ||||||||
| 2064 | "Only `or`, `and`, an `select`, partially invariant instructions "((void)0) | ||||||||
| 2065 | "can combine invariants being unswitched.")((void)0); | ||||||||
| 2066 | if (!match(BI->getCondition(), m_LogicalOr())) { | ||||||||
| 2067 | if (match(BI->getCondition(), m_LogicalAnd()) || | ||||||||
| 2068 | (PartiallyInvariant && !PartialIVInfo.KnownValue->isOneValue())) { | ||||||||
| 2069 | Direction = false; | ||||||||
| 2070 | ClonedSucc = 1; | ||||||||
| 2071 | } | ||||||||
| 2072 | } | ||||||||
| 2073 | } | ||||||||
| 2074 | |||||||||
| 2075 | BasicBlock *RetainedSuccBB = | ||||||||
| 2076 | BI ? BI->getSuccessor(1 - ClonedSucc) : SI->getDefaultDest(); | ||||||||
| 2077 | SmallSetVector<BasicBlock *, 4> UnswitchedSuccBBs; | ||||||||
| 2078 | if (BI) | ||||||||
| 2079 | UnswitchedSuccBBs.insert(BI->getSuccessor(ClonedSucc)); | ||||||||
| 2080 | else | ||||||||
| 2081 | for (auto Case : SI->cases()) | ||||||||
| 2082 | if (Case.getCaseSuccessor() != RetainedSuccBB) | ||||||||
| 2083 | UnswitchedSuccBBs.insert(Case.getCaseSuccessor()); | ||||||||
| 2084 | |||||||||
| 2085 | assert(!UnswitchedSuccBBs.count(RetainedSuccBB) &&((void)0) | ||||||||
| 2086 | "Should not unswitch the same successor we are retaining!")((void)0); | ||||||||
| 2087 | |||||||||
| 2088 | // The branch should be in this exact loop. Any inner loop's invariant branch | ||||||||
| 2089 | // should be handled by unswitching that inner loop. The caller of this | ||||||||
| 2090 | // routine should filter out any candidates that remain (but were skipped for | ||||||||
| 2091 | // whatever reason). | ||||||||
| 2092 | assert(LI.getLoopFor(ParentBB) == &L && "Branch in an inner loop!")((void)0); | ||||||||
| 2093 | |||||||||
| 2094 | // Compute the parent loop now before we start hacking on things. | ||||||||
| 2095 | Loop *ParentL = L.getParentLoop(); | ||||||||
| 2096 | // Get blocks in RPO order for MSSA update, before changing the CFG. | ||||||||
| 2097 | LoopBlocksRPO LBRPO(&L); | ||||||||
| 2098 | if (MSSAU) | ||||||||
| 2099 | LBRPO.perform(&LI); | ||||||||
| 2100 | |||||||||
| 2101 | // Compute the outer-most loop containing one of our exit blocks. This is the | ||||||||
| 2102 | // furthest up our loopnest which can be mutated, which we will use below to | ||||||||
| 2103 | // update things. | ||||||||
| 2104 | Loop *OuterExitL = &L; | ||||||||
| 2105 | for (auto *ExitBB : ExitBlocks) { | ||||||||
| 2106 | Loop *NewOuterExitL = LI.getLoopFor(ExitBB); | ||||||||
| 2107 | if (!NewOuterExitL) { | ||||||||
| 2108 | // We exited the entire nest with this block, so we're done. | ||||||||
| 2109 | OuterExitL = nullptr; | ||||||||
| 2110 | break; | ||||||||
| 2111 | } | ||||||||
| 2112 | if (NewOuterExitL != OuterExitL && NewOuterExitL->contains(OuterExitL)) | ||||||||
| 2113 | OuterExitL = NewOuterExitL; | ||||||||
| 2114 | } | ||||||||
| 2115 | |||||||||
| 2116 | // At this point, we're definitely going to unswitch something so invalidate | ||||||||
| 2117 | // any cached information in ScalarEvolution for the outer most loop | ||||||||
| 2118 | // containing an exit block and all nested loops. | ||||||||
| 2119 | if (SE) { | ||||||||
| 2120 | if (OuterExitL) | ||||||||
| 2121 | SE->forgetLoop(OuterExitL); | ||||||||
| 2122 | else | ||||||||
| 2123 | SE->forgetTopmostLoop(&L); | ||||||||
| 2124 | } | ||||||||
| 2125 | |||||||||
| 2126 | // If the edge from this terminator to a successor dominates that successor, | ||||||||
| 2127 | // store a map from each block in its dominator subtree to it. This lets us | ||||||||
| 2128 | // tell when cloning for a particular successor if a block is dominated by | ||||||||
| 2129 | // some *other* successor with a single data structure. We use this to | ||||||||
| 2130 | // significantly reduce cloning. | ||||||||
| 2131 | SmallDenseMap<BasicBlock *, BasicBlock *, 16> DominatingSucc; | ||||||||
| 2132 | for (auto *SuccBB : llvm::concat<BasicBlock *const>( | ||||||||
| 2133 | makeArrayRef(RetainedSuccBB), UnswitchedSuccBBs)) | ||||||||
| 2134 | if (SuccBB->getUniquePredecessor() || | ||||||||
| 2135 | llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) { | ||||||||
| 2136 | return PredBB == ParentBB || DT.dominates(SuccBB, PredBB); | ||||||||
| 2137 | })) | ||||||||
| 2138 | visitDomSubTree(DT, SuccBB, [&](BasicBlock *BB) { | ||||||||
| 2139 | DominatingSucc[BB] = SuccBB; | ||||||||
| 2140 | return true; | ||||||||
| 2141 | }); | ||||||||
| 2142 | |||||||||
| 2143 | // Split the preheader, so that we know that there is a safe place to insert | ||||||||
| 2144 | // the conditional branch. We will change the preheader to have a conditional | ||||||||
| 2145 | // branch on LoopCond. The original preheader will become the split point | ||||||||
| 2146 | // between the unswitched versions, and we will have a new preheader for the | ||||||||
| 2147 | // original loop. | ||||||||
| 2148 | BasicBlock *SplitBB = L.getLoopPreheader(); | ||||||||
| 2149 | BasicBlock *LoopPH = SplitEdge(SplitBB, L.getHeader(), &DT, &LI, MSSAU); | ||||||||
| 2150 | |||||||||
| 2151 | // Keep track of the dominator tree updates needed. | ||||||||
| 2152 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | ||||||||
| 2153 | |||||||||
| 2154 | // Clone the loop for each unswitched successor. | ||||||||
| 2155 | SmallVector<std::unique_ptr<ValueToValueMapTy>, 4> VMaps; | ||||||||
| 2156 | VMaps.reserve(UnswitchedSuccBBs.size()); | ||||||||
| 2157 | SmallDenseMap<BasicBlock *, BasicBlock *, 4> ClonedPHs; | ||||||||
| 2158 | for (auto *SuccBB : UnswitchedSuccBBs) { | ||||||||
| 2159 | VMaps.emplace_back(new ValueToValueMapTy()); | ||||||||
| 2160 | ClonedPHs[SuccBB] = buildClonedLoopBlocks( | ||||||||
| 2161 | L, LoopPH, SplitBB, ExitBlocks, ParentBB, SuccBB, RetainedSuccBB, | ||||||||
| 2162 | DominatingSucc, *VMaps.back(), DTUpdates, AC, DT, LI, MSSAU); | ||||||||
| 2163 | } | ||||||||
| 2164 | |||||||||
| 2165 | // Drop metadata if we may break its semantics by moving this instr into the | ||||||||
| 2166 | // split block. | ||||||||
| 2167 | if (TI.getMetadata(LLVMContext::MD_make_implicit)) { | ||||||||
| 2168 | if (DropNonTrivialImplicitNullChecks) | ||||||||
| 2169 | // Do not spend time trying to understand if we can keep it, just drop it | ||||||||
| 2170 | // to save compile time. | ||||||||
| 2171 | TI.setMetadata(LLVMContext::MD_make_implicit, nullptr); | ||||||||
| 2172 | else { | ||||||||
| 2173 | // It is only legal to preserve make.implicit metadata if we are | ||||||||
| 2174 | // guaranteed no reach implicit null check after following this branch. | ||||||||
| 2175 | ICFLoopSafetyInfo SafetyInfo; | ||||||||
| 2176 | SafetyInfo.computeLoopSafetyInfo(&L); | ||||||||
| 2177 | if (!SafetyInfo.isGuaranteedToExecute(TI, &DT, &L)) | ||||||||
| 2178 | TI.setMetadata(LLVMContext::MD_make_implicit, nullptr); | ||||||||
| 2179 | } | ||||||||
| 2180 | } | ||||||||
| 2181 | |||||||||
| 2182 | // The stitching of the branched code back together depends on whether we're | ||||||||
| 2183 | // doing full unswitching or not with the exception that we always want to | ||||||||
| 2184 | // nuke the initial terminator placed in the split block. | ||||||||
| 2185 | SplitBB->getTerminator()->eraseFromParent(); | ||||||||
| 2186 | if (FullUnswitch) { | ||||||||
| 2187 | // Splice the terminator from the original loop and rewrite its | ||||||||
| 2188 | // successors. | ||||||||
| 2189 | SplitBB->getInstList().splice(SplitBB->end(), ParentBB->getInstList(), TI); | ||||||||
| 2190 | |||||||||
| 2191 | // Keep a clone of the terminator for MSSA updates. | ||||||||
| 2192 | Instruction *NewTI = TI.clone(); | ||||||||
| 2193 | ParentBB->getInstList().push_back(NewTI); | ||||||||
| 2194 | |||||||||
| 2195 | // First wire up the moved terminator to the preheaders. | ||||||||
| 2196 | if (BI) { | ||||||||
| 2197 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | ||||||||
| 2198 | BI->setSuccessor(ClonedSucc, ClonedPH); | ||||||||
| 2199 | BI->setSuccessor(1 - ClonedSucc, LoopPH); | ||||||||
| 2200 | DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH}); | ||||||||
| 2201 | } else { | ||||||||
| 2202 | assert(SI && "Must either be a branch or switch!")((void)0); | ||||||||
| 2203 | |||||||||
| 2204 | // Walk the cases and directly update their successors. | ||||||||
| 2205 | assert(SI->getDefaultDest() == RetainedSuccBB &&((void)0) | ||||||||
| 2206 | "Not retaining default successor!")((void)0); | ||||||||
| 2207 | SI->setDefaultDest(LoopPH); | ||||||||
| 2208 | for (auto &Case : SI->cases()) | ||||||||
| 2209 | if (Case.getCaseSuccessor() == RetainedSuccBB) | ||||||||
| 2210 | Case.setSuccessor(LoopPH); | ||||||||
| 2211 | else | ||||||||
| 2212 | Case.setSuccessor(ClonedPHs.find(Case.getCaseSuccessor())->second); | ||||||||
| 2213 | |||||||||
| 2214 | // We need to use the set to populate domtree updates as even when there | ||||||||
| 2215 | // are multiple cases pointing at the same successor we only want to | ||||||||
| 2216 | // remove and insert one edge in the domtree. | ||||||||
| 2217 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||||||
| 2218 | DTUpdates.push_back( | ||||||||
| 2219 | {DominatorTree::Insert, SplitBB, ClonedPHs.find(SuccBB)->second}); | ||||||||
| 2220 | } | ||||||||
| 2221 | |||||||||
| 2222 | if (MSSAU) { | ||||||||
| 2223 | DT.applyUpdates(DTUpdates); | ||||||||
| 2224 | DTUpdates.clear(); | ||||||||
| 2225 | |||||||||
| 2226 | // Remove all but one edge to the retained block and all unswitched | ||||||||
| 2227 | // blocks. This is to avoid having duplicate entries in the cloned Phis, | ||||||||
| 2228 | // when we know we only keep a single edge for each case. | ||||||||
| 2229 | MSSAU->removeDuplicatePhiEdgesBetween(ParentBB, RetainedSuccBB); | ||||||||
| 2230 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||||||
| 2231 | MSSAU->removeDuplicatePhiEdgesBetween(ParentBB, SuccBB); | ||||||||
| 2232 | |||||||||
| 2233 | for (auto &VMap : VMaps) | ||||||||
| 2234 | MSSAU->updateForClonedLoop(LBRPO, ExitBlocks, *VMap, | ||||||||
| 2235 | /*IgnoreIncomingWithNoClones=*/true); | ||||||||
| 2236 | MSSAU->updateExitBlocksForClonedLoop(ExitBlocks, VMaps, DT); | ||||||||
| 2237 | |||||||||
| 2238 | // Remove all edges to unswitched blocks. | ||||||||
| 2239 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||||||
| 2240 | MSSAU->removeEdge(ParentBB, SuccBB); | ||||||||
| 2241 | } | ||||||||
| 2242 | |||||||||
| 2243 | // Now unhook the successor relationship as we'll be replacing | ||||||||
| 2244 | // the terminator with a direct branch. This is much simpler for branches | ||||||||
| 2245 | // than switches so we handle those first. | ||||||||
| 2246 | if (BI) { | ||||||||
| 2247 | // Remove the parent as a predecessor of the unswitched successor. | ||||||||
| 2248 | assert(UnswitchedSuccBBs.size() == 1 &&((void)0) | ||||||||
| 2249 | "Only one possible unswitched block for a branch!")((void)0); | ||||||||
| 2250 | BasicBlock *UnswitchedSuccBB = *UnswitchedSuccBBs.begin(); | ||||||||
| 2251 | UnswitchedSuccBB->removePredecessor(ParentBB, | ||||||||
| 2252 | /*KeepOneInputPHIs*/ true); | ||||||||
| 2253 | DTUpdates.push_back({DominatorTree::Delete, ParentBB, UnswitchedSuccBB}); | ||||||||
| 2254 | } else { | ||||||||
| 2255 | // Note that we actually want to remove the parent block as a predecessor | ||||||||
| 2256 | // of *every* case successor. The case successor is either unswitched, | ||||||||
| 2257 | // completely eliminating an edge from the parent to that successor, or it | ||||||||
| 2258 | // is a duplicate edge to the retained successor as the retained successor | ||||||||
| 2259 | // is always the default successor and as we'll replace this with a direct | ||||||||
| 2260 | // branch we no longer need the duplicate entries in the PHI nodes. | ||||||||
| 2261 | SwitchInst *NewSI = cast<SwitchInst>(NewTI); | ||||||||
| 2262 | assert(NewSI->getDefaultDest() == RetainedSuccBB &&((void)0) | ||||||||
| 2263 | "Not retaining default successor!")((void)0); | ||||||||
| 2264 | for (auto &Case : NewSI->cases()) | ||||||||
| 2265 | Case.getCaseSuccessor()->removePredecessor( | ||||||||
| 2266 | ParentBB, | ||||||||
| 2267 | /*KeepOneInputPHIs*/ true); | ||||||||
| 2268 | |||||||||
| 2269 | // We need to use the set to populate domtree updates as even when there | ||||||||
| 2270 | // are multiple cases pointing at the same successor we only want to | ||||||||
| 2271 | // remove and insert one edge in the domtree. | ||||||||
| 2272 | for (BasicBlock *SuccBB : UnswitchedSuccBBs) | ||||||||
| 2273 | DTUpdates.push_back({DominatorTree::Delete, ParentBB, SuccBB}); | ||||||||
| 2274 | } | ||||||||
| 2275 | |||||||||
| 2276 | // After MSSAU update, remove the cloned terminator instruction NewTI. | ||||||||
| 2277 | ParentBB->getTerminator()->eraseFromParent(); | ||||||||
| 2278 | |||||||||
| 2279 | // Create a new unconditional branch to the continuing block (as opposed to | ||||||||
| 2280 | // the one cloned). | ||||||||
| 2281 | BranchInst::Create(RetainedSuccBB, ParentBB); | ||||||||
| 2282 | } else { | ||||||||
| 2283 | assert(BI && "Only branches have partial unswitching.")((void)0); | ||||||||
| 2284 | assert(UnswitchedSuccBBs.size() == 1 &&((void)0) | ||||||||
| 2285 | "Only one possible unswitched block for a branch!")((void)0); | ||||||||
| 2286 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | ||||||||
| 2287 | // When doing a partial unswitch, we have to do a bit more work to build up | ||||||||
| 2288 | // the branch in the split block. | ||||||||
| 2289 | if (PartiallyInvariant) | ||||||||
| 2290 | buildPartialInvariantUnswitchConditionalBranch( | ||||||||
| 2291 | *SplitBB, Invariants, Direction, *ClonedPH, *LoopPH, L, MSSAU); | ||||||||
| 2292 | else | ||||||||
| 2293 | buildPartialUnswitchConditionalBranch(*SplitBB, Invariants, Direction, | ||||||||
| 2294 | *ClonedPH, *LoopPH); | ||||||||
| 2295 | DTUpdates.push_back({DominatorTree::Insert, SplitBB, ClonedPH}); | ||||||||
| 2296 | |||||||||
| 2297 | if (MSSAU) { | ||||||||
| 2298 | DT.applyUpdates(DTUpdates); | ||||||||
| 2299 | DTUpdates.clear(); | ||||||||
| 2300 | |||||||||
| 2301 | // Perform MSSA cloning updates. | ||||||||
| 2302 | for (auto &VMap : VMaps) | ||||||||
| 2303 | MSSAU->updateForClonedLoop(LBRPO, ExitBlocks, *VMap, | ||||||||
| 2304 | /*IgnoreIncomingWithNoClones=*/true); | ||||||||
| 2305 | MSSAU->updateExitBlocksForClonedLoop(ExitBlocks, VMaps, DT); | ||||||||
| 2306 | } | ||||||||
| 2307 | } | ||||||||
| 2308 | |||||||||
| 2309 | // Apply the updates accumulated above to get an up-to-date dominator tree. | ||||||||
| 2310 | DT.applyUpdates(DTUpdates); | ||||||||
| 2311 | |||||||||
| 2312 | // Now that we have an accurate dominator tree, first delete the dead cloned | ||||||||
| 2313 | // blocks so that we can accurately build any cloned loops. It is important to | ||||||||
| 2314 | // not delete the blocks from the original loop yet because we still want to | ||||||||
| 2315 | // reference the original loop to understand the cloned loop's structure. | ||||||||
| 2316 | deleteDeadClonedBlocks(L, ExitBlocks, VMaps, DT, MSSAU); | ||||||||
| 2317 | |||||||||
| 2318 | // Build the cloned loop structure itself. This may be substantially | ||||||||
| 2319 | // different from the original structure due to the simplified CFG. This also | ||||||||
| 2320 | // handles inserting all the cloned blocks into the correct loops. | ||||||||
| 2321 | SmallVector<Loop *, 4> NonChildClonedLoops; | ||||||||
| 2322 | for (std::unique_ptr<ValueToValueMapTy> &VMap : VMaps) | ||||||||
| 2323 | buildClonedLoops(L, ExitBlocks, *VMap, LI, NonChildClonedLoops); | ||||||||
| 2324 | |||||||||
| 2325 | // Now that our cloned loops have been built, we can update the original loop. | ||||||||
| 2326 | // First we delete the dead blocks from it and then we rebuild the loop | ||||||||
| 2327 | // structure taking these deletions into account. | ||||||||
| 2328 | deleteDeadBlocksFromLoop(L, ExitBlocks, DT, LI, MSSAU, DestroyLoopCB); | ||||||||
| 2329 | |||||||||
| 2330 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 2331 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 2332 | |||||||||
| 2333 | SmallVector<Loop *, 4> HoistedLoops; | ||||||||
| 2334 | bool IsStillLoop = rebuildLoopAfterUnswitch(L, ExitBlocks, LI, HoistedLoops); | ||||||||
| 2335 | |||||||||
| 2336 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 2337 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 2338 | |||||||||
| 2339 | // This transformation has a high risk of corrupting the dominator tree, and | ||||||||
| 2340 | // the below steps to rebuild loop structures will result in hard to debug | ||||||||
| 2341 | // errors in that case so verify that the dominator tree is sane first. | ||||||||
| 2342 | // FIXME: Remove this when the bugs stop showing up and rely on existing | ||||||||
| 2343 | // verification steps. | ||||||||
| 2344 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))((void)0); | ||||||||
| 2345 | |||||||||
| 2346 | if (BI && !PartiallyInvariant) { | ||||||||
| 2347 | // If we unswitched a branch which collapses the condition to a known | ||||||||
| 2348 | // constant we want to replace all the uses of the invariants within both | ||||||||
| 2349 | // the original and cloned blocks. We do this here so that we can use the | ||||||||
| 2350 | // now updated dominator tree to identify which side the users are on. | ||||||||
| 2351 | assert(UnswitchedSuccBBs.size() == 1 &&((void)0) | ||||||||
| 2352 | "Only one possible unswitched block for a branch!")((void)0); | ||||||||
| 2353 | BasicBlock *ClonedPH = ClonedPHs.begin()->second; | ||||||||
| 2354 | |||||||||
| 2355 | // When considering multiple partially-unswitched invariants | ||||||||
| 2356 | // we cant just go replace them with constants in both branches. | ||||||||
| 2357 | // | ||||||||
| 2358 | // For 'AND' we infer that true branch ("continue") means true | ||||||||
| 2359 | // for each invariant operand. | ||||||||
| 2360 | // For 'OR' we can infer that false branch ("continue") means false | ||||||||
| 2361 | // for each invariant operand. | ||||||||
| 2362 | // So it happens that for multiple-partial case we dont replace | ||||||||
| 2363 | // in the unswitched branch. | ||||||||
| 2364 | bool ReplaceUnswitched = | ||||||||
| 2365 | FullUnswitch || (Invariants.size() == 1) || PartiallyInvariant; | ||||||||
| 2366 | |||||||||
| 2367 | ConstantInt *UnswitchedReplacement = | ||||||||
| 2368 | Direction ? ConstantInt::getTrue(BI->getContext()) | ||||||||
| 2369 | : ConstantInt::getFalse(BI->getContext()); | ||||||||
| 2370 | ConstantInt *ContinueReplacement = | ||||||||
| 2371 | Direction ? ConstantInt::getFalse(BI->getContext()) | ||||||||
| 2372 | : ConstantInt::getTrue(BI->getContext()); | ||||||||
| 2373 | for (Value *Invariant : Invariants) | ||||||||
| 2374 | // Use make_early_inc_range here as set invalidates the iterator. | ||||||||
| 2375 | for (Use &U : llvm::make_early_inc_range(Invariant->uses())) { | ||||||||
| 2376 | Instruction *UserI = dyn_cast<Instruction>(U.getUser()); | ||||||||
| 2377 | if (!UserI) | ||||||||
| 2378 | continue; | ||||||||
| 2379 | |||||||||
| 2380 | // Replace it with the 'continue' side if in the main loop body, and the | ||||||||
| 2381 | // unswitched if in the cloned blocks. | ||||||||
| 2382 | if (DT.dominates(LoopPH, UserI->getParent())) | ||||||||
| 2383 | U.set(ContinueReplacement); | ||||||||
| 2384 | else if (ReplaceUnswitched && | ||||||||
| 2385 | DT.dominates(ClonedPH, UserI->getParent())) | ||||||||
| 2386 | U.set(UnswitchedReplacement); | ||||||||
| 2387 | } | ||||||||
| 2388 | } | ||||||||
| 2389 | |||||||||
| 2390 | // We can change which blocks are exit blocks of all the cloned sibling | ||||||||
| 2391 | // loops, the current loop, and any parent loops which shared exit blocks | ||||||||
| 2392 | // with the current loop. As a consequence, we need to re-form LCSSA for | ||||||||
| 2393 | // them. But we shouldn't need to re-form LCSSA for any child loops. | ||||||||
| 2394 | // FIXME: This could be made more efficient by tracking which exit blocks are | ||||||||
| 2395 | // new, and focusing on them, but that isn't likely to be necessary. | ||||||||
| 2396 | // | ||||||||
| 2397 | // In order to reasonably rebuild LCSSA we need to walk inside-out across the | ||||||||
| 2398 | // loop nest and update every loop that could have had its exits changed. We | ||||||||
| 2399 | // also need to cover any intervening loops. We add all of these loops to | ||||||||
| 2400 | // a list and sort them by loop depth to achieve this without updating | ||||||||
| 2401 | // unnecessary loops. | ||||||||
| 2402 | auto UpdateLoop = [&](Loop &UpdateL) { | ||||||||
| 2403 | #ifndef NDEBUG1 | ||||||||
| 2404 | UpdateL.verifyLoop(); | ||||||||
| 2405 | for (Loop *ChildL : UpdateL) { | ||||||||
| 2406 | ChildL->verifyLoop(); | ||||||||
| 2407 | assert(ChildL->isRecursivelyLCSSAForm(DT, LI) &&((void)0) | ||||||||
| 2408 | "Perturbed a child loop's LCSSA form!")((void)0); | ||||||||
| 2409 | } | ||||||||
| 2410 | #endif | ||||||||
| 2411 | // First build LCSSA for this loop so that we can preserve it when | ||||||||
| 2412 | // forming dedicated exits. We don't want to perturb some other loop's | ||||||||
| 2413 | // LCSSA while doing that CFG edit. | ||||||||
| 2414 | formLCSSA(UpdateL, DT, &LI, SE); | ||||||||
| 2415 | |||||||||
| 2416 | // For loops reached by this loop's original exit blocks we may | ||||||||
| 2417 | // introduced new, non-dedicated exits. At least try to re-form dedicated | ||||||||
| 2418 | // exits for these loops. This may fail if they couldn't have dedicated | ||||||||
| 2419 | // exits to start with. | ||||||||
| 2420 | formDedicatedExitBlocks(&UpdateL, &DT, &LI, MSSAU, /*PreserveLCSSA*/ true); | ||||||||
| 2421 | }; | ||||||||
| 2422 | |||||||||
| 2423 | // For non-child cloned loops and hoisted loops, we just need to update LCSSA | ||||||||
| 2424 | // and we can do it in any order as they don't nest relative to each other. | ||||||||
| 2425 | // | ||||||||
| 2426 | // Also check if any of the loops we have updated have become top-level loops | ||||||||
| 2427 | // as that will necessitate widening the outer loop scope. | ||||||||
| 2428 | for (Loop *UpdatedL : | ||||||||
| 2429 | llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) { | ||||||||
| 2430 | UpdateLoop(*UpdatedL); | ||||||||
| 2431 | if (UpdatedL->isOutermost()) | ||||||||
| 2432 | OuterExitL = nullptr; | ||||||||
| 2433 | } | ||||||||
| 2434 | if (IsStillLoop) { | ||||||||
| 2435 | UpdateLoop(L); | ||||||||
| 2436 | if (L.isOutermost()) | ||||||||
| 2437 | OuterExitL = nullptr; | ||||||||
| 2438 | } | ||||||||
| 2439 | |||||||||
| 2440 | // If the original loop had exit blocks, walk up through the outer most loop | ||||||||
| 2441 | // of those exit blocks to update LCSSA and form updated dedicated exits. | ||||||||
| 2442 | if (OuterExitL != &L) | ||||||||
| 2443 | for (Loop *OuterL = ParentL; OuterL != OuterExitL; | ||||||||
| 2444 | OuterL = OuterL->getParentLoop()) | ||||||||
| 2445 | UpdateLoop(*OuterL); | ||||||||
| 2446 | |||||||||
| 2447 | #ifndef NDEBUG1 | ||||||||
| 2448 | // Verify the entire loop structure to catch any incorrect updates before we | ||||||||
| 2449 | // progress in the pass pipeline. | ||||||||
| 2450 | LI.verify(DT); | ||||||||
| 2451 | #endif | ||||||||
| 2452 | |||||||||
| 2453 | // Now that we've unswitched something, make callbacks to report the changes. | ||||||||
| 2454 | // For that we need to merge together the updated loops and the cloned loops | ||||||||
| 2455 | // and check whether the original loop survived. | ||||||||
| 2456 | SmallVector<Loop *, 4> SibLoops; | ||||||||
| 2457 | for (Loop *UpdatedL : llvm::concat<Loop *>(NonChildClonedLoops, HoistedLoops)) | ||||||||
| 2458 | if (UpdatedL->getParentLoop() == ParentL) | ||||||||
| 2459 | SibLoops.push_back(UpdatedL); | ||||||||
| 2460 | UnswitchCB(IsStillLoop, PartiallyInvariant, SibLoops); | ||||||||
| 2461 | |||||||||
| 2462 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 2463 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 2464 | |||||||||
| 2465 | if (BI) | ||||||||
| 2466 | ++NumBranches; | ||||||||
| 2467 | else | ||||||||
| 2468 | ++NumSwitches; | ||||||||
| 2469 | } | ||||||||
| 2470 | |||||||||
| 2471 | /// Recursively compute the cost of a dominator subtree based on the per-block | ||||||||
| 2472 | /// cost map provided. | ||||||||
| 2473 | /// | ||||||||
| 2474 | /// The recursive computation is memozied into the provided DT-indexed cost map | ||||||||
| 2475 | /// to allow querying it for most nodes in the domtree without it becoming | ||||||||
| 2476 | /// quadratic. | ||||||||
| 2477 | static InstructionCost computeDomSubtreeCost( | ||||||||
| 2478 | DomTreeNode &N, | ||||||||
| 2479 | const SmallDenseMap<BasicBlock *, InstructionCost, 4> &BBCostMap, | ||||||||
| 2480 | SmallDenseMap<DomTreeNode *, InstructionCost, 4> &DTCostMap) { | ||||||||
| 2481 | // Don't accumulate cost (or recurse through) blocks not in our block cost | ||||||||
| 2482 | // map and thus not part of the duplication cost being considered. | ||||||||
| 2483 | auto BBCostIt = BBCostMap.find(N.getBlock()); | ||||||||
| 2484 | if (BBCostIt == BBCostMap.end()) | ||||||||
| 2485 | return 0; | ||||||||
| 2486 | |||||||||
| 2487 | // Lookup this node to see if we already computed its cost. | ||||||||
| 2488 | auto DTCostIt = DTCostMap.find(&N); | ||||||||
| 2489 | if (DTCostIt != DTCostMap.end()) | ||||||||
| 2490 | return DTCostIt->second; | ||||||||
| 2491 | |||||||||
| 2492 | // If not, we have to compute it. We can't use insert above and update | ||||||||
| 2493 | // because computing the cost may insert more things into the map. | ||||||||
| 2494 | InstructionCost Cost = std::accumulate( | ||||||||
| 2495 | N.begin(), N.end(), BBCostIt->second, | ||||||||
| 2496 | [&](InstructionCost Sum, DomTreeNode *ChildN) -> InstructionCost { | ||||||||
| 2497 | return Sum + computeDomSubtreeCost(*ChildN, BBCostMap, DTCostMap); | ||||||||
| 2498 | }); | ||||||||
| 2499 | bool Inserted = DTCostMap.insert({&N, Cost}).second; | ||||||||
| 2500 | (void)Inserted; | ||||||||
| 2501 | assert(Inserted && "Should not insert a node while visiting children!")((void)0); | ||||||||
| 2502 | return Cost; | ||||||||
| 2503 | } | ||||||||
| 2504 | |||||||||
| 2505 | /// Turns a llvm.experimental.guard intrinsic into implicit control flow branch, | ||||||||
| 2506 | /// making the following replacement: | ||||||||
| 2507 | /// | ||||||||
| 2508 | /// --code before guard-- | ||||||||
| 2509 | /// call void (i1, ...) @llvm.experimental.guard(i1 %cond) [ "deopt"() ] | ||||||||
| 2510 | /// --code after guard-- | ||||||||
| 2511 | /// | ||||||||
| 2512 | /// into | ||||||||
| 2513 | /// | ||||||||
| 2514 | /// --code before guard-- | ||||||||
| 2515 | /// br i1 %cond, label %guarded, label %deopt | ||||||||
| 2516 | /// | ||||||||
| 2517 | /// guarded: | ||||||||
| 2518 | /// --code after guard-- | ||||||||
| 2519 | /// | ||||||||
| 2520 | /// deopt: | ||||||||
| 2521 | /// call void (i1, ...) @llvm.experimental.guard(i1 false) [ "deopt"() ] | ||||||||
| 2522 | /// unreachable | ||||||||
| 2523 | /// | ||||||||
| 2524 | /// It also makes all relevant DT and LI updates, so that all structures are in | ||||||||
| 2525 | /// valid state after this transform. | ||||||||
| 2526 | static BranchInst * | ||||||||
| 2527 | turnGuardIntoBranch(IntrinsicInst *GI, Loop &L, | ||||||||
| 2528 | SmallVectorImpl<BasicBlock *> &ExitBlocks, | ||||||||
| 2529 | DominatorTree &DT, LoopInfo &LI, MemorySSAUpdater *MSSAU) { | ||||||||
| 2530 | SmallVector<DominatorTree::UpdateType, 4> DTUpdates; | ||||||||
| 2531 | LLVM_DEBUG(dbgs() << "Turning " << *GI << " into a branch.\n")do { } while (false); | ||||||||
| 2532 | BasicBlock *CheckBB = GI->getParent(); | ||||||||
| 2533 | |||||||||
| 2534 | if (MSSAU && VerifyMemorySSA) | ||||||||
| 2535 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 2536 | |||||||||
| 2537 | // Remove all CheckBB's successors from DomTree. A block can be seen among | ||||||||
| 2538 | // successors more than once, but for DomTree it should be added only once. | ||||||||
| 2539 | SmallPtrSet<BasicBlock *, 4> Successors; | ||||||||
| 2540 | for (auto *Succ : successors(CheckBB)) | ||||||||
| 2541 | if (Successors.insert(Succ).second) | ||||||||
| 2542 | DTUpdates.push_back({DominatorTree::Delete, CheckBB, Succ}); | ||||||||
| 2543 | |||||||||
| 2544 | Instruction *DeoptBlockTerm = | ||||||||
| 2545 | SplitBlockAndInsertIfThen(GI->getArgOperand(0), GI, true); | ||||||||
| 2546 | BranchInst *CheckBI = cast<BranchInst>(CheckBB->getTerminator()); | ||||||||
| 2547 | // SplitBlockAndInsertIfThen inserts control flow that branches to | ||||||||
| 2548 | // DeoptBlockTerm if the condition is true. We want the opposite. | ||||||||
| 2549 | CheckBI->swapSuccessors(); | ||||||||
| 2550 | |||||||||
| 2551 | BasicBlock *GuardedBlock = CheckBI->getSuccessor(0); | ||||||||
| 2552 | GuardedBlock->setName("guarded"); | ||||||||
| 2553 | CheckBI->getSuccessor(1)->setName("deopt"); | ||||||||
| 2554 | BasicBlock *DeoptBlock = CheckBI->getSuccessor(1); | ||||||||
| 2555 | |||||||||
| 2556 | // We now have a new exit block. | ||||||||
| 2557 | ExitBlocks.push_back(CheckBI->getSuccessor(1)); | ||||||||
| 2558 | |||||||||
| 2559 | if (MSSAU) | ||||||||
| 2560 | MSSAU->moveAllAfterSpliceBlocks(CheckBB, GuardedBlock, GI); | ||||||||
| 2561 | |||||||||
| 2562 | GI->moveBefore(DeoptBlockTerm); | ||||||||
| 2563 | GI->setArgOperand(0, ConstantInt::getFalse(GI->getContext())); | ||||||||
| 2564 | |||||||||
| 2565 | // Add new successors of CheckBB into DomTree. | ||||||||
| 2566 | for (auto *Succ : successors(CheckBB)) | ||||||||
| 2567 | DTUpdates.push_back({DominatorTree::Insert, CheckBB, Succ}); | ||||||||
| 2568 | |||||||||
| 2569 | // Now the blocks that used to be CheckBB's successors are GuardedBlock's | ||||||||
| 2570 | // successors. | ||||||||
| 2571 | for (auto *Succ : Successors) | ||||||||
| 2572 | DTUpdates.push_back({DominatorTree::Insert, GuardedBlock, Succ}); | ||||||||
| 2573 | |||||||||
| 2574 | // Make proper changes to DT. | ||||||||
| 2575 | DT.applyUpdates(DTUpdates); | ||||||||
| 2576 | // Inform LI of a new loop block. | ||||||||
| 2577 | L.addBasicBlockToLoop(GuardedBlock, LI); | ||||||||
| 2578 | |||||||||
| 2579 | if (MSSAU) { | ||||||||
| 2580 | MemoryDef *MD = cast<MemoryDef>(MSSAU->getMemorySSA()->getMemoryAccess(GI)); | ||||||||
| 2581 | MSSAU->moveToPlace(MD, DeoptBlock, MemorySSA::BeforeTerminator); | ||||||||
| 2582 | if (VerifyMemorySSA) | ||||||||
| 2583 | MSSAU->getMemorySSA()->verifyMemorySSA(); | ||||||||
| 2584 | } | ||||||||
| 2585 | |||||||||
| 2586 | ++NumGuards; | ||||||||
| 2587 | return CheckBI; | ||||||||
| 2588 | } | ||||||||
| 2589 | |||||||||
| 2590 | /// Cost multiplier is a way to limit potentially exponential behavior | ||||||||
| 2591 | /// of loop-unswitch. Cost is multipied in proportion of 2^number of unswitch | ||||||||
| 2592 | /// candidates available. Also accounting for the number of "sibling" loops with | ||||||||
| 2593 | /// the idea to account for previous unswitches that already happened on this | ||||||||
| 2594 | /// cluster of loops. There was an attempt to keep this formula simple, | ||||||||
| 2595 | /// just enough to limit the worst case behavior. Even if it is not that simple | ||||||||
| 2596 | /// now it is still not an attempt to provide a detailed heuristic size | ||||||||
| 2597 | /// prediction. | ||||||||
| 2598 | /// | ||||||||
| 2599 | /// TODO: Make a proper accounting of "explosion" effect for all kinds of | ||||||||
| 2600 | /// unswitch candidates, making adequate predictions instead of wild guesses. | ||||||||
| 2601 | /// That requires knowing not just the number of "remaining" candidates but | ||||||||
| 2602 | /// also costs of unswitching for each of these candidates. | ||||||||
| 2603 | static int CalculateUnswitchCostMultiplier( | ||||||||
| 2604 | Instruction &TI, Loop &L, LoopInfo &LI, DominatorTree &DT, | ||||||||
| 2605 | ArrayRef<std::pair<Instruction *, TinyPtrVector<Value *>>> | ||||||||
| 2606 | UnswitchCandidates) { | ||||||||
| 2607 | |||||||||
| 2608 | // Guards and other exiting conditions do not contribute to exponential | ||||||||
| 2609 | // explosion as soon as they dominate the latch (otherwise there might be | ||||||||
| 2610 | // another path to the latch remaining that does not allow to eliminate the | ||||||||
| 2611 | // loop copy on unswitch). | ||||||||
| 2612 | BasicBlock *Latch = L.getLoopLatch(); | ||||||||
| 2613 | BasicBlock *CondBlock = TI.getParent(); | ||||||||
| 2614 | if (DT.dominates(CondBlock, Latch) && | ||||||||
| 2615 | (isGuard(&TI) || | ||||||||
| 2616 | llvm::count_if(successors(&TI), [&L](BasicBlock *SuccBB) { | ||||||||
| 2617 | return L.contains(SuccBB); | ||||||||
| 2618 | }) <= 1)) { | ||||||||
| 2619 | NumCostMultiplierSkipped++; | ||||||||
| 2620 | return 1; | ||||||||
| 2621 | } | ||||||||
| 2622 | |||||||||
| 2623 | auto *ParentL = L.getParentLoop(); | ||||||||
| 2624 | int SiblingsCount = (ParentL ? ParentL->getSubLoopsVector().size() | ||||||||
| 2625 | : std::distance(LI.begin(), LI.end())); | ||||||||
| 2626 | // Count amount of clones that all the candidates might cause during | ||||||||
| 2627 | // unswitching. Branch/guard counts as 1, switch counts as log2 of its cases. | ||||||||
| 2628 | int UnswitchedClones = 0; | ||||||||
| 2629 | for (auto Candidate : UnswitchCandidates) { | ||||||||
| 2630 | Instruction *CI = Candidate.first; | ||||||||
| 2631 | BasicBlock *CondBlock = CI->getParent(); | ||||||||
| 2632 | bool SkipExitingSuccessors = DT.dominates(CondBlock, Latch); | ||||||||
| 2633 | if (isGuard(CI)) { | ||||||||
| 2634 | if (!SkipExitingSuccessors) | ||||||||
| 2635 | UnswitchedClones++; | ||||||||
| 2636 | continue; | ||||||||
| 2637 | } | ||||||||
| 2638 | int NonExitingSuccessors = llvm::count_if( | ||||||||
| 2639 | successors(CondBlock), [SkipExitingSuccessors, &L](BasicBlock *SuccBB) { | ||||||||
| 2640 | return !SkipExitingSuccessors || L.contains(SuccBB); | ||||||||
| 2641 | }); | ||||||||
| 2642 | UnswitchedClones += Log2_32(NonExitingSuccessors); | ||||||||
| 2643 | } | ||||||||
| 2644 | |||||||||
| 2645 | // Ignore up to the "unscaled candidates" number of unswitch candidates | ||||||||
| 2646 | // when calculating the power-of-two scaling of the cost. The main idea | ||||||||
| 2647 | // with this control is to allow a small number of unswitches to happen | ||||||||
| 2648 | // and rely more on siblings multiplier (see below) when the number | ||||||||
| 2649 | // of candidates is small. | ||||||||
| 2650 | unsigned ClonesPower = | ||||||||
| 2651 | std::max(UnswitchedClones - (int)UnswitchNumInitialUnscaledCandidates, 0); | ||||||||
| 2652 | |||||||||
| 2653 | // Allowing top-level loops to spread a bit more than nested ones. | ||||||||
| 2654 | int SiblingsMultiplier = | ||||||||
| 2655 | std::max((ParentL ? SiblingsCount | ||||||||
| 2656 | : SiblingsCount / (int)UnswitchSiblingsToplevelDiv), | ||||||||
| 2657 | 1); | ||||||||
| 2658 | // Compute the cost multiplier in a way that won't overflow by saturating | ||||||||
| 2659 | // at an upper bound. | ||||||||
| 2660 | int CostMultiplier; | ||||||||
| 2661 | if (ClonesPower > Log2_32(UnswitchThreshold) || | ||||||||
| 2662 | SiblingsMultiplier > UnswitchThreshold) | ||||||||
| 2663 | CostMultiplier = UnswitchThreshold; | ||||||||
| 2664 | else | ||||||||
| 2665 | CostMultiplier = std::min(SiblingsMultiplier * (1 << ClonesPower), | ||||||||
| 2666 | (int)UnswitchThreshold); | ||||||||
| 2667 | |||||||||
| 2668 | LLVM_DEBUG(dbgs() << " Computed multiplier " << CostMultiplierdo { } while (false) | ||||||||
| 2669 | << " (siblings " << SiblingsMultiplier << " * clones "do { } while (false) | ||||||||
| 2670 | << (1 << ClonesPower) << ")"do { } while (false) | ||||||||
| 2671 | << " for unswitch candidate: " << TI << "\n")do { } while (false); | ||||||||
| 2672 | return CostMultiplier; | ||||||||
| 2673 | } | ||||||||
| 2674 | |||||||||
| 2675 | static bool unswitchBestCondition( | ||||||||
| 2676 | Loop &L, DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | ||||||||
| 2677 | AAResults &AA, TargetTransformInfo &TTI, | ||||||||
| 2678 | function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB, | ||||||||
| 2679 | ScalarEvolution *SE, MemorySSAUpdater *MSSAU, | ||||||||
| 2680 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||||||
| 2681 | // Collect all invariant conditions within this loop (as opposed to an inner | ||||||||
| 2682 | // loop which would be handled when visiting that inner loop). | ||||||||
| 2683 | SmallVector<std::pair<Instruction *, TinyPtrVector<Value *>>, 4> | ||||||||
| 2684 | UnswitchCandidates; | ||||||||
| 2685 | |||||||||
| 2686 | // Whether or not we should also collect guards in the loop. | ||||||||
| 2687 | bool CollectGuards = false; | ||||||||
| 2688 | if (UnswitchGuards) { | ||||||||
| |||||||||
| 2689 | auto *GuardDecl = L.getHeader()->getParent()->getParent()->getFunction( | ||||||||
| 2690 | Intrinsic::getName(Intrinsic::experimental_guard)); | ||||||||
| 2691 | if (GuardDecl && !GuardDecl->use_empty()) | ||||||||
| 2692 | CollectGuards = true; | ||||||||
| 2693 | } | ||||||||
| 2694 | |||||||||
| 2695 | IVConditionInfo PartialIVInfo; | ||||||||
| 2696 | for (auto *BB : L.blocks()) { | ||||||||
| 2697 | if (LI.getLoopFor(BB) != &L) | ||||||||
| 2698 | continue; | ||||||||
| 2699 | |||||||||
| 2700 | if (CollectGuards) | ||||||||
| 2701 | for (auto &I : *BB) | ||||||||
| 2702 | if (isGuard(&I)) { | ||||||||
| 2703 | auto *Cond = cast<IntrinsicInst>(&I)->getArgOperand(0); | ||||||||
| 2704 | // TODO: Support AND, OR conditions and partial unswitching. | ||||||||
| 2705 | if (!isa<Constant>(Cond) && L.isLoopInvariant(Cond)) | ||||||||
| 2706 | UnswitchCandidates.push_back({&I, {Cond}}); | ||||||||
| 2707 | } | ||||||||
| 2708 | |||||||||
| 2709 | if (auto *SI = dyn_cast<SwitchInst>(BB->getTerminator())) { | ||||||||
| 2710 | // We can only consider fully loop-invariant switch conditions as we need | ||||||||
| 2711 | // to completely eliminate the switch after unswitching. | ||||||||
| 2712 | if (!isa<Constant>(SI->getCondition()) && | ||||||||
| 2713 | L.isLoopInvariant(SI->getCondition()) && !BB->getUniqueSuccessor()) | ||||||||
| 2714 | UnswitchCandidates.push_back({SI, {SI->getCondition()}}); | ||||||||
| 2715 | continue; | ||||||||
| 2716 | } | ||||||||
| 2717 | |||||||||
| 2718 | auto *BI = dyn_cast<BranchInst>(BB->getTerminator()); | ||||||||
| 2719 | if (!BI || !BI->isConditional() || isa<Constant>(BI->getCondition()) || | ||||||||
| 2720 | BI->getSuccessor(0) == BI->getSuccessor(1)) | ||||||||
| 2721 | continue; | ||||||||
| 2722 | |||||||||
| 2723 | // If BI's condition is 'select _, true, false', simplify it to confuse | ||||||||
| 2724 | // matchers | ||||||||
| 2725 | Value *Cond = BI->getCondition(), *CondNext; | ||||||||
| 2726 | while (match(Cond, m_Select(m_Value(CondNext), m_One(), m_Zero()))) | ||||||||
| 2727 | Cond = CondNext; | ||||||||
| 2728 | BI->setCondition(Cond); | ||||||||
| 2729 | |||||||||
| 2730 | if (L.isLoopInvariant(BI->getCondition())) { | ||||||||
| 2731 | UnswitchCandidates.push_back({BI, {BI->getCondition()}}); | ||||||||
| 2732 | continue; | ||||||||
| 2733 | } | ||||||||
| 2734 | |||||||||
| 2735 | Instruction &CondI = *cast<Instruction>(BI->getCondition()); | ||||||||
| 2736 | if (match(&CondI, m_CombineOr(m_LogicalAnd(), m_LogicalOr()))) { | ||||||||
| 2737 | TinyPtrVector<Value *> Invariants = | ||||||||
| 2738 | collectHomogenousInstGraphLoopInvariants(L, CondI, LI); | ||||||||
| 2739 | if (Invariants.empty()) | ||||||||
| 2740 | continue; | ||||||||
| 2741 | |||||||||
| 2742 | UnswitchCandidates.push_back({BI, std::move(Invariants)}); | ||||||||
| 2743 | continue; | ||||||||
| 2744 | } | ||||||||
| 2745 | } | ||||||||
| 2746 | |||||||||
| 2747 | Instruction *PartialIVCondBranch = nullptr; | ||||||||
| 2748 | if (MSSAU && !findOptionMDForLoop(&L, "llvm.loop.unswitch.partial.disable") && | ||||||||
| 2749 | !any_of(UnswitchCandidates, [&L](auto &TerminatorAndInvariants) { | ||||||||
| 2750 | return TerminatorAndInvariants.first == L.getHeader()->getTerminator(); | ||||||||
| 2751 | })) { | ||||||||
| 2752 | MemorySSA *MSSA = MSSAU->getMemorySSA(); | ||||||||
| 2753 | if (auto Info = hasPartialIVCondition(L, MSSAThreshold, *MSSA, AA)) { | ||||||||
| 2754 | LLVM_DEBUG(do { } while (false) | ||||||||
| 2755 | dbgs() << "simple-loop-unswitch: Found partially invariant condition "do { } while (false) | ||||||||
| 2756 | << *Info->InstToDuplicate[0] << "\n")do { } while (false); | ||||||||
| 2757 | PartialIVInfo = *Info; | ||||||||
| 2758 | PartialIVCondBranch = L.getHeader()->getTerminator(); | ||||||||
| 2759 | TinyPtrVector<Value *> ValsToDuplicate; | ||||||||
| 2760 | for (auto *Inst : Info->InstToDuplicate) | ||||||||
| 2761 | ValsToDuplicate.push_back(Inst); | ||||||||
| 2762 | UnswitchCandidates.push_back( | ||||||||
| 2763 | {L.getHeader()->getTerminator(), std::move(ValsToDuplicate)}); | ||||||||
| 2764 | } | ||||||||
| 2765 | } | ||||||||
| 2766 | |||||||||
| 2767 | // If we didn't find any candidates, we're done. | ||||||||
| 2768 | if (UnswitchCandidates.empty()) | ||||||||
| 2769 | return false; | ||||||||
| 2770 | |||||||||
| 2771 | // Check if there are irreducible CFG cycles in this loop. If so, we cannot | ||||||||
| 2772 | // easily unswitch non-trivial edges out of the loop. Doing so might turn the | ||||||||
| 2773 | // irreducible control flow into reducible control flow and introduce new | ||||||||
| 2774 | // loops "out of thin air". If we ever discover important use cases for doing | ||||||||
| 2775 | // this, we can add support to loop unswitch, but it is a lot of complexity | ||||||||
| 2776 | // for what seems little or no real world benefit. | ||||||||
| 2777 | LoopBlocksRPO RPOT(&L); | ||||||||
| 2778 | RPOT.perform(&LI); | ||||||||
| 2779 | if (containsIrreducibleCFG<const BasicBlock *>(RPOT, LI)) | ||||||||
| 2780 | return false; | ||||||||
| 2781 | |||||||||
| 2782 | SmallVector<BasicBlock *, 4> ExitBlocks; | ||||||||
| 2783 | L.getUniqueExitBlocks(ExitBlocks); | ||||||||
| 2784 | |||||||||
| 2785 | // We cannot unswitch if exit blocks contain a cleanuppad/catchswitch | ||||||||
| 2786 | // instruction as we don't know how to split those exit blocks. | ||||||||
| 2787 | // FIXME: We should teach SplitBlock to handle this and remove this | ||||||||
| 2788 | // restriction. | ||||||||
| 2789 | for (auto *ExitBB : ExitBlocks) { | ||||||||
| 2790 | auto *I = ExitBB->getFirstNonPHI(); | ||||||||
| 2791 | if (isa<CleanupPadInst>(I) || isa<CatchSwitchInst>(I)) { | ||||||||
| 2792 | LLVM_DEBUG(dbgs() << "Cannot unswitch because of cleanuppad/catchswitch "do { } while (false) | ||||||||
| 2793 | "in exit block\n")do { } while (false); | ||||||||
| 2794 | return false; | ||||||||
| 2795 | } | ||||||||
| 2796 | } | ||||||||
| 2797 | |||||||||
| 2798 | LLVM_DEBUG(do { } while (false) | ||||||||
| 2799 | dbgs() << "Considering " << UnswitchCandidates.size()do { } while (false) | ||||||||
| 2800 | << " non-trivial loop invariant conditions for unswitching.\n")do { } while (false); | ||||||||
| 2801 | |||||||||
| 2802 | // Given that unswitching these terminators will require duplicating parts of | ||||||||
| 2803 | // the loop, so we need to be able to model that cost. Compute the ephemeral | ||||||||
| 2804 | // values and set up a data structure to hold per-BB costs. We cache each | ||||||||
| 2805 | // block's cost so that we don't recompute this when considering different | ||||||||
| 2806 | // subsets of the loop for duplication during unswitching. | ||||||||
| 2807 | SmallPtrSet<const Value *, 4> EphValues; | ||||||||
| 2808 | CodeMetrics::collectEphemeralValues(&L, &AC, EphValues); | ||||||||
| 2809 | SmallDenseMap<BasicBlock *, InstructionCost, 4> BBCostMap; | ||||||||
| 2810 | |||||||||
| 2811 | // Compute the cost of each block, as well as the total loop cost. Also, bail | ||||||||
| 2812 | // out if we see instructions which are incompatible with loop unswitching | ||||||||
| 2813 | // (convergent, noduplicate, or cross-basic-block tokens). | ||||||||
| 2814 | // FIXME: We might be able to safely handle some of these in non-duplicated | ||||||||
| 2815 | // regions. | ||||||||
| 2816 | TargetTransformInfo::TargetCostKind CostKind = | ||||||||
| 2817 | L.getHeader()->getParent()->hasMinSize() | ||||||||
| 2818 | ? TargetTransformInfo::TCK_CodeSize | ||||||||
| 2819 | : TargetTransformInfo::TCK_SizeAndLatency; | ||||||||
| 2820 | InstructionCost LoopCost = 0; | ||||||||
| 2821 | for (auto *BB : L.blocks()) { | ||||||||
| 2822 | InstructionCost Cost = 0; | ||||||||
| 2823 | for (auto &I : *BB) { | ||||||||
| 2824 | if (EphValues.count(&I)) | ||||||||
| 2825 | continue; | ||||||||
| 2826 | |||||||||
| 2827 | if (I.getType()->isTokenTy() && I.isUsedOutsideOfBlock(BB)) | ||||||||
| 2828 | return false; | ||||||||
| 2829 | if (auto *CB = dyn_cast<CallBase>(&I)) | ||||||||
| 2830 | if (CB->isConvergent() || CB->cannotDuplicate()) | ||||||||
| 2831 | return false; | ||||||||
| 2832 | |||||||||
| 2833 | Cost += TTI.getUserCost(&I, CostKind); | ||||||||
| 2834 | } | ||||||||
| 2835 | assert(Cost >= 0 && "Must not have negative costs!")((void)0); | ||||||||
| 2836 | LoopCost += Cost; | ||||||||
| 2837 | assert(LoopCost >= 0 && "Must not have negative loop costs!")((void)0); | ||||||||
| 2838 | BBCostMap[BB] = Cost; | ||||||||
| 2839 | } | ||||||||
| 2840 | LLVM_DEBUG(dbgs() << " Total loop cost: " << LoopCost << "\n")do { } while (false); | ||||||||
| 2841 | |||||||||
| 2842 | // Now we find the best candidate by searching for the one with the following | ||||||||
| 2843 | // properties in order: | ||||||||
| 2844 | // | ||||||||
| 2845 | // 1) An unswitching cost below the threshold | ||||||||
| 2846 | // 2) The smallest number of duplicated unswitch candidates (to avoid | ||||||||
| 2847 | // creating redundant subsequent unswitching) | ||||||||
| 2848 | // 3) The smallest cost after unswitching. | ||||||||
| 2849 | // | ||||||||
| 2850 | // We prioritize reducing fanout of unswitch candidates provided the cost | ||||||||
| 2851 | // remains below the threshold because this has a multiplicative effect. | ||||||||
| 2852 | // | ||||||||
| 2853 | // This requires memoizing each dominator subtree to avoid redundant work. | ||||||||
| 2854 | // | ||||||||
| 2855 | // FIXME: Need to actually do the number of candidates part above. | ||||||||
| 2856 | SmallDenseMap<DomTreeNode *, InstructionCost, 4> DTCostMap; | ||||||||
| 2857 | // Given a terminator which might be unswitched, computes the non-duplicated | ||||||||
| 2858 | // cost for that terminator. | ||||||||
| 2859 | auto ComputeUnswitchedCost = [&](Instruction &TI, | ||||||||
| 2860 | bool FullUnswitch) -> InstructionCost { | ||||||||
| 2861 | BasicBlock &BB = *TI.getParent(); | ||||||||
| 2862 | SmallPtrSet<BasicBlock *, 4> Visited; | ||||||||
| 2863 | |||||||||
| 2864 | InstructionCost Cost = 0; | ||||||||
| 2865 | for (BasicBlock *SuccBB : successors(&BB)) { | ||||||||
| 2866 | // Don't count successors more than once. | ||||||||
| 2867 | if (!Visited.insert(SuccBB).second) | ||||||||
| 2868 | continue; | ||||||||
| 2869 | |||||||||
| 2870 | // If this is a partial unswitch candidate, then it must be a conditional | ||||||||
| 2871 | // branch with a condition of either `or`, `and`, their corresponding | ||||||||
| 2872 | // select forms or partially invariant instructions. In that case, one of | ||||||||
| 2873 | // the successors is necessarily duplicated, so don't even try to remove | ||||||||
| 2874 | // its cost. | ||||||||
| 2875 | if (!FullUnswitch) { | ||||||||
| 2876 | auto &BI = cast<BranchInst>(TI); | ||||||||
| 2877 | if (match(BI.getCondition(), m_LogicalAnd())) { | ||||||||
| 2878 | if (SuccBB == BI.getSuccessor(1)) | ||||||||
| 2879 | continue; | ||||||||
| 2880 | } else if (match(BI.getCondition(), m_LogicalOr())) { | ||||||||
| 2881 | if (SuccBB == BI.getSuccessor(0)) | ||||||||
| 2882 | continue; | ||||||||
| 2883 | } else if ((PartialIVInfo.KnownValue->isOneValue() && | ||||||||
| 2884 | SuccBB == BI.getSuccessor(0)) || | ||||||||
| 2885 | (!PartialIVInfo.KnownValue->isOneValue() && | ||||||||
| 2886 | SuccBB == BI.getSuccessor(1))) | ||||||||
| 2887 | continue; | ||||||||
| 2888 | } | ||||||||
| 2889 | |||||||||
| 2890 | // This successor's domtree will not need to be duplicated after | ||||||||
| 2891 | // unswitching if the edge to the successor dominates it (and thus the | ||||||||
| 2892 | // entire tree). This essentially means there is no other path into this | ||||||||
| 2893 | // subtree and so it will end up live in only one clone of the loop. | ||||||||
| 2894 | if (SuccBB->getUniquePredecessor() || | ||||||||
| 2895 | llvm::all_of(predecessors(SuccBB), [&](BasicBlock *PredBB) { | ||||||||
| 2896 | return PredBB == &BB || DT.dominates(SuccBB, PredBB); | ||||||||
| 2897 | })) { | ||||||||
| 2898 | Cost += computeDomSubtreeCost(*DT[SuccBB], BBCostMap, DTCostMap); | ||||||||
| 2899 | assert(Cost <= LoopCost &&((void)0) | ||||||||
| 2900 | "Non-duplicated cost should never exceed total loop cost!")((void)0); | ||||||||
| 2901 | } | ||||||||
| 2902 | } | ||||||||
| 2903 | |||||||||
| 2904 | // Now scale the cost by the number of unique successors minus one. We | ||||||||
| 2905 | // subtract one because there is already at least one copy of the entire | ||||||||
| 2906 | // loop. This is computing the new cost of unswitching a condition. | ||||||||
| 2907 | // Note that guards always have 2 unique successors that are implicit and | ||||||||
| 2908 | // will be materialized if we decide to unswitch it. | ||||||||
| 2909 | int SuccessorsCount = isGuard(&TI) ? 2 : Visited.size(); | ||||||||
| 2910 | assert(SuccessorsCount > 1 &&((void)0) | ||||||||
| 2911 | "Cannot unswitch a condition without multiple distinct successors!")((void)0); | ||||||||
| 2912 | return (LoopCost - Cost) * (SuccessorsCount - 1); | ||||||||
| 2913 | }; | ||||||||
| 2914 | Instruction *BestUnswitchTI = nullptr; | ||||||||
| 2915 | InstructionCost BestUnswitchCost = 0; | ||||||||
| 2916 | ArrayRef<Value *> BestUnswitchInvariants; | ||||||||
| 2917 | for (auto &TerminatorAndInvariants : UnswitchCandidates) { | ||||||||
| 2918 | Instruction &TI = *TerminatorAndInvariants.first; | ||||||||
| 2919 | ArrayRef<Value *> Invariants = TerminatorAndInvariants.second; | ||||||||
| 2920 | BranchInst *BI = dyn_cast<BranchInst>(&TI); | ||||||||
| 2921 | InstructionCost CandidateCost = ComputeUnswitchedCost( | ||||||||
| 2922 | TI, /*FullUnswitch*/ !BI || (Invariants.size() == 1 && | ||||||||
| 2923 | Invariants[0] == BI->getCondition())); | ||||||||
| 2924 | // Calculate cost multiplier which is a tool to limit potentially | ||||||||
| 2925 | // exponential behavior of loop-unswitch. | ||||||||
| 2926 | if (EnableUnswitchCostMultiplier) { | ||||||||
| 2927 | int CostMultiplier = | ||||||||
| 2928 | CalculateUnswitchCostMultiplier(TI, L, LI, DT, UnswitchCandidates); | ||||||||
| 2929 | assert(((void)0) | ||||||||
| 2930 | (CostMultiplier > 0 && CostMultiplier <= UnswitchThreshold) &&((void)0) | ||||||||
| 2931 | "cost multiplier needs to be in the range of 1..UnswitchThreshold")((void)0); | ||||||||
| 2932 | CandidateCost *= CostMultiplier; | ||||||||
| 2933 | LLVM_DEBUG(dbgs() << " Computed cost of " << CandidateCostdo { } while (false) | ||||||||
| 2934 | << " (multiplier: " << CostMultiplier << ")"do { } while (false) | ||||||||
| 2935 | << " for unswitch candidate: " << TI << "\n")do { } while (false); | ||||||||
| 2936 | } else { | ||||||||
| 2937 | LLVM_DEBUG(dbgs() << " Computed cost of " << CandidateCostdo { } while (false) | ||||||||
| 2938 | << " for unswitch candidate: " << TI << "\n")do { } while (false); | ||||||||
| 2939 | } | ||||||||
| 2940 | |||||||||
| 2941 | if (!BestUnswitchTI || CandidateCost < BestUnswitchCost) { | ||||||||
| 2942 | BestUnswitchTI = &TI; | ||||||||
| 2943 | BestUnswitchCost = CandidateCost; | ||||||||
| 2944 | BestUnswitchInvariants = Invariants; | ||||||||
| 2945 | } | ||||||||
| 2946 | } | ||||||||
| 2947 | assert(BestUnswitchTI && "Failed to find loop unswitch candidate")((void)0); | ||||||||
| 2948 | |||||||||
| 2949 | if (BestUnswitchCost >= UnswitchThreshold) { | ||||||||
| 2950 | LLVM_DEBUG(dbgs() << "Cannot unswitch, lowest cost found: "do { } while (false) | ||||||||
| 2951 | << BestUnswitchCost << "\n")do { } while (false); | ||||||||
| 2952 | return false; | ||||||||
| 2953 | } | ||||||||
| 2954 | |||||||||
| 2955 | if (BestUnswitchTI
| ||||||||
| 2956 | PartialIVInfo.InstToDuplicate.clear(); | ||||||||
| 2957 | |||||||||
| 2958 | // If the best candidate is a guard, turn it into a branch. | ||||||||
| 2959 | if (isGuard(BestUnswitchTI)) | ||||||||
| 2960 | BestUnswitchTI = turnGuardIntoBranch(cast<IntrinsicInst>(BestUnswitchTI), L, | ||||||||
| 2961 | ExitBlocks, DT, LI, MSSAU); | ||||||||
| 2962 | |||||||||
| 2963 | LLVM_DEBUG(dbgs() << " Unswitching non-trivial (cost = "do { } while (false) | ||||||||
| 2964 | << BestUnswitchCost << ") terminator: " << *BestUnswitchTIdo { } while (false) | ||||||||
| 2965 | << "\n")do { } while (false); | ||||||||
| 2966 | unswitchNontrivialInvariants(L, *BestUnswitchTI, BestUnswitchInvariants, | ||||||||
| |||||||||
| 2967 | ExitBlocks, PartialIVInfo, DT, LI, AC, | ||||||||
| 2968 | UnswitchCB, SE, MSSAU, DestroyLoopCB); | ||||||||
| 2969 | return true; | ||||||||
| 2970 | } | ||||||||
| 2971 | |||||||||
| 2972 | /// Unswitch control flow predicated on loop invariant conditions. | ||||||||
| 2973 | /// | ||||||||
| 2974 | /// This first hoists all branches or switches which are trivial (IE, do not | ||||||||
| 2975 | /// require duplicating any part of the loop) out of the loop body. It then | ||||||||
| 2976 | /// looks at other loop invariant control flows and tries to unswitch those as | ||||||||
| 2977 | /// well by cloning the loop if the result is small enough. | ||||||||
| 2978 | /// | ||||||||
| 2979 | /// The `DT`, `LI`, `AC`, `AA`, `TTI` parameters are required analyses that are | ||||||||
| 2980 | /// also updated based on the unswitch. The `MSSA` analysis is also updated if | ||||||||
| 2981 | /// valid (i.e. its use is enabled). | ||||||||
| 2982 | /// | ||||||||
| 2983 | /// If either `NonTrivial` is true or the flag `EnableNonTrivialUnswitch` is | ||||||||
| 2984 | /// true, we will attempt to do non-trivial unswitching as well as trivial | ||||||||
| 2985 | /// unswitching. | ||||||||
| 2986 | /// | ||||||||
| 2987 | /// The `UnswitchCB` callback provided will be run after unswitching is | ||||||||
| 2988 | /// complete, with the first parameter set to `true` if the provided loop | ||||||||
| 2989 | /// remains a loop, and a list of new sibling loops created. | ||||||||
| 2990 | /// | ||||||||
| 2991 | /// If `SE` is non-null, we will update that analysis based on the unswitching | ||||||||
| 2992 | /// done. | ||||||||
| 2993 | static bool | ||||||||
| 2994 | unswitchLoop(Loop &L, DominatorTree &DT, LoopInfo &LI, AssumptionCache &AC, | ||||||||
| 2995 | AAResults &AA, TargetTransformInfo &TTI, bool Trivial, | ||||||||
| 2996 | bool NonTrivial, | ||||||||
| 2997 | function_ref<void(bool, bool, ArrayRef<Loop *>)> UnswitchCB, | ||||||||
| 2998 | ScalarEvolution *SE, MemorySSAUpdater *MSSAU, | ||||||||
| 2999 | function_ref<void(Loop &, StringRef)> DestroyLoopCB) { | ||||||||
| 3000 | assert(L.isRecursivelyLCSSAForm(DT, LI) &&((void)0) | ||||||||
| 3001 | "Loops must be in LCSSA form before unswitching.")((void)0); | ||||||||
| 3002 | |||||||||
| 3003 | // Must be in loop simplified form: we need a preheader and dedicated exits. | ||||||||
| 3004 | if (!L.isLoopSimplifyForm()) | ||||||||
| 3005 | return false; | ||||||||
| 3006 | |||||||||
| 3007 | // Try trivial unswitch first before loop over other basic blocks in the loop. | ||||||||
| 3008 | if (Trivial && unswitchAllTrivialConditions(L, DT, LI, SE, MSSAU)) { | ||||||||
| 3009 | // If we unswitched successfully we will want to clean up the loop before | ||||||||
| 3010 | // processing it further so just mark it as unswitched and return. | ||||||||
| 3011 | UnswitchCB(/*CurrentLoopValid*/ true, false, {}); | ||||||||
| 3012 | return true; | ||||||||
| 3013 | } | ||||||||
| 3014 | |||||||||
| 3015 | // Check whether we should continue with non-trivial conditions. | ||||||||
| 3016 | // EnableNonTrivialUnswitch: Global variable that forces non-trivial | ||||||||
| 3017 | // unswitching for testing and debugging. | ||||||||
| 3018 | // NonTrivial: Parameter that enables non-trivial unswitching for this | ||||||||
| 3019 | // invocation of the transform. But this should be allowed only | ||||||||
| 3020 | // for targets without branch divergence. | ||||||||
| 3021 | // | ||||||||
| 3022 | // FIXME: If divergence analysis becomes available to a loop | ||||||||
| 3023 | // transform, we should allow unswitching for non-trivial uniform | ||||||||
| 3024 | // branches even on targets that have divergence. | ||||||||
| 3025 | // https://bugs.llvm.org/show_bug.cgi?id=48819 | ||||||||
| 3026 | bool ContinueWithNonTrivial = | ||||||||
| 3027 | EnableNonTrivialUnswitch || (NonTrivial && !TTI.hasBranchDivergence()); | ||||||||
| 3028 | if (!ContinueWithNonTrivial) | ||||||||
| 3029 | return false; | ||||||||
| 3030 | |||||||||
| 3031 | // Skip non-trivial unswitching for optsize functions. | ||||||||
| 3032 | if (L.getHeader()->getParent()->hasOptSize()) | ||||||||
| 3033 | return false; | ||||||||
| 3034 | |||||||||
| 3035 | // Skip non-trivial unswitching for loops that cannot be cloned. | ||||||||
| 3036 | if (!L.isSafeToClone()) | ||||||||
| 3037 | return false; | ||||||||
| 3038 | |||||||||
| 3039 | // For non-trivial unswitching, because it often creates new loops, we rely on | ||||||||
| 3040 | // the pass manager to iterate on the loops rather than trying to immediately | ||||||||
| 3041 | // reach a fixed point. There is no substantial advantage to iterating | ||||||||
| 3042 | // internally, and if any of the new loops are simplified enough to contain | ||||||||
| 3043 | // trivial unswitching we want to prefer those. | ||||||||
| 3044 | |||||||||
| 3045 | // Try to unswitch the best invariant condition. We prefer this full unswitch to | ||||||||
| 3046 | // a partial unswitch when possible below the threshold. | ||||||||
| 3047 | if (unswitchBestCondition(L, DT, LI, AC, AA, TTI, UnswitchCB, SE, MSSAU, | ||||||||
| 3048 | DestroyLoopCB)) | ||||||||
| 3049 | return true; | ||||||||
| 3050 | |||||||||
| 3051 | // No other opportunities to unswitch. | ||||||||
| 3052 | return false; | ||||||||
| 3053 | } | ||||||||
| 3054 | |||||||||
| 3055 | PreservedAnalyses SimpleLoopUnswitchPass::run(Loop &L, LoopAnalysisManager &AM, | ||||||||
| 3056 | LoopStandardAnalysisResults &AR, | ||||||||
| 3057 | LPMUpdater &U) { | ||||||||
| 3058 | Function &F = *L.getHeader()->getParent(); | ||||||||
| 3059 | (void)F; | ||||||||
| 3060 | |||||||||
| 3061 | LLVM_DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << Ldo { } while (false) | ||||||||
| 3062 | << "\n")do { } while (false); | ||||||||
| 3063 | |||||||||
| 3064 | // Save the current loop name in a variable so that we can report it even | ||||||||
| 3065 | // after it has been deleted. | ||||||||
| 3066 | std::string LoopName = std::string(L.getName()); | ||||||||
| 3067 | |||||||||
| 3068 | auto UnswitchCB = [&L, &U, &LoopName](bool CurrentLoopValid, | ||||||||
| 3069 | bool PartiallyInvariant, | ||||||||
| 3070 | ArrayRef<Loop *> NewLoops) { | ||||||||
| 3071 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | ||||||||
| 3072 | if (!NewLoops.empty()) | ||||||||
| 3073 | U.addSiblingLoops(NewLoops); | ||||||||
| 3074 | |||||||||
| 3075 | // If the current loop remains valid, we should revisit it to catch any | ||||||||
| 3076 | // other unswitch opportunities. Otherwise, we need to mark it as deleted. | ||||||||
| 3077 | if (CurrentLoopValid) { | ||||||||
| 3078 | if (PartiallyInvariant) { | ||||||||
| 3079 | // Mark the new loop as partially unswitched, to avoid unswitching on | ||||||||
| 3080 | // the same condition again. | ||||||||
| 3081 | auto &Context = L.getHeader()->getContext(); | ||||||||
| 3082 | MDNode *DisableUnswitchMD = MDNode::get( | ||||||||
| 3083 | Context, | ||||||||
| 3084 | MDString::get(Context, "llvm.loop.unswitch.partial.disable")); | ||||||||
| 3085 | MDNode *NewLoopID = makePostTransformationMetadata( | ||||||||
| 3086 | Context, L.getLoopID(), {"llvm.loop.unswitch.partial"}, | ||||||||
| 3087 | {DisableUnswitchMD}); | ||||||||
| 3088 | L.setLoopID(NewLoopID); | ||||||||
| 3089 | } else | ||||||||
| 3090 | U.revisitCurrentLoop(); | ||||||||
| 3091 | } else | ||||||||
| 3092 | U.markLoopAsDeleted(L, LoopName); | ||||||||
| 3093 | }; | ||||||||
| 3094 | |||||||||
| 3095 | auto DestroyLoopCB = [&U](Loop &L, StringRef Name) { | ||||||||
| 3096 | U.markLoopAsDeleted(L, Name); | ||||||||
| 3097 | }; | ||||||||
| 3098 | |||||||||
| 3099 | Optional<MemorySSAUpdater> MSSAU; | ||||||||
| 3100 | if (AR.MSSA) { | ||||||||
| 3101 | MSSAU = MemorySSAUpdater(AR.MSSA); | ||||||||
| 3102 | if (VerifyMemorySSA) | ||||||||
| 3103 | AR.MSSA->verifyMemorySSA(); | ||||||||
| 3104 | } | ||||||||
| 3105 | if (!unswitchLoop(L, AR.DT, AR.LI, AR.AC, AR.AA, AR.TTI, Trivial, NonTrivial, | ||||||||
| 3106 | UnswitchCB, &AR.SE, | ||||||||
| 3107 | MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, | ||||||||
| 3108 | DestroyLoopCB)) | ||||||||
| 3109 | return PreservedAnalyses::all(); | ||||||||
| 3110 | |||||||||
| 3111 | if (AR.MSSA && VerifyMemorySSA) | ||||||||
| 3112 | AR.MSSA->verifyMemorySSA(); | ||||||||
| 3113 | |||||||||
| 3114 | // Historically this pass has had issues with the dominator tree so verify it | ||||||||
| 3115 | // in asserts builds. | ||||||||
| 3116 | assert(AR.DT.verify(DominatorTree::VerificationLevel::Fast))((void)0); | ||||||||
| 3117 | |||||||||
| 3118 | auto PA = getLoopPassPreservedAnalyses(); | ||||||||
| 3119 | if (AR.MSSA) | ||||||||
| 3120 | PA.preserve<MemorySSAAnalysis>(); | ||||||||
| 3121 | return PA; | ||||||||
| 3122 | } | ||||||||
| 3123 | |||||||||
| 3124 | namespace { | ||||||||
| 3125 | |||||||||
| 3126 | class SimpleLoopUnswitchLegacyPass : public LoopPass { | ||||||||
| 3127 | bool NonTrivial; | ||||||||
| 3128 | |||||||||
| 3129 | public: | ||||||||
| 3130 | static char ID; // Pass ID, replacement for typeid | ||||||||
| 3131 | |||||||||
| 3132 | explicit SimpleLoopUnswitchLegacyPass(bool NonTrivial = false) | ||||||||
| 3133 | : LoopPass(ID), NonTrivial(NonTrivial) { | ||||||||
| 3134 | initializeSimpleLoopUnswitchLegacyPassPass( | ||||||||
| 3135 | *PassRegistry::getPassRegistry()); | ||||||||
| 3136 | } | ||||||||
| 3137 | |||||||||
| 3138 | bool runOnLoop(Loop *L, LPPassManager &LPM) override; | ||||||||
| 3139 | |||||||||
| 3140 | void getAnalysisUsage(AnalysisUsage &AU) const override { | ||||||||
| 3141 | AU.addRequired<AssumptionCacheTracker>(); | ||||||||
| 3142 | AU.addRequired<TargetTransformInfoWrapperPass>(); | ||||||||
| 3143 | if (EnableMSSALoopDependency) { | ||||||||
| 3144 | AU.addRequired<MemorySSAWrapperPass>(); | ||||||||
| 3145 | AU.addPreserved<MemorySSAWrapperPass>(); | ||||||||
| 3146 | } | ||||||||
| 3147 | getLoopAnalysisUsage(AU); | ||||||||
| 3148 | } | ||||||||
| 3149 | }; | ||||||||
| 3150 | |||||||||
| 3151 | } // end anonymous namespace | ||||||||
| 3152 | |||||||||
| 3153 | bool SimpleLoopUnswitchLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) { | ||||||||
| 3154 | if (skipLoop(L)) | ||||||||
| 3155 | return false; | ||||||||
| 3156 | |||||||||
| 3157 | Function &F = *L->getHeader()->getParent(); | ||||||||
| 3158 | |||||||||
| 3159 | LLVM_DEBUG(dbgs() << "Unswitching loop in " << F.getName() << ": " << *Ldo { } while (false) | ||||||||
| 3160 | << "\n")do { } while (false); | ||||||||
| 3161 | |||||||||
| 3162 | auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); | ||||||||
| 3163 | auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); | ||||||||
| 3164 | auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); | ||||||||
| 3165 | auto &AA = getAnalysis<AAResultsWrapperPass>().getAAResults(); | ||||||||
| 3166 | auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F); | ||||||||
| 3167 | MemorySSA *MSSA = nullptr; | ||||||||
| 3168 | Optional<MemorySSAUpdater> MSSAU; | ||||||||
| 3169 | if (EnableMSSALoopDependency) { | ||||||||
| 3170 | MSSA = &getAnalysis<MemorySSAWrapperPass>().getMSSA(); | ||||||||
| 3171 | MSSAU = MemorySSAUpdater(MSSA); | ||||||||
| 3172 | } | ||||||||
| 3173 | |||||||||
| 3174 | auto *SEWP = getAnalysisIfAvailable<ScalarEvolutionWrapperPass>(); | ||||||||
| 3175 | auto *SE = SEWP ? &SEWP->getSE() : nullptr; | ||||||||
| 3176 | |||||||||
| 3177 | auto UnswitchCB = [&L, &LPM](bool CurrentLoopValid, bool PartiallyInvariant, | ||||||||
| 3178 | ArrayRef<Loop *> NewLoops) { | ||||||||
| 3179 | // If we did a non-trivial unswitch, we have added new (cloned) loops. | ||||||||
| 3180 | for (auto *NewL : NewLoops) | ||||||||
| 3181 | LPM.addLoop(*NewL); | ||||||||
| 3182 | |||||||||
| 3183 | // If the current loop remains valid, re-add it to the queue. This is | ||||||||
| 3184 | // a little wasteful as we'll finish processing the current loop as well, | ||||||||
| 3185 | // but it is the best we can do in the old PM. | ||||||||
| 3186 | if (CurrentLoopValid) { | ||||||||
| 3187 | // If the current loop has been unswitched using a partially invariant | ||||||||
| 3188 | // condition, we should not re-add the current loop to avoid unswitching | ||||||||
| 3189 | // on the same condition again. | ||||||||
| 3190 | if (!PartiallyInvariant) | ||||||||
| 3191 | LPM.addLoop(*L); | ||||||||
| 3192 | } else | ||||||||
| 3193 | LPM.markLoopAsDeleted(*L); | ||||||||
| 3194 | }; | ||||||||
| 3195 | |||||||||
| 3196 | auto DestroyLoopCB = [&LPM](Loop &L, StringRef /* Name */) { | ||||||||
| 3197 | LPM.markLoopAsDeleted(L); | ||||||||
| 3198 | }; | ||||||||
| 3199 | |||||||||
| 3200 | if (MSSA && VerifyMemorySSA) | ||||||||
| 3201 | MSSA->verifyMemorySSA(); | ||||||||
| 3202 | |||||||||
| 3203 | bool Changed = | ||||||||
| 3204 | unswitchLoop(*L, DT, LI, AC, AA, TTI, true, NonTrivial, UnswitchCB, SE, | ||||||||
| 3205 | MSSAU.hasValue() ? MSSAU.getPointer() : nullptr, | ||||||||
| 3206 | DestroyLoopCB); | ||||||||
| 3207 | |||||||||
| 3208 | if (MSSA && VerifyMemorySSA) | ||||||||
| 3209 | MSSA->verifyMemorySSA(); | ||||||||
| 3210 | |||||||||
| 3211 | // Historically this pass has had issues with the dominator tree so verify it | ||||||||
| 3212 | // in asserts builds. | ||||||||
| 3213 | assert(DT.verify(DominatorTree::VerificationLevel::Fast))((void)0); | ||||||||
| 3214 | |||||||||
| 3215 | return Changed; | ||||||||
| 3216 | } | ||||||||
| 3217 | |||||||||
| 3218 | char SimpleLoopUnswitchLegacyPass::ID = 0; | ||||||||
| 3219 | INITIALIZE_PASS_BEGIN(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | ||||||||
| 3220 | "Simple unswitch loops", false, false)static void *initializeSimpleLoopUnswitchLegacyPassPassOnce(PassRegistry &Registry) { | ||||||||
| 3221 | INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry); | ||||||||
| 3222 | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry); | ||||||||
| 3223 | INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry); | ||||||||
| 3224 | INITIALIZE_PASS_DEPENDENCY(LoopPass)initializeLoopPassPass(Registry); | ||||||||
| 3225 | INITIALIZE_PASS_DEPENDENCY(MemorySSAWrapperPass)initializeMemorySSAWrapperPassPass(Registry); | ||||||||
| 3226 | INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry); | ||||||||
| 3227 | INITIALIZE_PASS_END(SimpleLoopUnswitchLegacyPass, "simple-loop-unswitch",PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch" , &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag ; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry &Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag , initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry )); } | ||||||||
| 3228 | "Simple unswitch loops", false, false)PassInfo *PI = new PassInfo( "Simple unswitch loops", "simple-loop-unswitch" , &SimpleLoopUnswitchLegacyPass::ID, PassInfo::NormalCtor_t (callDefaultCtor<SimpleLoopUnswitchLegacyPass>), false, false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeSimpleLoopUnswitchLegacyPassPassFlag ; void llvm::initializeSimpleLoopUnswitchLegacyPassPass(PassRegistry &Registry) { llvm::call_once(InitializeSimpleLoopUnswitchLegacyPassPassFlag , initializeSimpleLoopUnswitchLegacyPassPassOnce, std::ref(Registry )); } | ||||||||
| 3229 | |||||||||
| 3230 | Pass *llvm::createSimpleLoopUnswitchLegacyPass(bool NonTrivial) { | ||||||||
| 3231 | return new SimpleLoopUnswitchLegacyPass(NonTrivial); | ||||||||
| 3232 | } |
| 1 | //===- llvm/ADT/SmallVector.h - 'Normally small' vectors --------*- C++ -*-===// |
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | // |
| 9 | // This file defines the SmallVector class. |
| 10 | // |
| 11 | //===----------------------------------------------------------------------===// |
| 12 | |
| 13 | #ifndef LLVM_ADT_SMALLVECTOR_H |
| 14 | #define LLVM_ADT_SMALLVECTOR_H |
| 15 | |
| 16 | #include "llvm/ADT/iterator_range.h" |
| 17 | #include "llvm/Support/Compiler.h" |
| 18 | #include "llvm/Support/ErrorHandling.h" |
| 19 | #include "llvm/Support/MemAlloc.h" |
| 20 | #include "llvm/Support/type_traits.h" |
| 21 | #include <algorithm> |
| 22 | #include <cassert> |
| 23 | #include <cstddef> |
| 24 | #include <cstdlib> |
| 25 | #include <cstring> |
| 26 | #include <functional> |
| 27 | #include <initializer_list> |
| 28 | #include <iterator> |
| 29 | #include <limits> |
| 30 | #include <memory> |
| 31 | #include <new> |
| 32 | #include <type_traits> |
| 33 | #include <utility> |
| 34 | |
| 35 | namespace llvm { |
| 36 | |
| 37 | /// This is all the stuff common to all SmallVectors. |
| 38 | /// |
| 39 | /// The template parameter specifies the type which should be used to hold the |
| 40 | /// Size and Capacity of the SmallVector, so it can be adjusted. |
| 41 | /// Using 32 bit size is desirable to shrink the size of the SmallVector. |
| 42 | /// Using 64 bit size is desirable for cases like SmallVector<char>, where a |
| 43 | /// 32 bit size would limit the vector to ~4GB. SmallVectors are used for |
| 44 | /// buffering bitcode output - which can exceed 4GB. |
| 45 | template <class Size_T> class SmallVectorBase { |
| 46 | protected: |
| 47 | void *BeginX; |
| 48 | Size_T Size = 0, Capacity; |
| 49 | |
| 50 | /// The maximum value of the Size_T used. |
| 51 | static constexpr size_t SizeTypeMax() { |
| 52 | return std::numeric_limits<Size_T>::max(); |
| 53 | } |
| 54 | |
| 55 | SmallVectorBase() = delete; |
| 56 | SmallVectorBase(void *FirstEl, size_t TotalCapacity) |
| 57 | : BeginX(FirstEl), Capacity(TotalCapacity) {} |
| 58 | |
| 59 | /// This is a helper for \a grow() that's out of line to reduce code |
| 60 | /// duplication. This function will report a fatal error if it can't grow at |
| 61 | /// least to \p MinSize. |
| 62 | void *mallocForGrow(size_t MinSize, size_t TSize, size_t &NewCapacity); |
| 63 | |
| 64 | /// This is an implementation of the grow() method which only works |
| 65 | /// on POD-like data types and is out of line to reduce code duplication. |
| 66 | /// This function will report a fatal error if it cannot increase capacity. |
| 67 | void grow_pod(void *FirstEl, size_t MinSize, size_t TSize); |
| 68 | |
| 69 | public: |
| 70 | size_t size() const { return Size; } |
| 71 | size_t capacity() const { return Capacity; } |
| 72 | |
| 73 | LLVM_NODISCARD[[clang::warn_unused_result]] bool empty() const { return !Size; } |
| 74 | |
| 75 | /// Set the array size to \p N, which the current array must have enough |
| 76 | /// capacity for. |
| 77 | /// |
| 78 | /// This does not construct or destroy any elements in the vector. |
| 79 | /// |
| 80 | /// Clients can use this in conjunction with capacity() to write past the end |
| 81 | /// of the buffer when they know that more elements are available, and only |
| 82 | /// update the size later. This avoids the cost of value initializing elements |
| 83 | /// which will only be overwritten. |
| 84 | void set_size(size_t N) { |
| 85 | assert(N <= capacity())((void)0); |
| 86 | Size = N; |
| 87 | } |
| 88 | }; |
| 89 | |
| 90 | template <class T> |
| 91 | using SmallVectorSizeType = |
| 92 | typename std::conditional<sizeof(T) < 4 && sizeof(void *) >= 8, uint64_t, |
| 93 | uint32_t>::type; |
| 94 | |
| 95 | /// Figure out the offset of the first element. |
| 96 | template <class T, typename = void> struct SmallVectorAlignmentAndSize { |
| 97 | alignas(SmallVectorBase<SmallVectorSizeType<T>>) char Base[sizeof( |
| 98 | SmallVectorBase<SmallVectorSizeType<T>>)]; |
| 99 | alignas(T) char FirstEl[sizeof(T)]; |
| 100 | }; |
| 101 | |
| 102 | /// This is the part of SmallVectorTemplateBase which does not depend on whether |
| 103 | /// the type T is a POD. The extra dummy template argument is used by ArrayRef |
| 104 | /// to avoid unnecessarily requiring T to be complete. |
| 105 | template <typename T, typename = void> |
| 106 | class SmallVectorTemplateCommon |
| 107 | : public SmallVectorBase<SmallVectorSizeType<T>> { |
| 108 | using Base = SmallVectorBase<SmallVectorSizeType<T>>; |
| 109 | |
| 110 | /// Find the address of the first element. For this pointer math to be valid |
| 111 | /// with small-size of 0 for T with lots of alignment, it's important that |
| 112 | /// SmallVectorStorage is properly-aligned even for small-size of 0. |
| 113 | void *getFirstEl() const { |
| 114 | return const_cast<void *>(reinterpret_cast<const void *>( |
| 115 | reinterpret_cast<const char *>(this) + |
| 116 | offsetof(SmallVectorAlignmentAndSize<T>, FirstEl)__builtin_offsetof(SmallVectorAlignmentAndSize<T>, FirstEl ))); |
| 117 | } |
| 118 | // Space after 'FirstEl' is clobbered, do not add any instance vars after it. |
| 119 | |
| 120 | protected: |
| 121 | SmallVectorTemplateCommon(size_t Size) : Base(getFirstEl(), Size) {} |
| 122 | |
| 123 | void grow_pod(size_t MinSize, size_t TSize) { |
| 124 | Base::grow_pod(getFirstEl(), MinSize, TSize); |
| 125 | } |
| 126 | |
| 127 | /// Return true if this is a smallvector which has not had dynamic |
| 128 | /// memory allocated for it. |
| 129 | bool isSmall() const { return this->BeginX == getFirstEl(); } |
| 130 | |
| 131 | /// Put this vector in a state of being small. |
| 132 | void resetToSmall() { |
| 133 | this->BeginX = getFirstEl(); |
| 134 | this->Size = this->Capacity = 0; // FIXME: Setting Capacity to 0 is suspect. |
| 135 | } |
| 136 | |
| 137 | /// Return true if V is an internal reference to the given range. |
| 138 | bool isReferenceToRange(const void *V, const void *First, const void *Last) const { |
| 139 | // Use std::less to avoid UB. |
| 140 | std::less<> LessThan; |
| 141 | return !LessThan(V, First) && LessThan(V, Last); |
| 142 | } |
| 143 | |
| 144 | /// Return true if V is an internal reference to this vector. |
| 145 | bool isReferenceToStorage(const void *V) const { |
| 146 | return isReferenceToRange(V, this->begin(), this->end()); |
| 147 | } |
| 148 | |
| 149 | /// Return true if First and Last form a valid (possibly empty) range in this |
| 150 | /// vector's storage. |
| 151 | bool isRangeInStorage(const void *First, const void *Last) const { |
| 152 | // Use std::less to avoid UB. |
| 153 | std::less<> LessThan; |
| 154 | return !LessThan(First, this->begin()) && !LessThan(Last, First) && |
| 155 | !LessThan(this->end(), Last); |
| 156 | } |
| 157 | |
| 158 | /// Return true unless Elt will be invalidated by resizing the vector to |
| 159 | /// NewSize. |
| 160 | bool isSafeToReferenceAfterResize(const void *Elt, size_t NewSize) { |
| 161 | // Past the end. |
| 162 | if (LLVM_LIKELY(!isReferenceToStorage(Elt))__builtin_expect((bool)(!isReferenceToStorage(Elt)), true)) |
| 163 | return true; |
| 164 | |
| 165 | // Return false if Elt will be destroyed by shrinking. |
| 166 | if (NewSize <= this->size()) |
| 167 | return Elt < this->begin() + NewSize; |
| 168 | |
| 169 | // Return false if we need to grow. |
| 170 | return NewSize <= this->capacity(); |
| 171 | } |
| 172 | |
| 173 | /// Check whether Elt will be invalidated by resizing the vector to NewSize. |
| 174 | void assertSafeToReferenceAfterResize(const void *Elt, size_t NewSize) { |
| 175 | assert(isSafeToReferenceAfterResize(Elt, NewSize) &&((void)0) |
| 176 | "Attempting to reference an element of the vector in an operation "((void)0) |
| 177 | "that invalidates it")((void)0); |
| 178 | } |
| 179 | |
| 180 | /// Check whether Elt will be invalidated by increasing the size of the |
| 181 | /// vector by N. |
| 182 | void assertSafeToAdd(const void *Elt, size_t N = 1) { |
| 183 | this->assertSafeToReferenceAfterResize(Elt, this->size() + N); |
| 184 | } |
| 185 | |
| 186 | /// Check whether any part of the range will be invalidated by clearing. |
| 187 | void assertSafeToReferenceAfterClear(const T *From, const T *To) { |
| 188 | if (From == To) |
| 189 | return; |
| 190 | this->assertSafeToReferenceAfterResize(From, 0); |
| 191 | this->assertSafeToReferenceAfterResize(To - 1, 0); |
| 192 | } |
| 193 | template < |
| 194 | class ItTy, |
| 195 | std::enable_if_t<!std::is_same<std::remove_const_t<ItTy>, T *>::value, |
| 196 | bool> = false> |
| 197 | void assertSafeToReferenceAfterClear(ItTy, ItTy) {} |
| 198 | |
| 199 | /// Check whether any part of the range will be invalidated by growing. |
| 200 | void assertSafeToAddRange(const T *From, const T *To) { |
| 201 | if (From == To) |
| 202 | return; |
| 203 | this->assertSafeToAdd(From, To - From); |
| 204 | this->assertSafeToAdd(To - 1, To - From); |
| 205 | } |
| 206 | template < |
| 207 | class ItTy, |
| 208 | std::enable_if_t<!std::is_same<std::remove_const_t<ItTy>, T *>::value, |
| 209 | bool> = false> |
| 210 | void assertSafeToAddRange(ItTy, ItTy) {} |
| 211 | |
| 212 | /// Reserve enough space to add one element, and return the updated element |
| 213 | /// pointer in case it was a reference to the storage. |
| 214 | template <class U> |
| 215 | static const T *reserveForParamAndGetAddressImpl(U *This, const T &Elt, |
| 216 | size_t N) { |
| 217 | size_t NewSize = This->size() + N; |
| 218 | if (LLVM_LIKELY(NewSize <= This->capacity())__builtin_expect((bool)(NewSize <= This->capacity()), true )) |
| 219 | return &Elt; |
| 220 | |
| 221 | bool ReferencesStorage = false; |
| 222 | int64_t Index = -1; |
| 223 | if (!U::TakesParamByValue) { |
| 224 | if (LLVM_UNLIKELY(This->isReferenceToStorage(&Elt))__builtin_expect((bool)(This->isReferenceToStorage(&Elt )), false)) { |
| 225 | ReferencesStorage = true; |
| 226 | Index = &Elt - This->begin(); |
| 227 | } |
| 228 | } |
| 229 | This->grow(NewSize); |
| 230 | return ReferencesStorage ? This->begin() + Index : &Elt; |
| 231 | } |
| 232 | |
| 233 | public: |
| 234 | using size_type = size_t; |
| 235 | using difference_type = ptrdiff_t; |
| 236 | using value_type = T; |
| 237 | using iterator = T *; |
| 238 | using const_iterator = const T *; |
| 239 | |
| 240 | using const_reverse_iterator = std::reverse_iterator<const_iterator>; |
| 241 | using reverse_iterator = std::reverse_iterator<iterator>; |
| 242 | |
| 243 | using reference = T &; |
| 244 | using const_reference = const T &; |
| 245 | using pointer = T *; |
| 246 | using const_pointer = const T *; |
| 247 | |
| 248 | using Base::capacity; |
| 249 | using Base::empty; |
| 250 | using Base::size; |
| 251 | |
| 252 | // forward iterator creation methods. |
| 253 | iterator begin() { return (iterator)this->BeginX; } |
| 254 | const_iterator begin() const { return (const_iterator)this->BeginX; } |
| 255 | iterator end() { return begin() + size(); } |
| 256 | const_iterator end() const { return begin() + size(); } |
| 257 | |
| 258 | // reverse iterator creation methods. |
| 259 | reverse_iterator rbegin() { return reverse_iterator(end()); } |
| 260 | const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); } |
| 261 | reverse_iterator rend() { return reverse_iterator(begin()); } |
| 262 | const_reverse_iterator rend() const { return const_reverse_iterator(begin());} |
| 263 | |
| 264 | size_type size_in_bytes() const { return size() * sizeof(T); } |
| 265 | size_type max_size() const { |
| 266 | return std::min(this->SizeTypeMax(), size_type(-1) / sizeof(T)); |
| 267 | } |
| 268 | |
| 269 | size_t capacity_in_bytes() const { return capacity() * sizeof(T); } |
| 270 | |
| 271 | /// Return a pointer to the vector's buffer, even if empty(). |
| 272 | pointer data() { return pointer(begin()); } |
| 273 | /// Return a pointer to the vector's buffer, even if empty(). |
| 274 | const_pointer data() const { return const_pointer(begin()); } |
| 275 | |
| 276 | reference operator[](size_type idx) { |
| 277 | assert(idx < size())((void)0); |
| 278 | return begin()[idx]; |
| 279 | } |
| 280 | const_reference operator[](size_type idx) const { |
| 281 | assert(idx < size())((void)0); |
| 282 | return begin()[idx]; |
| 283 | } |
| 284 | |
| 285 | reference front() { |
| 286 | assert(!empty())((void)0); |
| 287 | return begin()[0]; |
| 288 | } |
| 289 | const_reference front() const { |
| 290 | assert(!empty())((void)0); |
| 291 | return begin()[0]; |
| 292 | } |
| 293 | |
| 294 | reference back() { |
| 295 | assert(!empty())((void)0); |
| 296 | return end()[-1]; |
| 297 | } |
| 298 | const_reference back() const { |
| 299 | assert(!empty())((void)0); |
| 300 | return end()[-1]; |
| 301 | } |
| 302 | }; |
| 303 | |
| 304 | /// SmallVectorTemplateBase<TriviallyCopyable = false> - This is where we put |
| 305 | /// method implementations that are designed to work with non-trivial T's. |
| 306 | /// |
| 307 | /// We approximate is_trivially_copyable with trivial move/copy construction and |
| 308 | /// trivial destruction. While the standard doesn't specify that you're allowed |
| 309 | /// copy these types with memcpy, there is no way for the type to observe this. |
| 310 | /// This catches the important case of std::pair<POD, POD>, which is not |
| 311 | /// trivially assignable. |
| 312 | template <typename T, bool = (is_trivially_copy_constructible<T>::value) && |
| 313 | (is_trivially_move_constructible<T>::value) && |
| 314 | std::is_trivially_destructible<T>::value> |
| 315 | class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> { |
| 316 | friend class SmallVectorTemplateCommon<T>; |
| 317 | |
| 318 | protected: |
| 319 | static constexpr bool TakesParamByValue = false; |
| 320 | using ValueParamT = const T &; |
| 321 | |
| 322 | SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {} |
| 323 | |
| 324 | static void destroy_range(T *S, T *E) { |
| 325 | while (S != E) { |
| 326 | --E; |
| 327 | E->~T(); |
| 328 | } |
| 329 | } |
| 330 | |
| 331 | /// Move the range [I, E) into the uninitialized memory starting with "Dest", |
| 332 | /// constructing elements as needed. |
| 333 | template<typename It1, typename It2> |
| 334 | static void uninitialized_move(It1 I, It1 E, It2 Dest) { |
| 335 | std::uninitialized_copy(std::make_move_iterator(I), |
| 336 | std::make_move_iterator(E), Dest); |
| 337 | } |
| 338 | |
| 339 | /// Copy the range [I, E) onto the uninitialized memory starting with "Dest", |
| 340 | /// constructing elements as needed. |
| 341 | template<typename It1, typename It2> |
| 342 | static void uninitialized_copy(It1 I, It1 E, It2 Dest) { |
| 343 | std::uninitialized_copy(I, E, Dest); |
| 344 | } |
| 345 | |
| 346 | /// Grow the allocated memory (without initializing new elements), doubling |
| 347 | /// the size of the allocated memory. Guarantees space for at least one more |
| 348 | /// element, or MinSize more elements if specified. |
| 349 | void grow(size_t MinSize = 0); |
| 350 | |
| 351 | /// Create a new allocation big enough for \p MinSize and pass back its size |
| 352 | /// in \p NewCapacity. This is the first section of \a grow(). |
| 353 | T *mallocForGrow(size_t MinSize, size_t &NewCapacity) { |
| 354 | return static_cast<T *>( |
| 355 | SmallVectorBase<SmallVectorSizeType<T>>::mallocForGrow( |
| 356 | MinSize, sizeof(T), NewCapacity)); |
| 357 | } |
| 358 | |
| 359 | /// Move existing elements over to the new allocation \p NewElts, the middle |
| 360 | /// section of \a grow(). |
| 361 | void moveElementsForGrow(T *NewElts); |
| 362 | |
| 363 | /// Transfer ownership of the allocation, finishing up \a grow(). |
| 364 | void takeAllocationForGrow(T *NewElts, size_t NewCapacity); |
| 365 | |
| 366 | /// Reserve enough space to add one element, and return the updated element |
| 367 | /// pointer in case it was a reference to the storage. |
| 368 | const T *reserveForParamAndGetAddress(const T &Elt, size_t N = 1) { |
| 369 | return this->reserveForParamAndGetAddressImpl(this, Elt, N); |
| 370 | } |
| 371 | |
| 372 | /// Reserve enough space to add one element, and return the updated element |
| 373 | /// pointer in case it was a reference to the storage. |
| 374 | T *reserveForParamAndGetAddress(T &Elt, size_t N = 1) { |
| 375 | return const_cast<T *>( |
| 376 | this->reserveForParamAndGetAddressImpl(this, Elt, N)); |
| 377 | } |
| 378 | |
| 379 | static T &&forward_value_param(T &&V) { return std::move(V); } |
| 380 | static const T &forward_value_param(const T &V) { return V; } |
| 381 | |
| 382 | void growAndAssign(size_t NumElts, const T &Elt) { |
| 383 | // Grow manually in case Elt is an internal reference. |
| 384 | size_t NewCapacity; |
| 385 | T *NewElts = mallocForGrow(NumElts, NewCapacity); |
| 386 | std::uninitialized_fill_n(NewElts, NumElts, Elt); |
| 387 | this->destroy_range(this->begin(), this->end()); |
| 388 | takeAllocationForGrow(NewElts, NewCapacity); |
| 389 | this->set_size(NumElts); |
| 390 | } |
| 391 | |
| 392 | template <typename... ArgTypes> T &growAndEmplaceBack(ArgTypes &&... Args) { |
| 393 | // Grow manually in case one of Args is an internal reference. |
| 394 | size_t NewCapacity; |
| 395 | T *NewElts = mallocForGrow(0, NewCapacity); |
| 396 | ::new ((void *)(NewElts + this->size())) T(std::forward<ArgTypes>(Args)...); |
| 397 | moveElementsForGrow(NewElts); |
| 398 | takeAllocationForGrow(NewElts, NewCapacity); |
| 399 | this->set_size(this->size() + 1); |
| 400 | return this->back(); |
| 401 | } |
| 402 | |
| 403 | public: |
| 404 | void push_back(const T &Elt) { |
| 405 | const T *EltPtr = reserveForParamAndGetAddress(Elt); |
| 406 | ::new ((void *)this->end()) T(*EltPtr); |
| 407 | this->set_size(this->size() + 1); |
| 408 | } |
| 409 | |
| 410 | void push_back(T &&Elt) { |
| 411 | T *EltPtr = reserveForParamAndGetAddress(Elt); |
| 412 | ::new ((void *)this->end()) T(::std::move(*EltPtr)); |
| 413 | this->set_size(this->size() + 1); |
| 414 | } |
| 415 | |
| 416 | void pop_back() { |
| 417 | this->set_size(this->size() - 1); |
| 418 | this->end()->~T(); |
| 419 | } |
| 420 | }; |
| 421 | |
| 422 | // Define this out-of-line to dissuade the C++ compiler from inlining it. |
| 423 | template <typename T, bool TriviallyCopyable> |
| 424 | void SmallVectorTemplateBase<T, TriviallyCopyable>::grow(size_t MinSize) { |
| 425 | size_t NewCapacity; |
| 426 | T *NewElts = mallocForGrow(MinSize, NewCapacity); |
| 427 | moveElementsForGrow(NewElts); |
| 428 | takeAllocationForGrow(NewElts, NewCapacity); |
| 429 | } |
| 430 | |
| 431 | // Define this out-of-line to dissuade the C++ compiler from inlining it. |
| 432 | template <typename T, bool TriviallyCopyable> |
| 433 | void SmallVectorTemplateBase<T, TriviallyCopyable>::moveElementsForGrow( |
| 434 | T *NewElts) { |
| 435 | // Move the elements over. |
| 436 | this->uninitialized_move(this->begin(), this->end(), NewElts); |
| 437 | |
| 438 | // Destroy the original elements. |
| 439 | destroy_range(this->begin(), this->end()); |
| 440 | } |
| 441 | |
| 442 | // Define this out-of-line to dissuade the C++ compiler from inlining it. |
| 443 | template <typename T, bool TriviallyCopyable> |
| 444 | void SmallVectorTemplateBase<T, TriviallyCopyable>::takeAllocationForGrow( |
| 445 | T *NewElts, size_t NewCapacity) { |
| 446 | // If this wasn't grown from the inline copy, deallocate the old space. |
| 447 | if (!this->isSmall()) |
| 448 | free(this->begin()); |
| 449 | |
| 450 | this->BeginX = NewElts; |
| 451 | this->Capacity = NewCapacity; |
| 452 | } |
| 453 | |
| 454 | /// SmallVectorTemplateBase<TriviallyCopyable = true> - This is where we put |
| 455 | /// method implementations that are designed to work with trivially copyable |
| 456 | /// T's. This allows using memcpy in place of copy/move construction and |
| 457 | /// skipping destruction. |
| 458 | template <typename T> |
| 459 | class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> { |
| 460 | friend class SmallVectorTemplateCommon<T>; |
| 461 | |
| 462 | protected: |
| 463 | /// True if it's cheap enough to take parameters by value. Doing so avoids |
| 464 | /// overhead related to mitigations for reference invalidation. |
| 465 | static constexpr bool TakesParamByValue = sizeof(T) <= 2 * sizeof(void *); |
| 466 | |
| 467 | /// Either const T& or T, depending on whether it's cheap enough to take |
| 468 | /// parameters by value. |
| 469 | using ValueParamT = |
| 470 | typename std::conditional<TakesParamByValue, T, const T &>::type; |
| 471 | |
| 472 | SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {} |
| 473 | |
| 474 | // No need to do a destroy loop for POD's. |
| 475 | static void destroy_range(T *, T *) {} |
| 476 | |
| 477 | /// Move the range [I, E) onto the uninitialized memory |
| 478 | /// starting with "Dest", constructing elements into it as needed. |
| 479 | template<typename It1, typename It2> |
| 480 | static void uninitialized_move(It1 I, It1 E, It2 Dest) { |
| 481 | // Just do a copy. |
| 482 | uninitialized_copy(I, E, Dest); |
| 483 | } |
| 484 | |
| 485 | /// Copy the range [I, E) onto the uninitialized memory |
| 486 | /// starting with "Dest", constructing elements into it as needed. |
| 487 | template<typename It1, typename It2> |
| 488 | static void uninitialized_copy(It1 I, It1 E, It2 Dest) { |
| 489 | // Arbitrary iterator types; just use the basic implementation. |
| 490 | std::uninitialized_copy(I, E, Dest); |
| 491 | } |
| 492 | |
| 493 | /// Copy the range [I, E) onto the uninitialized memory |
| 494 | /// starting with "Dest", constructing elements into it as needed. |
| 495 | template <typename T1, typename T2> |
| 496 | static void uninitialized_copy( |
| 497 | T1 *I, T1 *E, T2 *Dest, |
| 498 | std::enable_if_t<std::is_same<typename std::remove_const<T1>::type, |
| 499 | T2>::value> * = nullptr) { |
| 500 | // Use memcpy for PODs iterated by pointers (which includes SmallVector |
| 501 | // iterators): std::uninitialized_copy optimizes to memmove, but we can |
| 502 | // use memcpy here. Note that I and E are iterators and thus might be |
| 503 | // invalid for memcpy if they are equal. |
| 504 | if (I != E) |
| 505 | memcpy(reinterpret_cast<void *>(Dest), I, (E - I) * sizeof(T)); |
| 506 | } |
| 507 | |
| 508 | /// Double the size of the allocated memory, guaranteeing space for at |
| 509 | /// least one more element or MinSize if specified. |
| 510 | void grow(size_t MinSize = 0) { this->grow_pod(MinSize, sizeof(T)); } |
| 511 | |
| 512 | /// Reserve enough space to add one element, and return the updated element |
| 513 | /// pointer in case it was a reference to the storage. |
| 514 | const T *reserveForParamAndGetAddress(const T &Elt, size_t N = 1) { |
| 515 | return this->reserveForParamAndGetAddressImpl(this, Elt, N); |
| 516 | } |
| 517 | |
| 518 | /// Reserve enough space to add one element, and return the updated element |
| 519 | /// pointer in case it was a reference to the storage. |
| 520 | T *reserveForParamAndGetAddress(T &Elt, size_t N = 1) { |
| 521 | return const_cast<T *>( |
| 522 | this->reserveForParamAndGetAddressImpl(this, Elt, N)); |
| 523 | } |
| 524 | |
| 525 | /// Copy \p V or return a reference, depending on \a ValueParamT. |
| 526 | static ValueParamT forward_value_param(ValueParamT V) { return V; } |
| 527 | |
| 528 | void growAndAssign(size_t NumElts, T Elt) { |
| 529 | // Elt has been copied in case it's an internal reference, side-stepping |
| 530 | // reference invalidation problems without losing the realloc optimization. |
| 531 | this->set_size(0); |
| 532 | this->grow(NumElts); |
| 533 | std::uninitialized_fill_n(this->begin(), NumElts, Elt); |
| 534 | this->set_size(NumElts); |
| 535 | } |
| 536 | |
| 537 | template <typename... ArgTypes> T &growAndEmplaceBack(ArgTypes &&... Args) { |
| 538 | // Use push_back with a copy in case Args has an internal reference, |
| 539 | // side-stepping reference invalidation problems without losing the realloc |
| 540 | // optimization. |
| 541 | push_back(T(std::forward<ArgTypes>(Args)...)); |
| 542 | return this->back(); |
| 543 | } |
| 544 | |
| 545 | public: |
| 546 | void push_back(ValueParamT Elt) { |
| 547 | const T *EltPtr = reserveForParamAndGetAddress(Elt); |
| 548 | memcpy(reinterpret_cast<void *>(this->end()), EltPtr, sizeof(T)); |
| 549 | this->set_size(this->size() + 1); |
| 550 | } |
| 551 | |
| 552 | void pop_back() { this->set_size(this->size() - 1); } |
| 553 | }; |
| 554 | |
| 555 | /// This class consists of common code factored out of the SmallVector class to |
| 556 | /// reduce code duplication based on the SmallVector 'N' template parameter. |
| 557 | template <typename T> |
| 558 | class SmallVectorImpl : public SmallVectorTemplateBase<T> { |
| 559 | using SuperClass = SmallVectorTemplateBase<T>; |
| 560 | |
| 561 | public: |
| 562 | using iterator = typename SuperClass::iterator; |
| 563 | using const_iterator = typename SuperClass::const_iterator; |
| 564 | using reference = typename SuperClass::reference; |
| 565 | using size_type = typename SuperClass::size_type; |
| 566 | |
| 567 | protected: |
| 568 | using SmallVectorTemplateBase<T>::TakesParamByValue; |
| 569 | using ValueParamT = typename SuperClass::ValueParamT; |
| 570 | |
| 571 | // Default ctor - Initialize to empty. |
| 572 | explicit SmallVectorImpl(unsigned N) |
| 573 | : SmallVectorTemplateBase<T>(N) {} |
| 574 | |
| 575 | public: |
| 576 | SmallVectorImpl(const SmallVectorImpl &) = delete; |
| 577 | |
| 578 | ~SmallVectorImpl() { |
| 579 | // Subclass has already destructed this vector's elements. |
| 580 | // If this wasn't grown from the inline copy, deallocate the old space. |
| 581 | if (!this->isSmall()) |
| 582 | free(this->begin()); |
| 583 | } |
| 584 | |
| 585 | void clear() { |
| 586 | this->destroy_range(this->begin(), this->end()); |
| 587 | this->Size = 0; |
| 588 | } |
| 589 | |
| 590 | private: |
| 591 | template <bool ForOverwrite> void resizeImpl(size_type N) { |
| 592 | if (N < this->size()) { |
| 593 | this->pop_back_n(this->size() - N); |
| 594 | } else if (N > this->size()) { |
| 595 | this->reserve(N); |
| 596 | for (auto I = this->end(), E = this->begin() + N; I != E; ++I) |
| 597 | if (ForOverwrite) |
| 598 | new (&*I) T; |
| 599 | else |
| 600 | new (&*I) T(); |
| 601 | this->set_size(N); |
| 602 | } |
| 603 | } |
| 604 | |
| 605 | public: |
| 606 | void resize(size_type N) { resizeImpl<false>(N); } |
| 607 | |
| 608 | /// Like resize, but \ref T is POD, the new values won't be initialized. |
| 609 | void resize_for_overwrite(size_type N) { resizeImpl<true>(N); } |
| 610 | |
| 611 | void resize(size_type N, ValueParamT NV) { |
| 612 | if (N == this->size()) |
| 613 | return; |
| 614 | |
| 615 | if (N < this->size()) { |
| 616 | this->pop_back_n(this->size() - N); |
| 617 | return; |
| 618 | } |
| 619 | |
| 620 | // N > this->size(). Defer to append. |
| 621 | this->append(N - this->size(), NV); |
| 622 | } |
| 623 | |
| 624 | void reserve(size_type N) { |
| 625 | if (this->capacity() < N) |
| 626 | this->grow(N); |
| 627 | } |
| 628 | |
| 629 | void pop_back_n(size_type NumItems) { |
| 630 | assert(this->size() >= NumItems)((void)0); |
| 631 | this->destroy_range(this->end() - NumItems, this->end()); |
| 632 | this->set_size(this->size() - NumItems); |
| 633 | } |
| 634 | |
| 635 | LLVM_NODISCARD[[clang::warn_unused_result]] T pop_back_val() { |
| 636 | T Result = ::std::move(this->back()); |
| 637 | this->pop_back(); |
| 638 | return Result; |
| 639 | } |
| 640 | |
| 641 | void swap(SmallVectorImpl &RHS); |
| 642 | |
| 643 | /// Add the specified range to the end of the SmallVector. |
| 644 | template <typename in_iter, |
| 645 | typename = std::enable_if_t<std::is_convertible< |
| 646 | typename std::iterator_traits<in_iter>::iterator_category, |
| 647 | std::input_iterator_tag>::value>> |
| 648 | void append(in_iter in_start, in_iter in_end) { |
| 649 | this->assertSafeToAddRange(in_start, in_end); |
| 650 | size_type NumInputs = std::distance(in_start, in_end); |
| 651 | this->reserve(this->size() + NumInputs); |
| 652 | this->uninitialized_copy(in_start, in_end, this->end()); |
| 653 | this->set_size(this->size() + NumInputs); |
| 654 | } |
| 655 | |
| 656 | /// Append \p NumInputs copies of \p Elt to the end. |
| 657 | void append(size_type NumInputs, ValueParamT Elt) { |
| 658 | const T *EltPtr = this->reserveForParamAndGetAddress(Elt, NumInputs); |
| 659 | std::uninitialized_fill_n(this->end(), NumInputs, *EltPtr); |
| 660 | this->set_size(this->size() + NumInputs); |
| 661 | } |
| 662 | |
| 663 | void append(std::initializer_list<T> IL) { |
| 664 | append(IL.begin(), IL.end()); |
| 665 | } |
| 666 | |
| 667 | void append(const SmallVectorImpl &RHS) { append(RHS.begin(), RHS.end()); } |
| 668 | |
| 669 | void assign(size_type NumElts, ValueParamT Elt) { |
| 670 | // Note that Elt could be an internal reference. |
| 671 | if (NumElts > this->capacity()) { |
| 672 | this->growAndAssign(NumElts, Elt); |
| 673 | return; |
| 674 | } |
| 675 | |
| 676 | // Assign over existing elements. |
| 677 | std::fill_n(this->begin(), std::min(NumElts, this->size()), Elt); |
| 678 | if (NumElts > this->size()) |
| 679 | std::uninitialized_fill_n(this->end(), NumElts - this->size(), Elt); |
| 680 | else if (NumElts < this->size()) |
| 681 | this->destroy_range(this->begin() + NumElts, this->end()); |
| 682 | this->set_size(NumElts); |
| 683 | } |
| 684 | |
| 685 | // FIXME: Consider assigning over existing elements, rather than clearing & |
| 686 | // re-initializing them - for all assign(...) variants. |
| 687 | |
| 688 | template <typename in_iter, |
| 689 | typename = std::enable_if_t<std::is_convertible< |
| 690 | typename std::iterator_traits<in_iter>::iterator_category, |
| 691 | std::input_iterator_tag>::value>> |
| 692 | void assign(in_iter in_start, in_iter in_end) { |
| 693 | this->assertSafeToReferenceAfterClear(in_start, in_end); |
| 694 | clear(); |
| 695 | append(in_start, in_end); |
| 696 | } |
| 697 | |
| 698 | void assign(std::initializer_list<T> IL) { |
| 699 | clear(); |
| 700 | append(IL); |
| 701 | } |
| 702 | |
| 703 | void assign(const SmallVectorImpl &RHS) { assign(RHS.begin(), RHS.end()); } |
| 704 | |
| 705 | iterator erase(const_iterator CI) { |
| 706 | // Just cast away constness because this is a non-const member function. |
| 707 | iterator I = const_cast<iterator>(CI); |
| 708 | |
| 709 | assert(this->isReferenceToStorage(CI) && "Iterator to erase is out of bounds.")((void)0); |
| 710 | |
| 711 | iterator N = I; |
| 712 | // Shift all elts down one. |
| 713 | std::move(I+1, this->end(), I); |
| 714 | // Drop the last elt. |
| 715 | this->pop_back(); |
| 716 | return(N); |
| 717 | } |
| 718 | |
| 719 | iterator erase(const_iterator CS, const_iterator CE) { |
| 720 | // Just cast away constness because this is a non-const member function. |
| 721 | iterator S = const_cast<iterator>(CS); |
| 722 | iterator E = const_cast<iterator>(CE); |
| 723 | |
| 724 | assert(this->isRangeInStorage(S, E) && "Range to erase is out of bounds.")((void)0); |
| 725 | |
| 726 | iterator N = S; |
| 727 | // Shift all elts down. |
| 728 | iterator I = std::move(E, this->end(), S); |
| 729 | // Drop the last elts. |
| 730 | this->destroy_range(I, this->end()); |
| 731 | this->set_size(I - this->begin()); |
| 732 | return(N); |
| 733 | } |
| 734 | |
| 735 | private: |
| 736 | template <class ArgType> iterator insert_one_impl(iterator I, ArgType &&Elt) { |
| 737 | // Callers ensure that ArgType is derived from T. |
| 738 | static_assert( |
| 739 | std::is_same<std::remove_const_t<std::remove_reference_t<ArgType>>, |
| 740 | T>::value, |
| 741 | "ArgType must be derived from T!"); |
| 742 | |
| 743 | if (I == this->end()) { // Important special case for empty vector. |
| 744 | this->push_back(::std::forward<ArgType>(Elt)); |
| 745 | return this->end()-1; |
| 746 | } |
| 747 | |
| 748 | assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.")((void)0); |
| 749 | |
| 750 | // Grow if necessary. |
| 751 | size_t Index = I - this->begin(); |
| 752 | std::remove_reference_t<ArgType> *EltPtr = |
| 753 | this->reserveForParamAndGetAddress(Elt); |
| 754 | I = this->begin() + Index; |
| 755 | |
| 756 | ::new ((void*) this->end()) T(::std::move(this->back())); |
| 757 | // Push everything else over. |
| 758 | std::move_backward(I, this->end()-1, this->end()); |
| 759 | this->set_size(this->size() + 1); |
| 760 | |
| 761 | // If we just moved the element we're inserting, be sure to update |
| 762 | // the reference (never happens if TakesParamByValue). |
| 763 | static_assert(!TakesParamByValue || std::is_same<ArgType, T>::value, |
| 764 | "ArgType must be 'T' when taking by value!"); |
| 765 | if (!TakesParamByValue && this->isReferenceToRange(EltPtr, I, this->end())) |
| 766 | ++EltPtr; |
| 767 | |
| 768 | *I = ::std::forward<ArgType>(*EltPtr); |
| 769 | return I; |
| 770 | } |
| 771 | |
| 772 | public: |
| 773 | iterator insert(iterator I, T &&Elt) { |
| 774 | return insert_one_impl(I, this->forward_value_param(std::move(Elt))); |
| 775 | } |
| 776 | |
| 777 | iterator insert(iterator I, const T &Elt) { |
| 778 | return insert_one_impl(I, this->forward_value_param(Elt)); |
| 779 | } |
| 780 | |
| 781 | iterator insert(iterator I, size_type NumToInsert, ValueParamT Elt) { |
| 782 | // Convert iterator to elt# to avoid invalidating iterator when we reserve() |
| 783 | size_t InsertElt = I - this->begin(); |
| 784 | |
| 785 | if (I == this->end()) { // Important special case for empty vector. |
| 786 | append(NumToInsert, Elt); |
| 787 | return this->begin()+InsertElt; |
| 788 | } |
| 789 | |
| 790 | assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.")((void)0); |
| 791 | |
| 792 | // Ensure there is enough space, and get the (maybe updated) address of |
| 793 | // Elt. |
| 794 | const T *EltPtr = this->reserveForParamAndGetAddress(Elt, NumToInsert); |
| 795 | |
| 796 | // Uninvalidate the iterator. |
| 797 | I = this->begin()+InsertElt; |
| 798 | |
| 799 | // If there are more elements between the insertion point and the end of the |
| 800 | // range than there are being inserted, we can use a simple approach to |
| 801 | // insertion. Since we already reserved space, we know that this won't |
| 802 | // reallocate the vector. |
| 803 | if (size_t(this->end()-I) >= NumToInsert) { |
| 804 | T *OldEnd = this->end(); |
| 805 | append(std::move_iterator<iterator>(this->end() - NumToInsert), |
| 806 | std::move_iterator<iterator>(this->end())); |
| 807 | |
| 808 | // Copy the existing elements that get replaced. |
| 809 | std::move_backward(I, OldEnd-NumToInsert, OldEnd); |
| 810 | |
| 811 | // If we just moved the element we're inserting, be sure to update |
| 812 | // the reference (never happens if TakesParamByValue). |
| 813 | if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end()) |
| 814 | EltPtr += NumToInsert; |
| 815 | |
| 816 | std::fill_n(I, NumToInsert, *EltPtr); |
| 817 | return I; |
| 818 | } |
| 819 | |
| 820 | // Otherwise, we're inserting more elements than exist already, and we're |
| 821 | // not inserting at the end. |
| 822 | |
| 823 | // Move over the elements that we're about to overwrite. |
| 824 | T *OldEnd = this->end(); |
| 825 | this->set_size(this->size() + NumToInsert); |
| 826 | size_t NumOverwritten = OldEnd-I; |
| 827 | this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten); |
| 828 | |
| 829 | // If we just moved the element we're inserting, be sure to update |
| 830 | // the reference (never happens if TakesParamByValue). |
| 831 | if (!TakesParamByValue && I <= EltPtr && EltPtr < this->end()) |
| 832 | EltPtr += NumToInsert; |
| 833 | |
| 834 | // Replace the overwritten part. |
| 835 | std::fill_n(I, NumOverwritten, *EltPtr); |
| 836 | |
| 837 | // Insert the non-overwritten middle part. |
| 838 | std::uninitialized_fill_n(OldEnd, NumToInsert - NumOverwritten, *EltPtr); |
| 839 | return I; |
| 840 | } |
| 841 | |
| 842 | template <typename ItTy, |
| 843 | typename = std::enable_if_t<std::is_convertible< |
| 844 | typename std::iterator_traits<ItTy>::iterator_category, |
| 845 | std::input_iterator_tag>::value>> |
| 846 | iterator insert(iterator I, ItTy From, ItTy To) { |
| 847 | // Convert iterator to elt# to avoid invalidating iterator when we reserve() |
| 848 | size_t InsertElt = I - this->begin(); |
| 849 | |
| 850 | if (I == this->end()) { // Important special case for empty vector. |
| 851 | append(From, To); |
| 852 | return this->begin()+InsertElt; |
| 853 | } |
| 854 | |
| 855 | assert(this->isReferenceToStorage(I) && "Insertion iterator is out of bounds.")((void)0); |
| 856 | |
| 857 | // Check that the reserve that follows doesn't invalidate the iterators. |
| 858 | this->assertSafeToAddRange(From, To); |
| 859 | |
| 860 | size_t NumToInsert = std::distance(From, To); |
| 861 | |
| 862 | // Ensure there is enough space. |
| 863 | reserve(this->size() + NumToInsert); |
| 864 | |
| 865 | // Uninvalidate the iterator. |
| 866 | I = this->begin()+InsertElt; |
| 867 | |
| 868 | // If there are more elements between the insertion point and the end of the |
| 869 | // range than there are being inserted, we can use a simple approach to |
| 870 | // insertion. Since we already reserved space, we know that this won't |
| 871 | // reallocate the vector. |
| 872 | if (size_t(this->end()-I) >= NumToInsert) { |
| 873 | T *OldEnd = this->end(); |
| 874 | append(std::move_iterator<iterator>(this->end() - NumToInsert), |
| 875 | std::move_iterator<iterator>(this->end())); |
| 876 | |
| 877 | // Copy the existing elements that get replaced. |
| 878 | std::move_backward(I, OldEnd-NumToInsert, OldEnd); |
| 879 | |
| 880 | std::copy(From, To, I); |
| 881 | return I; |
| 882 | } |
| 883 | |
| 884 | // Otherwise, we're inserting more elements than exist already, and we're |
| 885 | // not inserting at the end. |
| 886 | |
| 887 | // Move over the elements that we're about to overwrite. |
| 888 | T *OldEnd = this->end(); |
| 889 | this->set_size(this->size() + NumToInsert); |
| 890 | size_t NumOverwritten = OldEnd-I; |
| 891 | this->uninitialized_move(I, OldEnd, this->end()-NumOverwritten); |
| 892 | |
| 893 | // Replace the overwritten part. |
| 894 | for (T *J = I; NumOverwritten > 0; --NumOverwritten) { |
| 895 | *J = *From; |
| 896 | ++J; ++From; |
| 897 | } |
| 898 | |
| 899 | // Insert the non-overwritten middle part. |
| 900 | this->uninitialized_copy(From, To, OldEnd); |
| 901 | return I; |
| 902 | } |
| 903 | |
| 904 | void insert(iterator I, std::initializer_list<T> IL) { |
| 905 | insert(I, IL.begin(), IL.end()); |
| 906 | } |
| 907 | |
| 908 | template <typename... ArgTypes> reference emplace_back(ArgTypes &&... Args) { |
| 909 | if (LLVM_UNLIKELY(this->size() >= this->capacity())__builtin_expect((bool)(this->size() >= this->capacity ()), false)) |
| 910 | return this->growAndEmplaceBack(std::forward<ArgTypes>(Args)...); |
| 911 | |
| 912 | ::new ((void *)this->end()) T(std::forward<ArgTypes>(Args)...); |
| 913 | this->set_size(this->size() + 1); |
| 914 | return this->back(); |
| 915 | } |
| 916 | |
| 917 | SmallVectorImpl &operator=(const SmallVectorImpl &RHS); |
| 918 | |
| 919 | SmallVectorImpl &operator=(SmallVectorImpl &&RHS); |
| 920 | |
| 921 | bool operator==(const SmallVectorImpl &RHS) const { |
| 922 | if (this->size() != RHS.size()) return false; |
| 923 | return std::equal(this->begin(), this->end(), RHS.begin()); |
| 924 | } |
| 925 | bool operator!=(const SmallVectorImpl &RHS) const { |
| 926 | return !(*this == RHS); |
| 927 | } |
| 928 | |
| 929 | bool operator<(const SmallVectorImpl &RHS) const { |
| 930 | return std::lexicographical_compare(this->begin(), this->end(), |
| 931 | RHS.begin(), RHS.end()); |
| 932 | } |
| 933 | }; |
| 934 | |
| 935 | template <typename T> |
| 936 | void SmallVectorImpl<T>::swap(SmallVectorImpl<T> &RHS) { |
| 937 | if (this == &RHS) return; |
| 938 | |
| 939 | // We can only avoid copying elements if neither vector is small. |
| 940 | if (!this->isSmall() && !RHS.isSmall()) { |
| 941 | std::swap(this->BeginX, RHS.BeginX); |
| 942 | std::swap(this->Size, RHS.Size); |
| 943 | std::swap(this->Capacity, RHS.Capacity); |
| 944 | return; |
| 945 | } |
| 946 | this->reserve(RHS.size()); |
| 947 | RHS.reserve(this->size()); |
| 948 | |
| 949 | // Swap the shared elements. |
| 950 | size_t NumShared = this->size(); |
| 951 | if (NumShared > RHS.size()) NumShared = RHS.size(); |
| 952 | for (size_type i = 0; i != NumShared; ++i) |
| 953 | std::swap((*this)[i], RHS[i]); |
| 954 | |
| 955 | // Copy over the extra elts. |
| 956 | if (this->size() > RHS.size()) { |
| 957 | size_t EltDiff = this->size() - RHS.size(); |
| 958 | this->uninitialized_copy(this->begin()+NumShared, this->end(), RHS.end()); |
| 959 | RHS.set_size(RHS.size() + EltDiff); |
| 960 | this->destroy_range(this->begin()+NumShared, this->end()); |
| 961 | this->set_size(NumShared); |
| 962 | } else if (RHS.size() > this->size()) { |
| 963 | size_t EltDiff = RHS.size() - this->size(); |
| 964 | this->uninitialized_copy(RHS.begin()+NumShared, RHS.end(), this->end()); |
| 965 | this->set_size(this->size() + EltDiff); |
| 966 | this->destroy_range(RHS.begin()+NumShared, RHS.end()); |
| 967 | RHS.set_size(NumShared); |
| 968 | } |
| 969 | } |
| 970 | |
| 971 | template <typename T> |
| 972 | SmallVectorImpl<T> &SmallVectorImpl<T>:: |
| 973 | operator=(const SmallVectorImpl<T> &RHS) { |
| 974 | // Avoid self-assignment. |
| 975 | if (this == &RHS) return *this; |
| 976 | |
| 977 | // If we already have sufficient space, assign the common elements, then |
| 978 | // destroy any excess. |
| 979 | size_t RHSSize = RHS.size(); |
| 980 | size_t CurSize = this->size(); |
| 981 | if (CurSize >= RHSSize) { |
| 982 | // Assign common elements. |
| 983 | iterator NewEnd; |
| 984 | if (RHSSize) |
| 985 | NewEnd = std::copy(RHS.begin(), RHS.begin()+RHSSize, this->begin()); |
| 986 | else |
| 987 | NewEnd = this->begin(); |
| 988 | |
| 989 | // Destroy excess elements. |
| 990 | this->destroy_range(NewEnd, this->end()); |
| 991 | |
| 992 | // Trim. |
| 993 | this->set_size(RHSSize); |
| 994 | return *this; |
| 995 | } |
| 996 | |
| 997 | // If we have to grow to have enough elements, destroy the current elements. |
| 998 | // This allows us to avoid copying them during the grow. |
| 999 | // FIXME: don't do this if they're efficiently moveable. |
| 1000 | if (this->capacity() < RHSSize) { |
| 1001 | // Destroy current elements. |
| 1002 | this->clear(); |
| 1003 | CurSize = 0; |
| 1004 | this->grow(RHSSize); |
| 1005 | } else if (CurSize) { |
| 1006 | // Otherwise, use assignment for the already-constructed elements. |
| 1007 | std::copy(RHS.begin(), RHS.begin()+CurSize, this->begin()); |
| 1008 | } |
| 1009 | |
| 1010 | // Copy construct the new elements in place. |
| 1011 | this->uninitialized_copy(RHS.begin()+CurSize, RHS.end(), |
| 1012 | this->begin()+CurSize); |
| 1013 | |
| 1014 | // Set end. |
| 1015 | this->set_size(RHSSize); |
| 1016 | return *this; |
| 1017 | } |
| 1018 | |
| 1019 | template <typename T> |
| 1020 | SmallVectorImpl<T> &SmallVectorImpl<T>::operator=(SmallVectorImpl<T> &&RHS) { |
| 1021 | // Avoid self-assignment. |
| 1022 | if (this == &RHS) return *this; |
| 1023 | |
| 1024 | // If the RHS isn't small, clear this vector and then steal its buffer. |
| 1025 | if (!RHS.isSmall()) { |
| 1026 | this->destroy_range(this->begin(), this->end()); |
| 1027 | if (!this->isSmall()) free(this->begin()); |
| 1028 | this->BeginX = RHS.BeginX; |
| 1029 | this->Size = RHS.Size; |
| 1030 | this->Capacity = RHS.Capacity; |
| 1031 | RHS.resetToSmall(); |
| 1032 | return *this; |
| 1033 | } |
| 1034 | |
| 1035 | // If we already have sufficient space, assign the common elements, then |
| 1036 | // destroy any excess. |
| 1037 | size_t RHSSize = RHS.size(); |
| 1038 | size_t CurSize = this->size(); |
| 1039 | if (CurSize >= RHSSize) { |
| 1040 | // Assign common elements. |
| 1041 | iterator NewEnd = this->begin(); |
| 1042 | if (RHSSize) |
| 1043 | NewEnd = std::move(RHS.begin(), RHS.end(), NewEnd); |
| 1044 | |
| 1045 | // Destroy excess elements and trim the bounds. |
| 1046 | this->destroy_range(NewEnd, this->end()); |
| 1047 | this->set_size(RHSSize); |
| 1048 | |
| 1049 | // Clear the RHS. |
| 1050 | RHS.clear(); |
| 1051 | |
| 1052 | return *this; |
| 1053 | } |
| 1054 | |
| 1055 | // If we have to grow to have enough elements, destroy the current elements. |
| 1056 | // This allows us to avoid copying them during the grow. |
| 1057 | // FIXME: this may not actually make any sense if we can efficiently move |
| 1058 | // elements. |
| 1059 | if (this->capacity() < RHSSize) { |
| 1060 | // Destroy current elements. |
| 1061 | this->clear(); |
| 1062 | CurSize = 0; |
| 1063 | this->grow(RHSSize); |
| 1064 | } else if (CurSize) { |
| 1065 | // Otherwise, use assignment for the already-constructed elements. |
| 1066 | std::move(RHS.begin(), RHS.begin()+CurSize, this->begin()); |
| 1067 | } |
| 1068 | |
| 1069 | // Move-construct the new elements in place. |
| 1070 | this->uninitialized_move(RHS.begin()+CurSize, RHS.end(), |
| 1071 | this->begin()+CurSize); |
| 1072 | |
| 1073 | // Set end. |
| 1074 | this->set_size(RHSSize); |
| 1075 | |
| 1076 | RHS.clear(); |
| 1077 | return *this; |
| 1078 | } |
| 1079 | |
| 1080 | /// Storage for the SmallVector elements. This is specialized for the N=0 case |
| 1081 | /// to avoid allocating unnecessary storage. |
| 1082 | template <typename T, unsigned N> |
| 1083 | struct SmallVectorStorage { |
| 1084 | alignas(T) char InlineElts[N * sizeof(T)]; |
| 1085 | }; |
| 1086 | |
| 1087 | /// We need the storage to be properly aligned even for small-size of 0 so that |
| 1088 | /// the pointer math in \a SmallVectorTemplateCommon::getFirstEl() is |
| 1089 | /// well-defined. |
| 1090 | template <typename T> struct alignas(T) SmallVectorStorage<T, 0> {}; |
| 1091 | |
| 1092 | /// Forward declaration of SmallVector so that |
| 1093 | /// calculateSmallVectorDefaultInlinedElements can reference |
| 1094 | /// `sizeof(SmallVector<T, 0>)`. |
| 1095 | template <typename T, unsigned N> class LLVM_GSL_OWNER[[gsl::Owner]] SmallVector; |
| 1096 | |
| 1097 | /// Helper class for calculating the default number of inline elements for |
| 1098 | /// `SmallVector<T>`. |
| 1099 | /// |
| 1100 | /// This should be migrated to a constexpr function when our minimum |
| 1101 | /// compiler support is enough for multi-statement constexpr functions. |
| 1102 | template <typename T> struct CalculateSmallVectorDefaultInlinedElements { |
| 1103 | // Parameter controlling the default number of inlined elements |
| 1104 | // for `SmallVector<T>`. |
| 1105 | // |
| 1106 | // The default number of inlined elements ensures that |
| 1107 | // 1. There is at least one inlined element. |
| 1108 | // 2. `sizeof(SmallVector<T>) <= kPreferredSmallVectorSizeof` unless |
| 1109 | // it contradicts 1. |
| 1110 | static constexpr size_t kPreferredSmallVectorSizeof = 64; |
| 1111 | |
| 1112 | // static_assert that sizeof(T) is not "too big". |
| 1113 | // |
| 1114 | // Because our policy guarantees at least one inlined element, it is possible |
| 1115 | // for an arbitrarily large inlined element to allocate an arbitrarily large |
| 1116 | // amount of inline storage. We generally consider it an antipattern for a |
| 1117 | // SmallVector to allocate an excessive amount of inline storage, so we want |
| 1118 | // to call attention to these cases and make sure that users are making an |
| 1119 | // intentional decision if they request a lot of inline storage. |
| 1120 | // |
| 1121 | // We want this assertion to trigger in pathological cases, but otherwise |
| 1122 | // not be too easy to hit. To accomplish that, the cutoff is actually somewhat |
| 1123 | // larger than kPreferredSmallVectorSizeof (otherwise, |
| 1124 | // `SmallVector<SmallVector<T>>` would be one easy way to trip it, and that |
| 1125 | // pattern seems useful in practice). |
| 1126 | // |
| 1127 | // One wrinkle is that this assertion is in theory non-portable, since |
| 1128 | // sizeof(T) is in general platform-dependent. However, we don't expect this |
| 1129 | // to be much of an issue, because most LLVM development happens on 64-bit |
| 1130 | // hosts, and therefore sizeof(T) is expected to *decrease* when compiled for |
| 1131 | // 32-bit hosts, dodging the issue. The reverse situation, where development |
| 1132 | // happens on a 32-bit host and then fails due to sizeof(T) *increasing* on a |
| 1133 | // 64-bit host, is expected to be very rare. |
| 1134 | static_assert( |
| 1135 | sizeof(T) <= 256, |
| 1136 | "You are trying to use a default number of inlined elements for " |
| 1137 | "`SmallVector<T>` but `sizeof(T)` is really big! Please use an " |
| 1138 | "explicit number of inlined elements with `SmallVector<T, N>` to make " |
| 1139 | "sure you really want that much inline storage."); |
| 1140 | |
| 1141 | // Discount the size of the header itself when calculating the maximum inline |
| 1142 | // bytes. |
| 1143 | static constexpr size_t PreferredInlineBytes = |
| 1144 | kPreferredSmallVectorSizeof - sizeof(SmallVector<T, 0>); |
| 1145 | static constexpr size_t NumElementsThatFit = PreferredInlineBytes / sizeof(T); |
| 1146 | static constexpr size_t value = |
| 1147 | NumElementsThatFit == 0 ? 1 : NumElementsThatFit; |
| 1148 | }; |
| 1149 | |
| 1150 | /// This is a 'vector' (really, a variable-sized array), optimized |
| 1151 | /// for the case when the array is small. It contains some number of elements |
| 1152 | /// in-place, which allows it to avoid heap allocation when the actual number of |
| 1153 | /// elements is below that threshold. This allows normal "small" cases to be |
| 1154 | /// fast without losing generality for large inputs. |
| 1155 | /// |
| 1156 | /// \note |
| 1157 | /// In the absence of a well-motivated choice for the number of inlined |
| 1158 | /// elements \p N, it is recommended to use \c SmallVector<T> (that is, |
| 1159 | /// omitting the \p N). This will choose a default number of inlined elements |
| 1160 | /// reasonable for allocation on the stack (for example, trying to keep \c |
| 1161 | /// sizeof(SmallVector<T>) around 64 bytes). |
| 1162 | /// |
| 1163 | /// \warning This does not attempt to be exception safe. |
| 1164 | /// |
| 1165 | /// \see https://llvm.org/docs/ProgrammersManual.html#llvm-adt-smallvector-h |
| 1166 | template <typename T, |
| 1167 | unsigned N = CalculateSmallVectorDefaultInlinedElements<T>::value> |
| 1168 | class LLVM_GSL_OWNER[[gsl::Owner]] SmallVector : public SmallVectorImpl<T>, |
| 1169 | SmallVectorStorage<T, N> { |
| 1170 | public: |
| 1171 | SmallVector() : SmallVectorImpl<T>(N) {} |
| 1172 | |
| 1173 | ~SmallVector() { |
| 1174 | // Destroy the constructed elements in the vector. |
| 1175 | this->destroy_range(this->begin(), this->end()); |
| 1176 | } |
| 1177 | |
| 1178 | explicit SmallVector(size_t Size, const T &Value = T()) |
| 1179 | : SmallVectorImpl<T>(N) { |
| 1180 | this->assign(Size, Value); |
| 1181 | } |
| 1182 | |
| 1183 | template <typename ItTy, |
| 1184 | typename = std::enable_if_t<std::is_convertible< |
| 1185 | typename std::iterator_traits<ItTy>::iterator_category, |
| 1186 | std::input_iterator_tag>::value>> |
| 1187 | SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(N) { |
| 1188 | this->append(S, E); |
| 1189 | } |
| 1190 | |
| 1191 | template <typename RangeTy> |
| 1192 | explicit SmallVector(const iterator_range<RangeTy> &R) |
| 1193 | : SmallVectorImpl<T>(N) { |
| 1194 | this->append(R.begin(), R.end()); |
| 1195 | } |
| 1196 | |
| 1197 | SmallVector(std::initializer_list<T> IL) : SmallVectorImpl<T>(N) { |
| 1198 | this->assign(IL); |
| 1199 | } |
| 1200 | |
| 1201 | SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(N) { |
| 1202 | if (!RHS.empty()) |
| 1203 | SmallVectorImpl<T>::operator=(RHS); |
| 1204 | } |
| 1205 | |
| 1206 | SmallVector &operator=(const SmallVector &RHS) { |
| 1207 | SmallVectorImpl<T>::operator=(RHS); |
| 1208 | return *this; |
| 1209 | } |
| 1210 | |
| 1211 | SmallVector(SmallVector &&RHS) : SmallVectorImpl<T>(N) { |
| 1212 | if (!RHS.empty()) |
| 1213 | SmallVectorImpl<T>::operator=(::std::move(RHS)); |
| 1214 | } |
| 1215 | |
| 1216 | SmallVector(SmallVectorImpl<T> &&RHS) : SmallVectorImpl<T>(N) { |
| 1217 | if (!RHS.empty()) |
| 1218 | SmallVectorImpl<T>::operator=(::std::move(RHS)); |
| 1219 | } |
| 1220 | |
| 1221 | SmallVector &operator=(SmallVector &&RHS) { |
| 1222 | SmallVectorImpl<T>::operator=(::std::move(RHS)); |
| 1223 | return *this; |
| 1224 | } |
| 1225 | |
| 1226 | SmallVector &operator=(SmallVectorImpl<T> &&RHS) { |
| 1227 | SmallVectorImpl<T>::operator=(::std::move(RHS)); |
| 1228 | return *this; |
| 1229 | } |
| 1230 | |
| 1231 | SmallVector &operator=(std::initializer_list<T> IL) { |
| 1232 | this->assign(IL); |
| 1233 | return *this; |
| 1234 | } |
| 1235 | }; |
| 1236 | |
| 1237 | template <typename T, unsigned N> |
| 1238 | inline size_t capacity_in_bytes(const SmallVector<T, N> &X) { |
| 1239 | return X.capacity_in_bytes(); |
| 1240 | } |
| 1241 | |
| 1242 | /// Given a range of type R, iterate the entire range and return a |
| 1243 | /// SmallVector with elements of the vector. This is useful, for example, |
| 1244 | /// when you want to iterate a range and then sort the results. |
| 1245 | template <unsigned Size, typename R> |
| 1246 | SmallVector<typename std::remove_const<typename std::remove_reference< |
| 1247 | decltype(*std::begin(std::declval<R &>()))>::type>::type, |
| 1248 | Size> |
| 1249 | to_vector(R &&Range) { |
| 1250 | return {std::begin(Range), std::end(Range)}; |
| 1251 | } |
| 1252 | |
| 1253 | } // end namespace llvm |
| 1254 | |
| 1255 | namespace std { |
| 1256 | |
| 1257 | /// Implement std::swap in terms of SmallVector swap. |
| 1258 | template<typename T> |
| 1259 | inline void |
| 1260 | swap(llvm::SmallVectorImpl<T> &LHS, llvm::SmallVectorImpl<T> &RHS) { |
| 1261 | LHS.swap(RHS); |
| 1262 | } |
| 1263 | |
| 1264 | /// Implement std::swap in terms of SmallVector swap. |
| 1265 | template<typename T, unsigned N> |
| 1266 | inline void |
| 1267 | swap(llvm::SmallVector<T, N> &LHS, llvm::SmallVector<T, N> &RHS) { |
| 1268 | LHS.swap(RHS); |
| 1269 | } |
| 1270 | |
| 1271 | } // end namespace std |
| 1272 | |
| 1273 | #endif // LLVM_ADT_SMALLVECTOR_H |
| 1 | //===-- Analysis/CFG.h - BasicBlock Analyses --------------------*- C++ -*-===// |
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | // |
| 9 | // This family of functions performs analyses on basic blocks, and instructions |
| 10 | // contained within basic blocks. |
| 11 | // |
| 12 | //===----------------------------------------------------------------------===// |
| 13 | |
| 14 | #ifndef LLVM_ANALYSIS_CFG_H |
| 15 | #define LLVM_ANALYSIS_CFG_H |
| 16 | |
| 17 | #include "llvm/ADT/GraphTraits.h" |
| 18 | #include "llvm/ADT/SmallPtrSet.h" |
| 19 | #include <utility> |
| 20 | |
| 21 | namespace llvm { |
| 22 | |
| 23 | class BasicBlock; |
| 24 | class DominatorTree; |
| 25 | class Function; |
| 26 | class Instruction; |
| 27 | class LoopInfo; |
| 28 | template <typename T> class SmallVectorImpl; |
| 29 | |
| 30 | /// Analyze the specified function to find all of the loop backedges in the |
| 31 | /// function and return them. This is a relatively cheap (compared to |
| 32 | /// computing dominators and loop info) analysis. |
| 33 | /// |
| 34 | /// The output is added to Result, as pairs of <from,to> edge info. |
| 35 | void FindFunctionBackedges( |
| 36 | const Function &F, |
| 37 | SmallVectorImpl<std::pair<const BasicBlock *, const BasicBlock *> > & |
| 38 | Result); |
| 39 | |
| 40 | /// Search for the specified successor of basic block BB and return its position |
| 41 | /// in the terminator instruction's list of successors. It is an error to call |
| 42 | /// this with a block that is not a successor. |
| 43 | unsigned GetSuccessorNumber(const BasicBlock *BB, const BasicBlock *Succ); |
| 44 | |
| 45 | /// Return true if the specified edge is a critical edge. Critical edges are |
| 46 | /// edges from a block with multiple successors to a block with multiple |
| 47 | /// predecessors. |
| 48 | /// |
| 49 | bool isCriticalEdge(const Instruction *TI, unsigned SuccNum, |
| 50 | bool AllowIdenticalEdges = false); |
| 51 | bool isCriticalEdge(const Instruction *TI, const BasicBlock *Succ, |
| 52 | bool AllowIdenticalEdges = false); |
| 53 | |
| 54 | /// Determine whether instruction 'To' is reachable from 'From', without passing |
| 55 | /// through any blocks in ExclusionSet, returning true if uncertain. |
| 56 | /// |
| 57 | /// Determine whether there is a path from From to To within a single function. |
| 58 | /// Returns false only if we can prove that once 'From' has been executed then |
| 59 | /// 'To' can not be executed. Conservatively returns true. |
| 60 | /// |
| 61 | /// This function is linear with respect to the number of blocks in the CFG, |
| 62 | /// walking down successors from From to reach To, with a fixed threshold. |
| 63 | /// Using DT or LI allows us to answer more quickly. LI reduces the cost of |
| 64 | /// an entire loop of any number of blocks to be the same as the cost of a |
| 65 | /// single block. DT reduces the cost by allowing the search to terminate when |
| 66 | /// we find a block that dominates the block containing 'To'. DT is most useful |
| 67 | /// on branchy code but not loops, and LI is most useful on code with loops but |
| 68 | /// does not help on branchy code outside loops. |
| 69 | bool isPotentiallyReachable( |
| 70 | const Instruction *From, const Instruction *To, |
| 71 | const SmallPtrSetImpl<BasicBlock *> *ExclusionSet = nullptr, |
| 72 | const DominatorTree *DT = nullptr, const LoopInfo *LI = nullptr); |
| 73 | |
| 74 | /// Determine whether block 'To' is reachable from 'From', returning |
| 75 | /// true if uncertain. |
| 76 | /// |
| 77 | /// Determine whether there is a path from From to To within a single function. |
| 78 | /// Returns false only if we can prove that once 'From' has been reached then |
| 79 | /// 'To' can not be executed. Conservatively returns true. |
| 80 | bool isPotentiallyReachable( |
| 81 | const BasicBlock *From, const BasicBlock *To, |
| 82 | const SmallPtrSetImpl<BasicBlock *> *ExclusionSet = nullptr, |
| 83 | const DominatorTree *DT = nullptr, const LoopInfo *LI = nullptr); |
| 84 | |
| 85 | /// Determine whether there is at least one path from a block in |
| 86 | /// 'Worklist' to 'StopBB' without passing through any blocks in |
| 87 | /// 'ExclusionSet', returning true if uncertain. |
| 88 | /// |
| 89 | /// Determine whether there is a path from at least one block in Worklist to |
| 90 | /// StopBB within a single function without passing through any of the blocks |
| 91 | /// in 'ExclusionSet'. Returns false only if we can prove that once any block |
| 92 | /// in 'Worklist' has been reached then 'StopBB' can not be executed. |
| 93 | /// Conservatively returns true. |
| 94 | bool isPotentiallyReachableFromMany( |
| 95 | SmallVectorImpl<BasicBlock *> &Worklist, BasicBlock *StopBB, |
| 96 | const SmallPtrSetImpl<BasicBlock *> *ExclusionSet, |
| 97 | const DominatorTree *DT = nullptr, const LoopInfo *LI = nullptr); |
| 98 | |
| 99 | /// Return true if the control flow in \p RPOTraversal is irreducible. |
| 100 | /// |
| 101 | /// This is a generic implementation to detect CFG irreducibility based on loop |
| 102 | /// info analysis. It can be used for any kind of CFG (Loop, MachineLoop, |
| 103 | /// Function, MachineFunction, etc.) by providing an RPO traversal (\p |
| 104 | /// RPOTraversal) and the loop info analysis (\p LI) of the CFG. This utility |
| 105 | /// function is only recommended when loop info analysis is available. If loop |
| 106 | /// info analysis isn't available, please, don't compute it explicitly for this |
| 107 | /// purpose. There are more efficient ways to detect CFG irreducibility that |
| 108 | /// don't require recomputing loop info analysis (e.g., T1/T2 or Tarjan's |
| 109 | /// algorithm). |
| 110 | /// |
| 111 | /// Requirements: |
| 112 | /// 1) GraphTraits must be implemented for NodeT type. It is used to access |
| 113 | /// NodeT successors. |
| 114 | // 2) \p RPOTraversal must be a valid reverse post-order traversal of the |
| 115 | /// target CFG with begin()/end() iterator interfaces. |
| 116 | /// 3) \p LI must be a valid LoopInfoBase that contains up-to-date loop |
| 117 | /// analysis information of the CFG. |
| 118 | /// |
| 119 | /// This algorithm uses the information about reducible loop back-edges already |
| 120 | /// computed in \p LI. When a back-edge is found during the RPO traversal, the |
| 121 | /// algorithm checks whether the back-edge is one of the reducible back-edges in |
| 122 | /// loop info. If it isn't, the CFG is irreducible. For example, for the CFG |
| 123 | /// below (canonical irreducible graph) loop info won't contain any loop, so the |
| 124 | /// algorithm will return that the CFG is irreducible when checking the B <- |
| 125 | /// -> C back-edge. |
| 126 | /// |
| 127 | /// (A->B, A->C, B->C, C->B, C->D) |
| 128 | /// A |
| 129 | /// / \ |
| 130 | /// B<- ->C |
| 131 | /// | |
| 132 | /// D |
| 133 | /// |
| 134 | template <class NodeT, class RPOTraversalT, class LoopInfoT, |
| 135 | class GT = GraphTraits<NodeT>> |
| 136 | bool containsIrreducibleCFG(RPOTraversalT &RPOTraversal, const LoopInfoT &LI) { |
| 137 | /// Check whether the edge (\p Src, \p Dst) is a reducible loop backedge |
| 138 | /// according to LI. I.e., check if there exists a loop that contains Src and |
| 139 | /// where Dst is the loop header. |
| 140 | auto isProperBackedge = [&](NodeT Src, NodeT Dst) { |
| 141 | for (const auto *Lp = LI.getLoopFor(Src); Lp; Lp = Lp->getParentLoop()) { |
| 142 | if (Lp->getHeader() == Dst) |
| 143 | return true; |
| 144 | } |
| 145 | return false; |
| 146 | }; |
| 147 | |
| 148 | SmallPtrSet<NodeT, 32> Visited; |
| 149 | for (NodeT Node : RPOTraversal) { |
| 150 | Visited.insert(Node); |
| 151 | for (NodeT Succ : make_range(GT::child_begin(Node), GT::child_end(Node))) { |
| 152 | // Succ hasn't been visited yet |
| 153 | if (!Visited.count(Succ)) |
| 154 | continue; |
| 155 | // We already visited Succ, thus Node->Succ must be a backedge. Check that |
| 156 | // the head matches what we have in the loop information. Otherwise, we |
| 157 | // have an irreducible graph. |
| 158 | if (!isProperBackedge(Node, Succ)) |
| 159 | return true; |
| 160 | } |
| 161 | } |
| 162 | |
| 163 | return false; |
| 164 | } |
| 165 | } // End llvm namespace |
| 166 | |
| 167 | #endif |
| 1 | //===- InstructionCost.h ----------------------------------------*- C++ -*-===// | ||||||||
| 2 | // | ||||||||
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. | ||||||||
| 4 | // See https://llvm.org/LICENSE.txt for license information. | ||||||||
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception | ||||||||
| 6 | // | ||||||||
| 7 | //===----------------------------------------------------------------------===// | ||||||||
| 8 | /// \file | ||||||||
| 9 | /// This file defines an InstructionCost class that is used when calculating | ||||||||
| 10 | /// the cost of an instruction, or a group of instructions. In addition to a | ||||||||
| 11 | /// numeric value representing the cost the class also contains a state that | ||||||||
| 12 | /// can be used to encode particular properties, such as a cost being invalid. | ||||||||
| 13 | /// Operations on InstructionCost implement saturation arithmetic, so that | ||||||||
| 14 | /// accumulating costs on large cost-values don't overflow. | ||||||||
| 15 | /// | ||||||||
| 16 | //===----------------------------------------------------------------------===// | ||||||||
| 17 | |||||||||
| 18 | #ifndef LLVM_SUPPORT_INSTRUCTIONCOST_H | ||||||||
| 19 | #define LLVM_SUPPORT_INSTRUCTIONCOST_H | ||||||||
| 20 | |||||||||
| 21 | #include "llvm/ADT/Optional.h" | ||||||||
| 22 | #include "llvm/Support/MathExtras.h" | ||||||||
| 23 | #include <limits> | ||||||||
| 24 | |||||||||
| 25 | namespace llvm { | ||||||||
| 26 | |||||||||
| 27 | class raw_ostream; | ||||||||
| 28 | |||||||||
| 29 | class InstructionCost { | ||||||||
| 30 | public: | ||||||||
| 31 | using CostType = int64_t; | ||||||||
| 32 | |||||||||
| 33 | /// CostState describes the state of a cost. | ||||||||
| 34 | enum CostState { | ||||||||
| 35 | Valid, /// < The cost value represents a valid cost, even when the | ||||||||
| 36 | /// cost-value is large. | ||||||||
| 37 | Invalid /// < Invalid indicates there is no way to represent the cost as a | ||||||||
| 38 | /// numeric value. This state exists to represent a possible issue, | ||||||||
| 39 | /// e.g. if the cost-model knows the operation cannot be expanded | ||||||||
| 40 | /// into a valid code-sequence by the code-generator. While some | ||||||||
| 41 | /// passes may assert that the calculated cost must be valid, it is | ||||||||
| 42 | /// up to individual passes how to interpret an Invalid cost. For | ||||||||
| 43 | /// example, a transformation pass could choose not to perform a | ||||||||
| 44 | /// transformation if the resulting cost would end up Invalid. | ||||||||
| 45 | /// Because some passes may assert a cost is Valid, it is not | ||||||||
| 46 | /// recommended to use Invalid costs to model 'Unknown'. | ||||||||
| 47 | /// Note that Invalid is semantically different from a (very) high, | ||||||||
| 48 | /// but valid cost, which intentionally indicates no issue, but | ||||||||
| 49 | /// rather a strong preference not to select a certain operation. | ||||||||
| 50 | }; | ||||||||
| 51 | |||||||||
| 52 | private: | ||||||||
| 53 | CostType Value = 0; | ||||||||
| 54 | CostState State = Valid; | ||||||||
| 55 | |||||||||
| 56 | void propagateState(const InstructionCost &RHS) { | ||||||||
| 57 | if (RHS.State == Invalid) | ||||||||
| 58 | State = Invalid; | ||||||||
| 59 | } | ||||||||
| 60 | |||||||||
| 61 | static CostType getMaxValue() { return std::numeric_limits<CostType>::max(); } | ||||||||
| 62 | static CostType getMinValue() { return std::numeric_limits<CostType>::min(); } | ||||||||
| 63 | |||||||||
| 64 | public: | ||||||||
| 65 | // A default constructed InstructionCost is a valid zero cost | ||||||||
| 66 | InstructionCost() = default; | ||||||||
| 67 | |||||||||
| 68 | InstructionCost(CostState) = delete; | ||||||||
| 69 | InstructionCost(CostType Val) : Value(Val), State(Valid) {} | ||||||||
| 70 | |||||||||
| 71 | static InstructionCost getMax() { return getMaxValue(); } | ||||||||
| 72 | static InstructionCost getMin() { return getMinValue(); } | ||||||||
| 73 | static InstructionCost getInvalid(CostType Val = 0) { | ||||||||
| 74 | InstructionCost Tmp(Val); | ||||||||
| 75 | Tmp.setInvalid(); | ||||||||
| 76 | return Tmp; | ||||||||
| 77 | } | ||||||||
| 78 | |||||||||
| 79 | bool isValid() const { return State == Valid; } | ||||||||
| 80 | void setValid() { State = Valid; } | ||||||||
| 81 | void setInvalid() { State = Invalid; } | ||||||||
| 82 | CostState getState() const { return State; } | ||||||||
| 83 | |||||||||
| 84 | /// This function is intended to be used as sparingly as possible, since the | ||||||||
| 85 | /// class provides the full range of operator support required for arithmetic | ||||||||
| 86 | /// and comparisons. | ||||||||
| 87 | Optional<CostType> getValue() const { | ||||||||
| 88 | if (isValid()) | ||||||||
| 89 | return Value; | ||||||||
| 90 | return None; | ||||||||
| 91 | } | ||||||||
| 92 | |||||||||
| 93 | /// For all of the arithmetic operators provided here any invalid state is | ||||||||
| 94 | /// perpetuated and cannot be removed. Once a cost becomes invalid it stays | ||||||||
| 95 | /// invalid, and it also inherits any invalid state from the RHS. | ||||||||
| 96 | /// Arithmetic work on the actual values is implemented with saturation, | ||||||||
| 97 | /// to avoid overflow when using more extreme cost values. | ||||||||
| 98 | |||||||||
| 99 | InstructionCost &operator+=(const InstructionCost &RHS) { | ||||||||
| 100 | propagateState(RHS); | ||||||||
| 101 | |||||||||
| 102 | // Saturating addition. | ||||||||
| 103 | InstructionCost::CostType Result; | ||||||||
| 104 | if (AddOverflow(Value, RHS.Value, Result)) | ||||||||
| 105 | Result = RHS.Value > 0 ? getMaxValue() : getMinValue(); | ||||||||
| 106 | |||||||||
| 107 | Value = Result; | ||||||||
| 108 | return *this; | ||||||||
| 109 | } | ||||||||
| 110 | |||||||||
| 111 | InstructionCost &operator+=(const CostType RHS) { | ||||||||
| 112 | InstructionCost RHS2(RHS); | ||||||||
| 113 | *this += RHS2; | ||||||||
| 114 | return *this; | ||||||||
| 115 | } | ||||||||
| 116 | |||||||||
| 117 | InstructionCost &operator-=(const InstructionCost &RHS) { | ||||||||
| 118 | propagateState(RHS); | ||||||||
| 119 | |||||||||
| 120 | // Saturating subtract. | ||||||||
| 121 | InstructionCost::CostType Result; | ||||||||
| 122 | if (SubOverflow(Value, RHS.Value, Result)) | ||||||||
| 123 | Result = RHS.Value > 0 ? getMinValue() : getMaxValue(); | ||||||||
| 124 | Value = Result; | ||||||||
| 125 | return *this; | ||||||||
| 126 | } | ||||||||
| 127 | |||||||||
| 128 | InstructionCost &operator-=(const CostType RHS) { | ||||||||
| 129 | InstructionCost RHS2(RHS); | ||||||||
| 130 | *this -= RHS2; | ||||||||
| 131 | return *this; | ||||||||
| 132 | } | ||||||||
| 133 | |||||||||
| 134 | InstructionCost &operator*=(const InstructionCost &RHS) { | ||||||||
| 135 | propagateState(RHS); | ||||||||
| 136 | |||||||||
| 137 | // Saturating multiply. | ||||||||
| 138 | InstructionCost::CostType Result; | ||||||||
| 139 | if (MulOverflow(Value, RHS.Value, Result)) { | ||||||||
| 140 | if ((Value > 0 && RHS.Value > 0) || (Value < 0 && RHS.Value < 0)) | ||||||||
| 141 | Result = getMaxValue(); | ||||||||
| 142 | else | ||||||||
| 143 | Result = getMinValue(); | ||||||||
| 144 | } | ||||||||
| 145 | |||||||||
| 146 | Value = Result; | ||||||||
| 147 | return *this; | ||||||||
| 148 | } | ||||||||
| 149 | |||||||||
| 150 | InstructionCost &operator*=(const CostType RHS) { | ||||||||
| 151 | InstructionCost RHS2(RHS); | ||||||||
| 152 | *this *= RHS2; | ||||||||
| 153 | return *this; | ||||||||
| 154 | } | ||||||||
| 155 | |||||||||
| 156 | InstructionCost &operator/=(const InstructionCost &RHS) { | ||||||||
| 157 | propagateState(RHS); | ||||||||
| 158 | Value /= RHS.Value; | ||||||||
| 159 | return *this; | ||||||||
| 160 | } | ||||||||
| 161 | |||||||||
| 162 | InstructionCost &operator/=(const CostType RHS) { | ||||||||
| 163 | InstructionCost RHS2(RHS); | ||||||||
| 164 | *this /= RHS2; | ||||||||
| 165 | return *this; | ||||||||
| 166 | } | ||||||||
| 167 | |||||||||
| 168 | InstructionCost &operator++() { | ||||||||
| 169 | *this += 1; | ||||||||
| 170 | return *this; | ||||||||
| 171 | } | ||||||||
| 172 | |||||||||
| 173 | InstructionCost operator++(int) { | ||||||||
| 174 | InstructionCost Copy = *this; | ||||||||
| 175 | ++*this; | ||||||||
| 176 | return Copy; | ||||||||
| 177 | } | ||||||||
| 178 | |||||||||
| 179 | InstructionCost &operator--() { | ||||||||
| 180 | *this -= 1; | ||||||||
| 181 | return *this; | ||||||||
| 182 | } | ||||||||
| 183 | |||||||||
| 184 | InstructionCost operator--(int) { | ||||||||
| 185 | InstructionCost Copy = *this; | ||||||||
| 186 | --*this; | ||||||||
| 187 | return Copy; | ||||||||
| 188 | } | ||||||||
| 189 | |||||||||
| 190 | /// For the comparison operators we have chosen to use lexicographical | ||||||||
| 191 | /// ordering where valid costs are always considered to be less than invalid | ||||||||
| 192 | /// costs. This avoids having to add asserts to the comparison operators that | ||||||||
| 193 | /// the states are valid and users can test for validity of the cost | ||||||||
| 194 | /// explicitly. | ||||||||
| 195 | bool operator<(const InstructionCost &RHS) const { | ||||||||
| 196 | if (State
| ||||||||
| 197 | return State < RHS.State; | ||||||||
| 198 | return Value < RHS.Value; | ||||||||
| 199 | } | ||||||||
| 200 | |||||||||
| 201 | // Implement in terms of operator< to ensure that the two comparisons stay in | ||||||||
| 202 | // sync | ||||||||
| 203 | bool operator==(const InstructionCost &RHS) const { | ||||||||
| 204 | return !(*this < RHS) && !(RHS < *this); | ||||||||
| 205 | } | ||||||||
| 206 | |||||||||
| 207 | bool operator!=(const InstructionCost &RHS) const { return !(*this == RHS); } | ||||||||
| 208 | |||||||||
| 209 | bool operator==(const CostType RHS) const { | ||||||||
| 210 | InstructionCost RHS2(RHS); | ||||||||
| 211 | return *this == RHS2; | ||||||||
| 212 | } | ||||||||
| 213 | |||||||||
| 214 | bool operator!=(const CostType RHS) const { return !(*this == RHS); } | ||||||||
| 215 | |||||||||
| 216 | bool operator>(const InstructionCost &RHS) const { return RHS < *this; } | ||||||||
| 217 | |||||||||
| 218 | bool operator<=(const InstructionCost &RHS) const { return !(RHS < *this); } | ||||||||
| 219 | |||||||||
| 220 | bool operator>=(const InstructionCost &RHS) const { return !(*this < RHS); } | ||||||||
| 221 | |||||||||
| 222 | bool operator<(const CostType RHS) const { | ||||||||
| 223 | InstructionCost RHS2(RHS); | ||||||||
| 224 | return *this < RHS2; | ||||||||
| 225 | } | ||||||||
| 226 | |||||||||
| 227 | bool operator>(const CostType RHS) const { | ||||||||
| 228 | InstructionCost RHS2(RHS); | ||||||||
| 229 | return *this > RHS2; | ||||||||
| 230 | } | ||||||||
| 231 | |||||||||
| 232 | bool operator<=(const CostType RHS) const { | ||||||||
| 233 | InstructionCost RHS2(RHS); | ||||||||
| 234 | return *this <= RHS2; | ||||||||
| 235 | } | ||||||||
| 236 | |||||||||
| 237 | bool operator>=(const CostType RHS) const { | ||||||||
| 238 | InstructionCost RHS2(RHS); | ||||||||
| 239 | return *this >= RHS2; | ||||||||
| 240 | } | ||||||||
| 241 | |||||||||
| 242 | void print(raw_ostream &OS) const; | ||||||||
| 243 | |||||||||
| 244 | template <class Function> | ||||||||
| 245 | auto map(const Function &F) const -> InstructionCost { | ||||||||
| 246 | if (isValid()) | ||||||||
| 247 | return F(*getValue()); | ||||||||
| 248 | return getInvalid(); | ||||||||
| 249 | } | ||||||||
| 250 | }; | ||||||||
| 251 | |||||||||
| 252 | inline InstructionCost operator+(const InstructionCost &LHS, | ||||||||
| 253 | const InstructionCost &RHS) { | ||||||||
| 254 | InstructionCost LHS2(LHS); | ||||||||
| 255 | LHS2 += RHS; | ||||||||
| 256 | return LHS2; | ||||||||
| 257 | } | ||||||||
| 258 | |||||||||
| 259 | inline InstructionCost operator-(const InstructionCost &LHS, | ||||||||
| 260 | const InstructionCost &RHS) { | ||||||||
| 261 | InstructionCost LHS2(LHS); | ||||||||
| 262 | LHS2 -= RHS; | ||||||||
| 263 | return LHS2; | ||||||||
| 264 | } | ||||||||
| 265 | |||||||||
| 266 | inline InstructionCost operator*(const InstructionCost &LHS, | ||||||||
| 267 | const InstructionCost &RHS) { | ||||||||
| 268 | InstructionCost LHS2(LHS); | ||||||||
| 269 | LHS2 *= RHS; | ||||||||
| 270 | return LHS2; | ||||||||
| 271 | } | ||||||||
| 272 | |||||||||
| 273 | inline InstructionCost operator/(const InstructionCost &LHS, | ||||||||
| 274 | const InstructionCost &RHS) { | ||||||||
| 275 | InstructionCost LHS2(LHS); | ||||||||
| 276 | LHS2 /= RHS; | ||||||||
| 277 | return LHS2; | ||||||||
| 278 | } | ||||||||
| 279 | |||||||||
| 280 | inline raw_ostream &operator<<(raw_ostream &OS, const InstructionCost &V) { | ||||||||
| 281 | V.print(OS); | ||||||||
| 282 | return OS; | ||||||||
| 283 | } | ||||||||
| 284 | |||||||||
| 285 | } // namespace llvm | ||||||||
| 286 | |||||||||
| 287 | #endif |