File: | src/gnu/usr.bin/clang/libLLVM/../../../llvm/llvm/lib/Transforms/IPO/WholeProgramDevirt.cpp |
Warning: | line 1570, column 20 Access to field 'TheKind' results in a dereference of a null pointer (loaded from variable 'Res') |
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1 | //===- WholeProgramDevirt.cpp - Whole program virtual call optimization ---===// | ||||
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 pass implements whole program optimization of virtual calls in cases | ||||
10 | // where we know (via !type metadata) that the list of callees is fixed. This | ||||
11 | // includes the following: | ||||
12 | // - Single implementation devirtualization: if a virtual call has a single | ||||
13 | // possible callee, replace all calls with a direct call to that callee. | ||||
14 | // - Virtual constant propagation: if the virtual function's return type is an | ||||
15 | // integer <=64 bits and all possible callees are readnone, for each class and | ||||
16 | // each list of constant arguments: evaluate the function, store the return | ||||
17 | // value alongside the virtual table, and rewrite each virtual call as a load | ||||
18 | // from the virtual table. | ||||
19 | // - Uniform return value optimization: if the conditions for virtual constant | ||||
20 | // propagation hold and each function returns the same constant value, replace | ||||
21 | // each virtual call with that constant. | ||||
22 | // - Unique return value optimization for i1 return values: if the conditions | ||||
23 | // for virtual constant propagation hold and a single vtable's function | ||||
24 | // returns 0, or a single vtable's function returns 1, replace each virtual | ||||
25 | // call with a comparison of the vptr against that vtable's address. | ||||
26 | // | ||||
27 | // This pass is intended to be used during the regular and thin LTO pipelines: | ||||
28 | // | ||||
29 | // During regular LTO, the pass determines the best optimization for each | ||||
30 | // virtual call and applies the resolutions directly to virtual calls that are | ||||
31 | // eligible for virtual call optimization (i.e. calls that use either of the | ||||
32 | // llvm.assume(llvm.type.test) or llvm.type.checked.load intrinsics). | ||||
33 | // | ||||
34 | // During hybrid Regular/ThinLTO, the pass operates in two phases: | ||||
35 | // - Export phase: this is run during the thin link over a single merged module | ||||
36 | // that contains all vtables with !type metadata that participate in the link. | ||||
37 | // The pass computes a resolution for each virtual call and stores it in the | ||||
38 | // type identifier summary. | ||||
39 | // - Import phase: this is run during the thin backends over the individual | ||||
40 | // modules. The pass applies the resolutions previously computed during the | ||||
41 | // import phase to each eligible virtual call. | ||||
42 | // | ||||
43 | // During ThinLTO, the pass operates in two phases: | ||||
44 | // - Export phase: this is run during the thin link over the index which | ||||
45 | // contains a summary of all vtables with !type metadata that participate in | ||||
46 | // the link. It computes a resolution for each virtual call and stores it in | ||||
47 | // the type identifier summary. Only single implementation devirtualization | ||||
48 | // is supported. | ||||
49 | // - Import phase: (same as with hybrid case above). | ||||
50 | // | ||||
51 | //===----------------------------------------------------------------------===// | ||||
52 | |||||
53 | #include "llvm/Transforms/IPO/WholeProgramDevirt.h" | ||||
54 | #include "llvm/ADT/ArrayRef.h" | ||||
55 | #include "llvm/ADT/DenseMap.h" | ||||
56 | #include "llvm/ADT/DenseMapInfo.h" | ||||
57 | #include "llvm/ADT/DenseSet.h" | ||||
58 | #include "llvm/ADT/MapVector.h" | ||||
59 | #include "llvm/ADT/SmallVector.h" | ||||
60 | #include "llvm/ADT/Triple.h" | ||||
61 | #include "llvm/ADT/iterator_range.h" | ||||
62 | #include "llvm/Analysis/AssumptionCache.h" | ||||
63 | #include "llvm/Analysis/BasicAliasAnalysis.h" | ||||
64 | #include "llvm/Analysis/OptimizationRemarkEmitter.h" | ||||
65 | #include "llvm/Analysis/TypeMetadataUtils.h" | ||||
66 | #include "llvm/Bitcode/BitcodeReader.h" | ||||
67 | #include "llvm/Bitcode/BitcodeWriter.h" | ||||
68 | #include "llvm/IR/Constants.h" | ||||
69 | #include "llvm/IR/DataLayout.h" | ||||
70 | #include "llvm/IR/DebugLoc.h" | ||||
71 | #include "llvm/IR/DerivedTypes.h" | ||||
72 | #include "llvm/IR/Dominators.h" | ||||
73 | #include "llvm/IR/Function.h" | ||||
74 | #include "llvm/IR/GlobalAlias.h" | ||||
75 | #include "llvm/IR/GlobalVariable.h" | ||||
76 | #include "llvm/IR/IRBuilder.h" | ||||
77 | #include "llvm/IR/InstrTypes.h" | ||||
78 | #include "llvm/IR/Instruction.h" | ||||
79 | #include "llvm/IR/Instructions.h" | ||||
80 | #include "llvm/IR/Intrinsics.h" | ||||
81 | #include "llvm/IR/LLVMContext.h" | ||||
82 | #include "llvm/IR/Metadata.h" | ||||
83 | #include "llvm/IR/Module.h" | ||||
84 | #include "llvm/IR/ModuleSummaryIndexYAML.h" | ||||
85 | #include "llvm/InitializePasses.h" | ||||
86 | #include "llvm/Pass.h" | ||||
87 | #include "llvm/PassRegistry.h" | ||||
88 | #include "llvm/Support/Casting.h" | ||||
89 | #include "llvm/Support/CommandLine.h" | ||||
90 | #include "llvm/Support/Errc.h" | ||||
91 | #include "llvm/Support/Error.h" | ||||
92 | #include "llvm/Support/FileSystem.h" | ||||
93 | #include "llvm/Support/GlobPattern.h" | ||||
94 | #include "llvm/Support/MathExtras.h" | ||||
95 | #include "llvm/Transforms/IPO.h" | ||||
96 | #include "llvm/Transforms/IPO/FunctionAttrs.h" | ||||
97 | #include "llvm/Transforms/Utils/BasicBlockUtils.h" | ||||
98 | #include "llvm/Transforms/Utils/Evaluator.h" | ||||
99 | #include <algorithm> | ||||
100 | #include <cstddef> | ||||
101 | #include <map> | ||||
102 | #include <set> | ||||
103 | #include <string> | ||||
104 | |||||
105 | using namespace llvm; | ||||
106 | using namespace wholeprogramdevirt; | ||||
107 | |||||
108 | #define DEBUG_TYPE"wholeprogramdevirt" "wholeprogramdevirt" | ||||
109 | |||||
110 | static cl::opt<PassSummaryAction> ClSummaryAction( | ||||
111 | "wholeprogramdevirt-summary-action", | ||||
112 | cl::desc("What to do with the summary when running this pass"), | ||||
113 | cl::values(clEnumValN(PassSummaryAction::None, "none", "Do nothing")llvm::cl::OptionEnumValue { "none", int(PassSummaryAction::None ), "Do nothing" }, | ||||
114 | clEnumValN(PassSummaryAction::Import, "import",llvm::cl::OptionEnumValue { "import", int(PassSummaryAction:: Import), "Import typeid resolutions from summary and globals" } | ||||
115 | "Import typeid resolutions from summary and globals")llvm::cl::OptionEnumValue { "import", int(PassSummaryAction:: Import), "Import typeid resolutions from summary and globals" }, | ||||
116 | clEnumValN(PassSummaryAction::Export, "export",llvm::cl::OptionEnumValue { "export", int(PassSummaryAction:: Export), "Export typeid resolutions to summary and globals" } | ||||
117 | "Export typeid resolutions to summary and globals")llvm::cl::OptionEnumValue { "export", int(PassSummaryAction:: Export), "Export typeid resolutions to summary and globals" }), | ||||
118 | cl::Hidden); | ||||
119 | |||||
120 | static cl::opt<std::string> ClReadSummary( | ||||
121 | "wholeprogramdevirt-read-summary", | ||||
122 | cl::desc( | ||||
123 | "Read summary from given bitcode or YAML file before running pass"), | ||||
124 | cl::Hidden); | ||||
125 | |||||
126 | static cl::opt<std::string> ClWriteSummary( | ||||
127 | "wholeprogramdevirt-write-summary", | ||||
128 | cl::desc("Write summary to given bitcode or YAML file after running pass. " | ||||
129 | "Output file format is deduced from extension: *.bc means writing " | ||||
130 | "bitcode, otherwise YAML"), | ||||
131 | cl::Hidden); | ||||
132 | |||||
133 | static cl::opt<unsigned> | ||||
134 | ClThreshold("wholeprogramdevirt-branch-funnel-threshold", cl::Hidden, | ||||
135 | cl::init(10), cl::ZeroOrMore, | ||||
136 | cl::desc("Maximum number of call targets per " | ||||
137 | "call site to enable branch funnels")); | ||||
138 | |||||
139 | static cl::opt<bool> | ||||
140 | PrintSummaryDevirt("wholeprogramdevirt-print-index-based", cl::Hidden, | ||||
141 | cl::init(false), cl::ZeroOrMore, | ||||
142 | cl::desc("Print index-based devirtualization messages")); | ||||
143 | |||||
144 | /// Provide a way to force enable whole program visibility in tests. | ||||
145 | /// This is needed to support legacy tests that don't contain | ||||
146 | /// !vcall_visibility metadata (the mere presense of type tests | ||||
147 | /// previously implied hidden visibility). | ||||
148 | static cl::opt<bool> | ||||
149 | WholeProgramVisibility("whole-program-visibility", cl::init(false), | ||||
150 | cl::Hidden, cl::ZeroOrMore, | ||||
151 | cl::desc("Enable whole program visibility")); | ||||
152 | |||||
153 | /// Provide a way to force disable whole program for debugging or workarounds, | ||||
154 | /// when enabled via the linker. | ||||
155 | static cl::opt<bool> DisableWholeProgramVisibility( | ||||
156 | "disable-whole-program-visibility", cl::init(false), cl::Hidden, | ||||
157 | cl::ZeroOrMore, | ||||
158 | cl::desc("Disable whole program visibility (overrides enabling options)")); | ||||
159 | |||||
160 | /// Provide way to prevent certain function from being devirtualized | ||||
161 | static cl::list<std::string> | ||||
162 | SkipFunctionNames("wholeprogramdevirt-skip", | ||||
163 | cl::desc("Prevent function(s) from being devirtualized"), | ||||
164 | cl::Hidden, cl::ZeroOrMore, cl::CommaSeparated); | ||||
165 | |||||
166 | /// Mechanism to add runtime checking of devirtualization decisions, trapping on | ||||
167 | /// any that are not correct. Useful for debugging undefined behavior leading to | ||||
168 | /// failures with WPD. | ||||
169 | static cl::opt<bool> | ||||
170 | CheckDevirt("wholeprogramdevirt-check", cl::init(false), cl::Hidden, | ||||
171 | cl::ZeroOrMore, | ||||
172 | cl::desc("Add code to trap on incorrect devirtualizations")); | ||||
173 | |||||
174 | namespace { | ||||
175 | struct PatternList { | ||||
176 | std::vector<GlobPattern> Patterns; | ||||
177 | template <class T> void init(const T &StringList) { | ||||
178 | for (const auto &S : StringList) | ||||
179 | if (Expected<GlobPattern> Pat = GlobPattern::create(S)) | ||||
180 | Patterns.push_back(std::move(*Pat)); | ||||
181 | } | ||||
182 | bool match(StringRef S) { | ||||
183 | for (const GlobPattern &P : Patterns) | ||||
184 | if (P.match(S)) | ||||
185 | return true; | ||||
186 | return false; | ||||
187 | } | ||||
188 | }; | ||||
189 | } // namespace | ||||
190 | |||||
191 | // Find the minimum offset that we may store a value of size Size bits at. If | ||||
192 | // IsAfter is set, look for an offset before the object, otherwise look for an | ||||
193 | // offset after the object. | ||||
194 | uint64_t | ||||
195 | wholeprogramdevirt::findLowestOffset(ArrayRef<VirtualCallTarget> Targets, | ||||
196 | bool IsAfter, uint64_t Size) { | ||||
197 | // Find a minimum offset taking into account only vtable sizes. | ||||
198 | uint64_t MinByte = 0; | ||||
199 | for (const VirtualCallTarget &Target : Targets) { | ||||
200 | if (IsAfter) | ||||
201 | MinByte = std::max(MinByte, Target.minAfterBytes()); | ||||
202 | else | ||||
203 | MinByte = std::max(MinByte, Target.minBeforeBytes()); | ||||
204 | } | ||||
205 | |||||
206 | // Build a vector of arrays of bytes covering, for each target, a slice of the | ||||
207 | // used region (see AccumBitVector::BytesUsed in | ||||
208 | // llvm/Transforms/IPO/WholeProgramDevirt.h) starting at MinByte. Effectively, | ||||
209 | // this aligns the used regions to start at MinByte. | ||||
210 | // | ||||
211 | // In this example, A, B and C are vtables, # is a byte already allocated for | ||||
212 | // a virtual function pointer, AAAA... (etc.) are the used regions for the | ||||
213 | // vtables and Offset(X) is the value computed for the Offset variable below | ||||
214 | // for X. | ||||
215 | // | ||||
216 | // Offset(A) | ||||
217 | // | | | ||||
218 | // |MinByte | ||||
219 | // A: ################AAAAAAAA|AAAAAAAA | ||||
220 | // B: ########BBBBBBBBBBBBBBBB|BBBB | ||||
221 | // C: ########################|CCCCCCCCCCCCCCCC | ||||
222 | // | Offset(B) | | ||||
223 | // | ||||
224 | // This code produces the slices of A, B and C that appear after the divider | ||||
225 | // at MinByte. | ||||
226 | std::vector<ArrayRef<uint8_t>> Used; | ||||
227 | for (const VirtualCallTarget &Target : Targets) { | ||||
228 | ArrayRef<uint8_t> VTUsed = IsAfter ? Target.TM->Bits->After.BytesUsed | ||||
229 | : Target.TM->Bits->Before.BytesUsed; | ||||
230 | uint64_t Offset = IsAfter ? MinByte - Target.minAfterBytes() | ||||
231 | : MinByte - Target.minBeforeBytes(); | ||||
232 | |||||
233 | // Disregard used regions that are smaller than Offset. These are | ||||
234 | // effectively all-free regions that do not need to be checked. | ||||
235 | if (VTUsed.size() > Offset) | ||||
236 | Used.push_back(VTUsed.slice(Offset)); | ||||
237 | } | ||||
238 | |||||
239 | if (Size == 1) { | ||||
240 | // Find a free bit in each member of Used. | ||||
241 | for (unsigned I = 0;; ++I) { | ||||
242 | uint8_t BitsUsed = 0; | ||||
243 | for (auto &&B : Used) | ||||
244 | if (I < B.size()) | ||||
245 | BitsUsed |= B[I]; | ||||
246 | if (BitsUsed != 0xff) | ||||
247 | return (MinByte + I) * 8 + | ||||
248 | countTrailingZeros(uint8_t(~BitsUsed), ZB_Undefined); | ||||
249 | } | ||||
250 | } else { | ||||
251 | // Find a free (Size/8) byte region in each member of Used. | ||||
252 | // FIXME: see if alignment helps. | ||||
253 | for (unsigned I = 0;; ++I) { | ||||
254 | for (auto &&B : Used) { | ||||
255 | unsigned Byte = 0; | ||||
256 | while ((I + Byte) < B.size() && Byte < (Size / 8)) { | ||||
257 | if (B[I + Byte]) | ||||
258 | goto NextI; | ||||
259 | ++Byte; | ||||
260 | } | ||||
261 | } | ||||
262 | return (MinByte + I) * 8; | ||||
263 | NextI:; | ||||
264 | } | ||||
265 | } | ||||
266 | } | ||||
267 | |||||
268 | void wholeprogramdevirt::setBeforeReturnValues( | ||||
269 | MutableArrayRef<VirtualCallTarget> Targets, uint64_t AllocBefore, | ||||
270 | unsigned BitWidth, int64_t &OffsetByte, uint64_t &OffsetBit) { | ||||
271 | if (BitWidth == 1) | ||||
272 | OffsetByte = -(AllocBefore / 8 + 1); | ||||
273 | else | ||||
274 | OffsetByte = -((AllocBefore + 7) / 8 + (BitWidth + 7) / 8); | ||||
275 | OffsetBit = AllocBefore % 8; | ||||
276 | |||||
277 | for (VirtualCallTarget &Target : Targets) { | ||||
278 | if (BitWidth == 1) | ||||
279 | Target.setBeforeBit(AllocBefore); | ||||
280 | else | ||||
281 | Target.setBeforeBytes(AllocBefore, (BitWidth + 7) / 8); | ||||
282 | } | ||||
283 | } | ||||
284 | |||||
285 | void wholeprogramdevirt::setAfterReturnValues( | ||||
286 | MutableArrayRef<VirtualCallTarget> Targets, uint64_t AllocAfter, | ||||
287 | unsigned BitWidth, int64_t &OffsetByte, uint64_t &OffsetBit) { | ||||
288 | if (BitWidth == 1) | ||||
289 | OffsetByte = AllocAfter / 8; | ||||
290 | else | ||||
291 | OffsetByte = (AllocAfter + 7) / 8; | ||||
292 | OffsetBit = AllocAfter % 8; | ||||
293 | |||||
294 | for (VirtualCallTarget &Target : Targets) { | ||||
295 | if (BitWidth == 1) | ||||
296 | Target.setAfterBit(AllocAfter); | ||||
297 | else | ||||
298 | Target.setAfterBytes(AllocAfter, (BitWidth + 7) / 8); | ||||
299 | } | ||||
300 | } | ||||
301 | |||||
302 | VirtualCallTarget::VirtualCallTarget(Function *Fn, const TypeMemberInfo *TM) | ||||
303 | : Fn(Fn), TM(TM), | ||||
304 | IsBigEndian(Fn->getParent()->getDataLayout().isBigEndian()), WasDevirt(false) {} | ||||
305 | |||||
306 | namespace { | ||||
307 | |||||
308 | // A slot in a set of virtual tables. The TypeID identifies the set of virtual | ||||
309 | // tables, and the ByteOffset is the offset in bytes from the address point to | ||||
310 | // the virtual function pointer. | ||||
311 | struct VTableSlot { | ||||
312 | Metadata *TypeID; | ||||
313 | uint64_t ByteOffset; | ||||
314 | }; | ||||
315 | |||||
316 | } // end anonymous namespace | ||||
317 | |||||
318 | namespace llvm { | ||||
319 | |||||
320 | template <> struct DenseMapInfo<VTableSlot> { | ||||
321 | static VTableSlot getEmptyKey() { | ||||
322 | return {DenseMapInfo<Metadata *>::getEmptyKey(), | ||||
323 | DenseMapInfo<uint64_t>::getEmptyKey()}; | ||||
324 | } | ||||
325 | static VTableSlot getTombstoneKey() { | ||||
326 | return {DenseMapInfo<Metadata *>::getTombstoneKey(), | ||||
327 | DenseMapInfo<uint64_t>::getTombstoneKey()}; | ||||
328 | } | ||||
329 | static unsigned getHashValue(const VTableSlot &I) { | ||||
330 | return DenseMapInfo<Metadata *>::getHashValue(I.TypeID) ^ | ||||
331 | DenseMapInfo<uint64_t>::getHashValue(I.ByteOffset); | ||||
332 | } | ||||
333 | static bool isEqual(const VTableSlot &LHS, | ||||
334 | const VTableSlot &RHS) { | ||||
335 | return LHS.TypeID == RHS.TypeID && LHS.ByteOffset == RHS.ByteOffset; | ||||
336 | } | ||||
337 | }; | ||||
338 | |||||
339 | template <> struct DenseMapInfo<VTableSlotSummary> { | ||||
340 | static VTableSlotSummary getEmptyKey() { | ||||
341 | return {DenseMapInfo<StringRef>::getEmptyKey(), | ||||
342 | DenseMapInfo<uint64_t>::getEmptyKey()}; | ||||
343 | } | ||||
344 | static VTableSlotSummary getTombstoneKey() { | ||||
345 | return {DenseMapInfo<StringRef>::getTombstoneKey(), | ||||
346 | DenseMapInfo<uint64_t>::getTombstoneKey()}; | ||||
347 | } | ||||
348 | static unsigned getHashValue(const VTableSlotSummary &I) { | ||||
349 | return DenseMapInfo<StringRef>::getHashValue(I.TypeID) ^ | ||||
350 | DenseMapInfo<uint64_t>::getHashValue(I.ByteOffset); | ||||
351 | } | ||||
352 | static bool isEqual(const VTableSlotSummary &LHS, | ||||
353 | const VTableSlotSummary &RHS) { | ||||
354 | return LHS.TypeID == RHS.TypeID && LHS.ByteOffset == RHS.ByteOffset; | ||||
355 | } | ||||
356 | }; | ||||
357 | |||||
358 | } // end namespace llvm | ||||
359 | |||||
360 | namespace { | ||||
361 | |||||
362 | // A virtual call site. VTable is the loaded virtual table pointer, and CS is | ||||
363 | // the indirect virtual call. | ||||
364 | struct VirtualCallSite { | ||||
365 | Value *VTable = nullptr; | ||||
366 | CallBase &CB; | ||||
367 | |||||
368 | // If non-null, this field points to the associated unsafe use count stored in | ||||
369 | // the DevirtModule::NumUnsafeUsesForTypeTest map below. See the description | ||||
370 | // of that field for details. | ||||
371 | unsigned *NumUnsafeUses = nullptr; | ||||
372 | |||||
373 | void | ||||
374 | emitRemark(const StringRef OptName, const StringRef TargetName, | ||||
375 | function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter) { | ||||
376 | Function *F = CB.getCaller(); | ||||
377 | DebugLoc DLoc = CB.getDebugLoc(); | ||||
378 | BasicBlock *Block = CB.getParent(); | ||||
379 | |||||
380 | using namespace ore; | ||||
381 | OREGetter(F).emit(OptimizationRemark(DEBUG_TYPE"wholeprogramdevirt", OptName, DLoc, Block) | ||||
382 | << NV("Optimization", OptName) | ||||
383 | << ": devirtualized a call to " | ||||
384 | << NV("FunctionName", TargetName)); | ||||
385 | } | ||||
386 | |||||
387 | void replaceAndErase( | ||||
388 | const StringRef OptName, const StringRef TargetName, bool RemarksEnabled, | ||||
389 | function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter, | ||||
390 | Value *New) { | ||||
391 | if (RemarksEnabled) | ||||
392 | emitRemark(OptName, TargetName, OREGetter); | ||||
393 | CB.replaceAllUsesWith(New); | ||||
394 | if (auto *II = dyn_cast<InvokeInst>(&CB)) { | ||||
395 | BranchInst::Create(II->getNormalDest(), &CB); | ||||
396 | II->getUnwindDest()->removePredecessor(II->getParent()); | ||||
397 | } | ||||
398 | CB.eraseFromParent(); | ||||
399 | // This use is no longer unsafe. | ||||
400 | if (NumUnsafeUses) | ||||
401 | --*NumUnsafeUses; | ||||
402 | } | ||||
403 | }; | ||||
404 | |||||
405 | // Call site information collected for a specific VTableSlot and possibly a list | ||||
406 | // of constant integer arguments. The grouping by arguments is handled by the | ||||
407 | // VTableSlotInfo class. | ||||
408 | struct CallSiteInfo { | ||||
409 | /// The set of call sites for this slot. Used during regular LTO and the | ||||
410 | /// import phase of ThinLTO (as well as the export phase of ThinLTO for any | ||||
411 | /// call sites that appear in the merged module itself); in each of these | ||||
412 | /// cases we are directly operating on the call sites at the IR level. | ||||
413 | std::vector<VirtualCallSite> CallSites; | ||||
414 | |||||
415 | /// Whether all call sites represented by this CallSiteInfo, including those | ||||
416 | /// in summaries, have been devirtualized. This starts off as true because a | ||||
417 | /// default constructed CallSiteInfo represents no call sites. | ||||
418 | bool AllCallSitesDevirted = true; | ||||
419 | |||||
420 | // These fields are used during the export phase of ThinLTO and reflect | ||||
421 | // information collected from function summaries. | ||||
422 | |||||
423 | /// Whether any function summary contains an llvm.assume(llvm.type.test) for | ||||
424 | /// this slot. | ||||
425 | bool SummaryHasTypeTestAssumeUsers = false; | ||||
426 | |||||
427 | /// CFI-specific: a vector containing the list of function summaries that use | ||||
428 | /// the llvm.type.checked.load intrinsic and therefore will require | ||||
429 | /// resolutions for llvm.type.test in order to implement CFI checks if | ||||
430 | /// devirtualization was unsuccessful. If devirtualization was successful, the | ||||
431 | /// pass will clear this vector by calling markDevirt(). If at the end of the | ||||
432 | /// pass the vector is non-empty, we will need to add a use of llvm.type.test | ||||
433 | /// to each of the function summaries in the vector. | ||||
434 | std::vector<FunctionSummary *> SummaryTypeCheckedLoadUsers; | ||||
435 | std::vector<FunctionSummary *> SummaryTypeTestAssumeUsers; | ||||
436 | |||||
437 | bool isExported() const { | ||||
438 | return SummaryHasTypeTestAssumeUsers || | ||||
439 | !SummaryTypeCheckedLoadUsers.empty(); | ||||
440 | } | ||||
441 | |||||
442 | void addSummaryTypeCheckedLoadUser(FunctionSummary *FS) { | ||||
443 | SummaryTypeCheckedLoadUsers.push_back(FS); | ||||
444 | AllCallSitesDevirted = false; | ||||
445 | } | ||||
446 | |||||
447 | void addSummaryTypeTestAssumeUser(FunctionSummary *FS) { | ||||
448 | SummaryTypeTestAssumeUsers.push_back(FS); | ||||
449 | SummaryHasTypeTestAssumeUsers = true; | ||||
450 | AllCallSitesDevirted = false; | ||||
451 | } | ||||
452 | |||||
453 | void markDevirt() { | ||||
454 | AllCallSitesDevirted = true; | ||||
455 | |||||
456 | // As explained in the comment for SummaryTypeCheckedLoadUsers. | ||||
457 | SummaryTypeCheckedLoadUsers.clear(); | ||||
458 | } | ||||
459 | }; | ||||
460 | |||||
461 | // Call site information collected for a specific VTableSlot. | ||||
462 | struct VTableSlotInfo { | ||||
463 | // The set of call sites which do not have all constant integer arguments | ||||
464 | // (excluding "this"). | ||||
465 | CallSiteInfo CSInfo; | ||||
466 | |||||
467 | // The set of call sites with all constant integer arguments (excluding | ||||
468 | // "this"), grouped by argument list. | ||||
469 | std::map<std::vector<uint64_t>, CallSiteInfo> ConstCSInfo; | ||||
470 | |||||
471 | void addCallSite(Value *VTable, CallBase &CB, unsigned *NumUnsafeUses); | ||||
472 | |||||
473 | private: | ||||
474 | CallSiteInfo &findCallSiteInfo(CallBase &CB); | ||||
475 | }; | ||||
476 | |||||
477 | CallSiteInfo &VTableSlotInfo::findCallSiteInfo(CallBase &CB) { | ||||
478 | std::vector<uint64_t> Args; | ||||
479 | auto *CBType = dyn_cast<IntegerType>(CB.getType()); | ||||
480 | if (!CBType || CBType->getBitWidth() > 64 || CB.arg_empty()) | ||||
481 | return CSInfo; | ||||
482 | for (auto &&Arg : drop_begin(CB.args())) { | ||||
483 | auto *CI = dyn_cast<ConstantInt>(Arg); | ||||
484 | if (!CI || CI->getBitWidth() > 64) | ||||
485 | return CSInfo; | ||||
486 | Args.push_back(CI->getZExtValue()); | ||||
487 | } | ||||
488 | return ConstCSInfo[Args]; | ||||
489 | } | ||||
490 | |||||
491 | void VTableSlotInfo::addCallSite(Value *VTable, CallBase &CB, | ||||
492 | unsigned *NumUnsafeUses) { | ||||
493 | auto &CSI = findCallSiteInfo(CB); | ||||
494 | CSI.AllCallSitesDevirted = false; | ||||
495 | CSI.CallSites.push_back({VTable, CB, NumUnsafeUses}); | ||||
496 | } | ||||
497 | |||||
498 | struct DevirtModule { | ||||
499 | Module &M; | ||||
500 | function_ref<AAResults &(Function &)> AARGetter; | ||||
501 | function_ref<DominatorTree &(Function &)> LookupDomTree; | ||||
502 | |||||
503 | ModuleSummaryIndex *ExportSummary; | ||||
504 | const ModuleSummaryIndex *ImportSummary; | ||||
505 | |||||
506 | IntegerType *Int8Ty; | ||||
507 | PointerType *Int8PtrTy; | ||||
508 | IntegerType *Int32Ty; | ||||
509 | IntegerType *Int64Ty; | ||||
510 | IntegerType *IntPtrTy; | ||||
511 | /// Sizeless array type, used for imported vtables. This provides a signal | ||||
512 | /// to analyzers that these imports may alias, as they do for example | ||||
513 | /// when multiple unique return values occur in the same vtable. | ||||
514 | ArrayType *Int8Arr0Ty; | ||||
515 | |||||
516 | bool RemarksEnabled; | ||||
517 | function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter; | ||||
518 | |||||
519 | MapVector<VTableSlot, VTableSlotInfo> CallSlots; | ||||
520 | |||||
521 | // Calls that have already been optimized. We may add a call to multiple | ||||
522 | // VTableSlotInfos if vtable loads are coalesced and need to make sure not to | ||||
523 | // optimize a call more than once. | ||||
524 | SmallPtrSet<CallBase *, 8> OptimizedCalls; | ||||
525 | |||||
526 | // This map keeps track of the number of "unsafe" uses of a loaded function | ||||
527 | // pointer. The key is the associated llvm.type.test intrinsic call generated | ||||
528 | // by this pass. An unsafe use is one that calls the loaded function pointer | ||||
529 | // directly. Every time we eliminate an unsafe use (for example, by | ||||
530 | // devirtualizing it or by applying virtual constant propagation), we | ||||
531 | // decrement the value stored in this map. If a value reaches zero, we can | ||||
532 | // eliminate the type check by RAUWing the associated llvm.type.test call with | ||||
533 | // true. | ||||
534 | std::map<CallInst *, unsigned> NumUnsafeUsesForTypeTest; | ||||
535 | PatternList FunctionsToSkip; | ||||
536 | |||||
537 | DevirtModule(Module &M, function_ref<AAResults &(Function &)> AARGetter, | ||||
538 | function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter, | ||||
539 | function_ref<DominatorTree &(Function &)> LookupDomTree, | ||||
540 | ModuleSummaryIndex *ExportSummary, | ||||
541 | const ModuleSummaryIndex *ImportSummary) | ||||
542 | : M(M), AARGetter(AARGetter), LookupDomTree(LookupDomTree), | ||||
543 | ExportSummary(ExportSummary), ImportSummary(ImportSummary), | ||||
544 | Int8Ty(Type::getInt8Ty(M.getContext())), | ||||
545 | Int8PtrTy(Type::getInt8PtrTy(M.getContext())), | ||||
546 | Int32Ty(Type::getInt32Ty(M.getContext())), | ||||
547 | Int64Ty(Type::getInt64Ty(M.getContext())), | ||||
548 | IntPtrTy(M.getDataLayout().getIntPtrType(M.getContext(), 0)), | ||||
549 | Int8Arr0Ty(ArrayType::get(Type::getInt8Ty(M.getContext()), 0)), | ||||
550 | RemarksEnabled(areRemarksEnabled()), OREGetter(OREGetter) { | ||||
551 | assert(!(ExportSummary && ImportSummary))((void)0); | ||||
552 | FunctionsToSkip.init(SkipFunctionNames); | ||||
553 | } | ||||
554 | |||||
555 | bool areRemarksEnabled(); | ||||
556 | |||||
557 | void | ||||
558 | scanTypeTestUsers(Function *TypeTestFunc, | ||||
559 | DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap); | ||||
560 | void scanTypeCheckedLoadUsers(Function *TypeCheckedLoadFunc); | ||||
561 | |||||
562 | void buildTypeIdentifierMap( | ||||
563 | std::vector<VTableBits> &Bits, | ||||
564 | DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap); | ||||
565 | bool | ||||
566 | tryFindVirtualCallTargets(std::vector<VirtualCallTarget> &TargetsForSlot, | ||||
567 | const std::set<TypeMemberInfo> &TypeMemberInfos, | ||||
568 | uint64_t ByteOffset); | ||||
569 | |||||
570 | void applySingleImplDevirt(VTableSlotInfo &SlotInfo, Constant *TheFn, | ||||
571 | bool &IsExported); | ||||
572 | bool trySingleImplDevirt(ModuleSummaryIndex *ExportSummary, | ||||
573 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
574 | VTableSlotInfo &SlotInfo, | ||||
575 | WholeProgramDevirtResolution *Res); | ||||
576 | |||||
577 | void applyICallBranchFunnel(VTableSlotInfo &SlotInfo, Constant *JT, | ||||
578 | bool &IsExported); | ||||
579 | void tryICallBranchFunnel(MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
580 | VTableSlotInfo &SlotInfo, | ||||
581 | WholeProgramDevirtResolution *Res, VTableSlot Slot); | ||||
582 | |||||
583 | bool tryEvaluateFunctionsWithArgs( | ||||
584 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
585 | ArrayRef<uint64_t> Args); | ||||
586 | |||||
587 | void applyUniformRetValOpt(CallSiteInfo &CSInfo, StringRef FnName, | ||||
588 | uint64_t TheRetVal); | ||||
589 | bool tryUniformRetValOpt(MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
590 | CallSiteInfo &CSInfo, | ||||
591 | WholeProgramDevirtResolution::ByArg *Res); | ||||
592 | |||||
593 | // Returns the global symbol name that is used to export information about the | ||||
594 | // given vtable slot and list of arguments. | ||||
595 | std::string getGlobalName(VTableSlot Slot, ArrayRef<uint64_t> Args, | ||||
596 | StringRef Name); | ||||
597 | |||||
598 | bool shouldExportConstantsAsAbsoluteSymbols(); | ||||
599 | |||||
600 | // This function is called during the export phase to create a symbol | ||||
601 | // definition containing information about the given vtable slot and list of | ||||
602 | // arguments. | ||||
603 | void exportGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args, StringRef Name, | ||||
604 | Constant *C); | ||||
605 | void exportConstant(VTableSlot Slot, ArrayRef<uint64_t> Args, StringRef Name, | ||||
606 | uint32_t Const, uint32_t &Storage); | ||||
607 | |||||
608 | // This function is called during the import phase to create a reference to | ||||
609 | // the symbol definition created during the export phase. | ||||
610 | Constant *importGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args, | ||||
611 | StringRef Name); | ||||
612 | Constant *importConstant(VTableSlot Slot, ArrayRef<uint64_t> Args, | ||||
613 | StringRef Name, IntegerType *IntTy, | ||||
614 | uint32_t Storage); | ||||
615 | |||||
616 | Constant *getMemberAddr(const TypeMemberInfo *M); | ||||
617 | |||||
618 | void applyUniqueRetValOpt(CallSiteInfo &CSInfo, StringRef FnName, bool IsOne, | ||||
619 | Constant *UniqueMemberAddr); | ||||
620 | bool tryUniqueRetValOpt(unsigned BitWidth, | ||||
621 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
622 | CallSiteInfo &CSInfo, | ||||
623 | WholeProgramDevirtResolution::ByArg *Res, | ||||
624 | VTableSlot Slot, ArrayRef<uint64_t> Args); | ||||
625 | |||||
626 | void applyVirtualConstProp(CallSiteInfo &CSInfo, StringRef FnName, | ||||
627 | Constant *Byte, Constant *Bit); | ||||
628 | bool tryVirtualConstProp(MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
629 | VTableSlotInfo &SlotInfo, | ||||
630 | WholeProgramDevirtResolution *Res, VTableSlot Slot); | ||||
631 | |||||
632 | void rebuildGlobal(VTableBits &B); | ||||
633 | |||||
634 | // Apply the summary resolution for Slot to all virtual calls in SlotInfo. | ||||
635 | void importResolution(VTableSlot Slot, VTableSlotInfo &SlotInfo); | ||||
636 | |||||
637 | // If we were able to eliminate all unsafe uses for a type checked load, | ||||
638 | // eliminate the associated type tests by replacing them with true. | ||||
639 | void removeRedundantTypeTests(); | ||||
640 | |||||
641 | bool run(); | ||||
642 | |||||
643 | // Lower the module using the action and summary passed as command line | ||||
644 | // arguments. For testing purposes only. | ||||
645 | static bool | ||||
646 | runForTesting(Module &M, function_ref<AAResults &(Function &)> AARGetter, | ||||
647 | function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter, | ||||
648 | function_ref<DominatorTree &(Function &)> LookupDomTree); | ||||
649 | }; | ||||
650 | |||||
651 | struct DevirtIndex { | ||||
652 | ModuleSummaryIndex &ExportSummary; | ||||
653 | // The set in which to record GUIDs exported from their module by | ||||
654 | // devirtualization, used by client to ensure they are not internalized. | ||||
655 | std::set<GlobalValue::GUID> &ExportedGUIDs; | ||||
656 | // A map in which to record the information necessary to locate the WPD | ||||
657 | // resolution for local targets in case they are exported by cross module | ||||
658 | // importing. | ||||
659 | std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap; | ||||
660 | |||||
661 | MapVector<VTableSlotSummary, VTableSlotInfo> CallSlots; | ||||
662 | |||||
663 | PatternList FunctionsToSkip; | ||||
664 | |||||
665 | DevirtIndex( | ||||
666 | ModuleSummaryIndex &ExportSummary, | ||||
667 | std::set<GlobalValue::GUID> &ExportedGUIDs, | ||||
668 | std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap) | ||||
669 | : ExportSummary(ExportSummary), ExportedGUIDs(ExportedGUIDs), | ||||
670 | LocalWPDTargetsMap(LocalWPDTargetsMap) { | ||||
671 | FunctionsToSkip.init(SkipFunctionNames); | ||||
672 | } | ||||
673 | |||||
674 | bool tryFindVirtualCallTargets(std::vector<ValueInfo> &TargetsForSlot, | ||||
675 | const TypeIdCompatibleVtableInfo TIdInfo, | ||||
676 | uint64_t ByteOffset); | ||||
677 | |||||
678 | bool trySingleImplDevirt(MutableArrayRef<ValueInfo> TargetsForSlot, | ||||
679 | VTableSlotSummary &SlotSummary, | ||||
680 | VTableSlotInfo &SlotInfo, | ||||
681 | WholeProgramDevirtResolution *Res, | ||||
682 | std::set<ValueInfo> &DevirtTargets); | ||||
683 | |||||
684 | void run(); | ||||
685 | }; | ||||
686 | |||||
687 | struct WholeProgramDevirt : public ModulePass { | ||||
688 | static char ID; | ||||
689 | |||||
690 | bool UseCommandLine = false; | ||||
691 | |||||
692 | ModuleSummaryIndex *ExportSummary = nullptr; | ||||
693 | const ModuleSummaryIndex *ImportSummary = nullptr; | ||||
694 | |||||
695 | WholeProgramDevirt() : ModulePass(ID), UseCommandLine(true) { | ||||
696 | initializeWholeProgramDevirtPass(*PassRegistry::getPassRegistry()); | ||||
697 | } | ||||
698 | |||||
699 | WholeProgramDevirt(ModuleSummaryIndex *ExportSummary, | ||||
700 | const ModuleSummaryIndex *ImportSummary) | ||||
701 | : ModulePass(ID), ExportSummary(ExportSummary), | ||||
702 | ImportSummary(ImportSummary) { | ||||
703 | initializeWholeProgramDevirtPass(*PassRegistry::getPassRegistry()); | ||||
704 | } | ||||
705 | |||||
706 | bool runOnModule(Module &M) override { | ||||
707 | if (skipModule(M)) | ||||
708 | return false; | ||||
709 | |||||
710 | // In the new pass manager, we can request the optimization | ||||
711 | // remark emitter pass on a per-function-basis, which the | ||||
712 | // OREGetter will do for us. | ||||
713 | // In the old pass manager, this is harder, so we just build | ||||
714 | // an optimization remark emitter on the fly, when we need it. | ||||
715 | std::unique_ptr<OptimizationRemarkEmitter> ORE; | ||||
716 | auto OREGetter = [&](Function *F) -> OptimizationRemarkEmitter & { | ||||
717 | ORE = std::make_unique<OptimizationRemarkEmitter>(F); | ||||
718 | return *ORE; | ||||
719 | }; | ||||
720 | |||||
721 | auto LookupDomTree = [this](Function &F) -> DominatorTree & { | ||||
722 | return this->getAnalysis<DominatorTreeWrapperPass>(F).getDomTree(); | ||||
723 | }; | ||||
724 | |||||
725 | if (UseCommandLine) | ||||
726 | return DevirtModule::runForTesting(M, LegacyAARGetter(*this), OREGetter, | ||||
727 | LookupDomTree); | ||||
728 | |||||
729 | return DevirtModule(M, LegacyAARGetter(*this), OREGetter, LookupDomTree, | ||||
730 | ExportSummary, ImportSummary) | ||||
731 | .run(); | ||||
732 | } | ||||
733 | |||||
734 | void getAnalysisUsage(AnalysisUsage &AU) const override { | ||||
735 | AU.addRequired<AssumptionCacheTracker>(); | ||||
736 | AU.addRequired<TargetLibraryInfoWrapperPass>(); | ||||
737 | AU.addRequired<DominatorTreeWrapperPass>(); | ||||
738 | } | ||||
739 | }; | ||||
740 | |||||
741 | } // end anonymous namespace | ||||
742 | |||||
743 | INITIALIZE_PASS_BEGIN(WholeProgramDevirt, "wholeprogramdevirt",static void *initializeWholeProgramDevirtPassOnce(PassRegistry &Registry) { | ||||
744 | "Whole program devirtualization", false, false)static void *initializeWholeProgramDevirtPassOnce(PassRegistry &Registry) { | ||||
745 | INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)initializeAssumptionCacheTrackerPass(Registry); | ||||
746 | INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)initializeTargetLibraryInfoWrapperPassPass(Registry); | ||||
747 | INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry); | ||||
748 | INITIALIZE_PASS_END(WholeProgramDevirt, "wholeprogramdevirt",PassInfo *PI = new PassInfo( "Whole program devirtualization" , "wholeprogramdevirt", &WholeProgramDevirt::ID, PassInfo ::NormalCtor_t(callDefaultCtor<WholeProgramDevirt>), false , false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeWholeProgramDevirtPassFlag; void llvm ::initializeWholeProgramDevirtPass(PassRegistry &Registry ) { llvm::call_once(InitializeWholeProgramDevirtPassFlag, initializeWholeProgramDevirtPassOnce , std::ref(Registry)); } | ||||
749 | "Whole program devirtualization", false, false)PassInfo *PI = new PassInfo( "Whole program devirtualization" , "wholeprogramdevirt", &WholeProgramDevirt::ID, PassInfo ::NormalCtor_t(callDefaultCtor<WholeProgramDevirt>), false , false); Registry.registerPass(*PI, true); return PI; } static llvm::once_flag InitializeWholeProgramDevirtPassFlag; void llvm ::initializeWholeProgramDevirtPass(PassRegistry &Registry ) { llvm::call_once(InitializeWholeProgramDevirtPassFlag, initializeWholeProgramDevirtPassOnce , std::ref(Registry)); } | ||||
750 | char WholeProgramDevirt::ID = 0; | ||||
751 | |||||
752 | ModulePass * | ||||
753 | llvm::createWholeProgramDevirtPass(ModuleSummaryIndex *ExportSummary, | ||||
754 | const ModuleSummaryIndex *ImportSummary) { | ||||
755 | return new WholeProgramDevirt(ExportSummary, ImportSummary); | ||||
756 | } | ||||
757 | |||||
758 | PreservedAnalyses WholeProgramDevirtPass::run(Module &M, | ||||
759 | ModuleAnalysisManager &AM) { | ||||
760 | auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); | ||||
761 | auto AARGetter = [&](Function &F) -> AAResults & { | ||||
762 | return FAM.getResult<AAManager>(F); | ||||
763 | }; | ||||
764 | auto OREGetter = [&](Function *F) -> OptimizationRemarkEmitter & { | ||||
765 | return FAM.getResult<OptimizationRemarkEmitterAnalysis>(*F); | ||||
766 | }; | ||||
767 | auto LookupDomTree = [&FAM](Function &F) -> DominatorTree & { | ||||
768 | return FAM.getResult<DominatorTreeAnalysis>(F); | ||||
769 | }; | ||||
770 | if (UseCommandLine) { | ||||
771 | if (DevirtModule::runForTesting(M, AARGetter, OREGetter, LookupDomTree)) | ||||
772 | return PreservedAnalyses::all(); | ||||
773 | return PreservedAnalyses::none(); | ||||
774 | } | ||||
775 | if (!DevirtModule(M, AARGetter, OREGetter, LookupDomTree, ExportSummary, | ||||
776 | ImportSummary) | ||||
777 | .run()) | ||||
778 | return PreservedAnalyses::all(); | ||||
779 | return PreservedAnalyses::none(); | ||||
780 | } | ||||
781 | |||||
782 | // Enable whole program visibility if enabled by client (e.g. linker) or | ||||
783 | // internal option, and not force disabled. | ||||
784 | static bool hasWholeProgramVisibility(bool WholeProgramVisibilityEnabledInLTO) { | ||||
785 | return (WholeProgramVisibilityEnabledInLTO || WholeProgramVisibility) && | ||||
786 | !DisableWholeProgramVisibility; | ||||
787 | } | ||||
788 | |||||
789 | namespace llvm { | ||||
790 | |||||
791 | /// If whole program visibility asserted, then upgrade all public vcall | ||||
792 | /// visibility metadata on vtable definitions to linkage unit visibility in | ||||
793 | /// Module IR (for regular or hybrid LTO). | ||||
794 | void updateVCallVisibilityInModule( | ||||
795 | Module &M, bool WholeProgramVisibilityEnabledInLTO, | ||||
796 | const DenseSet<GlobalValue::GUID> &DynamicExportSymbols) { | ||||
797 | if (!hasWholeProgramVisibility(WholeProgramVisibilityEnabledInLTO)) | ||||
798 | return; | ||||
799 | for (GlobalVariable &GV : M.globals()) | ||||
800 | // Add linkage unit visibility to any variable with type metadata, which are | ||||
801 | // the vtable definitions. We won't have an existing vcall_visibility | ||||
802 | // metadata on vtable definitions with public visibility. | ||||
803 | if (GV.hasMetadata(LLVMContext::MD_type) && | ||||
804 | GV.getVCallVisibility() == GlobalObject::VCallVisibilityPublic && | ||||
805 | // Don't upgrade the visibility for symbols exported to the dynamic | ||||
806 | // linker, as we have no information on their eventual use. | ||||
807 | !DynamicExportSymbols.count(GV.getGUID())) | ||||
808 | GV.setVCallVisibilityMetadata(GlobalObject::VCallVisibilityLinkageUnit); | ||||
809 | } | ||||
810 | |||||
811 | /// If whole program visibility asserted, then upgrade all public vcall | ||||
812 | /// visibility metadata on vtable definition summaries to linkage unit | ||||
813 | /// visibility in Module summary index (for ThinLTO). | ||||
814 | void updateVCallVisibilityInIndex( | ||||
815 | ModuleSummaryIndex &Index, bool WholeProgramVisibilityEnabledInLTO, | ||||
816 | const DenseSet<GlobalValue::GUID> &DynamicExportSymbols) { | ||||
817 | if (!hasWholeProgramVisibility(WholeProgramVisibilityEnabledInLTO)) | ||||
818 | return; | ||||
819 | for (auto &P : Index) { | ||||
820 | for (auto &S : P.second.SummaryList) { | ||||
821 | auto *GVar = dyn_cast<GlobalVarSummary>(S.get()); | ||||
822 | if (!GVar || | ||||
823 | GVar->getVCallVisibility() != GlobalObject::VCallVisibilityPublic || | ||||
824 | // Don't upgrade the visibility for symbols exported to the dynamic | ||||
825 | // linker, as we have no information on their eventual use. | ||||
826 | DynamicExportSymbols.count(P.first)) | ||||
827 | continue; | ||||
828 | GVar->setVCallVisibility(GlobalObject::VCallVisibilityLinkageUnit); | ||||
829 | } | ||||
830 | } | ||||
831 | } | ||||
832 | |||||
833 | void runWholeProgramDevirtOnIndex( | ||||
834 | ModuleSummaryIndex &Summary, std::set<GlobalValue::GUID> &ExportedGUIDs, | ||||
835 | std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap) { | ||||
836 | DevirtIndex(Summary, ExportedGUIDs, LocalWPDTargetsMap).run(); | ||||
837 | } | ||||
838 | |||||
839 | void updateIndexWPDForExports( | ||||
840 | ModuleSummaryIndex &Summary, | ||||
841 | function_ref<bool(StringRef, ValueInfo)> isExported, | ||||
842 | std::map<ValueInfo, std::vector<VTableSlotSummary>> &LocalWPDTargetsMap) { | ||||
843 | for (auto &T : LocalWPDTargetsMap) { | ||||
844 | auto &VI = T.first; | ||||
845 | // This was enforced earlier during trySingleImplDevirt. | ||||
846 | assert(VI.getSummaryList().size() == 1 &&((void)0) | ||||
847 | "Devirt of local target has more than one copy")((void)0); | ||||
848 | auto &S = VI.getSummaryList()[0]; | ||||
849 | if (!isExported(S->modulePath(), VI)) | ||||
850 | continue; | ||||
851 | |||||
852 | // It's been exported by a cross module import. | ||||
853 | for (auto &SlotSummary : T.second) { | ||||
854 | auto *TIdSum = Summary.getTypeIdSummary(SlotSummary.TypeID); | ||||
855 | assert(TIdSum)((void)0); | ||||
856 | auto WPDRes = TIdSum->WPDRes.find(SlotSummary.ByteOffset); | ||||
857 | assert(WPDRes != TIdSum->WPDRes.end())((void)0); | ||||
858 | WPDRes->second.SingleImplName = ModuleSummaryIndex::getGlobalNameForLocal( | ||||
859 | WPDRes->second.SingleImplName, | ||||
860 | Summary.getModuleHash(S->modulePath())); | ||||
861 | } | ||||
862 | } | ||||
863 | } | ||||
864 | |||||
865 | } // end namespace llvm | ||||
866 | |||||
867 | static Error checkCombinedSummaryForTesting(ModuleSummaryIndex *Summary) { | ||||
868 | // Check that summary index contains regular LTO module when performing | ||||
869 | // export to prevent occasional use of index from pure ThinLTO compilation | ||||
870 | // (-fno-split-lto-module). This kind of summary index is passed to | ||||
871 | // DevirtIndex::run, not to DevirtModule::run used by opt/runForTesting. | ||||
872 | const auto &ModPaths = Summary->modulePaths(); | ||||
873 | if (ClSummaryAction != PassSummaryAction::Import && | ||||
874 | ModPaths.find(ModuleSummaryIndex::getRegularLTOModuleName()) == | ||||
875 | ModPaths.end()) | ||||
876 | return createStringError( | ||||
877 | errc::invalid_argument, | ||||
878 | "combined summary should contain Regular LTO module"); | ||||
879 | return ErrorSuccess(); | ||||
880 | } | ||||
881 | |||||
882 | bool DevirtModule::runForTesting( | ||||
883 | Module &M, function_ref<AAResults &(Function &)> AARGetter, | ||||
884 | function_ref<OptimizationRemarkEmitter &(Function *)> OREGetter, | ||||
885 | function_ref<DominatorTree &(Function &)> LookupDomTree) { | ||||
886 | std::unique_ptr<ModuleSummaryIndex> Summary = | ||||
887 | std::make_unique<ModuleSummaryIndex>(/*HaveGVs=*/false); | ||||
888 | |||||
889 | // Handle the command-line summary arguments. This code is for testing | ||||
890 | // purposes only, so we handle errors directly. | ||||
891 | if (!ClReadSummary.empty()) { | ||||
892 | ExitOnError ExitOnErr("-wholeprogramdevirt-read-summary: " + ClReadSummary + | ||||
893 | ": "); | ||||
894 | auto ReadSummaryFile = | ||||
895 | ExitOnErr(errorOrToExpected(MemoryBuffer::getFile(ClReadSummary))); | ||||
896 | if (Expected<std::unique_ptr<ModuleSummaryIndex>> SummaryOrErr = | ||||
897 | getModuleSummaryIndex(*ReadSummaryFile)) { | ||||
898 | Summary = std::move(*SummaryOrErr); | ||||
899 | ExitOnErr(checkCombinedSummaryForTesting(Summary.get())); | ||||
900 | } else { | ||||
901 | // Try YAML if we've failed with bitcode. | ||||
902 | consumeError(SummaryOrErr.takeError()); | ||||
903 | yaml::Input In(ReadSummaryFile->getBuffer()); | ||||
904 | In >> *Summary; | ||||
905 | ExitOnErr(errorCodeToError(In.error())); | ||||
906 | } | ||||
907 | } | ||||
908 | |||||
909 | bool Changed = | ||||
910 | DevirtModule(M, AARGetter, OREGetter, LookupDomTree, | ||||
911 | ClSummaryAction == PassSummaryAction::Export ? Summary.get() | ||||
912 | : nullptr, | ||||
913 | ClSummaryAction == PassSummaryAction::Import ? Summary.get() | ||||
914 | : nullptr) | ||||
915 | .run(); | ||||
916 | |||||
917 | if (!ClWriteSummary.empty()) { | ||||
918 | ExitOnError ExitOnErr( | ||||
919 | "-wholeprogramdevirt-write-summary: " + ClWriteSummary + ": "); | ||||
920 | std::error_code EC; | ||||
921 | if (StringRef(ClWriteSummary).endswith(".bc")) { | ||||
922 | raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::OF_None); | ||||
923 | ExitOnErr(errorCodeToError(EC)); | ||||
924 | WriteIndexToFile(*Summary, OS); | ||||
925 | } else { | ||||
926 | raw_fd_ostream OS(ClWriteSummary, EC, sys::fs::OF_TextWithCRLF); | ||||
927 | ExitOnErr(errorCodeToError(EC)); | ||||
928 | yaml::Output Out(OS); | ||||
929 | Out << *Summary; | ||||
930 | } | ||||
931 | } | ||||
932 | |||||
933 | return Changed; | ||||
934 | } | ||||
935 | |||||
936 | void DevirtModule::buildTypeIdentifierMap( | ||||
937 | std::vector<VTableBits> &Bits, | ||||
938 | DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap) { | ||||
939 | DenseMap<GlobalVariable *, VTableBits *> GVToBits; | ||||
940 | Bits.reserve(M.getGlobalList().size()); | ||||
941 | SmallVector<MDNode *, 2> Types; | ||||
942 | for (GlobalVariable &GV : M.globals()) { | ||||
943 | Types.clear(); | ||||
944 | GV.getMetadata(LLVMContext::MD_type, Types); | ||||
945 | if (GV.isDeclaration() || Types.empty()) | ||||
946 | continue; | ||||
947 | |||||
948 | VTableBits *&BitsPtr = GVToBits[&GV]; | ||||
949 | if (!BitsPtr) { | ||||
950 | Bits.emplace_back(); | ||||
951 | Bits.back().GV = &GV; | ||||
952 | Bits.back().ObjectSize = | ||||
953 | M.getDataLayout().getTypeAllocSize(GV.getInitializer()->getType()); | ||||
954 | BitsPtr = &Bits.back(); | ||||
955 | } | ||||
956 | |||||
957 | for (MDNode *Type : Types) { | ||||
958 | auto TypeID = Type->getOperand(1).get(); | ||||
959 | |||||
960 | uint64_t Offset = | ||||
961 | cast<ConstantInt>( | ||||
962 | cast<ConstantAsMetadata>(Type->getOperand(0))->getValue()) | ||||
963 | ->getZExtValue(); | ||||
964 | |||||
965 | TypeIdMap[TypeID].insert({BitsPtr, Offset}); | ||||
966 | } | ||||
967 | } | ||||
968 | } | ||||
969 | |||||
970 | bool DevirtModule::tryFindVirtualCallTargets( | ||||
971 | std::vector<VirtualCallTarget> &TargetsForSlot, | ||||
972 | const std::set<TypeMemberInfo> &TypeMemberInfos, uint64_t ByteOffset) { | ||||
973 | for (const TypeMemberInfo &TM : TypeMemberInfos) { | ||||
974 | if (!TM.Bits->GV->isConstant()) | ||||
975 | return false; | ||||
976 | |||||
977 | // We cannot perform whole program devirtualization analysis on a vtable | ||||
978 | // with public LTO visibility. | ||||
979 | if (TM.Bits->GV->getVCallVisibility() == | ||||
980 | GlobalObject::VCallVisibilityPublic) | ||||
981 | return false; | ||||
982 | |||||
983 | Constant *Ptr = getPointerAtOffset(TM.Bits->GV->getInitializer(), | ||||
984 | TM.Offset + ByteOffset, M); | ||||
985 | if (!Ptr) | ||||
986 | return false; | ||||
987 | |||||
988 | auto Fn = dyn_cast<Function>(Ptr->stripPointerCasts()); | ||||
989 | if (!Fn) | ||||
990 | return false; | ||||
991 | |||||
992 | if (FunctionsToSkip.match(Fn->getName())) | ||||
993 | return false; | ||||
994 | |||||
995 | // We can disregard __cxa_pure_virtual as a possible call target, as | ||||
996 | // calls to pure virtuals are UB. | ||||
997 | if (Fn->getName() == "__cxa_pure_virtual") | ||||
998 | continue; | ||||
999 | |||||
1000 | TargetsForSlot.push_back({Fn, &TM}); | ||||
1001 | } | ||||
1002 | |||||
1003 | // Give up if we couldn't find any targets. | ||||
1004 | return !TargetsForSlot.empty(); | ||||
1005 | } | ||||
1006 | |||||
1007 | bool DevirtIndex::tryFindVirtualCallTargets( | ||||
1008 | std::vector<ValueInfo> &TargetsForSlot, const TypeIdCompatibleVtableInfo TIdInfo, | ||||
1009 | uint64_t ByteOffset) { | ||||
1010 | for (const TypeIdOffsetVtableInfo &P : TIdInfo) { | ||||
1011 | // Find a representative copy of the vtable initializer. | ||||
1012 | // We can have multiple available_externally, linkonce_odr and weak_odr | ||||
1013 | // vtable initializers. We can also have multiple external vtable | ||||
1014 | // initializers in the case of comdats, which we cannot check here. | ||||
1015 | // The linker should give an error in this case. | ||||
1016 | // | ||||
1017 | // Also, handle the case of same-named local Vtables with the same path | ||||
1018 | // and therefore the same GUID. This can happen if there isn't enough | ||||
1019 | // distinguishing path when compiling the source file. In that case we | ||||
1020 | // conservatively return false early. | ||||
1021 | const GlobalVarSummary *VS = nullptr; | ||||
1022 | bool LocalFound = false; | ||||
1023 | for (auto &S : P.VTableVI.getSummaryList()) { | ||||
1024 | if (GlobalValue::isLocalLinkage(S->linkage())) { | ||||
1025 | if (LocalFound) | ||||
1026 | return false; | ||||
1027 | LocalFound = true; | ||||
1028 | } | ||||
1029 | auto *CurVS = cast<GlobalVarSummary>(S->getBaseObject()); | ||||
1030 | if (!CurVS->vTableFuncs().empty() || | ||||
1031 | // Previously clang did not attach the necessary type metadata to | ||||
1032 | // available_externally vtables, in which case there would not | ||||
1033 | // be any vtable functions listed in the summary and we need | ||||
1034 | // to treat this case conservatively (in case the bitcode is old). | ||||
1035 | // However, we will also not have any vtable functions in the | ||||
1036 | // case of a pure virtual base class. In that case we do want | ||||
1037 | // to set VS to avoid treating it conservatively. | ||||
1038 | !GlobalValue::isAvailableExternallyLinkage(S->linkage())) { | ||||
1039 | VS = CurVS; | ||||
1040 | // We cannot perform whole program devirtualization analysis on a vtable | ||||
1041 | // with public LTO visibility. | ||||
1042 | if (VS->getVCallVisibility() == GlobalObject::VCallVisibilityPublic) | ||||
1043 | return false; | ||||
1044 | } | ||||
1045 | } | ||||
1046 | // There will be no VS if all copies are available_externally having no | ||||
1047 | // type metadata. In that case we can't safely perform WPD. | ||||
1048 | if (!VS) | ||||
1049 | return false; | ||||
1050 | if (!VS->isLive()) | ||||
1051 | continue; | ||||
1052 | for (auto VTP : VS->vTableFuncs()) { | ||||
1053 | if (VTP.VTableOffset != P.AddressPointOffset + ByteOffset) | ||||
1054 | continue; | ||||
1055 | |||||
1056 | TargetsForSlot.push_back(VTP.FuncVI); | ||||
1057 | } | ||||
1058 | } | ||||
1059 | |||||
1060 | // Give up if we couldn't find any targets. | ||||
1061 | return !TargetsForSlot.empty(); | ||||
1062 | } | ||||
1063 | |||||
1064 | void DevirtModule::applySingleImplDevirt(VTableSlotInfo &SlotInfo, | ||||
1065 | Constant *TheFn, bool &IsExported) { | ||||
1066 | // Don't devirtualize function if we're told to skip it | ||||
1067 | // in -wholeprogramdevirt-skip. | ||||
1068 | if (FunctionsToSkip.match(TheFn->stripPointerCasts()->getName())) | ||||
1069 | return; | ||||
1070 | auto Apply = [&](CallSiteInfo &CSInfo) { | ||||
1071 | for (auto &&VCallSite : CSInfo.CallSites) { | ||||
1072 | if (!OptimizedCalls.insert(&VCallSite.CB).second) | ||||
1073 | continue; | ||||
1074 | |||||
1075 | if (RemarksEnabled) | ||||
1076 | VCallSite.emitRemark("single-impl", | ||||
1077 | TheFn->stripPointerCasts()->getName(), OREGetter); | ||||
1078 | auto &CB = VCallSite.CB; | ||||
1079 | assert(!CB.getCalledFunction() && "devirtualizing direct call?")((void)0); | ||||
1080 | IRBuilder<> Builder(&CB); | ||||
1081 | Value *Callee = | ||||
1082 | Builder.CreateBitCast(TheFn, CB.getCalledOperand()->getType()); | ||||
1083 | |||||
1084 | // If checking is enabled, add support to compare the virtual function | ||||
1085 | // pointer to the devirtualized target. In case of a mismatch, perform a | ||||
1086 | // debug trap. | ||||
1087 | if (CheckDevirt) { | ||||
1088 | auto *Cond = Builder.CreateICmpNE(CB.getCalledOperand(), Callee); | ||||
1089 | Instruction *ThenTerm = | ||||
1090 | SplitBlockAndInsertIfThen(Cond, &CB, /*Unreachable=*/false); | ||||
1091 | Builder.SetInsertPoint(ThenTerm); | ||||
1092 | Function *TrapFn = Intrinsic::getDeclaration(&M, Intrinsic::debugtrap); | ||||
1093 | auto *CallTrap = Builder.CreateCall(TrapFn); | ||||
1094 | CallTrap->setDebugLoc(CB.getDebugLoc()); | ||||
1095 | } | ||||
1096 | |||||
1097 | // Devirtualize. | ||||
1098 | CB.setCalledOperand(Callee); | ||||
1099 | |||||
1100 | // This use is no longer unsafe. | ||||
1101 | if (VCallSite.NumUnsafeUses) | ||||
1102 | --*VCallSite.NumUnsafeUses; | ||||
1103 | } | ||||
1104 | if (CSInfo.isExported()) | ||||
1105 | IsExported = true; | ||||
1106 | CSInfo.markDevirt(); | ||||
1107 | }; | ||||
1108 | Apply(SlotInfo.CSInfo); | ||||
1109 | for (auto &P : SlotInfo.ConstCSInfo) | ||||
1110 | Apply(P.second); | ||||
1111 | } | ||||
1112 | |||||
1113 | static bool AddCalls(VTableSlotInfo &SlotInfo, const ValueInfo &Callee) { | ||||
1114 | // We can't add calls if we haven't seen a definition | ||||
1115 | if (Callee.getSummaryList().empty()) | ||||
1116 | return false; | ||||
1117 | |||||
1118 | // Insert calls into the summary index so that the devirtualized targets | ||||
1119 | // are eligible for import. | ||||
1120 | // FIXME: Annotate type tests with hotness. For now, mark these as hot | ||||
1121 | // to better ensure we have the opportunity to inline them. | ||||
1122 | bool IsExported = false; | ||||
1123 | auto &S = Callee.getSummaryList()[0]; | ||||
1124 | CalleeInfo CI(CalleeInfo::HotnessType::Hot, /* RelBF = */ 0); | ||||
1125 | auto AddCalls = [&](CallSiteInfo &CSInfo) { | ||||
1126 | for (auto *FS : CSInfo.SummaryTypeCheckedLoadUsers) { | ||||
1127 | FS->addCall({Callee, CI}); | ||||
1128 | IsExported |= S->modulePath() != FS->modulePath(); | ||||
1129 | } | ||||
1130 | for (auto *FS : CSInfo.SummaryTypeTestAssumeUsers) { | ||||
1131 | FS->addCall({Callee, CI}); | ||||
1132 | IsExported |= S->modulePath() != FS->modulePath(); | ||||
1133 | } | ||||
1134 | }; | ||||
1135 | AddCalls(SlotInfo.CSInfo); | ||||
1136 | for (auto &P : SlotInfo.ConstCSInfo) | ||||
1137 | AddCalls(P.second); | ||||
1138 | return IsExported; | ||||
1139 | } | ||||
1140 | |||||
1141 | bool DevirtModule::trySingleImplDevirt( | ||||
1142 | ModuleSummaryIndex *ExportSummary, | ||||
1143 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, VTableSlotInfo &SlotInfo, | ||||
1144 | WholeProgramDevirtResolution *Res) { | ||||
1145 | // See if the program contains a single implementation of this virtual | ||||
1146 | // function. | ||||
1147 | Function *TheFn = TargetsForSlot[0].Fn; | ||||
1148 | for (auto &&Target : TargetsForSlot) | ||||
1149 | if (TheFn != Target.Fn) | ||||
1150 | return false; | ||||
1151 | |||||
1152 | // If so, update each call site to call that implementation directly. | ||||
1153 | if (RemarksEnabled) | ||||
1154 | TargetsForSlot[0].WasDevirt = true; | ||||
1155 | |||||
1156 | bool IsExported = false; | ||||
1157 | applySingleImplDevirt(SlotInfo, TheFn, IsExported); | ||||
1158 | if (!IsExported) | ||||
1159 | return false; | ||||
1160 | |||||
1161 | // If the only implementation has local linkage, we must promote to external | ||||
1162 | // to make it visible to thin LTO objects. We can only get here during the | ||||
1163 | // ThinLTO export phase. | ||||
1164 | if (TheFn->hasLocalLinkage()) { | ||||
1165 | std::string NewName = (TheFn->getName() + ".llvm.merged").str(); | ||||
1166 | |||||
1167 | // Since we are renaming the function, any comdats with the same name must | ||||
1168 | // also be renamed. This is required when targeting COFF, as the comdat name | ||||
1169 | // must match one of the names of the symbols in the comdat. | ||||
1170 | if (Comdat *C = TheFn->getComdat()) { | ||||
1171 | if (C->getName() == TheFn->getName()) { | ||||
1172 | Comdat *NewC = M.getOrInsertComdat(NewName); | ||||
1173 | NewC->setSelectionKind(C->getSelectionKind()); | ||||
1174 | for (GlobalObject &GO : M.global_objects()) | ||||
1175 | if (GO.getComdat() == C) | ||||
1176 | GO.setComdat(NewC); | ||||
1177 | } | ||||
1178 | } | ||||
1179 | |||||
1180 | TheFn->setLinkage(GlobalValue::ExternalLinkage); | ||||
1181 | TheFn->setVisibility(GlobalValue::HiddenVisibility); | ||||
1182 | TheFn->setName(NewName); | ||||
1183 | } | ||||
1184 | if (ValueInfo TheFnVI = ExportSummary->getValueInfo(TheFn->getGUID())) | ||||
1185 | // Any needed promotion of 'TheFn' has already been done during | ||||
1186 | // LTO unit split, so we can ignore return value of AddCalls. | ||||
1187 | AddCalls(SlotInfo, TheFnVI); | ||||
1188 | |||||
1189 | Res->TheKind = WholeProgramDevirtResolution::SingleImpl; | ||||
1190 | Res->SingleImplName = std::string(TheFn->getName()); | ||||
1191 | |||||
1192 | return true; | ||||
1193 | } | ||||
1194 | |||||
1195 | bool DevirtIndex::trySingleImplDevirt(MutableArrayRef<ValueInfo> TargetsForSlot, | ||||
1196 | VTableSlotSummary &SlotSummary, | ||||
1197 | VTableSlotInfo &SlotInfo, | ||||
1198 | WholeProgramDevirtResolution *Res, | ||||
1199 | std::set<ValueInfo> &DevirtTargets) { | ||||
1200 | // See if the program contains a single implementation of this virtual | ||||
1201 | // function. | ||||
1202 | auto TheFn = TargetsForSlot[0]; | ||||
1203 | for (auto &&Target : TargetsForSlot) | ||||
1204 | if (TheFn != Target) | ||||
1205 | return false; | ||||
1206 | |||||
1207 | // Don't devirtualize if we don't have target definition. | ||||
1208 | auto Size = TheFn.getSummaryList().size(); | ||||
1209 | if (!Size) | ||||
1210 | return false; | ||||
1211 | |||||
1212 | // Don't devirtualize function if we're told to skip it | ||||
1213 | // in -wholeprogramdevirt-skip. | ||||
1214 | if (FunctionsToSkip.match(TheFn.name())) | ||||
1215 | return false; | ||||
1216 | |||||
1217 | // If the summary list contains multiple summaries where at least one is | ||||
1218 | // a local, give up, as we won't know which (possibly promoted) name to use. | ||||
1219 | for (auto &S : TheFn.getSummaryList()) | ||||
1220 | if (GlobalValue::isLocalLinkage(S->linkage()) && Size > 1) | ||||
1221 | return false; | ||||
1222 | |||||
1223 | // Collect functions devirtualized at least for one call site for stats. | ||||
1224 | if (PrintSummaryDevirt) | ||||
1225 | DevirtTargets.insert(TheFn); | ||||
1226 | |||||
1227 | auto &S = TheFn.getSummaryList()[0]; | ||||
1228 | bool IsExported = AddCalls(SlotInfo, TheFn); | ||||
1229 | if (IsExported) | ||||
1230 | ExportedGUIDs.insert(TheFn.getGUID()); | ||||
1231 | |||||
1232 | // Record in summary for use in devirtualization during the ThinLTO import | ||||
1233 | // step. | ||||
1234 | Res->TheKind = WholeProgramDevirtResolution::SingleImpl; | ||||
1235 | if (GlobalValue::isLocalLinkage(S->linkage())) { | ||||
1236 | if (IsExported) | ||||
1237 | // If target is a local function and we are exporting it by | ||||
1238 | // devirtualizing a call in another module, we need to record the | ||||
1239 | // promoted name. | ||||
1240 | Res->SingleImplName = ModuleSummaryIndex::getGlobalNameForLocal( | ||||
1241 | TheFn.name(), ExportSummary.getModuleHash(S->modulePath())); | ||||
1242 | else { | ||||
1243 | LocalWPDTargetsMap[TheFn].push_back(SlotSummary); | ||||
1244 | Res->SingleImplName = std::string(TheFn.name()); | ||||
1245 | } | ||||
1246 | } else | ||||
1247 | Res->SingleImplName = std::string(TheFn.name()); | ||||
1248 | |||||
1249 | // Name will be empty if this thin link driven off of serialized combined | ||||
1250 | // index (e.g. llvm-lto). However, WPD is not supported/invoked for the | ||||
1251 | // legacy LTO API anyway. | ||||
1252 | assert(!Res->SingleImplName.empty())((void)0); | ||||
1253 | |||||
1254 | return true; | ||||
1255 | } | ||||
1256 | |||||
1257 | void DevirtModule::tryICallBranchFunnel( | ||||
1258 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, VTableSlotInfo &SlotInfo, | ||||
1259 | WholeProgramDevirtResolution *Res, VTableSlot Slot) { | ||||
1260 | Triple T(M.getTargetTriple()); | ||||
1261 | if (T.getArch() != Triple::x86_64) | ||||
1262 | return; | ||||
1263 | |||||
1264 | if (TargetsForSlot.size() > ClThreshold) | ||||
1265 | return; | ||||
1266 | |||||
1267 | bool HasNonDevirt = !SlotInfo.CSInfo.AllCallSitesDevirted; | ||||
1268 | if (!HasNonDevirt) | ||||
1269 | for (auto &P : SlotInfo.ConstCSInfo) | ||||
1270 | if (!P.second.AllCallSitesDevirted) { | ||||
1271 | HasNonDevirt = true; | ||||
1272 | break; | ||||
1273 | } | ||||
1274 | |||||
1275 | if (!HasNonDevirt) | ||||
1276 | return; | ||||
1277 | |||||
1278 | FunctionType *FT = | ||||
1279 | FunctionType::get(Type::getVoidTy(M.getContext()), {Int8PtrTy}, true); | ||||
1280 | Function *JT; | ||||
1281 | if (isa<MDString>(Slot.TypeID)) { | ||||
1282 | JT = Function::Create(FT, Function::ExternalLinkage, | ||||
1283 | M.getDataLayout().getProgramAddressSpace(), | ||||
1284 | getGlobalName(Slot, {}, "branch_funnel"), &M); | ||||
1285 | JT->setVisibility(GlobalValue::HiddenVisibility); | ||||
1286 | } else { | ||||
1287 | JT = Function::Create(FT, Function::InternalLinkage, | ||||
1288 | M.getDataLayout().getProgramAddressSpace(), | ||||
1289 | "branch_funnel", &M); | ||||
1290 | } | ||||
1291 | JT->addAttribute(1, Attribute::Nest); | ||||
1292 | |||||
1293 | std::vector<Value *> JTArgs; | ||||
1294 | JTArgs.push_back(JT->arg_begin()); | ||||
1295 | for (auto &T : TargetsForSlot) { | ||||
1296 | JTArgs.push_back(getMemberAddr(T.TM)); | ||||
1297 | JTArgs.push_back(T.Fn); | ||||
1298 | } | ||||
1299 | |||||
1300 | BasicBlock *BB = BasicBlock::Create(M.getContext(), "", JT, nullptr); | ||||
1301 | Function *Intr = | ||||
1302 | Intrinsic::getDeclaration(&M, llvm::Intrinsic::icall_branch_funnel, {}); | ||||
1303 | |||||
1304 | auto *CI = CallInst::Create(Intr, JTArgs, "", BB); | ||||
1305 | CI->setTailCallKind(CallInst::TCK_MustTail); | ||||
1306 | ReturnInst::Create(M.getContext(), nullptr, BB); | ||||
1307 | |||||
1308 | bool IsExported = false; | ||||
1309 | applyICallBranchFunnel(SlotInfo, JT, IsExported); | ||||
1310 | if (IsExported) | ||||
1311 | Res->TheKind = WholeProgramDevirtResolution::BranchFunnel; | ||||
1312 | } | ||||
1313 | |||||
1314 | void DevirtModule::applyICallBranchFunnel(VTableSlotInfo &SlotInfo, | ||||
1315 | Constant *JT, bool &IsExported) { | ||||
1316 | auto Apply = [&](CallSiteInfo &CSInfo) { | ||||
1317 | if (CSInfo.isExported()) | ||||
1318 | IsExported = true; | ||||
1319 | if (CSInfo.AllCallSitesDevirted) | ||||
1320 | return; | ||||
1321 | for (auto &&VCallSite : CSInfo.CallSites) { | ||||
1322 | CallBase &CB = VCallSite.CB; | ||||
1323 | |||||
1324 | // Jump tables are only profitable if the retpoline mitigation is enabled. | ||||
1325 | Attribute FSAttr = CB.getCaller()->getFnAttribute("target-features"); | ||||
1326 | if (!FSAttr.isValid() || | ||||
1327 | !FSAttr.getValueAsString().contains("+retpoline")) | ||||
1328 | continue; | ||||
1329 | |||||
1330 | if (RemarksEnabled) | ||||
1331 | VCallSite.emitRemark("branch-funnel", | ||||
1332 | JT->stripPointerCasts()->getName(), OREGetter); | ||||
1333 | |||||
1334 | // Pass the address of the vtable in the nest register, which is r10 on | ||||
1335 | // x86_64. | ||||
1336 | std::vector<Type *> NewArgs; | ||||
1337 | NewArgs.push_back(Int8PtrTy); | ||||
1338 | append_range(NewArgs, CB.getFunctionType()->params()); | ||||
1339 | FunctionType *NewFT = | ||||
1340 | FunctionType::get(CB.getFunctionType()->getReturnType(), NewArgs, | ||||
1341 | CB.getFunctionType()->isVarArg()); | ||||
1342 | PointerType *NewFTPtr = PointerType::getUnqual(NewFT); | ||||
1343 | |||||
1344 | IRBuilder<> IRB(&CB); | ||||
1345 | std::vector<Value *> Args; | ||||
1346 | Args.push_back(IRB.CreateBitCast(VCallSite.VTable, Int8PtrTy)); | ||||
1347 | llvm::append_range(Args, CB.args()); | ||||
1348 | |||||
1349 | CallBase *NewCS = nullptr; | ||||
1350 | if (isa<CallInst>(CB)) | ||||
1351 | NewCS = IRB.CreateCall(NewFT, IRB.CreateBitCast(JT, NewFTPtr), Args); | ||||
1352 | else | ||||
1353 | NewCS = IRB.CreateInvoke(NewFT, IRB.CreateBitCast(JT, NewFTPtr), | ||||
1354 | cast<InvokeInst>(CB).getNormalDest(), | ||||
1355 | cast<InvokeInst>(CB).getUnwindDest(), Args); | ||||
1356 | NewCS->setCallingConv(CB.getCallingConv()); | ||||
1357 | |||||
1358 | AttributeList Attrs = CB.getAttributes(); | ||||
1359 | std::vector<AttributeSet> NewArgAttrs; | ||||
1360 | NewArgAttrs.push_back(AttributeSet::get( | ||||
1361 | M.getContext(), ArrayRef<Attribute>{Attribute::get( | ||||
1362 | M.getContext(), Attribute::Nest)})); | ||||
1363 | for (unsigned I = 0; I + 2 < Attrs.getNumAttrSets(); ++I) | ||||
1364 | NewArgAttrs.push_back(Attrs.getParamAttributes(I)); | ||||
1365 | NewCS->setAttributes( | ||||
1366 | AttributeList::get(M.getContext(), Attrs.getFnAttributes(), | ||||
1367 | Attrs.getRetAttributes(), NewArgAttrs)); | ||||
1368 | |||||
1369 | CB.replaceAllUsesWith(NewCS); | ||||
1370 | CB.eraseFromParent(); | ||||
1371 | |||||
1372 | // This use is no longer unsafe. | ||||
1373 | if (VCallSite.NumUnsafeUses) | ||||
1374 | --*VCallSite.NumUnsafeUses; | ||||
1375 | } | ||||
1376 | // Don't mark as devirtualized because there may be callers compiled without | ||||
1377 | // retpoline mitigation, which would mean that they are lowered to | ||||
1378 | // llvm.type.test and therefore require an llvm.type.test resolution for the | ||||
1379 | // type identifier. | ||||
1380 | }; | ||||
1381 | Apply(SlotInfo.CSInfo); | ||||
1382 | for (auto &P : SlotInfo.ConstCSInfo) | ||||
1383 | Apply(P.second); | ||||
1384 | } | ||||
1385 | |||||
1386 | bool DevirtModule::tryEvaluateFunctionsWithArgs( | ||||
1387 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
1388 | ArrayRef<uint64_t> Args) { | ||||
1389 | // Evaluate each function and store the result in each target's RetVal | ||||
1390 | // field. | ||||
1391 | for (VirtualCallTarget &Target : TargetsForSlot) { | ||||
1392 | if (Target.Fn->arg_size() != Args.size() + 1) | ||||
1393 | return false; | ||||
1394 | |||||
1395 | Evaluator Eval(M.getDataLayout(), nullptr); | ||||
1396 | SmallVector<Constant *, 2> EvalArgs; | ||||
1397 | EvalArgs.push_back( | ||||
1398 | Constant::getNullValue(Target.Fn->getFunctionType()->getParamType(0))); | ||||
1399 | for (unsigned I = 0; I != Args.size(); ++I) { | ||||
1400 | auto *ArgTy = dyn_cast<IntegerType>( | ||||
1401 | Target.Fn->getFunctionType()->getParamType(I + 1)); | ||||
1402 | if (!ArgTy) | ||||
1403 | return false; | ||||
1404 | EvalArgs.push_back(ConstantInt::get(ArgTy, Args[I])); | ||||
1405 | } | ||||
1406 | |||||
1407 | Constant *RetVal; | ||||
1408 | if (!Eval.EvaluateFunction(Target.Fn, RetVal, EvalArgs) || | ||||
1409 | !isa<ConstantInt>(RetVal)) | ||||
1410 | return false; | ||||
1411 | Target.RetVal = cast<ConstantInt>(RetVal)->getZExtValue(); | ||||
1412 | } | ||||
1413 | return true; | ||||
1414 | } | ||||
1415 | |||||
1416 | void DevirtModule::applyUniformRetValOpt(CallSiteInfo &CSInfo, StringRef FnName, | ||||
1417 | uint64_t TheRetVal) { | ||||
1418 | for (auto Call : CSInfo.CallSites) { | ||||
1419 | if (!OptimizedCalls.insert(&Call.CB).second) | ||||
1420 | continue; | ||||
1421 | Call.replaceAndErase( | ||||
1422 | "uniform-ret-val", FnName, RemarksEnabled, OREGetter, | ||||
1423 | ConstantInt::get(cast<IntegerType>(Call.CB.getType()), TheRetVal)); | ||||
1424 | } | ||||
1425 | CSInfo.markDevirt(); | ||||
1426 | } | ||||
1427 | |||||
1428 | bool DevirtModule::tryUniformRetValOpt( | ||||
1429 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, CallSiteInfo &CSInfo, | ||||
1430 | WholeProgramDevirtResolution::ByArg *Res) { | ||||
1431 | // Uniform return value optimization. If all functions return the same | ||||
1432 | // constant, replace all calls with that constant. | ||||
1433 | uint64_t TheRetVal = TargetsForSlot[0].RetVal; | ||||
1434 | for (const VirtualCallTarget &Target : TargetsForSlot) | ||||
1435 | if (Target.RetVal != TheRetVal) | ||||
1436 | return false; | ||||
1437 | |||||
1438 | if (CSInfo.isExported()) { | ||||
1439 | Res->TheKind = WholeProgramDevirtResolution::ByArg::UniformRetVal; | ||||
1440 | Res->Info = TheRetVal; | ||||
1441 | } | ||||
1442 | |||||
1443 | applyUniformRetValOpt(CSInfo, TargetsForSlot[0].Fn->getName(), TheRetVal); | ||||
1444 | if (RemarksEnabled) | ||||
1445 | for (auto &&Target : TargetsForSlot) | ||||
1446 | Target.WasDevirt = true; | ||||
1447 | return true; | ||||
1448 | } | ||||
1449 | |||||
1450 | std::string DevirtModule::getGlobalName(VTableSlot Slot, | ||||
1451 | ArrayRef<uint64_t> Args, | ||||
1452 | StringRef Name) { | ||||
1453 | std::string FullName = "__typeid_"; | ||||
1454 | raw_string_ostream OS(FullName); | ||||
1455 | OS << cast<MDString>(Slot.TypeID)->getString() << '_' << Slot.ByteOffset; | ||||
1456 | for (uint64_t Arg : Args) | ||||
1457 | OS << '_' << Arg; | ||||
1458 | OS << '_' << Name; | ||||
1459 | return OS.str(); | ||||
1460 | } | ||||
1461 | |||||
1462 | bool DevirtModule::shouldExportConstantsAsAbsoluteSymbols() { | ||||
1463 | Triple T(M.getTargetTriple()); | ||||
1464 | return T.isX86() && T.getObjectFormat() == Triple::ELF; | ||||
1465 | } | ||||
1466 | |||||
1467 | void DevirtModule::exportGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args, | ||||
1468 | StringRef Name, Constant *C) { | ||||
1469 | GlobalAlias *GA = GlobalAlias::create(Int8Ty, 0, GlobalValue::ExternalLinkage, | ||||
1470 | getGlobalName(Slot, Args, Name), C, &M); | ||||
1471 | GA->setVisibility(GlobalValue::HiddenVisibility); | ||||
1472 | } | ||||
1473 | |||||
1474 | void DevirtModule::exportConstant(VTableSlot Slot, ArrayRef<uint64_t> Args, | ||||
1475 | StringRef Name, uint32_t Const, | ||||
1476 | uint32_t &Storage) { | ||||
1477 | if (shouldExportConstantsAsAbsoluteSymbols()) { | ||||
1478 | exportGlobal( | ||||
1479 | Slot, Args, Name, | ||||
1480 | ConstantExpr::getIntToPtr(ConstantInt::get(Int32Ty, Const), Int8PtrTy)); | ||||
1481 | return; | ||||
1482 | } | ||||
1483 | |||||
1484 | Storage = Const; | ||||
1485 | } | ||||
1486 | |||||
1487 | Constant *DevirtModule::importGlobal(VTableSlot Slot, ArrayRef<uint64_t> Args, | ||||
1488 | StringRef Name) { | ||||
1489 | Constant *C = | ||||
1490 | M.getOrInsertGlobal(getGlobalName(Slot, Args, Name), Int8Arr0Ty); | ||||
1491 | auto *GV = dyn_cast<GlobalVariable>(C); | ||||
1492 | if (GV) | ||||
1493 | GV->setVisibility(GlobalValue::HiddenVisibility); | ||||
1494 | return C; | ||||
1495 | } | ||||
1496 | |||||
1497 | Constant *DevirtModule::importConstant(VTableSlot Slot, ArrayRef<uint64_t> Args, | ||||
1498 | StringRef Name, IntegerType *IntTy, | ||||
1499 | uint32_t Storage) { | ||||
1500 | if (!shouldExportConstantsAsAbsoluteSymbols()) | ||||
1501 | return ConstantInt::get(IntTy, Storage); | ||||
1502 | |||||
1503 | Constant *C = importGlobal(Slot, Args, Name); | ||||
1504 | auto *GV = cast<GlobalVariable>(C->stripPointerCasts()); | ||||
1505 | C = ConstantExpr::getPtrToInt(C, IntTy); | ||||
1506 | |||||
1507 | // We only need to set metadata if the global is newly created, in which | ||||
1508 | // case it would not have hidden visibility. | ||||
1509 | if (GV->hasMetadata(LLVMContext::MD_absolute_symbol)) | ||||
1510 | return C; | ||||
1511 | |||||
1512 | auto SetAbsRange = [&](uint64_t Min, uint64_t Max) { | ||||
1513 | auto *MinC = ConstantAsMetadata::get(ConstantInt::get(IntPtrTy, Min)); | ||||
1514 | auto *MaxC = ConstantAsMetadata::get(ConstantInt::get(IntPtrTy, Max)); | ||||
1515 | GV->setMetadata(LLVMContext::MD_absolute_symbol, | ||||
1516 | MDNode::get(M.getContext(), {MinC, MaxC})); | ||||
1517 | }; | ||||
1518 | unsigned AbsWidth = IntTy->getBitWidth(); | ||||
1519 | if (AbsWidth == IntPtrTy->getBitWidth()) | ||||
1520 | SetAbsRange(~0ull, ~0ull); // Full set. | ||||
1521 | else | ||||
1522 | SetAbsRange(0, 1ull << AbsWidth); | ||||
1523 | return C; | ||||
1524 | } | ||||
1525 | |||||
1526 | void DevirtModule::applyUniqueRetValOpt(CallSiteInfo &CSInfo, StringRef FnName, | ||||
1527 | bool IsOne, | ||||
1528 | Constant *UniqueMemberAddr) { | ||||
1529 | for (auto &&Call : CSInfo.CallSites) { | ||||
1530 | if (!OptimizedCalls.insert(&Call.CB).second) | ||||
1531 | continue; | ||||
1532 | IRBuilder<> B(&Call.CB); | ||||
1533 | Value *Cmp = | ||||
1534 | B.CreateICmp(IsOne ? ICmpInst::ICMP_EQ : ICmpInst::ICMP_NE, Call.VTable, | ||||
1535 | B.CreateBitCast(UniqueMemberAddr, Call.VTable->getType())); | ||||
1536 | Cmp = B.CreateZExt(Cmp, Call.CB.getType()); | ||||
1537 | Call.replaceAndErase("unique-ret-val", FnName, RemarksEnabled, OREGetter, | ||||
1538 | Cmp); | ||||
1539 | } | ||||
1540 | CSInfo.markDevirt(); | ||||
1541 | } | ||||
1542 | |||||
1543 | Constant *DevirtModule::getMemberAddr(const TypeMemberInfo *M) { | ||||
1544 | Constant *C = ConstantExpr::getBitCast(M->Bits->GV, Int8PtrTy); | ||||
1545 | return ConstantExpr::getGetElementPtr(Int8Ty, C, | ||||
1546 | ConstantInt::get(Int64Ty, M->Offset)); | ||||
1547 | } | ||||
1548 | |||||
1549 | bool DevirtModule::tryUniqueRetValOpt( | ||||
1550 | unsigned BitWidth, MutableArrayRef<VirtualCallTarget> TargetsForSlot, | ||||
1551 | CallSiteInfo &CSInfo, WholeProgramDevirtResolution::ByArg *Res, | ||||
1552 | VTableSlot Slot, ArrayRef<uint64_t> Args) { | ||||
1553 | // IsOne controls whether we look for a 0 or a 1. | ||||
1554 | auto tryUniqueRetValOptFor = [&](bool IsOne) { | ||||
1555 | const TypeMemberInfo *UniqueMember = nullptr; | ||||
1556 | for (const VirtualCallTarget &Target : TargetsForSlot) { | ||||
1557 | if (Target.RetVal == (IsOne
| ||||
1558 | if (UniqueMember
| ||||
1559 | return false; | ||||
1560 | UniqueMember = Target.TM; | ||||
1561 | } | ||||
1562 | } | ||||
1563 | |||||
1564 | // We should have found a unique member or bailed out by now. We already | ||||
1565 | // checked for a uniform return value in tryUniformRetValOpt. | ||||
1566 | assert(UniqueMember)((void)0); | ||||
1567 | |||||
1568 | Constant *UniqueMemberAddr = getMemberAddr(UniqueMember); | ||||
1569 | if (CSInfo.isExported()) { | ||||
1570 | Res->TheKind = WholeProgramDevirtResolution::ByArg::UniqueRetVal; | ||||
| |||||
1571 | Res->Info = IsOne; | ||||
1572 | |||||
1573 | exportGlobal(Slot, Args, "unique_member", UniqueMemberAddr); | ||||
1574 | } | ||||
1575 | |||||
1576 | // Replace each call with the comparison. | ||||
1577 | applyUniqueRetValOpt(CSInfo, TargetsForSlot[0].Fn->getName(), IsOne, | ||||
1578 | UniqueMemberAddr); | ||||
1579 | |||||
1580 | // Update devirtualization statistics for targets. | ||||
1581 | if (RemarksEnabled) | ||||
1582 | for (auto &&Target : TargetsForSlot) | ||||
1583 | Target.WasDevirt = true; | ||||
1584 | |||||
1585 | return true; | ||||
1586 | }; | ||||
1587 | |||||
1588 | if (BitWidth == 1) { | ||||
1589 | if (tryUniqueRetValOptFor(true)) | ||||
1590 | return true; | ||||
1591 | if (tryUniqueRetValOptFor(false)) | ||||
1592 | return true; | ||||
1593 | } | ||||
1594 | return false; | ||||
1595 | } | ||||
1596 | |||||
1597 | void DevirtModule::applyVirtualConstProp(CallSiteInfo &CSInfo, StringRef FnName, | ||||
1598 | Constant *Byte, Constant *Bit) { | ||||
1599 | for (auto Call : CSInfo.CallSites) { | ||||
1600 | if (!OptimizedCalls.insert(&Call.CB).second) | ||||
1601 | continue; | ||||
1602 | auto *RetType = cast<IntegerType>(Call.CB.getType()); | ||||
1603 | IRBuilder<> B(&Call.CB); | ||||
1604 | Value *Addr = | ||||
1605 | B.CreateGEP(Int8Ty, B.CreateBitCast(Call.VTable, Int8PtrTy), Byte); | ||||
1606 | if (RetType->getBitWidth() == 1) { | ||||
1607 | Value *Bits = B.CreateLoad(Int8Ty, Addr); | ||||
1608 | Value *BitsAndBit = B.CreateAnd(Bits, Bit); | ||||
1609 | auto IsBitSet = B.CreateICmpNE(BitsAndBit, ConstantInt::get(Int8Ty, 0)); | ||||
1610 | Call.replaceAndErase("virtual-const-prop-1-bit", FnName, RemarksEnabled, | ||||
1611 | OREGetter, IsBitSet); | ||||
1612 | } else { | ||||
1613 | Value *ValAddr = B.CreateBitCast(Addr, RetType->getPointerTo()); | ||||
1614 | Value *Val = B.CreateLoad(RetType, ValAddr); | ||||
1615 | Call.replaceAndErase("virtual-const-prop", FnName, RemarksEnabled, | ||||
1616 | OREGetter, Val); | ||||
1617 | } | ||||
1618 | } | ||||
1619 | CSInfo.markDevirt(); | ||||
1620 | } | ||||
1621 | |||||
1622 | bool DevirtModule::tryVirtualConstProp( | ||||
1623 | MutableArrayRef<VirtualCallTarget> TargetsForSlot, VTableSlotInfo &SlotInfo, | ||||
1624 | WholeProgramDevirtResolution *Res, VTableSlot Slot) { | ||||
1625 | // This only works if the function returns an integer. | ||||
1626 | auto RetType = dyn_cast<IntegerType>(TargetsForSlot[0].Fn->getReturnType()); | ||||
1627 | if (!RetType
| ||||
1628 | return false; | ||||
1629 | unsigned BitWidth = RetType->getBitWidth(); | ||||
1630 | if (BitWidth > 64) | ||||
1631 | return false; | ||||
1632 | |||||
1633 | // Make sure that each function is defined, does not access memory, takes at | ||||
1634 | // least one argument, does not use its first argument (which we assume is | ||||
1635 | // 'this'), and has the same return type. | ||||
1636 | // | ||||
1637 | // Note that we test whether this copy of the function is readnone, rather | ||||
1638 | // than testing function attributes, which must hold for any copy of the | ||||
1639 | // function, even a less optimized version substituted at link time. This is | ||||
1640 | // sound because the virtual constant propagation optimizations effectively | ||||
1641 | // inline all implementations of the virtual function into each call site, | ||||
1642 | // rather than using function attributes to perform local optimization. | ||||
1643 | for (VirtualCallTarget &Target : TargetsForSlot) { | ||||
1644 | if (Target.Fn->isDeclaration() || | ||||
1645 | computeFunctionBodyMemoryAccess(*Target.Fn, AARGetter(*Target.Fn)) != | ||||
1646 | MAK_ReadNone || | ||||
1647 | Target.Fn->arg_empty() || !Target.Fn->arg_begin()->use_empty() || | ||||
1648 | Target.Fn->getReturnType() != RetType) | ||||
1649 | return false; | ||||
1650 | } | ||||
1651 | |||||
1652 | for (auto &&CSByConstantArg : SlotInfo.ConstCSInfo) { | ||||
1653 | if (!tryEvaluateFunctionsWithArgs(TargetsForSlot, CSByConstantArg.first)) | ||||
1654 | continue; | ||||
1655 | |||||
1656 | WholeProgramDevirtResolution::ByArg *ResByArg = nullptr; | ||||
1657 | if (Res
| ||||
1658 | ResByArg = &Res->ResByArg[CSByConstantArg.first]; | ||||
1659 | |||||
1660 | if (tryUniformRetValOpt(TargetsForSlot, CSByConstantArg.second, ResByArg)) | ||||
1661 | continue; | ||||
1662 | |||||
1663 | if (tryUniqueRetValOpt(BitWidth, TargetsForSlot, CSByConstantArg.second, | ||||
1664 | ResByArg, Slot, CSByConstantArg.first)) | ||||
1665 | continue; | ||||
1666 | |||||
1667 | // Find an allocation offset in bits in all vtables associated with the | ||||
1668 | // type. | ||||
1669 | uint64_t AllocBefore = | ||||
1670 | findLowestOffset(TargetsForSlot, /*IsAfter=*/false, BitWidth); | ||||
1671 | uint64_t AllocAfter = | ||||
1672 | findLowestOffset(TargetsForSlot, /*IsAfter=*/true, BitWidth); | ||||
1673 | |||||
1674 | // Calculate the total amount of padding needed to store a value at both | ||||
1675 | // ends of the object. | ||||
1676 | uint64_t TotalPaddingBefore = 0, TotalPaddingAfter = 0; | ||||
1677 | for (auto &&Target : TargetsForSlot) { | ||||
1678 | TotalPaddingBefore += std::max<int64_t>( | ||||
1679 | (AllocBefore + 7) / 8 - Target.allocatedBeforeBytes() - 1, 0); | ||||
1680 | TotalPaddingAfter += std::max<int64_t>( | ||||
1681 | (AllocAfter + 7) / 8 - Target.allocatedAfterBytes() - 1, 0); | ||||
1682 | } | ||||
1683 | |||||
1684 | // If the amount of padding is too large, give up. | ||||
1685 | // FIXME: do something smarter here. | ||||
1686 | if (std::min(TotalPaddingBefore, TotalPaddingAfter) > 128) | ||||
1687 | continue; | ||||
1688 | |||||
1689 | // Calculate the offset to the value as a (possibly negative) byte offset | ||||
1690 | // and (if applicable) a bit offset, and store the values in the targets. | ||||
1691 | int64_t OffsetByte; | ||||
1692 | uint64_t OffsetBit; | ||||
1693 | if (TotalPaddingBefore <= TotalPaddingAfter) | ||||
1694 | setBeforeReturnValues(TargetsForSlot, AllocBefore, BitWidth, OffsetByte, | ||||
1695 | OffsetBit); | ||||
1696 | else | ||||
1697 | setAfterReturnValues(TargetsForSlot, AllocAfter, BitWidth, OffsetByte, | ||||
1698 | OffsetBit); | ||||
1699 | |||||
1700 | if (RemarksEnabled) | ||||
1701 | for (auto &&Target : TargetsForSlot) | ||||
1702 | Target.WasDevirt = true; | ||||
1703 | |||||
1704 | |||||
1705 | if (CSByConstantArg.second.isExported()) { | ||||
1706 | ResByArg->TheKind = WholeProgramDevirtResolution::ByArg::VirtualConstProp; | ||||
1707 | exportConstant(Slot, CSByConstantArg.first, "byte", OffsetByte, | ||||
1708 | ResByArg->Byte); | ||||
1709 | exportConstant(Slot, CSByConstantArg.first, "bit", 1ULL << OffsetBit, | ||||
1710 | ResByArg->Bit); | ||||
1711 | } | ||||
1712 | |||||
1713 | // Rewrite each call to a load from OffsetByte/OffsetBit. | ||||
1714 | Constant *ByteConst = ConstantInt::get(Int32Ty, OffsetByte); | ||||
1715 | Constant *BitConst = ConstantInt::get(Int8Ty, 1ULL << OffsetBit); | ||||
1716 | applyVirtualConstProp(CSByConstantArg.second, | ||||
1717 | TargetsForSlot[0].Fn->getName(), ByteConst, BitConst); | ||||
1718 | } | ||||
1719 | return true; | ||||
1720 | } | ||||
1721 | |||||
1722 | void DevirtModule::rebuildGlobal(VTableBits &B) { | ||||
1723 | if (B.Before.Bytes.empty() && B.After.Bytes.empty()) | ||||
1724 | return; | ||||
1725 | |||||
1726 | // Align the before byte array to the global's minimum alignment so that we | ||||
1727 | // don't break any alignment requirements on the global. | ||||
1728 | Align Alignment = M.getDataLayout().getValueOrABITypeAlignment( | ||||
1729 | B.GV->getAlign(), B.GV->getValueType()); | ||||
1730 | B.Before.Bytes.resize(alignTo(B.Before.Bytes.size(), Alignment)); | ||||
1731 | |||||
1732 | // Before was stored in reverse order; flip it now. | ||||
1733 | for (size_t I = 0, Size = B.Before.Bytes.size(); I != Size / 2; ++I) | ||||
1734 | std::swap(B.Before.Bytes[I], B.Before.Bytes[Size - 1 - I]); | ||||
1735 | |||||
1736 | // Build an anonymous global containing the before bytes, followed by the | ||||
1737 | // original initializer, followed by the after bytes. | ||||
1738 | auto NewInit = ConstantStruct::getAnon( | ||||
1739 | {ConstantDataArray::get(M.getContext(), B.Before.Bytes), | ||||
1740 | B.GV->getInitializer(), | ||||
1741 | ConstantDataArray::get(M.getContext(), B.After.Bytes)}); | ||||
1742 | auto NewGV = | ||||
1743 | new GlobalVariable(M, NewInit->getType(), B.GV->isConstant(), | ||||
1744 | GlobalVariable::PrivateLinkage, NewInit, "", B.GV); | ||||
1745 | NewGV->setSection(B.GV->getSection()); | ||||
1746 | NewGV->setComdat(B.GV->getComdat()); | ||||
1747 | NewGV->setAlignment(MaybeAlign(B.GV->getAlignment())); | ||||
1748 | |||||
1749 | // Copy the original vtable's metadata to the anonymous global, adjusting | ||||
1750 | // offsets as required. | ||||
1751 | NewGV->copyMetadata(B.GV, B.Before.Bytes.size()); | ||||
1752 | |||||
1753 | // Build an alias named after the original global, pointing at the second | ||||
1754 | // element (the original initializer). | ||||
1755 | auto Alias = GlobalAlias::create( | ||||
1756 | B.GV->getInitializer()->getType(), 0, B.GV->getLinkage(), "", | ||||
1757 | ConstantExpr::getGetElementPtr( | ||||
1758 | NewInit->getType(), NewGV, | ||||
1759 | ArrayRef<Constant *>{ConstantInt::get(Int32Ty, 0), | ||||
1760 | ConstantInt::get(Int32Ty, 1)}), | ||||
1761 | &M); | ||||
1762 | Alias->setVisibility(B.GV->getVisibility()); | ||||
1763 | Alias->takeName(B.GV); | ||||
1764 | |||||
1765 | B.GV->replaceAllUsesWith(Alias); | ||||
1766 | B.GV->eraseFromParent(); | ||||
1767 | } | ||||
1768 | |||||
1769 | bool DevirtModule::areRemarksEnabled() { | ||||
1770 | const auto &FL = M.getFunctionList(); | ||||
1771 | for (const Function &Fn : FL) { | ||||
1772 | const auto &BBL = Fn.getBasicBlockList(); | ||||
1773 | if (BBL.empty()) | ||||
1774 | continue; | ||||
1775 | auto DI = OptimizationRemark(DEBUG_TYPE"wholeprogramdevirt", "", DebugLoc(), &BBL.front()); | ||||
1776 | return DI.isEnabled(); | ||||
1777 | } | ||||
1778 | return false; | ||||
1779 | } | ||||
1780 | |||||
1781 | void DevirtModule::scanTypeTestUsers( | ||||
1782 | Function *TypeTestFunc, | ||||
1783 | DenseMap<Metadata *, std::set<TypeMemberInfo>> &TypeIdMap) { | ||||
1784 | // Find all virtual calls via a virtual table pointer %p under an assumption | ||||
1785 | // of the form llvm.assume(llvm.type.test(%p, %md)). This indicates that %p | ||||
1786 | // points to a member of the type identifier %md. Group calls by (type ID, | ||||
1787 | // offset) pair (effectively the identity of the virtual function) and store | ||||
1788 | // to CallSlots. | ||||
1789 | for (auto I = TypeTestFunc->use_begin(), E = TypeTestFunc->use_end(); | ||||
1790 | I != E;) { | ||||
1791 | auto CI = dyn_cast<CallInst>(I->getUser()); | ||||
1792 | ++I; | ||||
1793 | if (!CI) | ||||
1794 | continue; | ||||
1795 | |||||
1796 | // Search for virtual calls based on %p and add them to DevirtCalls. | ||||
1797 | SmallVector<DevirtCallSite, 1> DevirtCalls; | ||||
1798 | SmallVector<CallInst *, 1> Assumes; | ||||
1799 | auto &DT = LookupDomTree(*CI->getFunction()); | ||||
1800 | findDevirtualizableCallsForTypeTest(DevirtCalls, Assumes, CI, DT); | ||||
1801 | |||||
1802 | Metadata *TypeId = | ||||
1803 | cast<MetadataAsValue>(CI->getArgOperand(1))->getMetadata(); | ||||
1804 | // If we found any, add them to CallSlots. | ||||
1805 | if (!Assumes.empty()) { | ||||
1806 | Value *Ptr = CI->getArgOperand(0)->stripPointerCasts(); | ||||
1807 | for (DevirtCallSite Call : DevirtCalls) | ||||
1808 | CallSlots[{TypeId, Call.Offset}].addCallSite(Ptr, Call.CB, nullptr); | ||||
1809 | } | ||||
1810 | |||||
1811 | auto RemoveTypeTestAssumes = [&]() { | ||||
1812 | // We no longer need the assumes or the type test. | ||||
1813 | for (auto Assume : Assumes) | ||||
1814 | Assume->eraseFromParent(); | ||||
1815 | // We can't use RecursivelyDeleteTriviallyDeadInstructions here because we | ||||
1816 | // may use the vtable argument later. | ||||
1817 | if (CI->use_empty()) | ||||
1818 | CI->eraseFromParent(); | ||||
1819 | }; | ||||
1820 | |||||
1821 | // At this point we could remove all type test assume sequences, as they | ||||
1822 | // were originally inserted for WPD. However, we can keep these in the | ||||
1823 | // code stream for later analysis (e.g. to help drive more efficient ICP | ||||
1824 | // sequences). They will eventually be removed by a second LowerTypeTests | ||||
1825 | // invocation that cleans them up. In order to do this correctly, the first | ||||
1826 | // LowerTypeTests invocation needs to know that they have "Unknown" type | ||||
1827 | // test resolution, so that they aren't treated as Unsat and lowered to | ||||
1828 | // False, which will break any uses on assumes. Below we remove any type | ||||
1829 | // test assumes that will not be treated as Unknown by LTT. | ||||
1830 | |||||
1831 | // The type test assumes will be treated by LTT as Unsat if the type id is | ||||
1832 | // not used on a global (in which case it has no entry in the TypeIdMap). | ||||
1833 | if (!TypeIdMap.count(TypeId)) | ||||
1834 | RemoveTypeTestAssumes(); | ||||
1835 | |||||
1836 | // For ThinLTO importing, we need to remove the type test assumes if this is | ||||
1837 | // an MDString type id without a corresponding TypeIdSummary. Any | ||||
1838 | // non-MDString type ids are ignored and treated as Unknown by LTT, so their | ||||
1839 | // type test assumes can be kept. If the MDString type id is missing a | ||||
1840 | // TypeIdSummary (e.g. because there was no use on a vcall, preventing the | ||||
1841 | // exporting phase of WPD from analyzing it), then it would be treated as | ||||
1842 | // Unsat by LTT and we need to remove its type test assumes here. If not | ||||
1843 | // used on a vcall we don't need them for later optimization use in any | ||||
1844 | // case. | ||||
1845 | else if (ImportSummary && isa<MDString>(TypeId)) { | ||||
1846 | const TypeIdSummary *TidSummary = | ||||
1847 | ImportSummary->getTypeIdSummary(cast<MDString>(TypeId)->getString()); | ||||
1848 | if (!TidSummary) | ||||
1849 | RemoveTypeTestAssumes(); | ||||
1850 | else | ||||
1851 | // If one was created it should not be Unsat, because if we reached here | ||||
1852 | // the type id was used on a global. | ||||
1853 | assert(TidSummary->TTRes.TheKind != TypeTestResolution::Unsat)((void)0); | ||||
1854 | } | ||||
1855 | } | ||||
1856 | } | ||||
1857 | |||||
1858 | void DevirtModule::scanTypeCheckedLoadUsers(Function *TypeCheckedLoadFunc) { | ||||
1859 | Function *TypeTestFunc = Intrinsic::getDeclaration(&M, Intrinsic::type_test); | ||||
1860 | |||||
1861 | for (auto I = TypeCheckedLoadFunc->use_begin(), | ||||
1862 | E = TypeCheckedLoadFunc->use_end(); | ||||
1863 | I != E;) { | ||||
1864 | auto CI = dyn_cast<CallInst>(I->getUser()); | ||||
1865 | ++I; | ||||
1866 | if (!CI) | ||||
1867 | continue; | ||||
1868 | |||||
1869 | Value *Ptr = CI->getArgOperand(0); | ||||
1870 | Value *Offset = CI->getArgOperand(1); | ||||
1871 | Value *TypeIdValue = CI->getArgOperand(2); | ||||
1872 | Metadata *TypeId = cast<MetadataAsValue>(TypeIdValue)->getMetadata(); | ||||
1873 | |||||
1874 | SmallVector<DevirtCallSite, 1> DevirtCalls; | ||||
1875 | SmallVector<Instruction *, 1> LoadedPtrs; | ||||
1876 | SmallVector<Instruction *, 1> Preds; | ||||
1877 | bool HasNonCallUses = false; | ||||
1878 | auto &DT = LookupDomTree(*CI->getFunction()); | ||||
1879 | findDevirtualizableCallsForTypeCheckedLoad(DevirtCalls, LoadedPtrs, Preds, | ||||
1880 | HasNonCallUses, CI, DT); | ||||
1881 | |||||
1882 | // Start by generating "pessimistic" code that explicitly loads the function | ||||
1883 | // pointer from the vtable and performs the type check. If possible, we will | ||||
1884 | // eliminate the load and the type check later. | ||||
1885 | |||||
1886 | // If possible, only generate the load at the point where it is used. | ||||
1887 | // This helps avoid unnecessary spills. | ||||
1888 | IRBuilder<> LoadB( | ||||
1889 | (LoadedPtrs.size() == 1 && !HasNonCallUses) ? LoadedPtrs[0] : CI); | ||||
1890 | Value *GEP = LoadB.CreateGEP(Int8Ty, Ptr, Offset); | ||||
1891 | Value *GEPPtr = LoadB.CreateBitCast(GEP, PointerType::getUnqual(Int8PtrTy)); | ||||
1892 | Value *LoadedValue = LoadB.CreateLoad(Int8PtrTy, GEPPtr); | ||||
1893 | |||||
1894 | for (Instruction *LoadedPtr : LoadedPtrs) { | ||||
1895 | LoadedPtr->replaceAllUsesWith(LoadedValue); | ||||
1896 | LoadedPtr->eraseFromParent(); | ||||
1897 | } | ||||
1898 | |||||
1899 | // Likewise for the type test. | ||||
1900 | IRBuilder<> CallB((Preds.size() == 1 && !HasNonCallUses) ? Preds[0] : CI); | ||||
1901 | CallInst *TypeTestCall = CallB.CreateCall(TypeTestFunc, {Ptr, TypeIdValue}); | ||||
1902 | |||||
1903 | for (Instruction *Pred : Preds) { | ||||
1904 | Pred->replaceAllUsesWith(TypeTestCall); | ||||
1905 | Pred->eraseFromParent(); | ||||
1906 | } | ||||
1907 | |||||
1908 | // We have already erased any extractvalue instructions that refer to the | ||||
1909 | // intrinsic call, but the intrinsic may have other non-extractvalue uses | ||||
1910 | // (although this is unlikely). In that case, explicitly build a pair and | ||||
1911 | // RAUW it. | ||||
1912 | if (!CI->use_empty()) { | ||||
1913 | Value *Pair = UndefValue::get(CI->getType()); | ||||
1914 | IRBuilder<> B(CI); | ||||
1915 | Pair = B.CreateInsertValue(Pair, LoadedValue, {0}); | ||||
1916 | Pair = B.CreateInsertValue(Pair, TypeTestCall, {1}); | ||||
1917 | CI->replaceAllUsesWith(Pair); | ||||
1918 | } | ||||
1919 | |||||
1920 | // The number of unsafe uses is initially the number of uses. | ||||
1921 | auto &NumUnsafeUses = NumUnsafeUsesForTypeTest[TypeTestCall]; | ||||
1922 | NumUnsafeUses = DevirtCalls.size(); | ||||
1923 | |||||
1924 | // If the function pointer has a non-call user, we cannot eliminate the type | ||||
1925 | // check, as one of those users may eventually call the pointer. Increment | ||||
1926 | // the unsafe use count to make sure it cannot reach zero. | ||||
1927 | if (HasNonCallUses) | ||||
1928 | ++NumUnsafeUses; | ||||
1929 | for (DevirtCallSite Call : DevirtCalls) { | ||||
1930 | CallSlots[{TypeId, Call.Offset}].addCallSite(Ptr, Call.CB, | ||||
1931 | &NumUnsafeUses); | ||||
1932 | } | ||||
1933 | |||||
1934 | CI->eraseFromParent(); | ||||
1935 | } | ||||
1936 | } | ||||
1937 | |||||
1938 | void DevirtModule::importResolution(VTableSlot Slot, VTableSlotInfo &SlotInfo) { | ||||
1939 | auto *TypeId = dyn_cast<MDString>(Slot.TypeID); | ||||
1940 | if (!TypeId) | ||||
1941 | return; | ||||
1942 | const TypeIdSummary *TidSummary = | ||||
1943 | ImportSummary->getTypeIdSummary(TypeId->getString()); | ||||
1944 | if (!TidSummary) | ||||
1945 | return; | ||||
1946 | auto ResI = TidSummary->WPDRes.find(Slot.ByteOffset); | ||||
1947 | if (ResI == TidSummary->WPDRes.end()) | ||||
1948 | return; | ||||
1949 | const WholeProgramDevirtResolution &Res = ResI->second; | ||||
1950 | |||||
1951 | if (Res.TheKind == WholeProgramDevirtResolution::SingleImpl) { | ||||
1952 | assert(!Res.SingleImplName.empty())((void)0); | ||||
1953 | // The type of the function in the declaration is irrelevant because every | ||||
1954 | // call site will cast it to the correct type. | ||||
1955 | Constant *SingleImpl = | ||||
1956 | cast<Constant>(M.getOrInsertFunction(Res.SingleImplName, | ||||
1957 | Type::getVoidTy(M.getContext())) | ||||
1958 | .getCallee()); | ||||
1959 | |||||
1960 | // This is the import phase so we should not be exporting anything. | ||||
1961 | bool IsExported = false; | ||||
1962 | applySingleImplDevirt(SlotInfo, SingleImpl, IsExported); | ||||
1963 | assert(!IsExported)((void)0); | ||||
1964 | } | ||||
1965 | |||||
1966 | for (auto &CSByConstantArg : SlotInfo.ConstCSInfo) { | ||||
1967 | auto I = Res.ResByArg.find(CSByConstantArg.first); | ||||
1968 | if (I == Res.ResByArg.end()) | ||||
1969 | continue; | ||||
1970 | auto &ResByArg = I->second; | ||||
1971 | // FIXME: We should figure out what to do about the "function name" argument | ||||
1972 | // to the apply* functions, as the function names are unavailable during the | ||||
1973 | // importing phase. For now we just pass the empty string. This does not | ||||
1974 | // impact correctness because the function names are just used for remarks. | ||||
1975 | switch (ResByArg.TheKind) { | ||||
1976 | case WholeProgramDevirtResolution::ByArg::UniformRetVal: | ||||
1977 | applyUniformRetValOpt(CSByConstantArg.second, "", ResByArg.Info); | ||||
1978 | break; | ||||
1979 | case WholeProgramDevirtResolution::ByArg::UniqueRetVal: { | ||||
1980 | Constant *UniqueMemberAddr = | ||||
1981 | importGlobal(Slot, CSByConstantArg.first, "unique_member"); | ||||
1982 | applyUniqueRetValOpt(CSByConstantArg.second, "", ResByArg.Info, | ||||
1983 | UniqueMemberAddr); | ||||
1984 | break; | ||||
1985 | } | ||||
1986 | case WholeProgramDevirtResolution::ByArg::VirtualConstProp: { | ||||
1987 | Constant *Byte = importConstant(Slot, CSByConstantArg.first, "byte", | ||||
1988 | Int32Ty, ResByArg.Byte); | ||||
1989 | Constant *Bit = importConstant(Slot, CSByConstantArg.first, "bit", Int8Ty, | ||||
1990 | ResByArg.Bit); | ||||
1991 | applyVirtualConstProp(CSByConstantArg.second, "", Byte, Bit); | ||||
1992 | break; | ||||
1993 | } | ||||
1994 | default: | ||||
1995 | break; | ||||
1996 | } | ||||
1997 | } | ||||
1998 | |||||
1999 | if (Res.TheKind == WholeProgramDevirtResolution::BranchFunnel) { | ||||
2000 | // The type of the function is irrelevant, because it's bitcast at calls | ||||
2001 | // anyhow. | ||||
2002 | Constant *JT = cast<Constant>( | ||||
2003 | M.getOrInsertFunction(getGlobalName(Slot, {}, "branch_funnel"), | ||||
2004 | Type::getVoidTy(M.getContext())) | ||||
2005 | .getCallee()); | ||||
2006 | bool IsExported = false; | ||||
2007 | applyICallBranchFunnel(SlotInfo, JT, IsExported); | ||||
2008 | assert(!IsExported)((void)0); | ||||
2009 | } | ||||
2010 | } | ||||
2011 | |||||
2012 | void DevirtModule::removeRedundantTypeTests() { | ||||
2013 | auto True = ConstantInt::getTrue(M.getContext()); | ||||
2014 | for (auto &&U : NumUnsafeUsesForTypeTest) { | ||||
2015 | if (U.second == 0) { | ||||
2016 | U.first->replaceAllUsesWith(True); | ||||
2017 | U.first->eraseFromParent(); | ||||
2018 | } | ||||
2019 | } | ||||
2020 | } | ||||
2021 | |||||
2022 | bool DevirtModule::run() { | ||||
2023 | // If only some of the modules were split, we cannot correctly perform | ||||
2024 | // this transformation. We already checked for the presense of type tests | ||||
2025 | // with partially split modules during the thin link, and would have emitted | ||||
2026 | // an error if any were found, so here we can simply return. | ||||
2027 | if ((ExportSummary && ExportSummary->partiallySplitLTOUnits()) || | ||||
| |||||
2028 | (ImportSummary && ImportSummary->partiallySplitLTOUnits())) | ||||
2029 | return false; | ||||
2030 | |||||
2031 | Function *TypeTestFunc = | ||||
2032 | M.getFunction(Intrinsic::getName(Intrinsic::type_test)); | ||||
2033 | Function *TypeCheckedLoadFunc = | ||||
2034 | M.getFunction(Intrinsic::getName(Intrinsic::type_checked_load)); | ||||
2035 | Function *AssumeFunc = M.getFunction(Intrinsic::getName(Intrinsic::assume)); | ||||
2036 | |||||
2037 | // Normally if there are no users of the devirtualization intrinsics in the | ||||
2038 | // module, this pass has nothing to do. But if we are exporting, we also need | ||||
2039 | // to handle any users that appear only in the function summaries. | ||||
2040 | if (!ExportSummary
| ||||
2041 | (!TypeTestFunc || TypeTestFunc->use_empty() || !AssumeFunc || | ||||
2042 | AssumeFunc->use_empty()) && | ||||
2043 | (!TypeCheckedLoadFunc || TypeCheckedLoadFunc->use_empty())) | ||||
2044 | return false; | ||||
2045 | |||||
2046 | // Rebuild type metadata into a map for easy lookup. | ||||
2047 | std::vector<VTableBits> Bits; | ||||
2048 | DenseMap<Metadata *, std::set<TypeMemberInfo>> TypeIdMap; | ||||
2049 | buildTypeIdentifierMap(Bits, TypeIdMap); | ||||
2050 | |||||
2051 | if (TypeTestFunc
| ||||
2052 | scanTypeTestUsers(TypeTestFunc, TypeIdMap); | ||||
2053 | |||||
2054 | if (TypeCheckedLoadFunc) | ||||
2055 | scanTypeCheckedLoadUsers(TypeCheckedLoadFunc); | ||||
2056 | |||||
2057 | if (ImportSummary
| ||||
2058 | for (auto &S : CallSlots) | ||||
2059 | importResolution(S.first, S.second); | ||||
2060 | |||||
2061 | removeRedundantTypeTests(); | ||||
2062 | |||||
2063 | // We have lowered or deleted the type instrinsics, so we will no | ||||
2064 | // longer have enough information to reason about the liveness of virtual | ||||
2065 | // function pointers in GlobalDCE. | ||||
2066 | for (GlobalVariable &GV : M.globals()) | ||||
2067 | GV.eraseMetadata(LLVMContext::MD_vcall_visibility); | ||||
2068 | |||||
2069 | // The rest of the code is only necessary when exporting or during regular | ||||
2070 | // LTO, so we are done. | ||||
2071 | return true; | ||||
2072 | } | ||||
2073 | |||||
2074 | if (TypeIdMap.empty()) | ||||
2075 | return true; | ||||
2076 | |||||
2077 | // Collect information from summary about which calls to try to devirtualize. | ||||
2078 | if (ExportSummary
| ||||
2079 | DenseMap<GlobalValue::GUID, TinyPtrVector<Metadata *>> MetadataByGUID; | ||||
2080 | for (auto &P : TypeIdMap) { | ||||
2081 | if (auto *TypeId = dyn_cast<MDString>(P.first)) | ||||
2082 | MetadataByGUID[GlobalValue::getGUID(TypeId->getString())].push_back( | ||||
2083 | TypeId); | ||||
2084 | } | ||||
2085 | |||||
2086 | for (auto &P : *ExportSummary) { | ||||
2087 | for (auto &S : P.second.SummaryList) { | ||||
2088 | auto *FS = dyn_cast<FunctionSummary>(S.get()); | ||||
2089 | if (!FS) | ||||
2090 | continue; | ||||
2091 | // FIXME: Only add live functions. | ||||
2092 | for (FunctionSummary::VFuncId VF : FS->type_test_assume_vcalls()) { | ||||
2093 | for (Metadata *MD : MetadataByGUID[VF.GUID]) { | ||||
2094 | CallSlots[{MD, VF.Offset}].CSInfo.addSummaryTypeTestAssumeUser(FS); | ||||
2095 | } | ||||
2096 | } | ||||
2097 | for (FunctionSummary::VFuncId VF : FS->type_checked_load_vcalls()) { | ||||
2098 | for (Metadata *MD : MetadataByGUID[VF.GUID]) { | ||||
2099 | CallSlots[{MD, VF.Offset}].CSInfo.addSummaryTypeCheckedLoadUser(FS); | ||||
2100 | } | ||||
2101 | } | ||||
2102 | for (const FunctionSummary::ConstVCall &VC : | ||||
2103 | FS->type_test_assume_const_vcalls()) { | ||||
2104 | for (Metadata *MD : MetadataByGUID[VC.VFunc.GUID]) { | ||||
2105 | CallSlots[{MD, VC.VFunc.Offset}] | ||||
2106 | .ConstCSInfo[VC.Args] | ||||
2107 | .addSummaryTypeTestAssumeUser(FS); | ||||
2108 | } | ||||
2109 | } | ||||
2110 | for (const FunctionSummary::ConstVCall &VC : | ||||
2111 | FS->type_checked_load_const_vcalls()) { | ||||
2112 | for (Metadata *MD : MetadataByGUID[VC.VFunc.GUID]) { | ||||
2113 | CallSlots[{MD, VC.VFunc.Offset}] | ||||
2114 | .ConstCSInfo[VC.Args] | ||||
2115 | .addSummaryTypeCheckedLoadUser(FS); | ||||
2116 | } | ||||
2117 | } | ||||
2118 | } | ||||
2119 | } | ||||
2120 | } | ||||
2121 | |||||
2122 | // For each (type, offset) pair: | ||||
2123 | bool DidVirtualConstProp = false; | ||||
2124 | std::map<std::string, Function*> DevirtTargets; | ||||
2125 | for (auto &S : CallSlots) { | ||||
2126 | // Search each of the members of the type identifier for the virtual | ||||
2127 | // function implementation at offset S.first.ByteOffset, and add to | ||||
2128 | // TargetsForSlot. | ||||
2129 | std::vector<VirtualCallTarget> TargetsForSlot; | ||||
2130 | WholeProgramDevirtResolution *Res = nullptr; | ||||
2131 | const std::set<TypeMemberInfo> &TypeMemberInfos = TypeIdMap[S.first.TypeID]; | ||||
2132 | if (ExportSummary && isa<MDString>(S.first.TypeID) && | ||||
2133 | TypeMemberInfos.size()) | ||||
2134 | // For any type id used on a global's type metadata, create the type id | ||||
2135 | // summary resolution regardless of whether we can devirtualize, so that | ||||
2136 | // lower type tests knows the type id is not Unsat. If it was not used on | ||||
2137 | // a global's type metadata, the TypeIdMap entry set will be empty, and | ||||
2138 | // we don't want to create an entry (with the default Unknown type | ||||
2139 | // resolution), which can prevent detection of the Unsat. | ||||
2140 | Res = &ExportSummary | ||||
2141 | ->getOrInsertTypeIdSummary( | ||||
2142 | cast<MDString>(S.first.TypeID)->getString()) | ||||
2143 | .WPDRes[S.first.ByteOffset]; | ||||
2144 | if (tryFindVirtualCallTargets(TargetsForSlot, TypeMemberInfos, | ||||
2145 | S.first.ByteOffset)) { | ||||
2146 | |||||
2147 | if (!trySingleImplDevirt(ExportSummary, TargetsForSlot, S.second, Res)) { | ||||
2148 | DidVirtualConstProp |= | ||||
2149 | tryVirtualConstProp(TargetsForSlot, S.second, Res, S.first); | ||||
2150 | |||||
2151 | tryICallBranchFunnel(TargetsForSlot, S.second, Res, S.first); | ||||
2152 | } | ||||
2153 | |||||
2154 | // Collect functions devirtualized at least for one call site for stats. | ||||
2155 | if (RemarksEnabled) | ||||
2156 | for (const auto &T : TargetsForSlot) | ||||
2157 | if (T.WasDevirt) | ||||
2158 | DevirtTargets[std::string(T.Fn->getName())] = T.Fn; | ||||
2159 | } | ||||
2160 | |||||
2161 | // CFI-specific: if we are exporting and any llvm.type.checked.load | ||||
2162 | // intrinsics were *not* devirtualized, we need to add the resulting | ||||
2163 | // llvm.type.test intrinsics to the function summaries so that the | ||||
2164 | // LowerTypeTests pass will export them. | ||||
2165 | if (ExportSummary && isa<MDString>(S.first.TypeID)) { | ||||
2166 | auto GUID = | ||||
2167 | GlobalValue::getGUID(cast<MDString>(S.first.TypeID)->getString()); | ||||
2168 | for (auto FS : S.second.CSInfo.SummaryTypeCheckedLoadUsers) | ||||
2169 | FS->addTypeTest(GUID); | ||||
2170 | for (auto &CCS : S.second.ConstCSInfo) | ||||
2171 | for (auto FS : CCS.second.SummaryTypeCheckedLoadUsers) | ||||
2172 | FS->addTypeTest(GUID); | ||||
2173 | } | ||||
2174 | } | ||||
2175 | |||||
2176 | if (RemarksEnabled) { | ||||
2177 | // Generate remarks for each devirtualized function. | ||||
2178 | for (const auto &DT : DevirtTargets) { | ||||
2179 | Function *F = DT.second; | ||||
2180 | |||||
2181 | using namespace ore; | ||||
2182 | OREGetter(F).emit(OptimizationRemark(DEBUG_TYPE"wholeprogramdevirt", "Devirtualized", F) | ||||
2183 | << "devirtualized " | ||||
2184 | << NV("FunctionName", DT.first)); | ||||
2185 | } | ||||
2186 | } | ||||
2187 | |||||
2188 | removeRedundantTypeTests(); | ||||
2189 | |||||
2190 | // Rebuild each global we touched as part of virtual constant propagation to | ||||
2191 | // include the before and after bytes. | ||||
2192 | if (DidVirtualConstProp) | ||||
2193 | for (VTableBits &B : Bits) | ||||
2194 | rebuildGlobal(B); | ||||
2195 | |||||
2196 | // We have lowered or deleted the type instrinsics, so we will no | ||||
2197 | // longer have enough information to reason about the liveness of virtual | ||||
2198 | // function pointers in GlobalDCE. | ||||
2199 | for (GlobalVariable &GV : M.globals()) | ||||
2200 | GV.eraseMetadata(LLVMContext::MD_vcall_visibility); | ||||
2201 | |||||
2202 | return true; | ||||
2203 | } | ||||
2204 | |||||
2205 | void DevirtIndex::run() { | ||||
2206 | if (ExportSummary.typeIdCompatibleVtableMap().empty()) | ||||
2207 | return; | ||||
2208 | |||||
2209 | DenseMap<GlobalValue::GUID, std::vector<StringRef>> NameByGUID; | ||||
2210 | for (auto &P : ExportSummary.typeIdCompatibleVtableMap()) { | ||||
2211 | NameByGUID[GlobalValue::getGUID(P.first)].push_back(P.first); | ||||
2212 | } | ||||
2213 | |||||
2214 | // Collect information from summary about which calls to try to devirtualize. | ||||
2215 | for (auto &P : ExportSummary) { | ||||
2216 | for (auto &S : P.second.SummaryList) { | ||||
2217 | auto *FS = dyn_cast<FunctionSummary>(S.get()); | ||||
2218 | if (!FS) | ||||
2219 | continue; | ||||
2220 | // FIXME: Only add live functions. | ||||
2221 | for (FunctionSummary::VFuncId VF : FS->type_test_assume_vcalls()) { | ||||
2222 | for (StringRef Name : NameByGUID[VF.GUID]) { | ||||
2223 | CallSlots[{Name, VF.Offset}].CSInfo.addSummaryTypeTestAssumeUser(FS); | ||||
2224 | } | ||||
2225 | } | ||||
2226 | for (FunctionSummary::VFuncId VF : FS->type_checked_load_vcalls()) { | ||||
2227 | for (StringRef Name : NameByGUID[VF.GUID]) { | ||||
2228 | CallSlots[{Name, VF.Offset}].CSInfo.addSummaryTypeCheckedLoadUser(FS); | ||||
2229 | } | ||||
2230 | } | ||||
2231 | for (const FunctionSummary::ConstVCall &VC : | ||||
2232 | FS->type_test_assume_const_vcalls()) { | ||||
2233 | for (StringRef Name : NameByGUID[VC.VFunc.GUID]) { | ||||
2234 | CallSlots[{Name, VC.VFunc.Offset}] | ||||
2235 | .ConstCSInfo[VC.Args] | ||||
2236 | .addSummaryTypeTestAssumeUser(FS); | ||||
2237 | } | ||||
2238 | } | ||||
2239 | for (const FunctionSummary::ConstVCall &VC : | ||||
2240 | FS->type_checked_load_const_vcalls()) { | ||||
2241 | for (StringRef Name : NameByGUID[VC.VFunc.GUID]) { | ||||
2242 | CallSlots[{Name, VC.VFunc.Offset}] | ||||
2243 | .ConstCSInfo[VC.Args] | ||||
2244 | .addSummaryTypeCheckedLoadUser(FS); | ||||
2245 | } | ||||
2246 | } | ||||
2247 | } | ||||
2248 | } | ||||
2249 | |||||
2250 | std::set<ValueInfo> DevirtTargets; | ||||
2251 | // For each (type, offset) pair: | ||||
2252 | for (auto &S : CallSlots) { | ||||
2253 | // Search each of the members of the type identifier for the virtual | ||||
2254 | // function implementation at offset S.first.ByteOffset, and add to | ||||
2255 | // TargetsForSlot. | ||||
2256 | std::vector<ValueInfo> TargetsForSlot; | ||||
2257 | auto TidSummary = ExportSummary.getTypeIdCompatibleVtableSummary(S.first.TypeID); | ||||
2258 | assert(TidSummary)((void)0); | ||||
2259 | // Create the type id summary resolution regardlness of whether we can | ||||
2260 | // devirtualize, so that lower type tests knows the type id is used on | ||||
2261 | // a global and not Unsat. | ||||
2262 | WholeProgramDevirtResolution *Res = | ||||
2263 | &ExportSummary.getOrInsertTypeIdSummary(S.first.TypeID) | ||||
2264 | .WPDRes[S.first.ByteOffset]; | ||||
2265 | if (tryFindVirtualCallTargets(TargetsForSlot, *TidSummary, | ||||
2266 | S.first.ByteOffset)) { | ||||
2267 | |||||
2268 | if (!trySingleImplDevirt(TargetsForSlot, S.first, S.second, Res, | ||||
2269 | DevirtTargets)) | ||||
2270 | continue; | ||||
2271 | } | ||||
2272 | } | ||||
2273 | |||||
2274 | // Optionally have the thin link print message for each devirtualized | ||||
2275 | // function. | ||||
2276 | if (PrintSummaryDevirt) | ||||
2277 | for (const auto &DT : DevirtTargets) | ||||
2278 | errs() << "Devirtualized call to " << DT << "\n"; | ||||
2279 | } |