File: | src/lib/libm/src/s_remquof.c |
Warning: | line 96, column 37 The result of the left shift is undefined because the left operand is negative |
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1 | /* @(#)e_fmod.c 1.3 95/01/18 */ | |||
2 | /*- | |||
3 | * ==================================================== | |||
4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |||
5 | * | |||
6 | * Developed at SunSoft, a Sun Microsystems, Inc. business. | |||
7 | * Permission to use, copy, modify, and distribute this | |||
8 | * software is freely granted, provided that this notice | |||
9 | * is preserved. | |||
10 | * ==================================================== | |||
11 | */ | |||
12 | ||||
13 | #include "math.h" | |||
14 | #include "math_private.h" | |||
15 | ||||
16 | static const float Zero[] = {0.0, -0.0,}; | |||
17 | ||||
18 | /* | |||
19 | * Return the IEEE remainder and set *quo to the last n bits of the | |||
20 | * quotient, rounded to the nearest integer. We choose n=31 because | |||
21 | * we wind up computing all the integer bits of the quotient anyway as | |||
22 | * a side-effect of computing the remainder by the shift and subtract | |||
23 | * method. In practice, this is far more bits than are needed to use | |||
24 | * remquo in reduction algorithms. | |||
25 | */ | |||
26 | float | |||
27 | remquof(float x, float y, int *quo) | |||
28 | { | |||
29 | int32_t n,hx,hy,hz,ix,iy,sx,i; | |||
30 | u_int32_t q,sxy; | |||
31 | ||||
32 | GET_FLOAT_WORD(hx,x)do { ieee_float_shape_type gf_u; gf_u.value = (x); (hx) = gf_u .word; } while (0); | |||
| ||||
33 | GET_FLOAT_WORD(hy,y)do { ieee_float_shape_type gf_u; gf_u.value = (y); (hy) = gf_u .word; } while (0); | |||
34 | sxy = (hx ^ hy) & 0x80000000; | |||
35 | sx = hx&0x80000000; /* sign of x */ | |||
36 | hx ^=sx; /* |x| */ | |||
37 | hy &= 0x7fffffff; /* |y| */ | |||
38 | ||||
39 | /* purge off exception values */ | |||
40 | if(hy==0||hx>=0x7f800000||hy>0x7f800000) /* y=0,NaN;or x not finite */ | |||
41 | return (x*y)/(x*y); | |||
42 | if(hx<hy) { | |||
43 | q = 0; | |||
44 | goto fixup; /* |x|<|y| return x or x-y */ | |||
45 | } else if(hx==hy) { | |||
46 | *quo = 1; | |||
47 | return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ | |||
48 | } | |||
49 | ||||
50 | /* determine ix = ilogb(x) */ | |||
51 | if(hx<0x00800000) { /* subnormal x */ | |||
52 | for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; | |||
53 | } else ix = (hx>>23)-127; | |||
54 | ||||
55 | /* determine iy = ilogb(y) */ | |||
56 | if(hy<0x00800000) { /* subnormal y */ | |||
57 | for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1; | |||
58 | } else iy = (hy>>23)-127; | |||
59 | ||||
60 | /* set up {hx,lx}, {hy,ly} and align y to x */ | |||
61 | if(ix >= -126) | |||
62 | hx = 0x00800000|(0x007fffff&hx); | |||
63 | else { /* subnormal x, shift x to normal */ | |||
64 | n = -126-ix; | |||
65 | hx <<= n; | |||
66 | } | |||
67 | if(iy >= -126) | |||
68 | hy = 0x00800000|(0x007fffff&hy); | |||
69 | else { /* subnormal y, shift y to normal */ | |||
70 | n = -126-iy; | |||
71 | hy <<= n; | |||
72 | } | |||
73 | ||||
74 | /* fix point fmod */ | |||
75 | n = ix - iy; | |||
76 | q = 0; | |||
77 | while(n--) { | |||
78 | hz=hx-hy; | |||
79 | if(hz<0) hx = hx << 1; | |||
80 | else {hx = hz << 1; q++;} | |||
81 | q <<= 1; | |||
82 | } | |||
83 | hz=hx-hy; | |||
84 | if(hz>=0) {hx=hz;q++;} | |||
85 | ||||
86 | /* convert back to floating value and restore the sign */ | |||
87 | if(hx==0) { /* return sign(x)*0 */ | |||
88 | *quo = (sxy ? -q : q); | |||
89 | return Zero[(u_int32_t)sx>>31]; | |||
90 | } | |||
91 | while(hx<0x00800000) { /* normalize x */ | |||
92 | hx <<= 1; | |||
93 | iy -= 1; | |||
94 | } | |||
95 | if(iy>= -126) { /* normalize output */ | |||
96 | hx = ((hx-0x00800000)|((iy+127)<<23)); | |||
| ||||
97 | } else { /* subnormal output */ | |||
98 | n = -126 - iy; | |||
99 | hx >>= n; | |||
100 | } | |||
101 | fixup: | |||
102 | SET_FLOAT_WORD(x,hx)do { ieee_float_shape_type sf_u; sf_u.word = (hx); (x) = sf_u .value; } while (0); | |||
103 | y = fabsf(y); | |||
104 | if (y < 0x1p-125f) { | |||
105 | if (x+x>y || (x+x==y && (q & 1))) { | |||
106 | q++; | |||
107 | x-=y; | |||
108 | } | |||
109 | } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) { | |||
110 | q++; | |||
111 | x-=y; | |||
112 | } | |||
113 | GET_FLOAT_WORD(hx,x)do { ieee_float_shape_type gf_u; gf_u.value = (x); (hx) = gf_u .word; } while (0); | |||
114 | SET_FLOAT_WORD(x,hx^sx)do { ieee_float_shape_type sf_u; sf_u.word = (hx^sx); (x) = sf_u .value; } while (0); | |||
115 | q &= 0x7fffffff; | |||
116 | *quo = (sxy ? -q : q); | |||
117 | return x; | |||
118 | } |