| 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 | } |