Rev 4872 | Details | Compare with Previous | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 4349 | Serge | 1 | /* Adapted for Newlib, 2009. (Allow for int < 32 bits; return *quo=0 during |
| 2 | * errors to make test scripts easier.) */ |
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| 3 | /* @(#)e_fmod.c 1.3 95/01/18 */ |
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| 4 | /*- |
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| 5 | * ==================================================== |
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| 6 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 7 | * |
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| 8 | * Developed at SunSoft, a Sun Microsystems, Inc. business. |
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| 9 | * Permission to use, copy, modify, and distribute this |
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| 10 | * software is freely granted, provided that this notice |
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| 11 | * is preserved. |
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| 12 | * ==================================================== |
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| 13 | */ |
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| 14 | |||
| 15 | #include |
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| 16 | #include "fdlibm.h" |
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| 17 | |||
| 18 | /* For quotient, return either all 31 bits that can from calculation (using |
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| 19 | * int32_t), or as many as can fit into an int that is smaller than 32 bits. */ |
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| 20 | #if INT_MAX > 0x7FFFFFFFL |
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| 21 | #define QUO_MASK 0x7FFFFFFF |
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| 22 | # else |
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| 23 | #define QUO_MASK INT_MAX |
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| 24 | #endif |
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| 25 | |||
| 26 | static const float Zero[] = {0.0, -0.0,}; |
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| 27 | |||
| 28 | /* |
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| 29 | * Return the IEEE remainder and set *quo to the last n bits of the |
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| 30 | * quotient, rounded to the nearest integer. We choose n=31--if that many fit-- |
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| 31 | * we wind up computing all the integer bits of the quotient anyway as |
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| 32 | * a side-effect of computing the remainder by the shift and subtract |
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| 33 | * method. In practice, this is far more bits than are needed to use |
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| 34 | * remquo in reduction algorithms. |
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| 35 | */ |
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| 36 | float |
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| 37 | remquof(float x, float y, int *quo) |
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| 38 | { |
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| 39 | __int32_t n,hx,hy,hz,ix,iy,sx,i; |
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| 40 | __uint32_t q,sxy; |
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| 41 | |||
| 42 | GET_FLOAT_WORD(hx,x); |
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| 43 | GET_FLOAT_WORD(hy,y); |
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| 44 | sxy = (hx ^ hy) & 0x80000000; |
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| 45 | sx = hx&0x80000000; /* sign of x */ |
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| 46 | hx ^=sx; /* |x| */ |
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| 47 | hy &= 0x7fffffff; /* |y| */ |
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| 48 | |||
| 49 | /* purge off exception values */ |
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| 50 | if(hy==0||hx>=0x7f800000||hy>0x7f800000) { /* y=0,NaN;or x not finite */ |
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| 51 | *quo = 0; /* Not necessary, but return consistent value */ |
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| 52 | return (x*y)/(x*y); |
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| 53 | } |
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| 54 | if(hx |
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| 55 | q = 0; |
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| 56 | goto fixup; /* |x|<|y| return x or x-y */ |
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| 57 | } else if(hx==hy) { |
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| 58 | *quo = 1; |
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| 59 | return Zero[(__uint32_t)sx>>31]; /* |x|=|y| return x*0*/ |
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| 60 | } |
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| 61 | |||
| 62 | /* determine ix = ilogb(x) */ |
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| 63 | if(hx<0x00800000) { /* subnormal x */ |
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| 64 | for (ix = -126,i=(hx<<8); i>0; i<<=1) ix -=1; |
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| 65 | } else ix = (hx>>23)-127; |
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| 66 | |||
| 67 | /* determine iy = ilogb(y) */ |
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| 68 | if(hy<0x00800000) { /* subnormal y */ |
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| 69 | for (iy = -126,i=(hy<<8); i>0; i<<=1) iy -=1; |
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| 70 | } else iy = (hy>>23)-127; |
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| 71 | |||
| 72 | /* set up {hx,lx}, {hy,ly} and align y to x */ |
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| 73 | if(ix >= -126) |
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| 74 | hx = 0x00800000|(0x007fffff&hx); |
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| 75 | else { /* subnormal x, shift x to normal */ |
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| 76 | n = -126-ix; |
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| 77 | hx <<= n; |
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| 78 | } |
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| 79 | if(iy >= -126) |
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| 80 | hy = 0x00800000|(0x007fffff&hy); |
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| 81 | else { /* subnormal y, shift y to normal */ |
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| 82 | n = -126-iy; |
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| 83 | hy <<= n; |
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| 84 | } |
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| 85 | |||
| 86 | /* fix point fmod */ |
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| 87 | n = ix - iy; |
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| 88 | q = 0; |
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| 89 | while(n--) { |
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| 90 | hz=hx-hy; |
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| 91 | if(hz<0) hx = hx << 1; |
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| 92 | else {hx = hz << 1; q++;} |
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| 93 | q <<= 1; |
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| 94 | } |
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| 95 | hz=hx-hy; |
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| 96 | if(hz>=0) {hx=hz;q++;} |
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| 97 | |||
| 98 | /* convert back to floating value and restore the sign */ |
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| 99 | if(hx==0) { /* return sign(x)*0 */ |
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| 100 | *quo = (sxy ? -q : q); |
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| 101 | return Zero[(__uint32_t)sx>>31]; |
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| 102 | } |
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| 103 | while(hx<0x00800000) { /* normalize x */ |
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| 104 | hx <<= 1; |
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| 105 | iy -= 1; |
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| 106 | } |
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| 107 | if(iy>= -126) { /* normalize output */ |
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| 108 | hx = ((hx-0x00800000)|((iy+127)<<23)); |
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| 109 | } else { /* subnormal output */ |
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| 110 | n = -126 - iy; |
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| 111 | hx >>= n; |
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| 112 | } |
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| 113 | fixup: |
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| 114 | SET_FLOAT_WORD(x,hx); |
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| 115 | y = fabsf(y); |
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| 116 | if (y < 0x1p-125f) { |
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| 117 | if (x+x>y || (x+x==y && (q & 1))) { |
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| 118 | q++; |
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| 119 | x-=y; |
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| 120 | } |
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| 121 | } else if (x>0.5f*y || (x==0.5f*y && (q & 1))) { |
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| 122 | q++; |
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| 123 | x-=y; |
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| 124 | } |
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| 125 | GET_FLOAT_WORD(hx,x); |
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| 126 | SET_FLOAT_WORD(x,hx^sx); |
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| 127 | q &= 0x7fffffff; |
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| 128 | *quo = (sxy ? -q : q); |
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| 129 | return x; |
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| 130 | } |