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| Rev | Author | Line No. | Line |
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| 2 | pj | 1 | /* @(#)e_fmod.c 5.1 93/09/24 */ |
| 2 | /* |
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| 3 | * ==================================================== |
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| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
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| 5 | * |
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| 6 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
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| 7 | * Permission to use, copy, modify, and distribute this |
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| 8 | * software is freely granted, provided that this notice |
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| 9 | * is preserved. |
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| 10 | * ==================================================== |
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| 11 | */ |
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| 12 | |||
| 13 | #ifndef lint |
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| 14 | static char rcsid[] = "$\Id: e_fmod.c,v 1.2.6.1 1997/02/23 11:03:03 joerg Exp $"; |
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| 15 | #endif |
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| 16 | |||
| 17 | /* |
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| 18 | * __ieee754_fmod(x,y) |
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| 19 | * Return x mod y in exact arithmetic |
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| 20 | * Method: shift and subtract |
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| 21 | */ |
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| 22 | |||
| 23 | #include "math.h" |
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| 24 | #include "math_private.h" |
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| 25 | |||
| 26 | #ifdef __STDC__ |
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| 27 | static const double one = 1.0, Zero[] = {0.0, -0.0,}; |
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| 28 | #else |
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| 29 | static double one = 1.0, Zero[] = {0.0, -0.0,}; |
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| 30 | #endif |
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| 31 | |||
| 32 | #ifdef __STDC__ |
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| 33 | double __generic___ieee754_fmod(double x, double y) |
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| 34 | #else |
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| 35 | double __generic___ieee754_fmod(x,y) |
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| 36 | double x,y ; |
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| 37 | #endif |
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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 | u_int32_t lx,ly,lz; |
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| 41 | |||
| 42 | EXTRACT_WORDS(hx,lx,x); |
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| 43 | EXTRACT_WORDS(hy,ly,y); |
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| 44 | sx = hx&0x80000000; /* sign of x */ |
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| 45 | hx ^=sx; /* |x| */ |
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| 46 | hy &= 0x7fffffff; /* |y| */ |
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| 47 | |||
| 48 | /* purge off exception values */ |
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| 49 | if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */ |
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| 50 | ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */ |
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| 51 | return (x*y)/(x*y); |
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| 52 | if(hx<=hy) { |
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| 53 | if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */ |
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| 54 | if(lx==ly) |
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| 55 | return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ |
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| 56 | } |
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| 57 | |||
| 58 | /* determine ix = ilogb(x) */ |
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| 59 | if(hx<0x00100000) { /* subnormal x */ |
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| 60 | if(hx==0) { |
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| 61 | for (ix = -1043, i=lx; i>0; i<<=1) ix -=1; |
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| 62 | } else { |
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| 63 | for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1; |
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| 64 | } |
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| 65 | } else ix = (hx>>20)-1023; |
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| 66 | |||
| 67 | /* determine iy = ilogb(y) */ |
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| 68 | if(hy<0x00100000) { /* subnormal y */ |
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| 69 | if(hy==0) { |
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| 70 | for (iy = -1043, i=ly; i>0; i<<=1) iy -=1; |
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| 71 | } else { |
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| 72 | for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1; |
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| 73 | } |
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| 74 | } else iy = (hy>>20)-1023; |
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| 75 | |||
| 76 | /* set up {hx,lx}, {hy,ly} and align y to x */ |
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| 77 | if(ix >= -1022) |
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| 78 | hx = 0x00100000|(0x000fffff&hx); |
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| 79 | else { /* subnormal x, shift x to normal */ |
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| 80 | n = -1022-ix; |
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| 81 | if(n<=31) { |
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| 82 | hx = (hx<<n)|(lx>>(32-n)); |
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| 83 | lx <<= n; |
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| 84 | } else { |
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| 85 | hx = lx<<(n-32); |
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| 86 | lx = 0; |
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| 87 | } |
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| 88 | } |
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| 89 | if(iy >= -1022) |
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| 90 | hy = 0x00100000|(0x000fffff&hy); |
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| 91 | else { /* subnormal y, shift y to normal */ |
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| 92 | n = -1022-iy; |
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| 93 | if(n<=31) { |
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| 94 | hy = (hy<<n)|(ly>>(32-n)); |
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| 95 | ly <<= n; |
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| 96 | } else { |
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| 97 | hy = ly<<(n-32); |
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| 98 | ly = 0; |
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| 99 | } |
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| 100 | } |
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| 101 | |||
| 102 | /* fix point fmod */ |
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| 103 | n = ix - iy; |
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| 104 | while(n--) { |
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| 105 | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; |
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| 106 | if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;} |
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| 107 | else { |
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| 108 | if((hz|lz)==0) /* return sign(x)*0 */ |
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| 109 | return Zero[(u_int32_t)sx>>31]; |
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| 110 | hx = hz+hz+(lz>>31); lx = lz+lz; |
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| 111 | } |
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| 112 | } |
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| 113 | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; |
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| 114 | if(hz>=0) {hx=hz;lx=lz;} |
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| 115 | |||
| 116 | /* convert back to floating value and restore the sign */ |
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| 117 | if((hx|lx)==0) /* return sign(x)*0 */ |
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| 118 | return Zero[(u_int32_t)sx>>31]; |
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| 119 | while(hx<0x00100000) { /* normalize x */ |
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| 120 | hx = hx+hx+(lx>>31); lx = lx+lx; |
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| 121 | iy -= 1; |
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| 122 | } |
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| 123 | if(iy>= -1022) { /* normalize output */ |
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| 124 | hx = ((hx-0x00100000)|((iy+1023)<<20)); |
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| 125 | INSERT_WORDS(x,hx|sx,lx); |
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| 126 | } else { /* subnormal output */ |
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| 127 | n = -1022 - iy; |
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| 128 | if(n<=20) { |
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| 129 | lx = (lx>>n)|((u_int32_t)hx<<(32-n)); |
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| 130 | hx >>= n; |
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| 131 | } else if (n<=31) { |
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| 132 | lx = (hx<<(32-n))|(lx>>n); hx = sx; |
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| 133 | } else { |
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| 134 | lx = hx>>(n-32); hx = sx; |
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| 135 | } |
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| 136 | INSERT_WORDS(x,hx|sx,lx); |
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| 137 | x *= one; /* create necessary signal */ |
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| 138 | } |
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| 139 | return x; /* exact output */ |
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| 140 | } |