Details | Last modification | View Log | RSS feed
| Rev | Author | Line No. | Line |
|---|---|---|---|
| 2 | pj | 1 | /* @(#)e_fmod.c 5.1 93/09/24 */ |
| 2 | /* |
||
| 3 | * ==================================================== |
||
| 4 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
||
| 5 | * |
||
| 6 | * Developed at SunPro, 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 | #ifndef lint |
||
| 14 | static char rcsid[] = "$\Id: e_fmod.c,v 1.2.6.1 1997/02/23 11:03:03 joerg Exp $"; |
||
| 15 | #endif |
||
| 16 | |||
| 17 | /* |
||
| 18 | * __ieee754_fmod(x,y) |
||
| 19 | * Return x mod y in exact arithmetic |
||
| 20 | * Method: shift and subtract |
||
| 21 | */ |
||
| 22 | |||
| 23 | #include "math.h" |
||
| 24 | #include "math_private.h" |
||
| 25 | |||
| 26 | #ifdef __STDC__ |
||
| 27 | static const double one = 1.0, Zero[] = {0.0, -0.0,}; |
||
| 28 | #else |
||
| 29 | static double one = 1.0, Zero[] = {0.0, -0.0,}; |
||
| 30 | #endif |
||
| 31 | |||
| 32 | #ifdef __STDC__ |
||
| 33 | double __generic___ieee754_fmod(double x, double y) |
||
| 34 | #else |
||
| 35 | double __generic___ieee754_fmod(x,y) |
||
| 36 | double x,y ; |
||
| 37 | #endif |
||
| 38 | { |
||
| 39 | int32_t n,hx,hy,hz,ix,iy,sx,i; |
||
| 40 | u_int32_t lx,ly,lz; |
||
| 41 | |||
| 42 | EXTRACT_WORDS(hx,lx,x); |
||
| 43 | EXTRACT_WORDS(hy,ly,y); |
||
| 44 | sx = hx&0x80000000; /* sign of x */ |
||
| 45 | hx ^=sx; /* |x| */ |
||
| 46 | hy &= 0x7fffffff; /* |y| */ |
||
| 47 | |||
| 48 | /* purge off exception values */ |
||
| 49 | if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */ |
||
| 50 | ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */ |
||
| 51 | return (x*y)/(x*y); |
||
| 52 | if(hx<=hy) { |
||
| 53 | if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */ |
||
| 54 | if(lx==ly) |
||
| 55 | return Zero[(u_int32_t)sx>>31]; /* |x|=|y| return x*0*/ |
||
| 56 | } |
||
| 57 | |||
| 58 | /* determine ix = ilogb(x) */ |
||
| 59 | if(hx<0x00100000) { /* subnormal x */ |
||
| 60 | if(hx==0) { |
||
| 61 | for (ix = -1043, i=lx; i>0; i<<=1) ix -=1; |
||
| 62 | } else { |
||
| 63 | for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1; |
||
| 64 | } |
||
| 65 | } else ix = (hx>>20)-1023; |
||
| 66 | |||
| 67 | /* determine iy = ilogb(y) */ |
||
| 68 | if(hy<0x00100000) { /* subnormal y */ |
||
| 69 | if(hy==0) { |
||
| 70 | for (iy = -1043, i=ly; i>0; i<<=1) iy -=1; |
||
| 71 | } else { |
||
| 72 | for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1; |
||
| 73 | } |
||
| 74 | } else iy = (hy>>20)-1023; |
||
| 75 | |||
| 76 | /* set up {hx,lx}, {hy,ly} and align y to x */ |
||
| 77 | if(ix >= -1022) |
||
| 78 | hx = 0x00100000|(0x000fffff&hx); |
||
| 79 | else { /* subnormal x, shift x to normal */ |
||
| 80 | n = -1022-ix; |
||
| 81 | if(n<=31) { |
||
| 82 | hx = (hx<<n)|(lx>>(32-n)); |
||
| 83 | lx <<= n; |
||
| 84 | } else { |
||
| 85 | hx = lx<<(n-32); |
||
| 86 | lx = 0; |
||
| 87 | } |
||
| 88 | } |
||
| 89 | if(iy >= -1022) |
||
| 90 | hy = 0x00100000|(0x000fffff&hy); |
||
| 91 | else { /* subnormal y, shift y to normal */ |
||
| 92 | n = -1022-iy; |
||
| 93 | if(n<=31) { |
||
| 94 | hy = (hy<<n)|(ly>>(32-n)); |
||
| 95 | ly <<= n; |
||
| 96 | } else { |
||
| 97 | hy = ly<<(n-32); |
||
| 98 | ly = 0; |
||
| 99 | } |
||
| 100 | } |
||
| 101 | |||
| 102 | /* fix point fmod */ |
||
| 103 | n = ix - iy; |
||
| 104 | while(n--) { |
||
| 105 | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; |
||
| 106 | if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;} |
||
| 107 | else { |
||
| 108 | if((hz|lz)==0) /* return sign(x)*0 */ |
||
| 109 | return Zero[(u_int32_t)sx>>31]; |
||
| 110 | hx = hz+hz+(lz>>31); lx = lz+lz; |
||
| 111 | } |
||
| 112 | } |
||
| 113 | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1; |
||
| 114 | if(hz>=0) {hx=hz;lx=lz;} |
||
| 115 | |||
| 116 | /* convert back to floating value and restore the sign */ |
||
| 117 | if((hx|lx)==0) /* return sign(x)*0 */ |
||
| 118 | return Zero[(u_int32_t)sx>>31]; |
||
| 119 | while(hx<0x00100000) { /* normalize x */ |
||
| 120 | hx = hx+hx+(lx>>31); lx = lx+lx; |
||
| 121 | iy -= 1; |
||
| 122 | } |
||
| 123 | if(iy>= -1022) { /* normalize output */ |
||
| 124 | hx = ((hx-0x00100000)|((iy+1023)<<20)); |
||
| 125 | INSERT_WORDS(x,hx|sx,lx); |
||
| 126 | } else { /* subnormal output */ |
||
| 127 | n = -1022 - iy; |
||
| 128 | if(n<=20) { |
||
| 129 | lx = (lx>>n)|((u_int32_t)hx<<(32-n)); |
||
| 130 | hx >>= n; |
||
| 131 | } else if (n<=31) { |
||
| 132 | lx = (hx<<(32-n))|(lx>>n); hx = sx; |
||
| 133 | } else { |
||
| 134 | lx = hx>>(n-32); hx = sx; |
||
| 135 | } |
||
| 136 | INSERT_WORDS(x,hx|sx,lx); |
||
| 137 | x *= one; /* create necessary signal */ |
||
| 138 | } |
||
| 139 | return x; /* exact output */ |
||
| 140 | } |