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| 2 | /* @(#)e_fmod.c 5.1 93/09/24 */
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| 3 | /*
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| 4 | * ====================================================
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| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 6 | *
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| 7 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 8 | * Permission to use, copy, modify, and distribute this
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| 9 | * software is freely granted, provided that this notice
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| 10 | * is preserved.
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| 11 | * ====================================================
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| 12 | */
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| 13 |
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| 14 | /*
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| 15 | * __ieee754_fmod(x,y)
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| 16 | * Return x mod y in exact arithmetic
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| 17 | * Method: shift and subtract
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| 18 | */
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| 19 |
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| 20 | #include "fdlibm.h"
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| 21 |
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| 22 | #ifndef _DOUBLE_IS_32BITS
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| 23 |
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| 24 | #ifdef __STDC__
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| 25 | static const double one = 1.0, Zero[] = {0.0, -0.0,};
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| 26 | #else
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| 27 | static double one = 1.0, Zero[] = {0.0, -0.0,};
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| 28 | #endif
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| 29 |
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| 30 | #ifdef __STDC__
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| 31 | double __ieee754_fmod(double x, double y)
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| 32 | #else
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| 33 | double __ieee754_fmod(x,y)
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| 34 | double x,y ;
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| 35 | #endif
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| 36 | {
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| 37 | int32_t n,hx,hy,hz,ix,iy,sx,i;
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| 38 | uint32_t lx,ly,lz;
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| 39 |
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| 40 | EXTRACT_WORDS(hx,lx,x);
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| 41 | EXTRACT_WORDS(hy,ly,y);
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| 42 | sx = hx&0x80000000; /* sign of x */
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| 43 | hx ^=sx; /* |x| */
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| 44 | hy &= 0x7fffffff; /* |y| */
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| 45 |
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| 46 | /* purge off exception values */
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| 47 | if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */
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| 48 | ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */
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| 49 | return (x*y)/(x*y);
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| 50 | if(hx<=hy) {
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| 51 | if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */
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| 52 | if(lx==ly)
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| 53 | return Zero[(uint32_t)sx>>31]; /* |x|=|y| return x*0*/
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| 54 | }
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| 55 |
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| 56 | /* determine ix = ilogb(x) */
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| 57 | if(hx<0x00100000) { /* subnormal x */
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| 58 | if(hx==0) {
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| 59 | for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
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| 60 | } else {
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| 61 | for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
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| 62 | }
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| 63 | } else ix = (hx>>20)-1023;
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| 64 |
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| 65 | /* determine iy = ilogb(y) */
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| 66 | if(hy<0x00100000) { /* subnormal y */
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| 67 | if(hy==0) {
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| 68 | for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
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| 69 | } else {
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| 70 | for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
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| 71 | }
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| 72 | } else iy = (hy>>20)-1023;
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| 73 |
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| 74 | /* set up {hx,lx}, {hy,ly} and align y to x */
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| 75 | if(ix >= -1022)
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| 76 | hx = 0x00100000|(0x000fffff&hx);
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| 77 | else { /* subnormal x, shift x to normal */
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| 78 | n = -1022-ix;
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| 79 | if(n<=31) {
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| 80 | hx = (hx<<n)|(lx>>(32-n));
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| 81 | lx <<= n;
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| 82 | } else {
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| 83 | hx = lx<<(n-32);
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| 84 | lx = 0;
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| 85 | }
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| 86 | }
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| 87 | if(iy >= -1022)
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| 88 | hy = 0x00100000|(0x000fffff&hy);
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| 89 | else { /* subnormal y, shift y to normal */
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| 90 | n = -1022-iy;
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| 91 | if(n<=31) {
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| 92 | hy = (hy<<n)|(ly>>(32-n));
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| 93 | ly <<= n;
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| 94 | } else {
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| 95 | hy = ly<<(n-32);
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| 96 | ly = 0;
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| 97 | }
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| 98 | }
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| 99 |
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| 100 | /* fix point fmod */
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| 101 | n = ix - iy;
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| 102 | while(n--) {
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| 103 | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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| 104 | if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
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| 105 | else {
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| 106 | if((hz|lz)==0) /* return sign(x)*0 */
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| 107 | return Zero[(uint32_t)sx>>31];
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| 108 | hx = hz+hz+(lz>>31); lx = lz+lz;
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| 109 | }
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| 110 | }
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| 111 | hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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| 112 | if(hz>=0) {hx=hz;lx=lz;}
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| 113 |
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| 114 | /* convert back to floating value and restore the sign */
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| 115 | if((hx|lx)==0) /* return sign(x)*0 */
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| 116 | return Zero[(uint32_t)sx>>31];
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| 117 | while(hx<0x00100000) { /* normalize x */
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| 118 | hx = hx+hx+(lx>>31); lx = lx+lx;
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| 119 | iy -= 1;
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| 120 | }
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| 121 | if(iy>= -1022) { /* normalize output */
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| 122 | hx = ((hx-0x00100000)|((iy+1023)<<20));
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| 123 | INSERT_WORDS(x,hx|sx,lx);
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| 124 | } else { /* subnormal output */
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| 125 | n = -1022 - iy;
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| 126 | if(n<=20) {
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| 127 | lx = (lx>>n)|((uint32_t)hx<<(32-n));
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| 128 | hx >>= n;
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| 129 | } else if (n<=31) {
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| 130 | lx = (hx<<(32-n))|(lx>>n); hx = sx;
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| 131 | } else {
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| 132 | lx = hx>>(n-32); hx = sx;
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| 133 | }
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| 134 | INSERT_WORDS(x,hx|sx,lx);
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| 135 | x *= one; /* create necessary signal */
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| 136 | }
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| 137 | return x; /* exact output */
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| 138 | }
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| 139 |
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| 140 | #endif /* defined(_DOUBLE_IS_32BITS) */
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