compiler/stdc/math/e_fmod.c

   1
   2 /* @(#)e_fmod.c 1.3 95/01/18 */
   3 /*
   4  * ====================================================
   5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   6  *
   7  * Developed at SunSoft, a Sun Microsystems, Inc. business.
   8  * Permission to use, copy, modify, and distribute this
   9  * software is freely granted, provided that this notice
  10  * is preserved.
  11  * ====================================================
  12  */
  13
  14 #ifndef lint
  15 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_fmod.c,v 1.10 2008/02/22 02:30:34 das Exp $";
  16 #endif
  17
  18 /*
  19  * __ieee754_fmod(x,y)
  20  * Return x mod y in exact arithmetic
  21  * Method: shift and subtract
  22  */
  23
  24 #include <float.h>
  25 #include "math.h"
  26 #include "math_private.h"
  27
  28 static const double one = 1.0, Zero[] = {0.0, -0.0,};
  29
  30 double
  31 __ieee754_fmod(double x, double y)
  32 {
  33         int32_t n,hx,hy,hz,ix,iy,sx,i;
  34         uint32_t lx,ly,lz;
  35
  36         EXTRACT_WORDS(hx,lx,x);
  37         EXTRACT_WORDS(hy,ly,y);
  38         sx = hx&0x80000000;             /* sign of x */
  39         hx ^=sx;                /* |x| */
  40         hy &= 0x7fffffff;       /* |y| */
  41
  42     /* purge off exception values */
  43         if((hy|ly)==0||(hx>=0x7ff00000)||       /* y=0,or x not finite */
  44           ((hy|((ly|-ly)>>31))>0x7ff00000))     /* or y is NaN */
  45             return (x*y)/(x*y);
  46         if(hx<=hy) {
  47             if((hx<hy)||(lx<ly)) return x;      /* |x|<|y| return x */
  48             if(lx==ly)
  49                 return Zero[(uint32_t)sx>>31];  /* |x|=|y| return x*0*/
  50         }
  51
  52     /* determine ix = ilogb(x) */
  53         if(hx<0x00100000) {     /* subnormal x */
  54             if(hx==0) {
  55                 for (ix = -1043, i=lx; i>0; i<<=1) ix -=1;
  56             } else {
  57                 for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1;
  58             }
  59         } else ix = (hx>>20)-1023;
  60
  61     /* determine iy = ilogb(y) */
  62         if(hy<0x00100000) {     /* subnormal y */
  63             if(hy==0) {
  64                 for (iy = -1043, i=ly; i>0; i<<=1) iy -=1;
  65             } else {
  66                 for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1;
  67             }
  68         } else iy = (hy>>20)-1023;
  69
  70     /* set up {hx,lx}, {hy,ly} and align y to x */
  71         if(ix >= -1022)
  72             hx = 0x00100000|(0x000fffff&hx);
  73         else {          /* subnormal x, shift x to normal */
  74             n = -1022-ix;
  75             if(n<=31) {
  76                 hx = (hx<<n)|(lx>>(32-n));
  77                 lx <<= n;
  78             } else {
  79                 hx = lx<<(n-32);
  80                 lx = 0;
  81             }
  82         }
  83         if(iy >= -1022)
  84             hy = 0x00100000|(0x000fffff&hy);
  85         else {          /* subnormal y, shift y to normal */
  86             n = -1022-iy;
  87             if(n<=31) {
  88                 hy = (hy<<n)|(ly>>(32-n));
  89                 ly <<= n;
  90             } else {
  91                 hy = ly<<(n-32);
  92                 ly = 0;
  93             }
  94         }
  95
  96     /* fix point fmod */
  97         n = ix - iy;
  98         while(n--) {
  99             hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
 100             if(hz<0){hx = hx+hx+(lx>>31); lx = lx+lx;}
 101             else {
 102                 if((hz|lz)==0)          /* return sign(x)*0 */
 103                     return Zero[(uint32_t)sx>>31];
 104                 hx = hz+hz+(lz>>31); lx = lz+lz;
 105             }
 106         }
 107         hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
 108         if(hz>=0) {hx=hz;lx=lz;}
 109
 110     /* convert back to floating value and restore the sign */
 111         if((hx|lx)==0)                  /* return sign(x)*0 */
 112             return Zero[(uint32_t)sx>>31];
 113         while(hx<0x00100000) {          /* normalize x */
 114             hx = hx+hx+(lx>>31); lx = lx+lx;
 115             iy -= 1;
 116         }
 117         if(iy>= -1022) {        /* normalize output */
 118             hx = ((hx-0x00100000)|((iy+1023)<<20));
 119             INSERT_WORDS(x,hx|sx,lx);
 120         } else {                /* subnormal output */
 121             n = -1022 - iy;
 122             if(n<=20) {
 123                 lx = (lx>>n)|((uint32_t)hx<<(32-n));
 124                 hx >>= n;
 125             } else if (n<=31) {
 126                 lx = (hx<<(32-n))|(lx>>n); hx = sx;
 127             } else {
 128                 lx = hx>>(n-32); hx = sx;
 129             }
 130             INSERT_WORDS(x,hx|sx,lx);
 131             x *= one;           /* create necessary signal */
 132         }
 133         return x;               /* exact output */
 134 }
 135
 136 #if     LDBL_MANT_DIG == DBL_MANT_DIG
 137 AROS_MAKE_ASM_SYM(typeof(fmodl), fmodl, AROS_CSYM_FROM_ASM_NAME(fmodl), AROS_CSYM_FROM_ASM_NAME(fmod));
 138 AROS_EXPORT_ASM_SYM(AROS_CSYM_FROM_ASM_NAME(fmodl));
 139 #endif