libquadmath/math/fmodq.c

   1 /* e_fmodl.c -- long double version of e_fmod.c.
   2  * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz.
   3  */
   4 /*
   5  * ====================================================
   6  * Copyright (C) 1993, 2011 by Sun Microsystems, Inc. All rights reserved.
   7  *
   8  * Developed at SunPro, a Sun Microsystems, Inc. business.
   9  * Permission to use, copy, modify, and distribute this
  10  * software is freely granted, provided that this notice
  11  * is preserved.
  12  * ====================================================
  13  */
  14
  15 /*
  16  * fmodq(x,y)
  17  * Return x mod y in exact arithmetic
  18  * Method: shift and subtract
  19  */
  20
  21 #include "quadmath-imp.h"
  22
  23 static const __float128 one = 1.0, Zero[] = {0.0, -0.0,};
  24
  25 __float128
  26 fmodq (__float128 x, __float128 y)
  27 {
  28         int64_t n,hx,hy,hz,ix,iy,sx,i;
  29         uint64_t lx,ly,lz;
  30
  31         GET_FLT128_WORDS64(hx,lx,x);
  32         GET_FLT128_WORDS64(hy,ly,y);
  33         sx = hx&0x8000000000000000ULL;          /* sign of x */
  34         hx ^=sx;                                /* |x| */
  35         hy &= 0x7fffffffffffffffLL;             /* |y| */
  36
  37     /* purge off exception values */
  38         if((hy|ly)==0||(hx>=0x7fff000000000000LL)|| /* y=0,or x not finite */
  39           ((hy|((ly|-ly)>>63))>0x7fff000000000000LL))   /* or y is NaN */
  40             return (x*y)/(x*y);
  41         if(hx<=hy) {
  42             if((hx<hy)||(lx<ly)) return x;      /* |x|<|y| return x */
  43             if(lx==ly)
  44                 return Zero[(uint64_t)sx>>63];  /* |x|=|y| return x*0*/
  45         }
  46
  47     /* determine ix = ilogb(x) */
  48         if(hx<0x0001000000000000LL) {   /* subnormal x */
  49             if(hx==0) {
  50                 for (ix = -16431, i=lx; i>0; i<<=1) ix -=1;
  51             } else {
  52                 for (ix = -16382, i=hx<<15; i>0; i<<=1) ix -=1;
  53             }
  54         } else ix = (hx>>48)-0x3fff;
  55
  56     /* determine iy = ilogb(y) */
  57         if(hy<0x0001000000000000LL) {   /* subnormal y */
  58             if(hy==0) {
  59                 for (iy = -16431, i=ly; i>0; i<<=1) iy -=1;
  60             } else {
  61                 for (iy = -16382, i=hy<<15; i>0; i<<=1) iy -=1;
  62             }
  63         } else iy = (hy>>48)-0x3fff;
  64
  65     /* set up {hx,lx}, {hy,ly} and align y to x */
  66         if(ix >= -16382)
  67             hx = 0x0001000000000000LL|(0x0000ffffffffffffLL&hx);
  68         else {          /* subnormal x, shift x to normal */
  69             n = -16382-ix;
  70             if(n<=63) {
  71                 hx = (hx<<n)|(lx>>(64-n));
  72                 lx <<= n;
  73             } else {
  74                 hx = lx<<(n-64);
  75                 lx = 0;
  76             }
  77         }
  78         if(iy >= -16382)
  79             hy = 0x0001000000000000LL|(0x0000ffffffffffffLL&hy);
  80         else {          /* subnormal y, shift y to normal */
  81             n = -16382-iy;
  82             if(n<=63) {
  83                 hy = (hy<<n)|(ly>>(64-n));
  84                 ly <<= n;
  85             } else {
  86                 hy = ly<<(n-64);
  87                 ly = 0;
  88             }
  89         }
  90
  91     /* fix point fmod */
  92         n = ix - iy;
  93         while(n--) {
  94             hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
  95             if(hz<0){hx = hx+hx+(lx>>63); lx = lx+lx;}
  96             else {
  97                 if((hz|lz)==0)          /* return sign(x)*0 */
  98                     return Zero[(uint64_t)sx>>63];
  99                 hx = hz+hz+(lz>>63); lx = lz+lz;
 100             }
 101         }
 102         hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
 103         if(hz>=0) {hx=hz;lx=lz;}
 104
 105     /* convert back to floating value and restore the sign */
 106         if((hx|lx)==0)                  /* return sign(x)*0 */
 107             return Zero[(uint64_t)sx>>63];
 108         while(hx<0x0001000000000000LL) {        /* normalize x */
 109             hx = hx+hx+(lx>>63); lx = lx+lx;
 110             iy -= 1;
 111         }
 112         if(iy>= -16382) {       /* normalize output */
 113             hx = ((hx-0x0001000000000000LL)|((iy+16383)<<48));
 114             SET_FLT128_WORDS64(x,hx|sx,lx);
 115         } else {                /* subnormal output */
 116             n = -16382 - iy;
 117             if(n<=48) {
 118                 lx = (lx>>n)|((uint64_t)hx<<(64-n));
 119                 hx >>= n;
 120             } else if (n<=63) {
 121                 lx = (hx<<(64-n))|(lx>>n); hx = sx;
 122             } else {
 123                 lx = hx>>(n-64); hx = sx;
 124             }
 125             SET_FLT128_WORDS64(x,hx|sx,lx);
 126             x *= one;           /* create necessary signal */
 127         }
 128         return x;               /* exact output */
 129 }