sysdeps/ieee754/ldbl-128/e_fmodl.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 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  * __ieee754_fmodl(x,y)
  17  * Return x mod y in exact arithmetic
  18  * Method: shift and subtract
  19  */
  20
  21 #include "math.h"
  22 #include "math_private.h"
  23
  24 #ifdef __STDC__
  25 static const long double one = 1.0, Zero[] = {0.0, -0.0,};
  26 #else
  27 static long double one = 1.0, Zero[] = {0.0, -0.0,};
  28 #endif
  29
  30 #ifdef __STDC__
  31         long double __ieee754_fmodl(long double x, long double y)
  32 #else
  33         long double __ieee754_fmodl(x,y)
  34         long double x,y;
  35 #endif
  36 {
  37         int64_t n,hx,hy,hz,ix,iy,sx,i;
  38         u_int64_t lx,ly,lz;
  39
  40         GET_LDOUBLE_WORDS64(hx,lx,x);
  41         GET_LDOUBLE_WORDS64(hy,ly,y);
  42         sx = hx&0x8000000000000000ULL;          /* sign of x */
  43         hx ^=sx;                                /* |x| */
  44         hy &= 0x7fffffffffffffffLL;             /* |y| */
  45
  46     /* purge off exception values */
  47         if((hy|ly)==0||(hx>=0x7fff000000000000LL)|| /* y=0,or x not finite */
  48           ((hy|((ly|-ly)>>63))>0x7fff000000000000LL))   /* or y is NaN */
  49             return (x*y)/(x*y);
  50         if(hx<=hy) {
  51             if((hx<hy)||(lx<ly)) return x;      /* |x|<|y| return x */
  52             if(lx==ly)
  53                 return Zero[(u_int64_t)sx>>63]; /* |x|=|y| return x*0*/
  54         }
  55
  56     /* determine ix = ilogb(x) */
  57         if(hx<0x0001000000000000LL) {   /* subnormal x */
  58             if(hx==0) {
  59                 for (ix = -16431, i=lx; i>0; i<<=1) ix -=1;
  60             } else {
  61                 for (ix = -16382, i=hx<<15; i>0; i<<=1) ix -=1;
  62             }
  63         } else ix = (hx>>48)-0x3fff;
  64
  65     /* determine iy = ilogb(y) */
  66         if(hy<0x0001000000000000LL) {   /* subnormal y */
  67             if(hy==0) {
  68                 for (iy = -16431, i=ly; i>0; i<<=1) iy -=1;
  69             } else {
  70                 for (iy = -16382, i=hy<<15; i>0; i<<=1) iy -=1;
  71             }
  72         } else iy = (hy>>48)-0x3fff;
  73
  74     /* set up {hx,lx}, {hy,ly} and align y to x */
  75         if(ix >= -16382)
  76             hx = 0x0001000000000000LL|(0x0000ffffffffffffLL&hx);
  77         else {          /* subnormal x, shift x to normal */
  78             n = -16382-ix;
  79             if(n<=63) {
  80                 hx = (hx<<n)|(lx>>(64-n));
  81                 lx <<= n;
  82             } else {
  83                 hx = lx<<(n-64);
  84                 lx = 0;
  85             }
  86         }
  87         if(iy >= -16382)
  88             hy = 0x0001000000000000LL|(0x0000ffffffffffffLL&hy);
  89         else {          /* subnormal y, shift y to normal */
  90             n = -16382-iy;
  91             if(n<=63) {
  92                 hy = (hy<<n)|(ly>>(64-n));
  93                 ly <<= n;
  94             } else {
  95                 hy = ly<<(n-64);
  96                 ly = 0;
  97             }
  98         }
  99
 100     /* fix point fmod */
 101         n = ix - iy;
 102         while(n--) {
 103             hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
 104             if(hz<0){hx = hx+hx+(lx>>63); lx = lx+lx;}
 105             else {
 106                 if((hz|lz)==0)          /* return sign(x)*0 */
 107                     return Zero[(u_int64_t)sx>>63];
 108                 hx = hz+hz+(lz>>63); lx = lz+lz;
 109             }
 110         }
 111         hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
 112         if(hz>=0) {hx=hz;lx=lz;}
 113
 114     /* convert back to floating value and restore the sign */
 115         if((hx|lx)==0)                  /* return sign(x)*0 */
 116             return Zero[(u_int64_t)sx>>63];
 117         while(hx<0x0001000000000000LL) {        /* normalize x */
 118             hx = hx+hx+(lx>>63); lx = lx+lx;
 119             iy -= 1;
 120         }
 121         if(iy>= -16382) {       /* normalize output */
 122             hx = ((hx-0x0001000000000000LL)|((iy+16383)<<48));
 123             SET_LDOUBLE_WORDS64(x,hx|sx,lx);
 124         } else {                /* subnormal output */
 125             n = -16382 - iy;
 126             if(n<=48) {
 127                 lx = (lx>>n)|((u_int64_t)hx<<(64-n));
 128                 hx >>= n;
 129             } else if (n<=63) {
 130                 lx = (hx<<(64-n))|(lx>>n); hx = sx;
 131             } else {
 132                 lx = hx>>(n-64); hx = sx;
 133             }
 134             SET_LDOUBLE_WORDS64(x,hx|sx,lx);
 135             x *= one;           /* create necessary signal */
 136         }
 137         return x;               /* exact output */
 138 }