blob: 9ad1e4c2775d616eaf4369900242377b499dec7f [file] [log] [blame]
 /* @(#)e_fmod.c 1.3 95/01/18 */ /*- * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ #include /* __FBSDID("\$FreeBSD: src/lib/msun/src/s_remquo.c,v 1.1 2005/03/25 04:40:44 das Exp \$"); */ #include "math.h" #include "math_private.h" static const double Zero[] = {0.0, -0.0,}; /* * Return the IEEE remainder and set *quo to the last n bits of the * quotient, rounded to the nearest integer. We choose n=31 because * we wind up computing all the integer bits of the quotient anyway as * a side-effect of computing the remainder by the shift and subtract * method. In practice, this is far more bits than are needed to use * remquo in reduction algorithms. */ double remquo(double x, double y, int *quo) { int32_t n,hx,hy,hz,ix,iy,sx,i; u_int32_t lx,ly,lz,q,sxy; EXTRACT_WORDS(hx,lx,x); EXTRACT_WORDS(hy,ly,y); sxy = (hx ^ hy) & 0x80000000; sx = hx&0x80000000; /* sign of x */ hx ^=sx; /* |x| */ hy &= 0x7fffffff; /* |y| */ /* purge off exception values */ if((hy|ly)==0||(hx>=0x7ff00000)|| /* y=0,or x not finite */ ((hy|((ly|-ly)>>31))>0x7ff00000)) /* or y is NaN */ return (x*y)/(x*y); if(hx<=hy) { if((hx>31]; /* |x|=|y| return x*0*/ } } /* determine ix = ilogb(x) */ if(hx<0x00100000) { /* subnormal x */ if(hx==0) { for (ix = -1043, i=lx; i>0; i<<=1) ix -=1; } else { for (ix = -1022,i=(hx<<11); i>0; i<<=1) ix -=1; } } else ix = (hx>>20)-1023; /* determine iy = ilogb(y) */ if(hy<0x00100000) { /* subnormal y */ if(hy==0) { for (iy = -1043, i=ly; i>0; i<<=1) iy -=1; } else { for (iy = -1022,i=(hy<<11); i>0; i<<=1) iy -=1; } } else iy = (hy>>20)-1023; /* set up {hx,lx}, {hy,ly} and align y to x */ if(ix >= -1022) hx = 0x00100000|(0x000fffff&hx); else { /* subnormal x, shift x to normal */ n = -1022-ix; if(n<=31) { hx = (hx<>(32-n)); lx <<= n; } else { hx = lx<<(n-32); lx = 0; } } if(iy >= -1022) hy = 0x00100000|(0x000fffff&hy); else { /* subnormal y, shift y to normal */ n = -1022-iy; if(n<=31) { hy = (hy<>(32-n)); ly <<= n; } else { hy = ly<<(n-32); ly = 0; } } /* fix point fmod */ n = ix - iy; q = 0; while(n--) { hz=hx-hy;lz=lx-ly; if(lx>31); lx = lx+lx;} else {hx = hz+hz+(lz>>31); lx = lz+lz; q++;} q <<= 1; } hz=hx-hy;lz=lx-ly; if(lx=0) {hx=hz;lx=lz;q++;} /* convert back to floating value and restore the sign */ if((hx|lx)==0) { /* return sign(x)*0 */ q &= 0x7fffffff; *quo = (sxy ? -q : q); return Zero[(u_int32_t)sx>>31]; } while(hx<0x00100000) { /* normalize x */ hx = hx+hx+(lx>>31); lx = lx+lx; iy -= 1; } if(iy>= -1022) { /* normalize output */ hx = ((hx-0x00100000)|((iy+1023)<<20)); } else { /* subnormal output */ n = -1022 - iy; if(n<=20) { lx = (lx>>n)|((u_int32_t)hx<<(32-n)); hx >>= n; } else if (n<=31) { lx = (hx<<(32-n))|(lx>>n); hx = 0; } else { lx = hx>>(n-32); hx = 0; } } fixup: INSERT_WORDS(x,hx,lx); y = fabs(y); if (y < 0x1p-1021) { if (x+x>y || (x+x==y && (q & 1))) { q++; x-=y; } } else if (x>0.5*y || (x==0.5*y && (q & 1))) { q++; x-=y; } GET_HIGH_WORD(hx,x); SET_HIGH_WORD(x,hx^sx); q &= 0x7fffffff; *quo = (sxy ? -q : q); return x; }