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https://git.planet-casio.com/Lephenixnoir/OpenLibm.git
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129 lines
3.3 KiB
C
129 lines
3.3 KiB
C
/* @(#)e_fmod.c 5.1 93/09/24 */
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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/*
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* fmodl(x,y)
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* Return x mod y in exact arithmetic
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* Method: shift and subtract
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*/
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#include <openlibm.h>
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#include "math_private.h"
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static const long double one = 1.0, Zero[] = {0.0, -0.0,};
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long double
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fmodl(long double x, long double y)
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{
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int64_t n,hx,hy,hz,ix,iy,sx,i;
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u_int64_t lx,ly,lz;
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GET_LDOUBLE_WORDS64(hx,lx,x);
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GET_LDOUBLE_WORDS64(hy,ly,y);
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sx = hx&0x8000000000000000ULL; /* sign of x */
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hx ^=sx; /* |x| */
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hy &= 0x7fffffffffffffffLL; /* |y| */
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/* purge off exception values */
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if((hy|ly)==0||(hx>=0x7fff000000000000LL)|| /* y=0,or x not finite */
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((hy|((ly|-ly)>>63))>0x7fff000000000000LL)) /* or y is NaN */
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return (x*y)/(x*y);
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if(hx<=hy) {
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if((hx<hy)||(lx<ly)) return x; /* |x|<|y| return x */
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if(lx==ly)
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return Zero[(u_int64_t)sx>>63]; /* |x|=|y| return x*0*/
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}
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/* determine ix = ilogb(x) */
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if(hx<0x0001000000000000LL) { /* subnormal x */
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if(hx==0) {
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for (ix = -16431, i=lx; i>0; i<<=1) ix -=1;
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} else {
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for (ix = -16382, i=hx<<15; i>0; i<<=1) ix -=1;
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}
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} else ix = (hx>>48)-0x3fff;
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/* determine iy = ilogb(y) */
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if(hy<0x0001000000000000LL) { /* subnormal y */
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if(hy==0) {
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for (iy = -16431, i=ly; i>0; i<<=1) iy -=1;
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} else {
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for (iy = -16382, i=hy<<15; i>0; i<<=1) iy -=1;
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}
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} else iy = (hy>>48)-0x3fff;
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/* set up {hx,lx}, {hy,ly} and align y to x */
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if(ix >= -16382)
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hx = 0x0001000000000000LL|(0x0000ffffffffffffLL&hx);
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else { /* subnormal x, shift x to normal */
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n = -16382-ix;
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if(n<=63) {
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hx = (hx<<n)|(lx>>(64-n));
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lx <<= n;
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} else {
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hx = lx<<(n-64);
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lx = 0;
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}
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}
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if(iy >= -16382)
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hy = 0x0001000000000000LL|(0x0000ffffffffffffLL&hy);
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else { /* subnormal y, shift y to normal */
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n = -16382-iy;
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if(n<=63) {
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hy = (hy<<n)|(ly>>(64-n));
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ly <<= n;
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} else {
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hy = ly<<(n-64);
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ly = 0;
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}
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}
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/* fix point fmod */
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n = ix - iy;
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while(n--) {
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hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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if(hz<0){hx = hx+hx+(lx>>63); lx = lx+lx;}
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else {
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if((hz|lz)==0) /* return sign(x)*0 */
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return Zero[(u_int64_t)sx>>63];
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hx = hz+hz+(lz>>63); lx = lz+lz;
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}
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}
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hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
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if(hz>=0) {hx=hz;lx=lz;}
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/* convert back to floating value and restore the sign */
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if((hx|lx)==0) /* return sign(x)*0 */
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return Zero[(u_int64_t)sx>>63];
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while(hx<0x0001000000000000LL) { /* normalize x */
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hx = hx+hx+(lx>>63); lx = lx+lx;
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iy -= 1;
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}
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if(iy>= -16382) { /* normalize output */
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hx = ((hx-0x0001000000000000LL)|((iy+16383)<<48));
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SET_LDOUBLE_WORDS64(x,hx|sx,lx);
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} else { /* subnormal output */
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n = -16382 - iy;
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if(n<=48) {
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lx = (lx>>n)|((u_int64_t)hx<<(64-n));
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hx >>= n;
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} else if (n<=63) {
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lx = (hx<<(64-n))|(lx>>n); hx = sx;
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} else {
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lx = hx>>(n-64); hx = sx;
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}
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SET_LDOUBLE_WORDS64(x,hx|sx,lx);
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x *= one; /* create necessary signal */
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}
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return x; /* exact output */
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}
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