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-rw-r--r--src/math/s_remquo.c149
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diff --git a/src/math/s_remquo.c b/src/math/s_remquo.c
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+/* @(#)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 <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;
+ uint32_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<hy)||(lx<ly)) {
+ q = 0;
+ goto fixup; /* |x|<|y| return x or x-y */
+ }
+ if(lx==ly) {
+ *quo = 1;
+ return Zero[(uint32_t)sx>>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<<n)|(lx>>(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<<n)|(ly>>(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<ly) hz -= 1;
+ if(hz<0){hx = hx+hx+(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<ly) hz -= 1;
+ if(hz>=0) {hx=hz;lx=lz;q++;}
+
+ /* convert back to floating value and restore the sign */
+ if((hx|lx)==0) { /* return sign(x)*0 */
+ *quo = (sxy ? -q : q);
+ return Zero[(uint32_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)|((uint32_t)hx<<(32-n));
+ hx >>= n;
+ } else if (n<=31) {
+ lx = (hx<<(32-n))|(lx>>n); hx = sx;
+ } else {
+ lx = hx>>(n-32); hx = sx;
+ }
+ }
+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;
+}