-/* origin: FreeBSD /usr/src/lib/msun/src/s_remquof.c */
-/*-
- * ====================================================
- * 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.
- * ====================================================
- */
-/*
- * 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.
- */
-
-#include "libm.h"
-
-static const float Zero[] = {0.0, -0.0,};
+#include <math.h>
+#include <stdint.h>
float remquof(float x, float y, int *quo)
{
- int32_t n,hx,hy,hz,ix,iy,sx,i;
- uint32_t q,sxy;
+ union {float f; uint32_t i;} ux = {x}, uy = {y};
+ int ex = ux.i>>23 & 0xff;
+ int ey = uy.i>>23 & 0xff;
+ int sx = ux.i>>31;
+ int sy = uy.i>>31;
+ uint32_t q;
+ uint32_t i;
+ uint32_t uxi = ux.i;
- GET_FLOAT_WORD(hx, x);
- GET_FLOAT_WORD(hy, y);
- sxy = (hx ^ hy) & 0x80000000;
- sx = hx & 0x80000000; /* sign of x */
- hx ^= sx; /* |x| */
- hy &= 0x7fffffff; /* |y| */
-
- /* purge off exception values */
- if (hy == 0 || hx >= 0x7f800000 || hy > 0x7f800000) /* y=0,NaN;or x not finite */
+ *quo = 0;
+ if (uy.i<<1 == 0 || isnan(y) || ex == 0xff)
return (x*y)/(x*y);
- if (hx < hy) { /* |x| < |y| return x or x-y */
- q = 0;
- goto fixup;
- } else if(hx==hy) { /* |x| = |y| return x*0*/
- *quo = 1;
- return Zero[(uint32_t)sx>>31];
- }
+ if (ux.i<<1 == 0)
+ return x;
- /* determine ix = ilogb(x) */
- if (hx < 0x00800000) { /* subnormal x */
- for (ix = -126, i=hx<<8; i>0; i<<=1) ix--;
- } else
- ix = (hx>>23) - 127;
-
- /* determine iy = ilogb(y) */
- if (hy < 0x00800000) { /* subnormal y */
- for (iy = -126, i=hy<<8; i>0; i<<=1) iy--;
- } else
- iy = (hy>>23) - 127;
-
- /* set up {hx,lx}, {hy,ly} and align y to x */
- if (ix >= -126)
- hx = 0x00800000|(0x007fffff&hx);
- else { /* subnormal x, shift x to normal */
- n = -126 - ix;
- hx <<= n;
+ /* normalize x and y */
+ if (!ex) {
+ for (i = uxi<<9; i>>31 == 0; ex--, i <<= 1);
+ uxi <<= -ex + 1;
+ } else {
+ uxi &= -1U >> 9;
+ uxi |= 1U << 23;
}
- if (iy >= -126)
- hy = 0x00800000|(0x007fffff&hy);
- else { /* subnormal y, shift y to normal */
- n = -126 - iy;
- hy <<= n;
+ if (!ey) {
+ for (i = uy.i<<9; i>>31 == 0; ey--, i <<= 1);
+ uy.i <<= -ey + 1;
+ } else {
+ uy.i &= -1U >> 9;
+ uy.i |= 1U << 23;
}
- /* fix point fmod */
- n = ix - iy;
q = 0;
- while (n--) {
- hz = hx - hy;
- if (hz < 0)
- hx = hx << 1;
- else {
- hx = hz << 1;
+ if (ex < ey) {
+ if (ex+1 == ey)
+ goto end;
+ return x;
+ }
+
+ /* x mod y */
+ for (; ex > ey; ex--) {
+ i = uxi - uy.i;
+ if (i >> 31 == 0) {
+ uxi = i;
q++;
}
+ uxi <<= 1;
q <<= 1;
}
- hz = hx - hy;
- if (hz >= 0) {
- hx = hz;
+ i = uxi - uy.i;
+ if (i >> 31 == 0) {
+ uxi = i;
q++;
}
-
- /* convert back to floating value and restore the sign */
- if (hx == 0) { /* return sign(x)*0 */
- *quo = sxy ? -q : q;
- return Zero[(uint32_t)sx>>31];
- }
- while (hx < 0x00800000) { /* normalize x */
- hx <<= 1;
- iy--;
+ if (uxi == 0)
+ ex = -30;
+ else
+ for (; uxi>>23 == 0; uxi <<= 1, ex--);
+end:
+ /* scale result and decide between |x| and |x|-|y| */
+ if (ex > 0) {
+ uxi -= 1U << 23;
+ uxi |= (uint32_t)ex << 23;
+ } else {
+ uxi >>= -ex + 1;
}
- if (iy >= -126) { /* normalize output */
- hx = (hx-0x00800000)|((iy+127)<<23);
- } else { /* subnormal output */
- n = -126 - iy;
- hx >>= n;
- }
-fixup:
- SET_FLOAT_WORD(x,hx);
- y = fabsf(y);
- if (y < 0x1p-125f) {
- if (x + x > y || (x + x == y && (q & 1))) {
- q++;
- x -= y;
- }
- } else if (x > 0.5f*y || (x == 0.5f*y && (q & 1))) {
- q++;
+ ux.i = uxi;
+ x = ux.f;
+ if (sy)
+ y = -y;
+ if (ex == ey || (ex+1 == ey && (2*x > y || (2*x == y && q%2)))) {
x -= y;
+ q++;
}
- GET_FLOAT_WORD(hx, x);
- SET_FLOAT_WORD(x, hx ^ sx);
q &= 0x7fffffff;
- *quo = sxy ? -q : q;
- return x;
+ *quo = sx^sy ? -(int)q : (int)q;
+ return sx ? -x : x;
}
projects / musl / blobdiff