math: rewrite remainder functions (remainder, remquo, fmod, modf)

* results are exact
* modfl follows truncl (raises inexact flag spuriously now)
* modf and modff only had cosmetic cleanup
* remainder is just a wrapper around remquo now
* using iterative shift+subtract for remquo and fmod
* ld80 and ld128 are supported as well

1 files changed, 4 insertions, 63 deletions

diff --git a/src/math/remainder.c b/src/math/remainder.c
index 2dede3a8..ed5c477e 100644
--- a/src/math/remainder.c
+++ b/src/math/remainder.c
@@ -1,66 +1,7 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/e_remainder.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.
- * ====================================================
- */
-/* remainder(x,p)
- * Return :
- *      returns  x REM p  =  x - [x/p]*p as if in infinite
- *      precise arithmetic, where [x/p] is the (infinite bit)
- *      integer nearest x/p (in half way case choose the even one).
- * Method :
- *      Based on fmod() return x-[x/p]chopped*p exactlp.
- */
+#include <math.h>
 
-#include "libm.h"
-
-double remainder(double x, double p)
+double remainder(double x, double y)
 {
-	int32_t hx,hp;
-	uint32_t sx,lx,lp;
-	double p_half;
-
-	EXTRACT_WORDS(hx, lx, x);
-	EXTRACT_WORDS(hp, lp, p);
-	sx = hx & 0x80000000;
-	hp &= 0x7fffffff;
-	hx &= 0x7fffffff;
-
-	/* purge off exception values */
-	if ((hp|lp) == 0 ||                                  /* p = 0 */
-	    hx >= 0x7ff00000 ||                              /* x not finite */
-	    (hp >= 0x7ff00000 && (hp-0x7ff00000 | lp) != 0)) /* p is NaN */
-		return (x*p)/(x*p);
-
-	if (hp <= 0x7fdfffff)
-		x = fmod(x, p+p);  /* now x < 2p */
-	if (((hx-hp)|(lx-lp)) == 0)
-		return 0.0*x;
-	x = fabs(x);
-	p = fabs(p);
-	if (hp < 0x00200000) {
-		if (x + x > p) {
-			x -= p;
-			if (x + x >= p)
-				x -= p;
-		}
-	} else {
-		p_half = 0.5*p;
-		if (x > p_half) {
-			x -= p;
-			if (x >= p_half)
-				x -= p;
-		}
-	}
-	GET_HIGH_WORD(hx, x);
-	if ((hx&0x7fffffff) == 0)
-		hx = 0;
-	SET_HIGH_WORD(x, hx^sx);
-	return x;
+	int q;
+	return remquo(x, y, &q);
 }