math: rewrite rounding functions (ceil, floor, trunc, round, rint)

* faster, smaller, cleaner implementation than the bit hacks of fdlibm
* use arithmetics like y=(double)(x+0x1p52)-0x1p52, which is an integer
neighbor of x in all rounding modes (0<=x<0x1p52) and only use bithacks
when that's faster and smaller (for float it usually is)
* the code assumes standard excess precision handling for casts
* long double code supports both ld80 and ld128
* nearbyint is not changed (it is a wrapper around rint)

1 files changed, 26 insertions, 43 deletions

diff --git a/src/math/roundl.c b/src/math/roundl.c
index 99146f07..8f3f28b3 100644
--- a/src/math/roundl.c
+++ b/src/math/roundl.c
@@ -1,56 +1,39 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/s_roundl.c */
-/*-
- * Copyright (c) 2003, Steven G. Kargl
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice unmodified, this list of conditions, and the following
- *    disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
- * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
- * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
- * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include <math.h>
-#include <float.h>
+#include "libm.h"
 
 #if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
 long double roundl(long double x)
 {
 	return round(x);
 }
-#else
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+#if LDBL_MANT_DIG == 64
+#define TOINT 0x1p63
+#elif LDBL_MANT_DIG == 113
+#define TOINT 0x1p112
+#endif
 long double roundl(long double x)
 {
-	long double t;
+	union ldshape u = {x};
+	int e = u.i.se & 0x7fff;
+	long double y;
 
-	if (!isfinite(x))
+	if (e >= 0x3fff+LDBL_MANT_DIG-1)
 		return x;
-
-	if (x >= 0.0) {
-		t = floorl(x);
-		if (t - x <= -0.5)
-			t += 1.0;
-		return t;
-	} else {
-		t = floorl(-x);
-		if (t + x <= -0.5)
-			t += 1.0;
-		return -t;
+	if (u.i.se >> 15)
+		x = -x;
+	if (e < 0x3fff-1) {
+		FORCE_EVAL(x + TOINT);
+		return 0*u.f;
 	}
+	y = x + TOINT - TOINT - x;
+	if (y > 0.5)
+		y = y + x - 1;
+	else if (y <= -0.5)
+		y = y + x + 1;
+	else
+		y = y + x;
+	if (u.i.se >> 15)
+		y = -y;
+	return y;
 }
 #endif