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authorSzabolcs Nagy <nsz@port70.net>2013-09-03 03:27:02 +0000
committerSzabolcs Nagy <nsz@port70.net>2013-09-05 11:30:07 +0000
commitd1a2ead878c27ac4ec600740320f8b76e1f961e9 (patch)
tree4da00576cf5df93d9170bdf76a26d9c2c96d3978 /src/math/roundf.c
parent98be442ee8a2b8b7e0802b604e384d5a2c43282e (diff)
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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)
Diffstat (limited to 'src/math/roundf.c')
-rw-r--r--src/math/roundf.c61
1 files changed, 20 insertions, 41 deletions
diff --git a/src/math/roundf.c b/src/math/roundf.c
index 662a454b..c6b27797 100644
--- a/src/math/roundf.c
+++ b/src/math/roundf.c
@@ -1,48 +1,27 @@
-/* origin: FreeBSD /usr/src/lib/msun/src/s_roundf.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 "libm.h"
float roundf(float x)
{
- float t;
+ union {float f; uint32_t i;} u = {x};
+ int e = u.i >> 23 & 0xff;
+ float_t y;
- if (!isfinite(x))
+ if (e >= 0x7f+23)
return x;
-
- if (x >= 0.0) {
- t = floorf(x);
- if (t - x <= -0.5)
- t += 1.0;
- return t;
- } else {
- t = floorf(-x);
- if (t + x <= -0.5)
- t += 1.0;
- return -t;
+ if (u.i >> 31)
+ x = -x;
+ if (e < 0x7f-1) {
+ FORCE_EVAL(x + 0x1p23f);
+ return 0*u.f;
}
+ y = (float)(x + 0x1p23f) - 0x1p23f - x;
+ if (y > 0.5f)
+ y = y + x - 1;
+ else if (y <= -0.5f)
+ y = y + x + 1;
+ else
+ y = y + x;
+ if (u.i >> 31)
+ y = -y;
+ return y;
}