From d1a2ead878c27ac4ec600740320f8b76e1f961e9 Mon Sep 17 00:00:00 2001 From: Szabolcs Nagy Date: Tue, 3 Sep 2013 03:27:02 +0000 Subject: 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) --- src/math/round.c | 62 +++++++++++++++++++------------------------------------- 1 file changed, 21 insertions(+), 41 deletions(-) (limited to 'src/math/round.c') diff --git a/src/math/round.c b/src/math/round.c index bf0b453f..4b38d1fd 100644 --- a/src/math/round.c +++ b/src/math/round.c @@ -1,48 +1,28 @@ -/* origin: FreeBSD /usr/src/lib/msun/src/s_round.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 +#include "libm.h" double round(double x) { - double t; + union {double f; uint64_t i;} u = {x}; + int e = u.i >> 52 & 0x7ff; + double_t y; - if (!isfinite(x)) + if (e >= 0x3ff+52) return x; - - if (x >= 0.0) { - t = floor(x); - if (t - x <= -0.5) - t += 1.0; - return t; - } else { - t = floor(-x); - if (t + x <= -0.5) - t += 1.0; - return -t; + if (u.i >> 63) + x = -x; + if (e < 0x3ff-1) { + /* raise inexact if x!=0 */ + FORCE_EVAL(x + 0x1p52); + return 0*u.f; } + y = (double)(x + 0x1p52) - 0x1p52 - 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 >> 63) + y = -y; + return y; } -- cgit v1.2.1