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/floorf.c | 75 ++++++++++++++----------------------------------------- 1 file changed, 19 insertions(+), 56 deletions(-) (limited to 'src/math/floorf.c') diff --git a/src/math/floorf.c b/src/math/floorf.c index 23fa5e7d..dceec739 100644 --- a/src/math/floorf.c +++ b/src/math/floorf.c @@ -1,64 +1,27 @@ -/* origin: FreeBSD /usr/src/lib/msun/src/s_floorf.c */ -/* - * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. - */ -/* - * ==================================================== - * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. - * - * Developed at SunPro, a Sun Microsystems, Inc. business. - * Permission to use, copy, modify, and distribute this - * software is freely granted, provided that this notice - * is preserved. - * ==================================================== - */ -/* - * floorf(x) - * Return x rounded toward -inf to integral value - * Method: - * Bit twiddling. - * Exception: - * Inexact flag raised if x not equal to floorf(x). - */ - #include "libm.h" -static const float huge = 1.0e30; - float floorf(float x) { - int32_t i0,j0; - uint32_t i; + union {float f; uint32_t i;} u = {x}; + int e = (int)(u.i >> 23 & 0xff) - 0x7f; + uint32_t m; - GET_FLOAT_WORD(i0, x); - // FIXME: signed shift - j0 = ((i0>>23)&0xff) - 0x7f; - if (j0 < 23) { - if (j0 < 0) { /* |x| < 1 */ - /* raise inexact if x != 0 */ - if (huge+x > 0.0f) { - if (i0 >= 0) /* x >= 0 */ - i0 = 0; - else if ((i0&0x7fffffff) != 0) - i0 = 0xbf800000; - } - } else { - i = 0x007fffff>>j0; - if ((i0&i) == 0) - return x; /* x is integral */ - /* raise inexact flag */ - if (huge+x > 0.0f) { - if (i0 < 0) - i0 += 0x00800000>>j0; - i0 &= ~i; - } - } + if (e >= 23) + return x; + if (e >= 0) { + m = 0x007fffff >> e; + if ((u.i & m) == 0) + return x; + FORCE_EVAL(x + 0x1p120f); + if (u.i >> 31) + u.i += m; + u.i &= ~m; } else { - if (j0 == 0x80) /* inf or NaN */ - return x+x; - else - return x; /* x is integral */ + FORCE_EVAL(x + 0x1p120f); + if (u.i >> 31 == 0) + u.i = 0; + else if (u.i << 1) + u.f = -1.0; } - SET_FLOAT_WORD(x, i0); - return x; + return u.f; } -- cgit v1.2.1