gonzui: t2ex/bsd_source/lib/libc/src_bsd/math/s

    1: /*      $OpenBSD: s_fmaf.c,v 1.1 2011/07/06 00:02:42 martynas Exp $  */
    2: 
    3: /*-
    4:  * Copyright (c) 2005 David Schultz <das@FreeBSD.ORG>
    5:  * All rights reserved.
    6:  *
    7:  * Redistribution and use in source and binary forms, with or without
    8:  * modification, are permitted provided that the following conditions
    9:  * are met:
   10:  * 1. Redistributions of source code must retain the above copyright
   11:  *    notice, this list of conditions and the following disclaimer.
   12:  * 2. Redistributions in binary form must reproduce the above copyright
   13:  *    notice, this list of conditions and the following disclaimer in the
   14:  *    documentation and/or other materials provided with the distribution.
   15:  *
   16:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26:  * SUCH DAMAGE.
   27:  */
   28: 
   29: #include <sys/cdefs.h>
   30: #if 0
   31: __FBSDID("$FreeBSD: src/lib/msun/src/s_fmaf.c,v 1.2 2008/03/29 16:38:29 das Exp $");
   32: #endif
   33: 
   34: #include <math.h>
   35: 
   36: /*
   37:  * Fused multiply-add: Compute x * y + z with a single rounding error.
   38:  *
   39:  * A double has more than twice as much precision than a float, so
   40:  * direct double-precision arithmetic suffices.
   41:  *
   42:  * XXX We are relying on the compiler to convert from double to float
   43:  *     using the current rounding mode and with the appropriate
   44:  *     side-effects.  But on at least one platform (gcc 3.4.2/sparc64),
   45:  *     this appears to be too much to ask for.  The precision
   46:  *     reduction should be done manually.
   47:  */
   48: float
   49: fmaf(float x, float y, float z)
   50: {
   51:         return ((double)x * y + z);
   52: }