lib/libc/i386/gen/ldexp.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * This code is derived from software contributed to Berkeley by
   6  * Sean Eric Fagan.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in the
  15  *    documentation and/or other materials provided with the distribution.
  16  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * $FreeBSD: src/lib/libc/i386/gen/ldexp.c,v 1.6 1999/08/27 23:59:21 peter Exp $
  37  * $DragonFly: src/lib/libc/i386/gen/ldexp.c,v 1.5 2005/11/20 09:18:36 swildner Exp $
  38  */
  39
  40 #include <math.h>
  41
  42 /*
  43  * ldexp(value, exp): return value * (2 ** exp).
  44  *
  45  * Written by Sean Eric Fagan (sef@kithrup.COM)
  46  * Sun Mar 11 20:27:09 PST 1990
  47  */
  48
  49 /*
  50  * We do the conversion in C to let gcc optimize it away, if possible.
  51  * The "fxch ; fstp" stuff is because value is still on the stack
  52  * (stupid 8087!).
  53  */
  54 double
  55 ldexp (double value, int expo)
  56 {
  57         double temp;
  58 #ifdef __GNUC__
  59         __asm ("fscale"
  60                 : "=t" (temp)
  61                 : "0" (value), "u" ((double)expo));
  62 #else
  63 #error "Compiler not supported"
  64 #endif
  65         return (temp);
  66 }