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/* $OpenBSD: e_exp.S,v 1.7 2006/03/18 23:56:14 kettenis Exp $ */
/* $NetBSD: e_exp.S,v 1.12 2002/02/27 16:32:46 christos Exp $ */
/*
* Copyright (c) 1993,94 Winning Strategies, Inc.
* 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, 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Winning Strategies, Inc.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* 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.
*/
/*
* Written by:
* J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
*/
#include <machine/asm.h>
/* e^x = 2^(x * log2(e)) */
ENTRY(__ieee754_exp)
/*
* If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
* Avoid this. Also avoid it if x is NaN for convenience.
*/
movl 8(%esp),%eax
andl $0x7fffffff,%eax
cmpl $0x7ff00000,%eax
jae x_Inf_or_NaN
fldl 4(%esp)
/*
* Ensure that the rounding mode is to nearest (to give the smallest
* possible fraction) and that the precision is as high as possible.
* We may as well mask interrupts if we switch the mode.
*/
fstcw 4(%esp)
movl 4(%esp),%eax
andl $0x0300,%eax
cmpl $0x0300,%eax /* RC == 0 && PC == 3? */
je 1f /* jump if mode is good */
movl $0x137f,8(%esp)
fldcw 8(%esp)
1:
fldl2e
fmulp /* x * log2(e) */
fst %st(1)
frndint /* int(x * log2(e)) */
fst %st(2)
fsubrp /* fract(x * log2(e)) */
f2xm1 /* 2^(fract(x * log2(e))) - 1 */
fld1
faddp /* 2^(fract(x * log2(e))) */
fscale /* e^x */
fstp %st(1)
je 1f
fldcw 4(%esp)
1:
ret
x_Inf_or_NaN:
/*
* Return 0 if x is -Inf. Otherwise just return x, although the
* C version would return (x + x) (Real Indefinite) if x is a NaN.
*/
cmpl $0xfff00000,8(%esp)
jne x_not_minus_Inf
cmpl $0,4(%esp)
jne x_not_minus_Inf
fldz
ret
x_not_minus_Inf:
fldl 4(%esp)
ret
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