PR/15748: Ray Brownrigg: exp(log(0)) is broken.
Use FreeBSD's version. Handles inf/nan and rounding modes.
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christos
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76fed8b638
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47c5991d7a
@ -1,28 +1,55 @@
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/* $NetBSD: e_exp.S,v 1.12 2002/02/27 16:32:46 christos Exp $ */
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/*
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* Written by J.T. Conklin <jtc@netbsd.org>.
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* Public domain.
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* Copyright (c) 1993,94 Winning Strategies, Inc.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by Winning Strategies, Inc.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Written by:
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* J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
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*/
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#include <machine/asm.h>
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#include "abi.h"
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RCSID("$NetBSD: e_exp.S,v 1.11 2001/06/19 17:49:36 fvdl Exp $")
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RCSID("$NetBSD: e_exp.S,v 1.12 2002/02/27 16:32:46 christos Exp $")
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#if 0
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RCSID("$FreeBSD: src/lib/msun/i387/e_exp.S,v 1.8.2.1 2000/07/10 09:16:28 obrien Exp $")
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#endif
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/* e^x = 2^(x * log2(e)) */
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ENTRY(__ieee754_exp)
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#ifdef __i386__
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pushl %ebp
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movl %esp,%ebp
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subl $8,%esp
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fstcw -12(%ebp) /* store fpu control word */
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movw -12(%ebp),%dx
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orw $0x0180,%dx
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movw %dx,-16(%ebp)
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fldcw -16(%ebp) /* load modfied control word */
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fldl 8(%ebp)
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#else
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#ifndef __i386__
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/*
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* XXX: This code is broken and needs to be merged with the i386 case.
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*/
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fstcw -12(%rsp)
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movw -12(%rsp),%dx
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orw $0x0180,%dx
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@ -30,7 +57,6 @@ ENTRY(__ieee754_exp)
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fldcw -16(%rsp)
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movsd %xmm0,-8(%rsp)
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fldl -8(%rsp)
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#endif
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fldl2e
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fmulp /* x * log2(e) */
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@ -44,12 +70,64 @@ ENTRY(__ieee754_exp)
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fscale /* e^x */
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fstp %st(1)
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#ifdef __i386__
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fldcw -12(%ebp) /* restore original control word */
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leave
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#else
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fstpl -8(%rsp)
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movsd -8(%rsp),%xmm0
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fldcw -12(%rsp)
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#endif
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ret
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#else
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/*
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* If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
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* Avoid this. Also avoid it if x is NaN for convenience.
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*/
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movl 8(%esp),%eax
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andl $0x7fffffff,%eax
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cmpl $0x7ff00000,%eax
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jae x_Inf_or_NaN
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fldl 4(%esp)
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/*
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* Ensure that the rounding mode is to nearest (to give the smallest
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* possible fraction) and that the precision is as high as possible.
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* We may as well mask interrupts if we switch the mode.
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*/
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fstcw 4(%esp)
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movl 4(%esp),%eax
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andl $0x0300,%eax
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cmpl $0x0300,%eax /* RC == 0 && PC == 3? */
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je 1f /* jump if mode is good */
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movl $0x137f,8(%esp)
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fldcw 8(%esp)
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1:
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fldl2e
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fmulp /* x * log2(e) */
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fst %st(1)
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frndint /* int(x * log2(e)) */
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fst %st(2)
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fsubrp /* fract(x * log2(e)) */
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f2xm1 /* 2^(fract(x * log2(e))) - 1 */
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fld1
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faddp /* 2^(fract(x * log2(e))) */
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fscale /* e^x */
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fstp %st(1)
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je 1f
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fldcw 4(%esp)
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1:
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ret
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x_Inf_or_NaN:
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/*
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* Return 0 if x is -Inf. Otherwise just return x, although the
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* C version would return (x + x) (Real Indefinite) if x is a NaN.
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*/
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cmpl $0xfff00000,8(%esp)
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jne x_not_minus_Inf
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cmpl $0,4(%esp)
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jne x_not_minus_Inf
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fldz
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ret
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x_not_minus_Inf:
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fldl 4(%esp)
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ret
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#endif
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