e_exp.S revision 23577
12116Sjkh/*
22116Sjkh * Copyright (c) 1993,94 Winning Strategies, Inc.
32116Sjkh * All rights reserved.
42116Sjkh *
52116Sjkh * Redistribution and use in source and binary forms, with or without
62116Sjkh * modification, are permitted provided that the following conditions
72116Sjkh * are met:
82116Sjkh * 1. Redistributions of source code must retain the above copyright
92116Sjkh *    notice, this list of conditions and the following disclaimer.
102116Sjkh * 2. Redistributions in binary form must reproduce the above copyright
112116Sjkh *    notice, this list of conditions and the following disclaimer in the
122116Sjkh *    documentation and/or other materials provided with the distribution.
132116Sjkh * 3. All advertising materials mentioning features or use of this software
142116Sjkh *    must display the following acknowledgement:
152116Sjkh *      This product includes software developed by Winning Strategies, Inc.
162116Sjkh * 4. The name of the author may not be used to endorse or promote products
172116Sjkh *    derived from this software without specific prior written permission.
182116Sjkh *
192116Sjkh * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
202116Sjkh * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
212116Sjkh * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
222116Sjkh * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
232116Sjkh * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
242116Sjkh * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
252116Sjkh * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
262116Sjkh * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
272116Sjkh * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
282116Sjkh * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
292116Sjkh */
302116Sjkh
312116Sjkh/*
322116Sjkh * Written by:
332116Sjkh *	J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
342116Sjkh */
352116Sjkh
3623577Sbde#include <machine/asm.h>
372116Sjkh
3823577SbdeRCSID("$Id: e_exp.S,v 1.6 1997/02/22 15:08:46 peter Exp $")
392116Sjkh
402116Sjkh/* e^x = 2^(x * log2(e)) */
412116SjkhENTRY(__ieee754_exp)
4222802Sbde	/*
4322802Sbde	 * If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
4422802Sbde	 * Avoid this.  Also avoid it if x is NaN for convenience.
4522802Sbde	 */
4622802Sbde	movl	8(%esp),%eax
4722802Sbde	andl	$0x7fffffff,%eax
4822802Sbde	cmpl	$0x7ff00000,%eax
4922802Sbde	jae	x_Inf_or_NaN
5022802Sbde
512116Sjkh	fldl	4(%esp)
5222802Sbde
5322802Sbde	/*
5422802Sbde	 * Ensure that the rounding mode is to nearest (to give the smallest
5522802Sbde	 * possible fraction) and that the precision is as high as possible.
5622802Sbde	 * We may as well mask interrupts if we switch the mode.
5722802Sbde	 */
5822802Sbde	fstcw	4(%esp)
5922802Sbde	movl	4(%esp),%eax
6022802Sbde	andl	$0x0300,%eax
6122802Sbde	cmpl	$0x0300,%eax		/* RC == 0 && PC == 3? */
6222802Sbde	je	1f			/* jump if mode is good */
6322802Sbde	movl	$0x137f,8(%esp)
6422802Sbde	fldcw	8(%esp)
6522802Sbde1:
662116Sjkh	fldl2e
672116Sjkh	fmulp				/* x * log2(e) */
682116Sjkh	fstl	%st(1)
692116Sjkh	frndint				/* int(x * log2(e)) */
702116Sjkh	fstl	%st(2)
712116Sjkh	fsubrp				/* fract(x * log2(e)) */
722116Sjkh	f2xm1				/* 2^(fract(x * log2(e))) - 1 */
732116Sjkh	fld1
742116Sjkh	faddp				/* 2^(fract(x * log2(e))) */
752116Sjkh	fscale				/* e^x */
7616054Sbde	fstpl	%st(1)
7722802Sbde	je	1f
7822802Sbde	fldcw	4(%esp)
7922802Sbde1:
802116Sjkh	ret
8122802Sbde
8222802Sbdex_Inf_or_NaN:
8322802Sbde	/*
8422802Sbde	 * Return 0 if x is -Inf.  Otherwise just return x, although the
8522802Sbde	 * C version would return (x + x) (Real Indefinite) if x is a NaN.
8622802Sbde	 */
8722802Sbde	cmpl	$0xfff00000,8(%esp)
8822802Sbde	jne	x_not_minus_Inf
8922802Sbde	cmpl	$0,4(%esp)
9022802Sbde	jne	x_not_minus_Inf
9122802Sbde	fldz
9222802Sbde	ret
9322802Sbde
9422802Sbdex_not_minus_Inf:
9522802Sbde	fldl	4(%esp)
9622802Sbde	ret
97