1/*	$OpenBSD: e_exp.S,v 1.9 2016/09/12 19:47:02 guenther Exp $	*/
2/*	$NetBSD: e_exp.S,v 1.12 2002/02/27 16:32:46 christos Exp $	*/
3
4/*
5 * Copyright (c) 1993,94 Winning Strategies, Inc.
6 * All rights reserved.
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 Winning Strategies, Inc.
19 * 4. The name of the author may not be used to endorse or promote products
20 *    derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34/*
35 * Written by:
36 *	J.T. Conklin (jtc@wimsey.com), Winning Strategies, Inc.
37 */
38
39#include "DEFS.h"
40
41/* e^x = 2^(x * log2(e)) */
42ENTRY(exp)
43	/*
44	 * If x is +-Inf, then the subtraction would give Inf-Inf = NaN.
45	 * Avoid this.  Also avoid it if x is NaN for convenience.
46	 */
47	movl	8(%esp),%eax
48	andl	$0x7fffffff,%eax
49	cmpl	$0x7ff00000,%eax
50	jae	x_Inf_or_NaN
51
52	fldl	4(%esp)
53
54	/*
55	 * Ensure that the rounding mode is to nearest (to give the smallest
56	 * possible fraction) and that the precision is as high as possible.
57	 * We may as well mask interrupts if we switch the mode.
58	 */
59	fstcw	4(%esp)
60	movl	4(%esp),%eax
61	andl	$0x0300,%eax
62	cmpl	$0x0300,%eax		/* RC == 0 && PC == 3? */
63	je	1f			/* jump if mode is good */
64	movl	$0x137f,8(%esp)
65	fldcw	8(%esp)
661:
67	fldl2e
68	fmulp				/* x * log2(e) */
69	fst	%st(1)
70	frndint				/* int(x * log2(e)) */
71	fst	%st(2)
72	fsubrp				/* fract(x * log2(e)) */
73	f2xm1				/* 2^(fract(x * log2(e))) - 1 */
74	fld1
75	faddp				/* 2^(fract(x * log2(e))) */
76	fscale				/* e^x */
77	fstp	%st(1)
78	je	1f
79	fldcw	4(%esp)
801:
81	ret
82
83x_Inf_or_NaN:
84	/*
85	 * Return 0 if x is -Inf.  Otherwise just return x, although the
86	 * C version would return (x + x) (Real Indefinite) if x is a NaN.
87	 */
88	cmpl	$0xfff00000,8(%esp)
89	jne	x_not_minus_Inf
90	cmpl	$0,4(%esp)
91	jne	x_not_minus_Inf
92	fldz
93	ret
94
95x_not_minus_Inf:
96	fldl	4(%esp)
97	ret
98END_STD(exp)
99