1/*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21/*
22 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
23 */
24/*
25 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
26 * Use is subject to license terms.
27 */
28
29        .file "exp2.s"
30
31#include "libm.h"
32LIBM_ANSI_PRAGMA_WEAK(exp2,function)
33
34	ENTRY(exp2)
35	movl	8(%esp),%ecx		/ ecx <-- hi_32(x)
36	andl	$0x7fffffff,%ecx	/ ecx <-- hi_32(|x|)
37	cmpl	$0x3ff00000,%ecx	/ Is |x| < 1?
38	jb	.shortcut		/ If so, take a shortcut.
39	je	.check_tail		/ |x| may be only slightly < ln(2)
40	cmpl	$0x7ff00000,%ecx	/ hi_32(|x|) >= hi_32(INF)?
41	jae	.not_finite		/ if so, x is not finite
42.finite_non_special:			/ Here, 1 < |x| < INF
43	fldl	4(%esp)			/ push arg
44	fld	%st(0)			/ duplicate stack top
45	frndint				/ [x],x
46	fucom				/ x integral?
47	fstsw	%ax
48	sahf
49	je      .x_integral		/ branch if x integral
50	fxch				/ x, [x]
51	fsub	%st(1),%st		/ x-[x], [x]
52	f2xm1				/ 2**(x-[x])-1, [x]
53	fld1				/ 1,2**(x-[x])-1, [x]
54	faddp	%st,%st(1)		/ 2**(x-[x]), [x]
55	fscale				/ 2**x = 2**(arg), [x]
56	fstp	%st(1)
57	ret
58
59.x_integral:
60	fstp	%st(0)			/ ,x
61	fld1				/ 1 = 2**0, x
62	fscale				/ 2**(0 + x) = 2**x, x
63	fstp	%st(1)			/ 2**x
64	ret
65
66.check_tail:
67	movl	4(%esp),%edx		/ edx <-- lo_32(x)
68	cmpl	$0x00000000,%edx	/ Is |x| slightly > 1?
69	ja	.finite_non_special	/ branch if |x| slightly > 1
70.shortcut:
71	/ Here, |x| <= 1,
72	/ whence x is in f2xm1's domain.
73	fldl	4(%esp)			/ push x
74	f2xm1				/ 2**x - 1
75	fld1				/ 1,2**x - 1
76	faddp	%st,%st(1)		/ 2**x
77	ret
78
79.not_finite:
80	cmpl	$0x7ff00000,%ecx	/ hi_32(|x|) > hi_32(INF)?
81	ja	.NaN_or_pinf		/ if so, x is NaN
82	movl	4(%esp),%edx		/ edx <-- lo_32(x)
83	cmpl	$0,%edx			/ lo_32(x) = 0?
84	jne	.NaN_or_pinf		/ if not, x is NaN
85	movl	8(%esp),%eax		/ eax <-- hi_32(x)
86	andl	$0x80000000,%eax	/ here, x is infinite, but +/-?
87	jz	.NaN_or_pinf		/ branch if x = +INF
88	fldz				/ Here, x = -inf, so return 0
89	ret
90
91.NaN_or_pinf:
92	/ Here, x = NaN or +inf, so load x and return immediately.
93	fldl	4(%esp)
94	fwait
95	ret
96	.align	4
97	SET_SIZE(exp2)
98