xref: /titanic_41/usr/src/lib/libm/i386/src/ilogb.s (revision a9d3dcd5820128b4f34bf38f447e47aa95c004e8)
1*5b2ba9d3SPiotr Jasiukajtis/*
2*5b2ba9d3SPiotr Jasiukajtis * CDDL HEADER START
3*5b2ba9d3SPiotr Jasiukajtis *
4*5b2ba9d3SPiotr Jasiukajtis * The contents of this file are subject to the terms of the
5*5b2ba9d3SPiotr Jasiukajtis * Common Development and Distribution License (the "License").
6*5b2ba9d3SPiotr Jasiukajtis * You may not use this file except in compliance with the License.
7*5b2ba9d3SPiotr Jasiukajtis *
8*5b2ba9d3SPiotr Jasiukajtis * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9*5b2ba9d3SPiotr Jasiukajtis * or http://www.opensolaris.org/os/licensing.
10*5b2ba9d3SPiotr Jasiukajtis * See the License for the specific language governing permissions
11*5b2ba9d3SPiotr Jasiukajtis * and limitations under the License.
12*5b2ba9d3SPiotr Jasiukajtis *
13*5b2ba9d3SPiotr Jasiukajtis * When distributing Covered Code, include this CDDL HEADER in each
14*5b2ba9d3SPiotr Jasiukajtis * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15*5b2ba9d3SPiotr Jasiukajtis * If applicable, add the following below this CDDL HEADER, with the
16*5b2ba9d3SPiotr Jasiukajtis * fields enclosed by brackets "[]" replaced with your own identifying
17*5b2ba9d3SPiotr Jasiukajtis * information: Portions Copyright [yyyy] [name of copyright owner]
18*5b2ba9d3SPiotr Jasiukajtis *
19*5b2ba9d3SPiotr Jasiukajtis * CDDL HEADER END
20*5b2ba9d3SPiotr Jasiukajtis */
21*5b2ba9d3SPiotr Jasiukajtis/*
22*5b2ba9d3SPiotr Jasiukajtis * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
23*5b2ba9d3SPiotr Jasiukajtis */
24*5b2ba9d3SPiotr Jasiukajtis/*
25*5b2ba9d3SPiotr Jasiukajtis * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
26*5b2ba9d3SPiotr Jasiukajtis * Use is subject to license terms.
27*5b2ba9d3SPiotr Jasiukajtis */
28*5b2ba9d3SPiotr Jasiukajtis
29*5b2ba9d3SPiotr Jasiukajtis        .file "ilogb.s"
30*5b2ba9d3SPiotr Jasiukajtis
31*5b2ba9d3SPiotr Jasiukajtis#include "libm.h"
32*5b2ba9d3SPiotr JasiukajtisLIBM_ANSI_PRAGMA_WEAK(ilogb,function)
33*5b2ba9d3SPiotr Jasiukajtis#include "xpg6.h"
34*5b2ba9d3SPiotr Jasiukajtis
35*5b2ba9d3SPiotr Jasiukajtis	.data
36*5b2ba9d3SPiotr Jasiukajtis	.align	8
37*5b2ba9d3SPiotr Jasiukajtistwo52:	.long	0x0,0x43300000	/ 2**52
38*5b2ba9d3SPiotr Jasiukajtis
39*5b2ba9d3SPiotr Jasiukajtis	ENTRY(ilogb)
40*5b2ba9d3SPiotr Jasiukajtis	movl	8(%esp),%eax		/ eax <-- hi_32(x)
41*5b2ba9d3SPiotr Jasiukajtis	andl	$0x7fffffff,%eax	/ eax <-- hi_32(abs(x))
42*5b2ba9d3SPiotr Jasiukajtis	testl	$0x7ff00000,%eax	/ is bexp(x) 0?
43*5b2ba9d3SPiotr Jasiukajtis	jz	.bexp_0 		/ jump if x is 0 or subnormal
44*5b2ba9d3SPiotr Jasiukajtis					/ biased exponent is non-zero
45*5b2ba9d3SPiotr Jasiukajtis	cmpl	$0x7ff00000,%eax	/ is bexp(x) 0x7ff?
46*5b2ba9d3SPiotr Jasiukajtis	jae	.bexp_all_1		/ jump if x is NaN or Inf
47*5b2ba9d3SPiotr Jasiukajtis	shrl	$20,%eax		/ eax <-- bexp(x)
48*5b2ba9d3SPiotr Jasiukajtis	subl	$1023,%eax		/ unbias exponent by 1023
49*5b2ba9d3SPiotr Jasiukajtis	ret
50*5b2ba9d3SPiotr Jasiukajtis
51*5b2ba9d3SPiotr Jasiukajtis.bexp_all_1:
52*5b2ba9d3SPiotr Jasiukajtis	movl	$0x7fffffff,%eax	/ x is NaN or inf, so return 0x7fffffff
53*5b2ba9d3SPiotr Jasiukajtis	jmp	0f
54*5b2ba9d3SPiotr Jasiukajtis
55*5b2ba9d3SPiotr Jasiukajtis.bexp_0:
56*5b2ba9d3SPiotr Jasiukajtis	orl	4(%esp),%eax		/ test whether x is 0
57*5b2ba9d3SPiotr Jasiukajtis	jnz	.ilogb_subnorm
58*5b2ba9d3SPiotr Jasiukajtis	movl	$0x80000001,%eax	/ x is +/-0, so return 0x80000001
59*5b2ba9d3SPiotr Jasiukajtis0:
60*5b2ba9d3SPiotr Jasiukajtis	PIC_SETUP(0)
61*5b2ba9d3SPiotr Jasiukajtis	PIC_G_LOAD(movzwl,__xpg6,ecx)
62*5b2ba9d3SPiotr Jasiukajtis	PIC_WRAPUP
63*5b2ba9d3SPiotr Jasiukajtis	andl	$_C99SUSv3_ilogb_0InfNaN_raises_invalid,%ecx
64*5b2ba9d3SPiotr Jasiukajtis	cmpl	$0,%ecx
65*5b2ba9d3SPiotr Jasiukajtis	je	1f
66*5b2ba9d3SPiotr Jasiukajtis	fldz
67*5b2ba9d3SPiotr Jasiukajtis	fdivp	%st,%st(0)		/ raise invalid as per SUSv3
68*5b2ba9d3SPiotr Jasiukajtis1:
69*5b2ba9d3SPiotr Jasiukajtis	ret
70*5b2ba9d3SPiotr Jasiukajtis
71*5b2ba9d3SPiotr Jasiukajtis.ilogb_subnorm:				/ subnormal input
72*5b2ba9d3SPiotr Jasiukajtis	fldl	4(%esp)			/ push x
73*5b2ba9d3SPiotr Jasiukajtis	PIC_SETUP(1)
74*5b2ba9d3SPiotr Jasiukajtis	fmull	PIC_L(two52)		/ x*2**52
75*5b2ba9d3SPiotr Jasiukajtis	PIC_WRAPUP
76*5b2ba9d3SPiotr Jasiukajtis	subl	$8,%esp			/ set up storage area
77*5b2ba9d3SPiotr Jasiukajtis	fstpl	(%esp)			/ store x*2**52 in storage are
78*5b2ba9d3SPiotr Jasiukajtis	movl	$0x7ff00000,%eax
79*5b2ba9d3SPiotr Jasiukajtis	andl	4(%esp),%eax
80*5b2ba9d3SPiotr Jasiukajtis	shrl	$20,%eax		/ extract exponent of x*2**52
81*5b2ba9d3SPiotr Jasiukajtis	subl	$1075,%eax		/ unbias it by 1075 (= 1023 + 52)
82*5b2ba9d3SPiotr Jasiukajtis	addl	$8,%esp
83*5b2ba9d3SPiotr Jasiukajtis	ret
84*5b2ba9d3SPiotr Jasiukajtis	.align	4
85*5b2ba9d3SPiotr Jasiukajtis	SET_SIZE(ilogb)
86