1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License (the "License").
* You may not use this file except in compliance with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
.ident "@(#)ilogbf.s 1.6 06/01/23 SMI"
.file "ilogbf.s"
#include "libm.h"
LIBM_ANSI_PRAGMA_WEAK(ilogbf,function)
#include "libm_synonyms.h"
#include "xpg6.h"
.data
.align 8
two23: .long 0x4b000000 / 2**23
ENTRY(ilogbf)
movl 4(%esp),%eax / eax <-- x
testl $0x7f800000,%eax / is bexp(x) 0?
jz .bexp_0 / jump if x is 0 or subnormal
/ here, biased exponent is non-zero
andl $0x7fffffff,%eax / eax <-- abs(x)
cmpl $0x7f800000,%eax / is bexp(x) 0xff?
jae .bexp_all_1 / jump if x is NaN or Inf
shrl $23,%eax / eax <-- zero_xtnd(bexp(x))
subl $127,%eax / unbias exponent by 127
ret
.bexp_all_1:
movl $0x7fffffff,%eax / x is NaN or inf, so return 0x7fffffff
jmp 0f
.bexp_0:
andl $0x7fffffff,%eax / eax <-- abs(x), and
/ ZF = 1 iff x = 0.0
jnz .ilogb_subnorm
movl $0x80000001,%eax / x is +/-0, so return 0x80000001
0:
PIC_SETUP(0)
PIC_G_LOAD(movzwl,__xpg6,ecx)
PIC_WRAPUP
andl $_C99SUSv3_ilogb_0InfNaN_raises_invalid,%ecx
cmpl $0,%ecx
je 1f
fldz
fdivp %st,%st(0) / raise invalid as per SUSv3
1:
ret
.ilogb_subnorm: / subnormal input
flds 4(%esp) / push x
PIC_SETUP(1)
fmuls PIC_L(two23) / x*2**23; rebias x by 127+23,
/ instead of 127
PIC_WRAPUP
subl $4,%esp / set up storage area
fstps (%esp) / store x*2**23 in storage area
fwait / (shouldn't raise exception, but
/ just in case)
movl $0x7f800000,%eax / eax <-- single_bexp_mask
andl (%esp),%eax / eax[23..30] <-- bexp(x*2**23),
/ rest_of(eax) <-- 0
shrl $23,%eax / eax <-- zero_xtnd(bexp(x*2**23))
subl $150,%eax / unbias rebiased x by 150 (= 127 + 23)
addl $4,%esp / restore stack for caller
ret
.align 4
SET_SIZE(ilogbf)
|
