ilogb.s revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8
/*
* 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 2011 Nexenta Systems, Inc. All rights reserved.
*/
/*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
.file "ilogb.s"
#include "libm.h"
LIBM_ANSI_PRAGMA_WEAK(ilogb,function)
#include "libm_synonyms.h"
#include "xpg6.h"
.data
.align 8
two52: .long 0x0,0x43300000 / 2**52
ENTRY(ilogb)
movl 8(%esp),%eax / eax <-- hi_32(x)
andl $0x7fffffff,%eax / eax <-- hi_32(abs(x))
testl $0x7ff00000,%eax / is bexp(x) 0?
jz .bexp_0 / jump if x is 0 or subnormal
/ biased exponent is non-zero
cmpl $0x7ff00000,%eax / is bexp(x) 0x7ff?
jae .bexp_all_1 / jump if x is NaN or Inf
shrl $20,%eax / eax <-- bexp(x)
subl $1023,%eax / unbias exponent by 1023
ret
.bexp_all_1:
movl $0x7fffffff,%eax / x is NaN or inf, so return 0x7fffffff
jmp 0f
.bexp_0:
orl 4(%esp),%eax / test whether x is 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
fldl 4(%esp) / push x
PIC_SETUP(1)
fmull PIC_L(two52) / x*2**52
PIC_WRAPUP
subl $8,%esp / set up storage area
fstpl (%esp) / store x*2**52 in storage are
movl $0x7ff00000,%eax
andl 4(%esp),%eax
shrl $20,%eax / extract exponent of x*2**52
subl $1075,%eax / unbias it by 1075 (= 1023 + 52)
addl $8,%esp
ret
.align 4
SET_SIZE(ilogb)