exp2.s revision ddc0e0b53c661f6e439e3b7072b3ef353eadb4af
/*
* 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 "exp2.s"
#include "libm.h"
LIBM_ANSI_PRAGMA_WEAK(exp2,function)
ENTRY(exp2)
movl 8(%esp),%ecx / ecx <-- hi_32(x)
andl $0x7fffffff,%ecx / ecx <-- hi_32(|x|)
cmpl $0x3ff00000,%ecx / Is |x| < 1?
jb .shortcut / If so, take a shortcut.
je .check_tail / |x| may be only slightly < ln(2)
cmpl $0x7ff00000,%ecx / hi_32(|x|) >= hi_32(INF)?
jae .not_finite / if so, x is not finite
.finite_non_special: / Here, 1 < |x| < INF
fldl 4(%esp) / push arg
fld %st(0) / duplicate stack top
frndint / [x],x
fucom / x integral?
fstsw %ax
sahf
je .x_integral / branch if x integral
fxch / x, [x]
fsub %st(1),%st / x-[x], [x]
f2xm1 / 2**(x-[x])-1, [x]
fld1 / 1,2**(x-[x])-1, [x]
faddp %st,%st(1) / 2**(x-[x]), [x]
fscale / 2**x = 2**(arg), [x]
fstp %st(1)
ret
.x_integral:
fstp %st(0) / ,x
fld1 / 1 = 2**0, x
fscale / 2**(0 + x) = 2**x, x
fstp %st(1) / 2**x
ret
.check_tail:
movl 4(%esp),%edx / edx <-- lo_32(x)
cmpl $0x00000000,%edx / Is |x| slightly > 1?
ja .finite_non_special / branch if |x| slightly > 1
.shortcut:
/ Here, |x| <= 1,
/ whence x is in f2xm1's domain.
fldl 4(%esp) / push x
f2xm1 / 2**x - 1
fld1 / 1,2**x - 1
faddp %st,%st(1) / 2**x
ret
.not_finite:
cmpl $0x7ff00000,%ecx / hi_32(|x|) > hi_32(INF)?
ja .NaN_or_pinf / if so, x is NaN
movl 4(%esp),%edx / edx <-- lo_32(x)
cmpl $0,%edx / lo_32(x) = 0?
jne .NaN_or_pinf / if not, x is NaN
movl 8(%esp),%eax / eax <-- hi_32(x)
andl $0x80000000,%eax / here, x is infinite, but +/-?
jz .NaN_or_pinf / branch if x = +INF
fldz / Here, x = -inf, so return 0
ret
.NaN_or_pinf:
/ Here, x = NaN or +inf, so load x and return immediately.
fldl 4(%esp)
fwait
ret
.align 4
SET_SIZE(exp2)