kolibrios/programs/develop/libraries/newlib/math/s_expm1.S

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/* ix87 specific implementation of exp(x)-1.
Copyright (C) 1996, 1997, 2005 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
Based on code by John C. Bowman <bowman@ipp-garching.mpg.de>.
Corrections by H.J. Lu (hjl@gnu.ai.mit.edu), 1997.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
/* Using: e^x - 1 = 2^(x * log2(e)) - 1 */
.file "s_expm1.s"
.text
.align 4
minus1: .double -1.0
one: .double 1.0
l2e: .tfloat 1.442695040888963407359924681002
.align 4
.globl ___expm1
.def __expm1; .scl 2; .type 32; .endef
___expm1:
fldl 4(%esp) # x
fxam # Is NaN or +-Inf?
fstsw %ax
movb $0x45, %ch
andb %ah, %ch
cmpb $0x40, %ch
je 3f # If +-0, jump.
cmpb $0x05, %ch
je 2f # If +-Inf, jump.
fldt l2e # log2(e) : x
fmulp # log2(e)*x
fld %st # log2(e)*x : log2(e)*x
frndint # int(log2(e)*x) : log2(e)*x
fsubr %st, %st(1) # int(log2(e)*x) : fract(log2(e)*x)
fxch # fract(log2(e)*x) : int(log2(e)*x)
f2xm1 # 2^fract(log2(e)*x)-1 : int(log2(e)*x)
fscale # 2^(log2(e)*x)-2^int(log2(e)*x) : int(log2(e)*x)
fxch # int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
fldl one # 1 : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
fscale # 2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
fsubrl one # 1-2^int(log2(e)*x) : int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
fstp %st(1) # 1-2^int(log2(e)*x) : 2^(log2(e)*x)-2^int(log2(e)*x)
fsubrp %st, %st(1) # 2^(log2(e)*x)
ret
2: testl $0x200, %eax # Test sign.
jz 3f # If positive, jump.
fstp %st
fldl minus1 # Set result to -1.0.
3: ret