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glibc/sysdeps/x86_64/fpu/s_log1pl.S
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/* | |
* Written by J.T. Conklin <jtc@netbsd.org>. | |
* Public domain. | |
* | |
* Adapted for `long double' by Ulrich Drepper <drepper@cygnus.com>. | |
* Adapted for x86-64 by Andreas Jaeger <aj@suse.de>. | |
*/ | |
#include <machine/asm.h> | |
RCSID("$NetBSD: s_log1p.S,v 1.7 1995/05/09 00:10:58 jtc Exp $") | |
.section .rodata | |
.align ALIGNARG(4) | |
/* The fyl2xp1 can only be used for values in | |
-1 + sqrt(2) / 2 <= x <= 1 - sqrt(2) / 2 | |
0.29 is a safe value. | |
*/ | |
limit: .tfloat 0.29 | |
/* Please note: we use a double value here. Since 1.0 has | |
an exact representation this does not effect the accuracy | |
but it helps to optimize the code. */ | |
one: .double 1.0 | |
/* | |
* Use the fyl2xp1 function when the argument is in the range -0.29 to 0.29, | |
* otherwise fyl2x with the needed extra computation. | |
*/ | |
#ifdef PIC | |
#define MO(op) op##(%rip) | |
#else | |
#define MO(op) op | |
#endif | |
.text | |
ENTRY(__log1pl) | |
fldln2 | |
fldt 8(%rsp) | |
fxam | |
fnstsw | |
fld %st | |
testb $1, %ah | |
jnz 3f // in case x is NaN or ±Inf | |
4: | |
fabs | |
fldt MO(limit) | |
fcompp | |
fnstsw | |
andb $1,%ah | |
jz 2f | |
movzwl 8+8(%rsp), %eax | |
xorb $0x80, %ah | |
cmpl $0xc040, %eax | |
jae 5f | |
faddl MO(one) | |
5: fyl2x | |
ret | |
2: fyl2xp1 | |
ret | |
3: testb $4, %ah | |
jnz 4b // in case x is ±Inf | |
fstp %st(1) | |
fstp %st(1) | |
ret | |
END (__log1pl) |