/*
* Public domain.
*
*/
#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: .quad 0x947ae147ae147ae1 /* 0.29 */
.short 0x3ffd
/* 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 ħInf
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 ħInf
fstp %st(1)
fstp %st(1)
fadd %st(0)
ret
END (__log1pl)