about summary refs log tree commit diff
path: root/sysdeps/i386/fpu/e_log10.S
blob: 9d24d74024e340231d6385d66afdd073fb2d07c5 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
/*
 * Written by J.T. Conklin <jtc@netbsd.org>.
 * Public domain.
 *
 * Changed to use fyl2xp1 for values near 1, <drepper@cygnus.com>.
 */

#include <machine/asm.h>

#ifdef __ELF__
	.section .rodata.cst8,"aM",@progbits,8
#else
	.text
#endif
	.p2align 3
	ASM_TYPE_DIRECTIVE(one,@object)
one:	.double 1.0
	ASM_SIZE_DIRECTIVE(one)
	/* It is not important that this constant is precise.  It is only
	   a value which is known to be on the safe side for using the
	   fyl2xp1 instruction.  */
	ASM_TYPE_DIRECTIVE(limit,@object)
limit:	.double 0.29
	ASM_SIZE_DIRECTIVE(limit)


#ifdef PIC
# define MO(op) op##@GOTOFF(%edx)
#else
# define MO(op) op
#endif

	.text
ENTRY(__ieee754_log10)
	fldlg2			// log10(2)
	fldl	4(%esp)		// x : log10(2)
#ifdef PIC
	LOAD_PIC_REG (dx)
#endif
	fxam
	fnstsw
	fld	%st		// x : x : log10(2)
	sahf
	jc	3f		// in case x is NaN or ±Inf
4:	fsubl	MO(one)		// x-1 : x : log10(2)
	fld	%st		// x-1 : x-1 : x : log10(2)
	fabs			// |x-1| : x-1 : x : log10(2)
	fcompl	MO(limit)	// x-1 : x : log10(2)
	fnstsw			// x-1 : x : log10(2)
	andb	$0x45, %ah
	jz	2f
	fstp	%st(1)		// x-1 : log10(2)
	fyl2xp1			// log10(x)
	ret

2:	fstp	%st(0)		// x : log10(2)
	fyl2x			// log10(x)
	ret

3:	jp	4b		// in case x is ±Inf
	fstp	%st(1)
	fstp	%st(1)
	ret
END (__ieee754_log10)
strong_alias (__ieee754_log10, __log10_finite)