libm: Add .section .note.GNU-stack to all assembly files
[dragonfly.git] / lib / libm / arch / i386 / s_log1pf.S
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1/*
2 * Written by J.T. Conklin <jtc@NetBSD.org>.
3 * Public domain.
4 *
5 * $NetBSD: s_log1pf.S,v 1.10 2003/09/16 18:17:11 wennmach Exp $
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6 */
7
8/*
9 * Modified by Lex Wennmacher <wennmach@NetBSD.org>
10 * Still public domain.
11 */
12
13#include <machine/asm.h>
14
15#include "abi.h"
16
17/*
18 * The log1pf() function is provided to compute an accurate value of
19 * log(1 + x), even for tiny values of x. The i387 FPU provides the
20 * fyl2xp1 instruction for this purpose. However, the range of this
21 * instruction is limited to:
22 * -(1 - (sqrt(2) / 2)) <= x <= sqrt(2) - 1
23 * -0.292893 <= x <= 0.414214
24 * at least on older processor versions.
25 *
26 * log1pf() is implemented by testing the range of the argument.
27 * If it is appropriate for fyl2xp1, this instruction is used.
28 * Else, we compute log1pf(x) = ln(2)*ld(1 + x) the traditional way
29 * (using fyl2x).
30 *
31 * The range testing costs speed, but as the rationale for the very
32 * existence of this function is accuracy, we accept that.
33 *
34 * In order to reduce the cost for testing the range, we check if
35 * the argument is in the range
36 * -0.25 <= x <= 0.25
37 * which can be done with just one conditional branch. If x is
38 * inside this range, we use fyl2xp1. Outside of this range,
39 * the use of fyl2x is accurate enough.
40 *
41 */
42
43.text
44 .align 4
45ENTRY(log1pf)
46 XMM_ONE_ARG_FLOAT_PROLOGUE
47 flds ARG_FLOAT_ONE
48 fabs
49 fld1 /* ... x 1 */
50 fadd %st(0) /* ... x 2 */
51 fadd %st(0) /* ... x 4 */
52 fld1 /* ... 4 1 */
53 fdivp /* ... x 0.25 */
54 fcompp
55 fnstsw %ax
56 andb $69,%ah
57 jne use_fyl2x
58 jmp use_fyl2xp1
59
60 .align 4
61use_fyl2x:
62 fldln2
63 flds ARG_FLOAT_ONE
64 fld1
65 faddp
66 fyl2x
67 XMM_FLOAT_EPILOGUE
68 ret
69
70 .align 4
71use_fyl2xp1:
72 fldln2
73 flds ARG_FLOAT_ONE
74 fyl2xp1
75 XMM_FLOAT_EPILOGUE
76 ret
d04e8698 77END(log1pf)
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78
79 .section .note.GNU-stack,"",%progbits