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
66
67
68
69
70
71
72
|
/*
* Copyright (C) 2005 Free Software Foundation, Inc.
*
* This file is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2, or (at your option) any
* later version.
*
* In addition to the permissions in the GNU General Public License, the
* Free Software Foundation gives you unlimited permission to link the
* compiled version of this file with other programs, and to distribute
* those programs without any restriction coming from the use of this
* file. (The General Public License restrictions do apply in other
* respects; for example, they cover modification of the file, and
* distribution when not linked into another program.)
*
* This file 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
* As a special exception, if you link this library with files
* compiled with GCC to produce an executable, this does not cause
* the resulting executable to be covered by the GNU General Public License.
* This exception does not however invalidate any other reasons why
* the executable file might be covered by the GNU General Public License.
*/
#define MXCSR_DAZ (1 << 6) /* Enable denormals are zero mode */
#define MXCSR_FTZ (1 << 15) /* Enable flush to zero mode */
static void __attribute__((constructor))
set_fast_math (void)
{
#ifndef __x86_64__
/* SSE is the part of 64bit. Only need to check it for 32bit. */
unsigned int eax, ebx, ecx, edx;
/* See if we can use cpuid. */
asm volatile ("pushfl; pushfl; popl %0; movl %0,%1; xorl %2,%0;"
"pushl %0; popfl; pushfl; popl %0; popfl"
: "=&r" (eax), "=&r" (ebx)
: "i" (0x00200000));
if (((eax ^ ebx) & 0x00200000) == 0)
return;
/* Check the highest input value for eax. */
asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1"
: "=a" (eax), "=r" (ebx), "=c" (ecx), "=d" (edx)
: "0" (0));
if (eax == 0)
return;
asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1"
: "=a" (eax), "=r" (ebx), "=c" (ecx), "=d" (edx)
: "0" (1));
if (edx & (1 << 25))
#endif
{
unsigned int mxcsr = __builtin_ia32_stmxcsr ();
mxcsr |= MXCSR_DAZ | MXCSR_FTZ;
__builtin_ia32_ldmxcsr (mxcsr);
}
}
|
