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gcc.gnu.org Git - gcc.git/blob - gcc/config/i386/crtfastmath.c
2 * Copyright (C) 2005 Free Software Foundation, Inc.
4 * This file is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License as published by the
6 * Free Software Foundation; either version 2, or (at your option) any
9 * In addition to the permissions in the GNU General Public License, the
10 * Free Software Foundation gives you unlimited permission to link the
11 * compiled version of this file with other programs, and to distribute
12 * those programs without any restriction coming from the use of this
13 * file. (The General Public License restrictions do apply in other
14 * respects; for example, they cover modification of the file, and
15 * distribution when not linked into another program.)
17 * This file is distributed in the hope that it will be useful, but
18 * WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * General Public License for more details.
22 * You should have received a copy of the GNU General Public License
23 * along with this program; see the file COPYING. If not, write to
24 * the Free Software Foundation, 51 Franklin Street, Fifth Floor,
25 * Boston, MA 02110-1301, USA.
27 * As a special exception, if you link this library with files
28 * compiled with GCC to produce an executable, this does not cause
29 * the resulting executable to be covered by the GNU General Public License.
30 * This exception does not however invalidate any other reasons why
31 * the executable file might be covered by the GNU General Public License.
34 #define MXCSR_DAZ (1 << 6) /* Enable denormals are zero mode */
35 #define MXCSR_FTZ (1 << 15) /* Enable flush to zero mode */
37 #define FXSAVE (1 << 24)
40 static void __attribute__((constructor
))
44 /* All 64-bit targets have SSE and DAZ; only check them explicitly
46 unsigned int eax
, ebx
, ecx
, edx
;
48 /* See if we can use cpuid. */
49 asm volatile ("pushfl; pushfl; popl %0; movl %0,%1; xorl %2,%0;"
50 "pushl %0; popfl; pushfl; popl %0; popfl"
51 : "=&r" (eax
), "=&r" (ebx
)
54 if (((eax
^ ebx
) & 0x00200000) == 0)
57 /* Check the highest input value for eax. */
58 asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1"
59 : "=a" (eax
), "=r" (ebx
), "=c" (ecx
), "=d" (edx
)
65 asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1"
66 : "=a" (eax
), "=r" (ebx
), "=c" (ecx
), "=d" (edx
)
71 unsigned int mxcsr
= __builtin_ia32_stmxcsr ();
77 /* Check if DAZ is available. */
80 unsigned short int cwd
;
81 unsigned short int swd
;
82 unsigned short int twd
;
83 unsigned short int fop
;
90 long int st_space
[32];
91 long int xmm_space
[32];
93 } __attribute__ ((aligned (16))) fxsave
;
95 __builtin_memset (&fxsave
, 0, sizeof (fxsave
));
97 asm volatile ("fxsave %0" : "=m" (fxsave
) : "m" (fxsave
));
99 if (fxsave
.mxcsr_mask
& MXCSR_DAZ
)
103 __builtin_ia32_ldmxcsr (mxcsr
);
106 unsigned int mxcsr
= __builtin_ia32_stmxcsr ();
107 mxcsr
|= MXCSR_DAZ
| MXCSR_FTZ
;
108 __builtin_ia32_ldmxcsr (mxcsr
);
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