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git.ipfire.org Git - thirdparty/gcc.git/blob - libgcc/config/i386/crtfastmath.c
2 * Copyright (C) 2005-2021 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 3, or (at your option) any
9 * This file is distributed in the hope that it will be useful, but
10 * WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
14 * Under Section 7 of GPL version 3, you are granted additional
15 * permissions described in the GCC Runtime Library Exception, version
16 * 3.1, as published by the Free Software Foundation.
18 * You should have received a copy of the GNU General Public License and
19 * a copy of the GCC Runtime Library Exception along with this program;
20 * see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
21 * <http://www.gnu.org/licenses/>.
25 #define MXCSR_DAZ (1 << 6) /* Enable denormals are zero mode */
26 #define MXCSR_FTZ (1 << 15) /* Enable flush to zero mode */
29 /* All 64-bit targets have SSE and DAZ;
30 only check them explicitly for 32-bit ones. */
33 __attribute__ ((target("fxsr,sse")))
35 /* The i386 ABI only requires 4-byte stack alignment, so this is necessary
36 to make sure the fxsave struct gets correct alignment.
37 See PR27537 and PR28621. */
38 __attribute__ ((force_align_arg_pointer
))
39 set_fast_math_sse (unsigned int edx
)
45 /* Check if DAZ is available. */
57 unsigned int mxcsr_mask
;
58 unsigned int st_space
[32];
59 unsigned int xmm_space
[32];
60 unsigned int padding
[56];
61 } __attribute__ ((aligned (16))) fxsave
;
63 /* This is necessary since some implementations of FXSAVE
64 do not modify reserved areas within the image. */
65 fxsave
.mxcsr_mask
= 0;
67 __builtin_ia32_fxsave (&fxsave
);
71 if (fxsave
.mxcsr_mask
& MXCSR_DAZ
)
75 mxcsr
= __builtin_ia32_stmxcsr ();
78 __builtin_ia32_ldmxcsr (mxcsr
);
82 static void __attribute__((constructor
))
86 unsigned int eax
, ebx
, ecx
, edx
;
88 if (!__get_cpuid (1, &eax
, &ebx
, &ecx
, &edx
))
92 set_fast_math_sse (edx
);
94 unsigned int mxcsr
= __builtin_ia32_stmxcsr ();
95 mxcsr
|= MXCSR_DAZ
| MXCSR_FTZ
;
96 __builtin_ia32_ldmxcsr (mxcsr
);