1 /*
2 * Copyright (C) 2005-2020 Free Software Foundation, Inc.
3 *
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
7 * later version.
8 *
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.
13 *
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.
17 *
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/>.
22 */
23
24 #ifndef _SOFT_FLOAT
25 #define MXCSR_DAZ (1 << 6) /* Enable denormals are zero mode */
26 #define MXCSR_FTZ (1 << 15) /* Enable flush to zero mode */
27
28 #ifndef __x86_64__
29 /* All 64-bit targets have SSE and DAZ;
30 only check them explicitly for 32-bit ones. */
31 #include "cpuid.h"
32
33 __attribute__ ((target("fxsr,sse")))
34 static void
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))
set_fast_math_sse(unsigned int edx)39 set_fast_math_sse (unsigned int edx)
40 {
41 unsigned int mxcsr;
42
43 if (edx & bit_FXSAVE)
44 {
45 /* Check if DAZ is available. */
46 struct
47 {
48 unsigned short cwd;
49 unsigned short swd;
50 unsigned short twd;
51 unsigned short fop;
52 unsigned int fip;
53 unsigned int fcs;
54 unsigned int foo;
55 unsigned int fos;
56 unsigned int mxcsr;
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;
62
63 /* This is necessary since some implementations of FXSAVE
64 do not modify reserved areas within the image. */
65 fxsave.mxcsr_mask = 0;
66
67 __builtin_ia32_fxsave (&fxsave);
68
69 mxcsr = fxsave.mxcsr;
70
71 if (fxsave.mxcsr_mask & MXCSR_DAZ)
72 mxcsr |= MXCSR_DAZ;
73 }
74 else
75 mxcsr = __builtin_ia32_stmxcsr ();
76
77 mxcsr |= MXCSR_FTZ;
78 __builtin_ia32_ldmxcsr (mxcsr);
79 }
80 #endif
81
82 static void __attribute__((constructor))
set_fast_math(void)83 set_fast_math (void)
84 {
85 #ifndef __x86_64__
86 unsigned int eax, ebx, ecx, edx;
87
88 if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
89 return;
90
91 if (edx & bit_SSE)
92 set_fast_math_sse (edx);
93 #else
94 unsigned int mxcsr = __builtin_ia32_stmxcsr ();
95 mxcsr |= MXCSR_DAZ | MXCSR_FTZ;
96 __builtin_ia32_ldmxcsr (mxcsr);
97 #endif
98 }
99 #endif
100