2 * Copyright (C) 2005-2015 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. */
34 static void __attribute__((constructor))
36 /* The i386 ABI only requires 4-byte stack alignment, so this is necessary
37 to make sure the fxsave struct gets correct alignment.
38 See PR27537 and PR28621. */
39 __attribute__ ((force_align_arg_pointer))
44 unsigned int eax, ebx, ecx, edx;
46 if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
55 /* Check if DAZ is available. */
67 unsigned int mxcsr_mask;
68 unsigned int st_space[32];
69 unsigned int xmm_space[32];
70 unsigned int padding[56];
71 } __attribute__ ((aligned (16))) fxsave;
73 /* This is necessary since some implementations of FXSAVE
74 do not modify reserved areas within the image. */
75 fxsave.mxcsr_mask = 0;
77 __builtin_ia32_fxsave (&fxsave);
81 if (fxsave.mxcsr_mask & MXCSR_DAZ)
85 mxcsr = __builtin_ia32_stmxcsr ();
88 __builtin_ia32_ldmxcsr (mxcsr);
91 unsigned int mxcsr = __builtin_ia32_stmxcsr ();
92 mxcsr |= MXCSR_DAZ | MXCSR_FTZ;
93 __builtin_ia32_ldmxcsr (mxcsr);