2 * Copyright (C) 2005, 2007, 2009 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/>.
24 #define MXCSR_DAZ (1 << 6) /* Enable denormals are zero mode */
25 #define MXCSR_FTZ (1 << 15) /* Enable flush to zero mode */
28 /* All 64-bit targets have SSE and DAZ;
29 only check them explicitly for 32-bit ones. */
33 static void __attribute__((constructor))
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))
43 unsigned int eax, ebx, ecx, edx;
45 if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
50 unsigned int mxcsr = __builtin_ia32_stmxcsr ();
56 /* Check if DAZ is available. */
59 unsigned short int cwd;
60 unsigned short int swd;
61 unsigned short int twd;
62 unsigned short int fop;
69 long int st_space[32];
70 long int xmm_space[32];
72 } __attribute__ ((aligned (16))) fxsave;
74 __builtin_memset (&fxsave, 0, sizeof (fxsave));
76 asm volatile ("fxsave %0" : "=m" (fxsave) : "m" (fxsave));
78 if (fxsave.mxcsr_mask & MXCSR_DAZ)
82 __builtin_ia32_ldmxcsr (mxcsr);
85 unsigned int mxcsr = __builtin_ia32_stmxcsr ();
86 mxcsr |= MXCSR_DAZ | MXCSR_FTZ;
87 __builtin_ia32_ldmxcsr (mxcsr);