| /* |
| * Copyright (C) 2005 Free Software Foundation, Inc. |
| * |
| * This file is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License as published by the |
| * Free Software Foundation; either version 2, or (at your option) any |
| * later version. |
| * |
| * In addition to the permissions in the GNU General Public License, the |
| * Free Software Foundation gives you unlimited permission to link the |
| * compiled version of this file with other programs, and to distribute |
| * those programs without any restriction coming from the use of this |
| * file. (The General Public License restrictions do apply in other |
| * respects; for example, they cover modification of the file, and |
| * distribution when not linked into another program.) |
| * |
| * This file is distributed in the hope that it will be useful, but |
| * WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; see the file COPYING. If not, write to |
| * the Free Software Foundation, 51 Franklin Street, Fifth Floor, |
| * Boston, MA 02110-1301, USA. |
| * |
| * As a special exception, if you link this library with files |
| * compiled with GCC to produce an executable, this does not cause |
| * the resulting executable to be covered by the GNU General Public License. |
| * This exception does not however invalidate any other reasons why |
| * the executable file might be covered by the GNU General Public License. |
| */ |
| |
| #define MXCSR_DAZ (1 << 6) /* Enable denormals are zero mode */ |
| #define MXCSR_FTZ (1 << 15) /* Enable flush to zero mode */ |
| |
| #define FXSAVE (1 << 24) |
| #define SSE (1 << 25) |
| |
| static void __attribute__((constructor)) |
| #ifndef __x86_64__ |
| /* The i386 ABI only requires 4-byte stack alignment, so this is necessary |
| to make sure the fxsave struct gets correct alignment. |
| See PR27537 and PR28621. */ |
| __attribute__ ((force_align_arg_pointer)) |
| #endif |
| set_fast_math (void) |
| { |
| #ifndef __x86_64__ |
| /* All 64-bit targets have SSE and DAZ; only check them explicitly |
| for 32-bit ones. */ |
| unsigned int eax, ebx, ecx, edx; |
| |
| /* See if we can use cpuid. */ |
| asm volatile ("pushfl; pushfl; popl %0; movl %0,%1; xorl %2,%0;" |
| "pushl %0; popfl; pushfl; popl %0; popfl" |
| : "=&r" (eax), "=&r" (ebx) |
| : "i" (0x00200000)); |
| |
| if (((eax ^ ebx) & 0x00200000) == 0) |
| return; |
| |
| /* Check the highest input value for eax. */ |
| asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1" |
| : "=a" (eax), "=r" (ebx), "=c" (ecx), "=d" (edx) |
| : "0" (0)); |
| |
| if (eax == 0) |
| return; |
| |
| asm volatile ("xchgl %%ebx, %1; cpuid; xchgl %%ebx, %1" |
| : "=a" (eax), "=r" (ebx), "=c" (ecx), "=d" (edx) |
| : "0" (1)); |
| |
| if (edx & SSE) |
| { |
| unsigned int mxcsr = __builtin_ia32_stmxcsr (); |
| |
| mxcsr |= MXCSR_FTZ; |
| |
| if (edx & FXSAVE) |
| { |
| /* Check if DAZ is available. */ |
| struct |
| { |
| unsigned short int cwd; |
| unsigned short int swd; |
| unsigned short int twd; |
| unsigned short int fop; |
| long int fip; |
| long int fcs; |
| long int foo; |
| long int fos; |
| long int mxcsr; |
| long int mxcsr_mask; |
| long int st_space[32]; |
| long int xmm_space[32]; |
| long int padding[56]; |
| } __attribute__ ((aligned (16))) fxsave; |
| |
| __builtin_memset (&fxsave, 0, sizeof (fxsave)); |
| |
| asm volatile ("fxsave %0" : "=m" (fxsave) : "m" (fxsave)); |
| |
| if (fxsave.mxcsr_mask & MXCSR_DAZ) |
| mxcsr |= MXCSR_DAZ; |
| } |
| |
| __builtin_ia32_ldmxcsr (mxcsr); |
| } |
| #else |
| unsigned int mxcsr = __builtin_ia32_stmxcsr (); |
| mxcsr |= MXCSR_DAZ | MXCSR_FTZ; |
| __builtin_ia32_ldmxcsr (mxcsr); |
| #endif |
| } |