1 /* 2 * Copyright (C) 2005-2019 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)) 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)) 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