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/* Initialize CPU features for use by the math library.
This file is part of the GNU C Library.
Copyright (C) 2008-2018 Free Software Foundation, Inc.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <x86-math-features.h>
#include <atomic.h>
#include <cpuid.h>
#include <cpu-features.h>
#include <stdbool.h>
static unsigned int features;
unsigned int
__x86_math_features (void)
{
unsigned int features_local = atomic_load_relaxed (&features);
if (features_local != 0)
/* At least the initialization bit is set, which means that we
have a proper value. */
return features_local;
/* Perform initialization. */
features_local = x86_math_feature_initialized;
unsigned int eax, ebx, ecx, edx;
unsigned int max_cpuid;
__cpuid (0, max_cpuid, ebx, ecx, edx);
bool cpu_amd = ebx == 0x68747541 && ecx == 0x444d4163 && edx == 0x69746e65;
if (max_cpuid >= 7)
{
__cpuid (1, eax, ebx, ecx, edx);
bool flag_fma = ecx & bit_cpu_FMA;
bool flag_osxsave = ecx & bit_cpu_OSXSAVE;
bool flag_avx = ecx & bit_cpu_AVX;
bool flag_sse41 = ecx & bit_cpu_SSE4_1;
if (flag_sse41)
features_local |= x86_math_feature_sse41;
__cpuid_count (7, 0, eax, ebx, ecx, edx);
bool flag_avx2 = ebx & bit_cpu_AVX2;
if (flag_osxsave)
{
unsigned int xcrlow;
unsigned int xcrhigh;
asm ("xgetbv" : "=a" (xcrlow), "=d" (xcrhigh) : "c" (0));
bool ymm_xmm_usable
= (xcrlow & (bit_YMM_state | bit_XMM_state))
== (bit_YMM_state | bit_XMM_state);
/* Is YMM and XMM state usable? */
if (ymm_xmm_usable)
{
if (flag_avx)
{
features_local |= x86_math_feature_avx;
if (flag_avx2)
features_local |= x86_math_feature_avx2;
if (flag_fma)
features_local |= x86_math_feature_fma;
if (cpu_amd)
{
__cpuid (0x80000000, eax, ebx, ecx, edx);
if (eax >= 0x80000001)
{
__cpuid (0x80000001, eax, ebx, ecx, edx);
bool flag_fma4 = ecx & bit_cpu_FMA4;
if (flag_fma4)
features_local |= x86_math_feature_fma4;
}
}
}
}
}
}
atomic_store_relaxed (&features, features_local);
return features_local;
}
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