simddetect.cpp

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// File:        simddetect.cpp
// Description: Architecture detector.
// Author:      Stefan Weil (based on code from Ray Smith)
//
// (C) Copyright 2014, Google Inc.
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "simddetect.h"

#undef X86_BUILD
#if defined(__x86_64__) || defined(__i386__) || defined(_WIN32)
#if !defined(ANDROID_BUILD)
#define X86_BUILD 1
#endif  // !ANDROID_BUILD
#endif  // x86 target

#if defined(X86_BUILD)
#if defined(__GNUC__)
#include <cpuid.h>
#elif defined(_WIN32)
#include <intrin.h>
#endif
#endif

SIMDDetect SIMDDetect::detector;

// If true, then AVX has been detected.
bool SIMDDetect::avx_available_;
bool SIMDDetect::avx2_available_;
bool SIMDDetect::avx512F_available_;
bool SIMDDetect::avx512BW_available_;
// If true, then SSe4.1 has been detected.
bool SIMDDetect::sse_available_;

// Constructor.
// Tests the architecture in a system-dependent way to detect AVX, SSE and
// any other available SIMD equipment.
// __GNUC__ is also defined by compilers that include GNU extensions such as
// clang.
SIMDDetect::SIMDDetect() {
#if defined(X86_BUILD)
#if defined(__GNUC__)
  unsigned int eax, ebx, ecx, edx;
  if (__get_cpuid(1, &eax, &ebx, &ecx, &edx) != 0) {
    // Note that these tests all use hex because the older compilers don't have
    // the newer flags.
    sse_available_ = (ecx & 0x00080000) != 0;
    avx_available_ = (ecx & 0x10000000) != 0;
    if (avx_available_) {
      // There is supposed to be a __get_cpuid_count function, but this is all
      // there is in my cpuid.h. It is a macro for an asm statement and cannot
      // be used inside an if.
      __cpuid_count(7, 0, eax, ebx, ecx, edx);
      avx2_available_ = (ebx & 0x00000020) != 0;
      avx512F_available_ = (ebx & 0x00010000) != 0;
      avx512BW_available_ = (ebx & 0x40000000) != 0;
    }
  }
#elif defined(_WIN32)
  int cpuInfo[4];
  __cpuid(cpuInfo, 0);
  if (cpuInfo[0] >= 1) {
    __cpuid(cpuInfo, 1);
    sse_available_ = (cpuInfo[2] & 0x00080000) != 0;
    avx_available_ = (cpuInfo[2] & 0x10000000) != 0;
  }
#else
#error "I don't know how to test for SIMD with this compiler"
#endif
#endif  // X86_BUILD
}