system_wrappers/source/cpu_features.cc

/*
 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "cpu_features_wrapper.h"

// No CPU feature is available => straight C path.
int GetCPUInfoNoASM(CPUFeature feature) {
  (void)feature;
  return 0;
}

// Intrinsic for "cpuid".
#if defined(__pic__) && defined(__i386__)
static inline void cpuid(int cpu_info[4], int info_type) {
  __asm__ volatile (
    "mov %%ebx, %%edi\n"
    "cpuid\n"
    "xchg %%edi, %%ebx\n"
    : "=a"(cpu_info[0]), "=D"(cpu_info[1]), "=c"(cpu_info[2]), "=d"(cpu_info[3])
    : "a"(info_type));
}
#elif defined(__i386__) || defined(__x86_64__)
static inline void cpuid(int cpu_info[4], int info_type) {
  __asm__ volatile (
    "cpuid\n"
    : "=a"(cpu_info[0]), "=b"(cpu_info[1]), "=c"(cpu_info[2]), "=d"(cpu_info[3])
    : "a"(info_type));
}
#endif

#if defined(__i386__) || defined(__x86_64__)
// Actual feature detection for x86.
static int GetCPUInfo(CPUFeature feature) {
  int cpu_info[4];
  cpuid(cpu_info, 1);
  if (feature == kSSE2) {
    return 0 != (cpu_info[3] & 0x04000000);
  }
  if (feature == kSSE3) {
    return 0 != (cpu_info[2] & 0x00000001);
  }
  return 0;
}
#else
// Default to straight C for other platforms.
static int GetCPUInfo(CPUFeature feature) {
  (void)feature;
  return 0;
}
#endif

WebRtc_CPUInfo WebRtc_GetCPUInfo = GetCPUInfo;
WebRtc_CPUInfo WebRtc_GetCPUInfoNoASM = GetCPUInfoNoASM;