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/*
* 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.
*/
// Parts of this file derived from Chromium's base/cpu.cc.
#include "rtc_base/system/arch.h"
#include "system_wrappers/include/cpu_features_wrapper.h"
#include "system_wrappers/include/field_trial.h"
#if defined(WEBRTC_ARCH_X86_FAMILY) && defined(_MSC_VER)
#include <intrin.h>
#endif
namespace webrtc {
// No CPU feature is available => straight C path.
int GetCPUInfoNoASM(CPUFeature feature) {
(void)feature;
return 0;
}
#if defined(WEBRTC_ARCH_X86_FAMILY)
#if defined(WEBRTC_ENABLE_AVX2)
// xgetbv returns the value of an Intel Extended Control Register (XCR).
// Currently only XCR0 is defined by Intel so |xcr| should always be zero.
static uint64_t xgetbv(uint32_t xcr) {
#if defined(_MSC_VER)
return _xgetbv(xcr);
#else
uint32_t eax, edx;
__asm__ volatile("xgetbv" : "=a"(eax), "=d"(edx) : "c"(xcr));
return (static_cast<uint64_t>(edx) << 32) | eax;
#endif // _MSC_VER
}
#endif // WEBRTC_ENABLE_AVX2
#ifndef _MSC_VER
// 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));
}
#else
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), "c"(0));
}
#endif
#endif // _MSC_VER
#endif // WEBRTC_ARCH_X86_FAMILY
#if defined(WEBRTC_ARCH_X86_FAMILY)
// Actual feature detection for x86.
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);
}
#if defined(WEBRTC_ENABLE_AVX2)
if (feature == kAVX2 &&
!webrtc::field_trial::IsEnabled("WebRTC-Avx2SupportKillSwitch")) {
int cpu_info7[4];
__cpuid(cpu_info7, 0);
int num_ids = cpu_info7[0];
if (num_ids < 7) {
return 0;
}
// Interpret CPU feature information.
__cpuid(cpu_info7, 7);
// AVX instructions can be used when
// a) AVX are supported by the CPU,
// b) XSAVE is supported by the CPU,
// c) XSAVE is enabled by the kernel.
// See http://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled
// AVX2 support needs (avx_support && (cpu_info7[1] & 0x00000020) != 0;).
return (cpu_info[2] & 0x10000000) != 0 &&
(cpu_info[2] & 0x04000000) != 0 /* XSAVE */ &&
(cpu_info[2] & 0x08000000) != 0 /* OSXSAVE */ &&
(xgetbv(0) & 0x00000006) == 6 /* XSAVE enabled by kernel */ &&
(cpu_info7[1] & 0x00000020) != 0;
}
#endif // WEBRTC_ENABLE_AVX2
return 0;
}
#else
// Default to straight C for other platforms.
int GetCPUInfo(CPUFeature feature) {
(void)feature;
return 0;
}
#endif
} // namespace webrtc
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