1 files changed, 116 insertions, 0 deletions
diff --git a/third_party/libwebrtc/system_wrappers/source/cpu_features.cc b/third_party/libwebrtc/system_wrappers/source/cpu_features.cc
new file mode 100644
index 0000000000..b676339eea
--- /dev/null
+++ b/third_party/libwebrtc/system_wrappers/source/cpu_features.cc
@@ -0,0 +1,116 @@
+/*
+ *  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.
+    // Compiling with MSVC and /arch:AVX2 surprisingly generates BMI2
+    // instructions (see crbug.com/1315519).
+    return (cpu_info[2] & 0x10000000) != 0 /* AVX */ &&
+           (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 /* AVX2 */ &&
+           (cpu_info7[1] & 0x00000100) != 0 /* BMI2 */;
+  }
+#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