1 /*
2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 // Parts of this file derived from Chromium's base/cpu.cc.
12
13 #include "rtc_base/system/arch.h"
14 #include "system_wrappers/include/cpu_features_wrapper.h"
15 #include "system_wrappers/include/field_trial.h"
16
17 #if defined(WEBRTC_ARCH_X86_FAMILY) && defined(_MSC_VER)
18 #include <intrin.h>
19 #endif
20
21 namespace webrtc {
22
23 // No CPU feature is available => straight C path.
GetCPUInfoNoASM(CPUFeature feature)24 int GetCPUInfoNoASM(CPUFeature feature) {
25 (void)feature;
26 return 0;
27 }
28
29 #if defined(WEBRTC_ARCH_X86_FAMILY)
30
31 #if defined(WEBRTC_ENABLE_AVX2)
32 // xgetbv returns the value of an Intel Extended Control Register (XCR).
33 // Currently only XCR0 is defined by Intel so |xcr| should always be zero.
xgetbv(uint32_t xcr)34 static uint64_t xgetbv(uint32_t xcr) {
35 #if defined(_MSC_VER)
36 return _xgetbv(xcr);
37 #else
38 uint32_t eax, edx;
39
40 __asm__ volatile("xgetbv" : "=a"(eax), "=d"(edx) : "c"(xcr));
41 return (static_cast<uint64_t>(edx) << 32) | eax;
42 #endif // _MSC_VER
43 }
44 #endif // WEBRTC_ENABLE_AVX2
45
46 #ifndef _MSC_VER
47 // Intrinsic for "cpuid".
48 #if defined(__pic__) && defined(__i386__)
__cpuid(int cpu_info[4],int info_type)49 static inline void __cpuid(int cpu_info[4], int info_type) {
50 __asm__ volatile(
51 "mov %%ebx, %%edi\n"
52 "cpuid\n"
53 "xchg %%edi, %%ebx\n"
54 : "=a"(cpu_info[0]), "=D"(cpu_info[1]), "=c"(cpu_info[2]),
55 "=d"(cpu_info[3])
56 : "a"(info_type));
57 }
58 #else
__cpuid(int cpu_info[4],int info_type)59 static inline void __cpuid(int cpu_info[4], int info_type) {
60 __asm__ volatile("cpuid\n"
61 : "=a"(cpu_info[0]), "=b"(cpu_info[1]), "=c"(cpu_info[2]),
62 "=d"(cpu_info[3])
63 : "a"(info_type), "c"(0));
64 }
65 #endif
66 #endif // _MSC_VER
67 #endif // WEBRTC_ARCH_X86_FAMILY
68
69 #if defined(WEBRTC_ARCH_X86_FAMILY)
70 // Actual feature detection for x86.
GetCPUInfo(CPUFeature feature)71 int GetCPUInfo(CPUFeature feature) {
72 int cpu_info[4];
73 __cpuid(cpu_info, 1);
74 if (feature == kSSE2) {
75 return 0 != (cpu_info[3] & 0x04000000);
76 }
77 if (feature == kSSE3) {
78 return 0 != (cpu_info[2] & 0x00000001);
79 }
80 #if defined(WEBRTC_ENABLE_AVX2)
81 if (feature == kAVX2 &&
82 !webrtc::field_trial::IsEnabled("WebRTC-Avx2SupportKillSwitch")) {
83 int cpu_info7[4];
84 __cpuid(cpu_info7, 0);
85 int num_ids = cpu_info7[0];
86 if (num_ids < 7) {
87 return 0;
88 }
89 // Interpret CPU feature information.
90 __cpuid(cpu_info7, 7);
91
92 // AVX instructions can be used when
93 // a) AVX are supported by the CPU,
94 // b) XSAVE is supported by the CPU,
95 // c) XSAVE is enabled by the kernel.
96 // See http://software.intel.com/en-us/blogs/2011/04/14/is-avx-enabled
97 // AVX2 support needs (avx_support && (cpu_info7[1] & 0x00000020) != 0;).
98 return (cpu_info[2] & 0x10000000) != 0 &&
99 (cpu_info[2] & 0x04000000) != 0 /* XSAVE */ &&
100 (cpu_info[2] & 0x08000000) != 0 /* OSXSAVE */ &&
101 (xgetbv(0) & 0x00000006) == 6 /* XSAVE enabled by kernel */ &&
102 (cpu_info7[1] & 0x00000020) != 0;
103 }
104 #endif // WEBRTC_ENABLE_AVX2
105 return 0;
106 }
107 #else
108 // Default to straight C for other platforms.
GetCPUInfo(CPUFeature feature)109 int GetCPUInfo(CPUFeature feature) {
110 (void)feature;
111 return 0;
112 }
113 #endif
114
115 } // namespace webrtc
116