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cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

Community bindings

Links provided here are not affiliated with Google but are kindly provided by the OSS Community.

Send PR to showcase your wrapper here

About

A cross platform C99 library to get cpu features at runtime.

Resources

Contributing

Stars

0 stars

Watchers

0 watching

Forks

Releases

Packages

Contributors

Languages

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all
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}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
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Repository files navigation

cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

Community bindings

Links provided here are not affiliated with Google but are kindly provided by the OSS Community.

Send PR to showcase your wrapper here

About

A cross platform C99 library to get cpu features at runtime.

Resources

Contributing

Stars

0 stars

Watchers

0 watching

Forks

Releases

Packages

Contributors

Languages

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix"); } } catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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Repository files navigation

cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

Community bindings

Links provided here are not affiliated with Google but are kindly provided by the OSS Community.

Send PR to showcase your wrapper here

About

A cross platform C99 library to get cpu features at runtime.

Resources

Contributing

Stars

0 stars

Watchers

0 watching

Forks

Releases

Packages

Contributors

Languages

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms"); } } catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
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Repository files navigation

cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

Community bindings

Links provided here are not affiliated with Google but are kindly provided by the OSS Community.

Send PR to showcase your wrapper here

About

A cross platform C99 library to get cpu features at runtime.

Resources

Contributing

Stars

0 stars

Watchers

0 watching

Forks

Releases

Packages

Contributors

Languages

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links"); } } catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); } })(); (function(){ try { var __m = "youtube.com"; var __re = new RegExp('^' + "youtube\\.com" + '
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cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

Community bindings

Links provided here are not affiliated with Google but are kindly provided by the OSS Community.

Send PR to showcase your wrapper here

About

A cross platform C99 library to get cpu features at runtime.

Resources

Contributing

Stars

0 stars

Watchers

0 watching

Forks

Releases

Packages

Contributors

Languages

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default"); } } catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
Skip to content

Repository files navigation

cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

Community bindings

Links provided here are not affiliated with Google but are kindly provided by the OSS Community.

Send PR to showcase your wrapper here

About

A cross platform C99 library to get cpu features at runtime.

Resources

Contributing

Stars

0 stars

Watchers

0 watching

Forks

Releases

Packages

Contributors

Languages

, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers"); } } catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); } })(); (function(){ try { var __m = "*"; var __re = new RegExp('^' + ".*" + '
Skip to content

Repository files navigation

cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode"); } } catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); } })(); })();
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cpu_features

A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.

GitHub-CI Status

Osamd64AArch64ARMMIPSPOWERRISCVs390x
Linux






FreeBSD






MacOS






Windows






Table of Contents

Design Rationale

  • Simple to use. See the snippets below for examples.
  • Extensible. Easy to add missing features or architectures.
  • Compatible with old compilers and available on many architectures so it can be used widely. To ensure that cpu_features works on as many platforms as possible, we implemented it in a highly portable version of C: C99.
  • Sandbox-compatible. The library uses a variety of strategies to cope with sandboxed environments or when cpuid is unavailable. This is useful when running integration tests in hermetic environments.
  • Thread safe, no memory allocation, and raises no exceptions. cpu_features is suitable for implementing fundamental libc functions like malloc, memcpy, and memcmp.
  • Unit tested.

Code samples

Note: For C++ code, the library functions are defined in the cpu_features namespace.

Checking features at runtime

Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:

#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
voidCompute(void) {
if (features.aes&&features.sse4_2) {
// Run optimized code.
} else {
// Run standard code.
}
}

Caching for faster evaluation of complex checks

If you wish, you can read all the features at once into a global variable, and then query for the specific features you care about. Below, we store all the ARM features and then check whether AES and NEON are supported.

#include<stdbool.h>#include"cpuinfo_arm.h"// For C++, add `using namespace cpu_features;`staticconstArmFeaturesfeatures=GetArmInfo().features;
staticconstboolhas_aes_and_neon=features.aes&&features.neon;
// use has_aes_and_neon.

This is a good approach to take if you're checking for combinations of features when using a compiler that is slow to extract individual bits from bit-packed structures.

Checking compile time flags

The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx) and sets has_avx accordingly.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Featuresfeatures=GetX86Info().features;
staticconstboolhas_avx=CPU_FEATURES_COMPILED_X86_AVX||features.avx;
// use has_avx.

CPU_FEATURES_COMPILED_X86_AVX is set to 1 if the compiler was instructed to use AVX and 0 otherwise, combining compile time and runtime knowledge.

Rejecting poor hardware implementations based on microarchitecture

On x86, the first incarnation of a feature in a microarchitecture might not be the most efficient (e.g. AVX on Sandy Bridge). We provide a function to retrieve the underlying microarchitecture so you can decide whether to use it.

Below, has_fast_avx is set to 1 if the CPU supports the AVX instruction set—but only if it's not Sandy Bridge.

#include<stdbool.h>#include"cpuinfo_x86.h"// For C++, add `using namespace cpu_features;`staticconstX86Infoinfo=GetX86Info();
staticconstX86Microarchitectureuarch=GetX86Microarchitecture(&info);
staticconstboolhas_fast_avx=info.features.avx&&uarch!=INTEL_SNB;
// use has_fast_avx.

This feature is currently available only for x86 microarchitectures.

Running sample code

Building cpu_features (check quickstart below) brings a small executable to test the library.

 % ./build/list_cpu_features
arch : x86
brand : Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz
family : 6 (0x06)
model : 45 (0x2D)
stepping : 7 (0x07)
uarch : INTEL_SNB
flags : aes,avx,cx16,smx,sse4_1,sse4_2,ssse3
% ./build/list_cpu_features --json
{"arch":"x86","brand":" Intel(R) Xeon(R) CPU E5-1650 0 @ 3.20GHz","family":6,"model":45,"stepping":7,"uarch":"INTEL_SNB","flags":["aes","avx","cx16","smx","sse4_1","sse4_2","ssse3"]}

What's supported

x86³AArch64ARMMIPS⁴POWERRISCVs390x
Linuxyes²yes¹yes¹yes¹yes¹yes¹yes¹
FreeBSDyes²not yetnot yetnot yetnot yetN/Anot yet
MacOsyes²not yetN/AN/AnoN/Ano
Windowsyes²not yetnot yetN/AN/AN/AN/A
Androidyes²yes¹yes¹yes¹N/AN/AN/A
iOSN/Anot yetnot yetN/AN/AN/AN/A
  1. Features revealed from Linux. We gather data from several sources depending on availability:
    • from glibc's getauxval
    • by parsing /proc/self/auxv
    • by parsing /proc/cpuinfo
  2. Features revealed from CPU. features are retrieved by using the cpuid instruction.
  3. Microarchitecture detection. On x86 some features are not always implemented efficiently in hardware (e.g. AVX on Sandybridge). Exposing the microarchitecture allows the client to reject particular microarchitectures.
  4. All flavors of Mips are supported, little and big endian as well as 32/64 bits.

Android NDK's drop in replacement

cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see ndk_compat folder for details.

License

The cpu_features library is licensed under the terms of the Apache license. See LICENSE for more information.

Build with CMake

Please check the CMake build instructions.

Quickstart

  • Run list_cpu_features

    cmake -S. -Bbuild -DBUILD_TESTING=OFF -DCMAKE_BUILD_TYPE=Release
    cmake --build build --config Release -j
    ./build/list_cpu_features --json

    Note: Use --target ALL_BUILD on the second line for Visual Studio and XCode.

  • run tests

    cmake -S. -Bbuild -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Debug
    cmake --build build --config Debug -j
    cmake --build build --config Debug --target test

    Note: Use --target RUN_TESTS on the last line for Visual Studio and --target RUN_TEST for XCode.

  • install cpu_features

    cmake --build build --config Release --target install -v

    Note: Use --target INSTALL for Visual Studio.

    Note: When using Makefile or XCode generator, you can use DESTDIR to install on a local repository.
    e.g.

    cmake --build build --config Release --target install -v -- DESTDIR=install

Community bindings

Links provided here are not affiliated with Google but are kindly provided by the OSS Community.

Send PR to showcase your wrapper here

About

A cross platform C99 library to get cpu features at runtime.

Resources

Contributing

Stars

0 stars

Watchers

0 watching

Forks

Releases

Packages

Contributors

Languages