cpu_features

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

GitHub-CI Status

	Linux	FreeBSD	MacOS	Windows
amd64
AArch64
ARM
MIPS
POWER
RISCV
LOONGARCH
s390x

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.

#include “cpuinfo_x86.h”

// For C++, add using namespace cpu_features; static const X86Features features = GetX86Info().features;

void Compute(void) { if (features.aes && features.sse4_2) {

// Run optimized code.

} else {

// Run standard code.

} }

#include <stdbool.h>
#include "cpuinfo_arm.h"

// For C++, add `using namespace cpu_features;`
static const ArmFeatures features = GetArmInfo().features;
static const bool has_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;`
static const X86Features features = GetX86Info().features;
static const bool has_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.

#include

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.

• .Net
  • https://github.com/toor1245/cpu_features.NET
• Python
  • https://github.com/Narasimha1997/py_cpu
• Java
  • https://github.com/aecsocket/cpu-features-java

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