A cross-platform C library to retrieve CPU features (such as available instructions) at runtime.
cpuid
is unavailable. This is useful when running integration tests in hermetic environments.malloc
, memcpy
, and memcmp
.Note: For C++ code, the library functions are defined in the CpuFeatures
namespace.
Here's a simple example that executes a codepath if the CPU supports both the AES and the SSE4.2 instruction sets:
```c #include "cpuinfo_x86.h"
// For C++, add using namespace CpuFeatures;
static const X86Features features = GetX86Info().features;
void Compute(void) { if (features.aes && features.sse4_2) { // Run optimized code. } else { // Run standard code. } } ```
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.
```c #include <stdbool.h> #include "cpuinfo_arm.h"
// For C++, add using namespace CpuFeatures;
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.
The following code determines whether the compiler was told to use the AVX instruction set (e.g., g++ -mavx
) and sets has_avx
accordingly.
```c #include <stdbool.h> #include "cpuinfo_x86.h"
// For C++, add using namespace CpuFeatures;
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.
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.
```c #include <stdbool.h> #include "cpuinfo_x86.h"
// For C++, add using namespace CpuFeatures;
static const X86Info info = GetX86Info(); static const X86Microarchitecture uarch = GetX86Microarchitecture(&info); static const bool has_fast_avx = info.features.avx && uarch != INTEL_SNB;
// use has_fast_avx.
x86³ | ARM | AArch64 | MIPS⁴ | POWER | |
---|---|---|---|---|---|
Android | yes² | yes¹ | yes¹ | yes¹ | N/A |
iOS | N/A | not yet | not yet | N/A | N/A |
Linux | yes² | yes¹ | yes¹ | yes¹ | yes¹ |
MacOs | yes² | N/A | not yet | N/A | no |
Windows | yes² | not yet | not yet | N/A | N/A |
/proc/self/auxv
/proc/cpuinfo
cpuid
instruction.cpu_features is now officially supporting Android and offers a drop in replacement of for the NDK's cpu-features.h , see [ndk_compat](ndk_compat) folder for details.
The cpu_features library is licensed under the terms of the Apache license. See [LICENSE](LICENSE) for more information.
Please check the CMake build instructions.
Ninja
list_cpu_features