1<html><body><pre>Android NDK CPU Features detection library: 2------------------------------------------- 3 4This NDK provides a small library named "cpufeatures" that can be used at 5runtime to detect the target device's CPU family and the optional features 6it supports. 7 8Usage: 9------ 10 11The library is available as an import module. To use it, you must: 12 13To use it, you must: 14 15 * List 'cpufeatures' in your list of static library dependencies, as in: 16 17 LOCAL_STATIC_LIBRARIES := cpufeatures 18 19 * At the end of your Android.mk, import the 'android/cpufeatures' module, 20 as in: 21 22 $(call import-module,android/cpufeatures) 23 24 * In your source code, include the header named <cpu-features.h> 25 26 27Here is a simple example: 28 29<project-path>/jni/Android.mk: 30 LOCAL_PATH := $(call my-dir) 31 32 include $(CLEAR_VARS) 33 LOCAL_MODULE := <your-module-name> 34 LOCAL_SRC_FILES := <your-source-files> 35 LOCAL_STATIC_LIBRARIES := cpufeatures 36 include $(BUILD_SHARED_LIBRARY) 37 38 $(call import-module,android/cpufeatures) 39 40 41Features: 42--------- 43 44Two functions are provided for now: 45 46 AndroidCpuFamily android_getCpuFamily(); 47 48Returns the target device's CPU Family as an enum. For now, the only 49supported family is ANDROID_CPU_FAMILY_ARM. 50 51 52 uint64_t android_getCpuFeatures(); 53 54Returns the set of optional features supported by the device's CPU. 55The result is a set of bit-flags, each corresponding to one CPU 56Family-specific optional feature. 57 58Currently, only the following flags are defined, for the ARM CPU Family: 59 60 ANDROID_CPU_ARM_FEATURE_ARMv7 61 Indicates that the device's CPU supports the ARMv7-A instruction 62 set as supported by the "armeabi-v7a" abi (see CPU-ARCH-ABIS.html). 63 This corresponds to Thumb-2 and VFPv3-D16 instructions. 64 65 ANDROID_CPU_ARM_FEATURE_VFPv3 66 Indicates that the device's CPU supports the VFPv3 hardware FPU 67 instruction set extension. Due to the definition of 'armeabi-v7a', 68 this will always be the case if ANDROID_CPU_ARM_FEATURE_ARMv7 is 69 returned. 70 71 Note that this corresponds to the minimum profile VFPv3-D16 that 72 _only_ provides 16 hardware FP registers. 73 74 ANDROID_CPU_ARM_FEATURE_NEON 75 Indicates that the device's CPU supports the ARM Advanced SIMD 76 (a.k.a. NEON) vector instruction set extension. Note that ARM 77 mandates that such CPUs also implement VFPv3-D32, which provides 78 32 hardware FP registers (shared with the NEON unit). 79 80 81Important Note: 82--------------- 83 84The cpufeatures library will be updated to support more CPU families and 85optional features in the future. It is designed to work as-is on all 86official Android platform versions. 87 88 89Change History: 90--------------- 91 92Please see the comments in $NDK/sources/android/cpufeatures/cpu-features.c 93for the complete change history for this library. 94</pre></body></html>