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Android NDK CPU Features detection library:
-------------------------------------------
This NDK provides a small library named "cpufeatures" that can be used at
runtime to detect the target device's CPU family and the optional features
it supports.
Usage:
------
The library is available from sources/cpufeatures. It provides an Android.mk
build script that can be used to build it as a static library.
To use it, you must:
* include '$(NDK_ROOT)/sources/cpufeatures/Android.mk' at the start or end of your
Android.mk file.
* add '$(NDK_ROOT)/sources/cpufeatures' to your LOCAL_C_INCLUDES definition.
* add 'cpufeatures' to your LOCAL_STATIC_LIBRARIES definition when building
your final shared library.
your source code can then #include <cpu-features.h> to compile against it.
Here is a simple example:
<project-path>/jni/Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := <your-module-name>
LOCAL_C_INCLUDES += $(NDK_ROOT)/sources/cpufeatures
LOCAL_SRC_FILES := <your-source-files>
LOCAL_STATIC_LIBRARIES += cpufeatures
include $(BUILD_SHARED_LIBRARY)
include $(NDK_ROOT)/sources/cpufeature/Android.mk
Features:
---------
Two functions are provided for now:
AndroidCpuFamily android_getCpuFamily();
Returns the target device's CPU Family as an enum. For now, the only
supported family is ANDROID_CPU_FAMILY_ARM.
uint64_t android_getCpuFeatures();
Returns the set of optional features supported by the device's CPU.
The result is a set of bit-flags, each corresponding to one CPU
Family-specific optional feature.
Currently, only the following flags are defined, for the ARM CPU Family:
ANDROID_CPU_ARM_FEATURE_ARMv7
Indicates that the device's CPU supports the ARMv7-A instruction
set as supported by the "armeabi-v7a" abi (see CPU-ARCH-ABIS.TXT).
This corresponds to Thumb-2 and VFPv3-D16 instructions.
ANDROID_CPU_ARM_FEATURE_VFPv3
Indicates that the device's CPU supports the VFPv3 hardware FPU
instruction set extension. Due to the definition of 'armeabi-v7a',
this will always be the case if ANDROID_CPU_ARM_FEATURE_ARMv7 is
returned.
Note that this corresponds to the minimum profile VFPv3-D16 that
_only_ provides 16 hardware FP registers.
ANDROID_CPU_ARM_FEATURE_NEON
Indicates that the device's CPU supports the ARM Advanced SIMD
(a.k.a. NEON) vector instruction set extension. Note that ARM
mandates that such CPUs also implement VFPv3-D32, which provides
32 hardware FP registers (shared with the NEON unit).
Important Note:
---------------
The cpufeatures library will be updated to support more CPU families and
optional features in the future. It is designed to work as-is on all
official Android platform versions.
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