<html><body><pre>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 as an import module. To use it, you must:
To use it, you must:
* List 'cpufeatures' in your list of static library dependencies, as in:
LOCAL_STATIC_LIBRARIES := cpufeatures
* At the end of your Android.mk, import the 'android/cpufeatures' module,
as in:
$(call import-module,android/cpufeatures)
* In your source code, include the header named <cpu-features.h>
Here is a simple example:
<project-path>/jni/Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := <your-module-name>
LOCAL_SRC_FILES := <your-source-files>
LOCAL_STATIC_LIBRARIES := cpufeatures
include $(BUILD_SHARED_LIBRARY)
$(call import-module,android/cpufeatures)
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.html).
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.
Change History:
---------------
Please see the comments in $NDK/sources/android/cpufeatures/cpu-features.c
for the complete change history for this library.
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