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      1 <html><body><pre>Android NDK CPU Features detection library:
      2 -------------------------------------------
      3 
      4 This NDK provides a small library named "cpufeatures" that can be used at
      5 runtime to detect the target device's CPU family and the optional features
      6 it supports.
      7 
      8 Usage:
      9 ------
     10 
     11 The library is available as an import module. To use it, you must:
     12 
     13 To 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 &lt;cpu-features.h&gt;
     25 
     26 
     27 Here is a simple example:
     28 
     29 &lt;project-path&gt;/jni/Android.mk:
     30     LOCAL_PATH := $(call my-dir)
     31 
     32     include $(CLEAR_VARS)
     33     LOCAL_MODULE := &lt;your-module-name&gt;
     34     LOCAL_SRC_FILES := &lt;your-source-files&gt;
     35     LOCAL_STATIC_LIBRARIES := cpufeatures
     36     include $(BUILD_SHARED_LIBRARY)
     37 
     38     $(call import-module,android/cpufeatures)
     39 
     40 
     41 Features:
     42 ---------
     43 
     44 Two functions are provided for now:
     45 
     46    AndroidCpuFamily   android_getCpuFamily();
     47 
     48 Returns the target device's CPU Family as an enum. For now, the only
     49 supported family is ANDROID_CPU_FAMILY_ARM.
     50 
     51 
     52    uint64_t   android_getCpuFeatures();
     53 
     54 Returns the set of optional features supported by the device's CPU.
     55 The result is a set of bit-flags, each corresponding to one CPU
     56 Family-specific optional feature.
     57 
     58 Currently, 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 
     81 Important Note:
     82 ---------------
     83 
     84 The cpufeatures library will be updated to support more CPU families and
     85 optional features in the future. It is designed to work as-is on all
     86 official Android platform versions.
     87 
     88 
     89 Change History:
     90 ---------------
     91 
     92 Please see the comments in $NDK/sources/android/cpufeatures/cpu-features.c
     93 for the complete change history for this library.
     94 </pre></body></html>