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  • 【翻译】(9)CPU Features

    ------

    英文文档见android-ndk-r5b的documentation.html

    属于Android Native Development Kit (NDK)的一部分

    见http://developer.android.com/sdk/ndk/(需要代理)

    翻译仅个人见解

    -----------------

    Android NDK CPU Features detection library:

    Android NDK CPU特性检测库:

    -------------------------------------------

    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.

    NDK提供一个名为cpufeatures的小型库,它可以用于在运行期检测目标设备的CPU家族和它支持的可选特性。

    Usage:

    用法:

    ------

    The library is available as an import module. To use it, you must:

    这个库作为导入模块可用。要使用它,你必须:

    To use it, you must:

    要使用它,你必须:

      * List 'cpufeatures' in your list of static library dependencies, as in:

      * 在你的静态库依赖列表中列出cpufeatures,正如这样:

            LOCAL_STATIC_LIBRARIES := cpufeatures

      * At the end of your Android.mk, import the 'android/cpufeatures' module, as in:

      * 在你的Android.mk结束处,导入android/cpufeatures模块,正如这样:

            $(call import-module,android/cpufeatures)

      * In your source code, include the header named <cpu-features.h>

      * 在你的源代码中,包含名为<cpu-features.h>的头文件

    Here is a simple example:

    这里是一个简单示例:

    <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:

    特性:

    ---------

    Two functions are provided for now:

    现在提供两个函数:

       AndroidCpuFamily   android_getCpuFamily();

    Returns the target device's CPU Family as an enum. For now, the only supported family is ANDROID_CPU_FAMILY_ARM.

    用一个枚举值返回目标设备的CPU家族。现在,唯一支持的家族是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.

    返回设备CPU支持的可选特性。结构是一个位标志集合,每个位标志对应一项CPU家族特定的可选特性。

    Currently, only the following flags are defined, for the ARM CPU Family:

    目前,只为ARM CPU家族定义了如下标志:

       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_ARMv7

          指出设备的CPU支持ARMv7-A指令集,它由armeabi-v7a的ABI(注:应用程序二进制接口,操作系统暴露的接口,使二进制程序不需要重新编译即可在兼容ABI的操作系统上运行)支持(参考CPU-ARCH-ABIS.html)。它对应Thumb-2和VFPv3-D16指令。

       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.

       ANDROID_CPU_ARM_FEATURE_VFPv3

          指出设备CPU支持VFPv3硬件FPU(注:FPU是浮点运算单元的缩写)指令集扩展。由于armeabi-v7a的定义,它将总是返回ANDROID_CPU_ARM_FEATURE_ARMv7(注:这里的意思可能是,它总是和ANDROID_CPU_ARM_FEATURE_ARMv7一起返回)。

          Note that this corresponds to the minimum profile VFPv3-D16 that _only_ provides 16 hardware FP registers.

      注意它对应最小型号是VFPv3-D16,它只提供16个硬件浮点寄存器。

       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).

       ANDROID_CPU_ARM_FEATURE_NEON

          指出设备CPU支持ARM高级SIMD(即NEON)(注:NEON技术是ARM SIMD扩展指令,用于多媒体处理的硬件加速)向量指令集扩展。注意ARM授权这种CPU还实现了VFPv3-D32,提供32个硬件浮点寄存器(与NEON单元共享)。

    Important Note:

    重要注意事项:

    ---------------

    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.

    cpufeatures库将被更新以支持未来更多CPU家族和可选特性。它被设计为在所有官方Android平台版本上保持原样地工作。

    Change History:

    修改历史:

    ---------------

    Please see the comments in $NDK/sources/android/cpufeatures/cpu-features.c for the complete change history for this library.

    请参考$NDK/sources/android/cpufeatures/cpu-features.c中的注释以获得这个库的完整修改历史。(注:估计写文档的人太懒...)

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  • 原文地址:https://www.cnblogs.com/qq78292959/p/2232954.html
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