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 <cpu-features.h> 25 26 27 Here 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 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_VFPv2 61 Indicates that the device's CPU supports VFPv2 instruction set. 62 Most ARMv6 CPUs support these. 63 64 ANDROID_CPU_ARM_FEATURE_ARMv7 65 Indicates that the device's CPU supports the ARMv7-A instruction 66 set as supported by the "armeabi-v7a" abi (see CPU-ARCH-ABIS.html). 67 This corresponds to Thumb-2 and VFPv3-D16 instructions. 68 69 ANDROID_CPU_ARM_FEATURE_VFPv3 70 Indicates that the device's CPU supports the VFPv3 hardware FPU 71 instruction set extension. Due to the definition of 'armeabi-v7a', 72 this will always be the case if ANDROID_CPU_ARM_FEATURE_ARMv7 is 73 returned. 74 75 Note that this corresponds to the minimum profile VFPv3-D16 that 76 _only_ provides 16 hardware double-precision FP registers. 77 78 ANDROID_CPU_ARM_FEATURE_VFP_D32 79 Indicates that the device's CPU supports 32 hardware double-precision 80 FP registers instead of 16. Note that there are still only 32 single- 81 precision registers mapped to the same register banks. 82 83 ANDROID_CPU_ARM_FEATURE_NEON 84 Indicates that the device's CPU supports the ARM Advanced SIMD 85 (a.k.a. NEON) vector instruction set extension. Note that ARM 86 mandates that such CPUs also implement VFPv3-D32, which provides 87 32 hardware FP registers (shared with the NEON unit). 88 89 ANDROID_CPU_ARM_FEATURE_VFP_FP16 90 Indicates that the device's CPU supports instructions to perform 91 floating-point operations on 16-bit registers. This is part of the 92 VFPv4 specification. 93 94 ANDROID_CPU_ARM_FEATURE_VFP_FMA 95 Indicates that the device's CPU supports fused multiply-accumulate 96 VFP instructions extension. Also part of the VFPv4 specification. 97 98 ANDROID_CPU_ARM_FEATURE_NEON_FMA 99 Indicates that the device's CPU supports fused multiply-accumulate 100 NEON instructions extension. Also part of the VFPv4 specification. 101 102 ANDROID_CPU_ARM_FEATURE_IDIV_ARM 103 Indicates that the device's CPU supports Integer division in ARM mode. 104 Only available on recent CPUs (e.g. Cortex-A15). 105 106 ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2 107 Indicates that the device's CPU supports Integer division in Thumb-2 108 mode. Only available on recent CPUs (e.g. Cortex-A15). 109 110 ANDROID_CPU_ARM_FEATURE_iWMMXt 111 Indicates that the device's CPU supports extension that adds MMX 112 registers and instructions. This is only available on a few XScale- 113 based CPU. 114 115 ANDROID_CPU_ARM_FEATURE_LDREX_STREX 116 Indicates that the device's CPU supports LDREX and STREX instructions 117 available since ARMv6. Together they provide atomic update on memory 118 with the help of exclusive monitor. 119 120 And the following flags for the x86 CPU Family: 121 122 ANDROID_CPU_X86_FEATURE_SSSE3 123 Indicates that the device's CPU supports the SSSE3 instruction 124 extension set. Note that this is unlike SSE3 which is required 125 by the x86 NDK ABI. 126 127 ANDROID_CPU_X86_FEATURE_POPCNT 128 Indicates that the device's CPU supports the POPCNT instruction. 129 130 ANDROID_CPU_X86_FEATURE_MOVBE 131 Indicates that the device's CPU supports the MOVBE instruction. 132 This one is specific to some Intel IA-32 CPUs, like the Atom. 133 134 135 The following function is also defined to return the max number of 136 CPU cores on the target device: 137 138 int android_getCpuCount(void); 139 140 141 Important Note: 142 --------------- 143 144 The cpufeatures library will be updated to support more CPU families and 145 optional features in the future. It is designed to work as-is on all 146 official Android platform versions. 147 148 149 Change History: 150 --------------- 151 152 Please see the comments in $NDK/sources/android/cpufeatures/cpu-features.c 153 for the complete change history for this library. 154 </pre></body></html>
