1page.title=The cpufeatures Library 2@jd:body 3 4<div id="qv-wrapper"> 5 <div id="qv"> 6 <h2>On this page</h2> 7 8 <ol> 9 <li><a href="#usage">Usage</a></li> 10 <li><a href="#functions">Functions</a></li> 11 <li><a href="#ch">Change History</a></li> 12 </ol> 13 </div> 14 </div> 15 16<p>The NDK provides a small library named {@code cpufeatures} that your app can use at runtime to 17detect the target device's CPU family and the optional features it supports. It is designed to work 18as-is on all official Android platform versions.</p> 19 20<h2 id="usage">Usage</h2> 21<p>The {@code cpufeatures} library is available as an import module. To use it, follow the procedure 22below:</p> 23 24<ol> 25<li>List {@code cpufeatures} in your list of static library dependencies. For example: 26 27<pre class="no-pretty-print"> 28LOCAL_STATIC_LIBRARIES := cpufeatures 29</pre> 30</li> 31 32<li>In your source code, include the {@code <cpu-features.h>} header file.</li> 33 34<li>At the end of your <a href="{@docRoot}ndk/guides/android_mk.html">{@code Android.mk}</a> file, 35insert an instruction to import the {@code android/cpufeatures} module. For example: 36 37<pre class="no-pretty-print"> 38$(call import-module,android/cpufeatures) 39</pre> 40 41<p>Here is a simple example of an {@code Android.mk} file that imports the {@code cpufeatures} 42library:</p> 43 44<pre class="no-pretty-print"> 45<project-path>/jni/Android.mk: 46LOCAL_PATH := $(call my-dir) 47 48include $(CLEAR_VARS) 49LOCAL_MODULE := <your-module-name> 50LOCAL_SRC_FILES := <your-source-files> 51LOCAL_STATIC_LIBRARIES := cpufeatures 52include $(BUILD_SHARED_LIBRARY) 53 54$(call import-module,android/cpufeatures) 55</pre> 56</li> 57</ol> 58 59<h2 id="functions">Functions</h2> 60<p>The {@code cpufeatures} library provides two functions. The first function returns the family to 61which the device's CPU belongs. Declare it as follows:</p> 62 63<pre class="no-pretty-print"> 64AndroidCpuFamily android_getCpuFamily(); 65</pre> 66 67<p>The function returns one of the following enums, representing the CPU family/architecture that 68the device supports.</p> 69<ul> 70<li>{@code ANDROID_CPU_FAMILY_ARM}</li> 71<li>{@code ANDROID_CPU_FAMILY_X86}</li> 72<li>{@code ANDROID_CPU_FAMILY_MIPS}</li> 73<li>{@code ANDROID_CPU_FAMILY_ARM64}</li> 74<li>{@code ANDROID_CPU_FAMILY_X86_64}</li> 75<li>{@code ANDROID_CPU_FAMILY_MIPS64}</li> 76</ul> 77 78<p>For a 32-bit executable on a 64-bit system, this function returns only the 32-bit value.</p> 79 80<p>The second function returns the set of optional features that the device's CPU supports. Declare 81it as follows: 82 83<pre class="no-pretty-print"> 84uint64_t android_getCpuFeatures(); 85</pre> 86 87<p>The return value takes the form of a set of bit flags, each flag representing one 88CPU-family-specific feature. The rest of this section provides information on features for 89the respective families.</p> 90 91<h4>32-bit ARM CPU family</h4> 92 93<p>The following flags are available for the 32-bit ARM CPU family:</p> 94<dl> 95<dt>{@code ANDROID_CPU_ARM_FEATURE_VFPv2}</dt> 96<dd>Indicates that the device's CPU supports the VFPv2 instruction set. Most ARMv6 CPUs support 97this instruction set.</dd> 98 99<dt>{@code ANDROID_CPU_ARM_FEATURE_ARMv7}</dt> 100<dd>Indicates that the device's CPU supports the ARMv7-A instruction set as supported by the 101<a href="{@docRoot}ndk/guides/abis.html#v7a">armeabi-v7a</a> ABI. This instruction set supports both 102Thumb-2 and VFPv3-D16 instructions. This return value also indicates support for the VFPv3 hardware 103FPU instruction-set extension.</dd> 104 105<dt>{@code ANDROID_CPU_ARM_FEATURE_VFPv3}</dt> 106<dd>Indicates that the device's CPU supports the VFPv3 hardware FPU instruction-set extension. 107<p>This value is equivalent to the {@code VFPv3-D16} instruction set, which provides provides only 10816 hardware double-precision FP registers.</p></dd> 109 110<dt>{@code ANDROID_CPU_ARM_FEATURE_VFP_D32}</dt> 111<dd> Indicates that the device's CPU supports 32 hardware double-precision FP registers instead of 11216. Even when there are 32 hardware double-precision FP registers, there are still only 32 113single-precision registers mapped to the same register banks.</dd> 114 115<dt>{@code ANDROID_CPU_ARM_FEATURE_NEON}</dt> 116<dd>Indicates that the device's CPU supports the ARM Advanced SIMD (NEON) vector instruction set 117extension. Note that ARM mandates that such CPUs also implement VFPv3-D32, which provides 32 118hardware FP registers (shared with the NEON unit).</dd> 119 120<dt>{@code ANDROID_CPU_ARM_FEATURE_VFP_FP16}</dt> 121<dd>Indicates that the device's CPU supports instructions to perform floating-point operations on 12216-bit registers. This feature is part of the VFPv4 specification.</dd> 123 124<dt>{@code ANDROID_CPU_ARM_FEATURE_VFP_FMA}</dt> 125<dd>Indicates that the device's CPU supports the fused multiply-accumulate extension for the VFP 126instruction set. Also part of the VFPv4 specification.</dd> 127 128<dt>{@code ANDROID_CPU_ARM_FEATURE_NEON_FMA}</dt> 129<dd>Indicates that the device's CPU supports the fused multiply-accumulate extension for the NEON 130instruction set. Also part of the VFPv4 specification.</dd> 131 132<dt>{@code ANDROID_CPU_ARM_FEATURE_IDIV_ARM}</dt> 133<dd>Indicates that the device's CPU supports integer division in ARM mode. Only available on later- 134model CPUs, such as Cortex-A15.</dd> 135 136<dt>{@code ANDROID_CPU_ARM_FEATURE_IDIV_THUMB2}</dt> 137<dd>Indicates that the device's CPU supports Integer division in Thumb-2 mode. Only available on 138later-model CPUs, such as Cortex-A15.</dd> 139 140<dt>{@code ANDROID_CPU_ARM_FEATURE_iWMMXt}</dt> 141<dd>Indicates that the device's CPU supports an instruction-set extension that adds MMX registers 142and instructions. This feature is only available on a few XScale- based CPUs.</dd> 143 144<dt>{@code ANDROID_CPU_ARM_FEATURE_LDREX_STREX}</dt> 145<dd>Indicates that the device's CPU supports LDREX and STREX instructions available since ARMv6. 146Together, these instructions provide atomic updates on memory with the help of exclusive 147monitor.</dd> 148</dl> 149 150<h4>64-bit ARM CPU family</h4> 151 152<p>The following flags are available for the 64-bit ARM CPU family:</p> 153<dl> 154<dt>{@code ANDROID_CPU_ARM64_FEATURE_FP}</dt> 155<dd>Indicates that the device's CPU has a Floating Point Unit (FPU). All Android ARM64 devices must 156support this feature.</dd> 157<dt>{@code ANDROID_CPU_ARM64_FEATURE_ASIMD}</dt> 158<dd>Indicates that the device's CPU has an Advanced SIMD (ASIMD) unit. All Android ARM64 devices 159must support this feature.</dd> 160<dt>{@code ANDROID_CPU_ARM64_FEATURE_AES}</dt> 161<dd>Indicates that the device's CPU supports {@code AES} instructions.</dd> 162<dt>{@code ANDROID_CPU_ARM64_FEATURE_CRC32}</dt> 163<dd>Indicates that the device's CPU supports {@code CRC32} instructions.</dd> 164<dt>{@code ANDROID_CPU_ARM64_FEATURE_SHA1}</dt> 165<dd>Indicates that the device's CPU supports {@code SHA1} instructions.</dd> 166<dt>{@code ANDROID_CPU_ARM64_FEATURE_SHA2}</dt> 167<dd>Indicates that the device's CPU supports {@code SHA2} instructions.</dd> 168<dt>{@code ANDROID_CPU_ARM64_FEATURE_PMULL}</dt> 169<dd>Indicates that the device's CPU supports 64-bit {@code PMULL} and {@code PMULL2} 170instructions.</dd> 171</dl> 172 173<h4>32-bit x86 CPU family</h4> 174 175<p>The following flags are available for the 32-bit x86 CPU family.<p> 176<dl> 177<dt>{@code ANDROID_CPU_X86_FEATURE_SSSE3}</dt> 178Indicates that the device's CPU supports the SSSE3 instruction extension set.</dd> 179 180<dt>{@code ANDROID_CPU_X86_FEATURE_POPCNT}</dt> 181<dd>Indicates that the device's CPU supports the {@code POPCNT} instruction.</dd> 182 183<dt>{@code ANDROID_CPU_X86_FEATURE_MOVBE}</dt> 184<dd>Indicates that the device's CPU supports the {@code MOVBE} instruction. This instruction is 185specific to some Intel IA-32 CPUs, such as Atom.</dd> 186<dl> 187 188<p>{@code android_getCpuFeatures()} returns {@code 0} for CPU families for which there are no 189listed extensions.</p> 190 191<p>The following function returns the maximum number of CPU cores on the target device: </p> 192 193<pre class="no-pretty-print"> 194int android_getCpuCount(void); 195</pre> 196 197<h4>MIPS CPU family</h4> 198 199<dl> 200<dt>{@code ANDROID_CPU_MIPS_FEATURE_R6}</dt> 201<dd>Indicates that the CPU executes MIPS Release 6 instructions natively, and supports obsoleted R1..R5 instructions only via kernel traps.</dd> 202 203<dt>{@code ANDROID_CPU_MIPS_FEATURE_MSA}</dt> 204<dd>Indicates that the CPU supports MIPS SIMD Architecture instructions.</dd> 205</dl> 206 207<h2 id="ch">Change History</h2> 208<p>For the complete change history of this library, see the comments in 209{@code $NDK/sources/android/cpufeatures/cpu-features.c}, where {@code $NDK} is the root of your 210NDK installation.</p>