Compile for armv8.

[hedaoyuan]

Cmake support for the compilation of armv8(Android).

[Xreki]

I create a standalone toolchain use following command:

../android-ndk-r12b/build/tools/make-standalone-toolchain.sh \
    --arch=arm64 \
    --platform=android-21 \
    --install-dir=arm64-android-21-gcc

Here is my cmake command:

cmake -DCMAKE_SYSTEM_NAME=Android \
      -DANDROID_STANDALONE_TOOLCHAIN=$ANDROID_ARM64_TOOLCHAIN_ROOT \
      -DANDROID_ABI=arm64-v8a \
      -DCMAKE_INSTALL_PREFIX=$PROJ_ROOT/dist \
      -DCMAKE_BUILD_TYPE=RelWithDebInfo \
      -DCMAKE_C_FLAGS_RELWITHDEBINFO="-O3" \
      -DCMAKE_CXX_FLAGS_RELWITHDEBINFO="-O3" \
      -DWITH_C_API=ON \
      -DWITH_SWIG_PY=OFF \
      -DWITH_STYLE_CHECK=OFF \
      -DCMAKE_PREFIX_PATH="$JUMBO_ROOT" \
      ..

And I met some error:

[ 27%] Building CXX object proto/CMakeFiles/paddle_proto.dir/DataConfig.pb.cc.o
In file included from /usr/include/features.h:385:0,
                 from /usr/include/wchar.h:28,
                 from /home/liuyiqun01/install/android/toolchains/arm64-android-21-gcc/include/c++/4.9.x/cwchar:44,
                 from /home/liuyiqun01/install/android/toolchains/arm64-android-21-gcc/include/c++/4.9.x/bits/postypes.h:40,
                 from /home/liuyiqun01/install/android/toolchains/arm64-android-21-gcc/include/c++/4.9.x/bits/char_traits.h:40,
                 from /home/liuyiqun01/install/android/toolchains/arm64-android-21-gcc/include/c++/4.9.x/string:40,
                 from /home/liuyiqun01/github/Paddle/build_android/proto/DataConfig.pb.h:7,
                 from /home/liuyiqun01/github/Paddle/build_android/proto/DataConfig.pb.cc:5:
/usr/include/gnu/stubs.h:7:27: fatal error: gnu/stubs-32.h: No such file or directory
 # include <gnu/stubs-32.h>
                           ^
compilation terminated.
make[2]: *** [proto/CMakeFiles/paddle_proto.dir/DataConfig.pb.cc.o] Error 1
make[1]: *** [proto/CMakeFiles/paddle_proto.dir/all] Error 2
make: *** [all] Error 2

Are there any extra limits to the ndk version or android api level?

[Xreki]

Discussed with @hedaoyuan , we found the error is caused by wrongly finding the host boost library. Current solution is to disable all the boost-related and refactor-related codes.

[Xreki]

It is almost ok and I can compile for armv8, but not run the unittests because I have no android phone of armv8 architecture.
Another change suggested to made to support cmake of higher version. Change line 196-197 in android.cmake to:

IF(ANDROID_ABI MATCHES "^armeabi(-v7a)?$")
    SET(CMAKE_ANDROID_ARM_MODE ${ANDROID_ARM_MODE})
    IF(ANDROID_ABI STREQUAL "armeabi-v7a")
        SET(CMAKE_ANDROID_ARM_NEON ${ANDROID_ARM_NEON})
    ENDIF()
ENDIF()

[Xreki]

Just remind here, ARM_SOFTFP_ABI=1 is of no use for ARMV8, however, it won't make any difference for the building process. And there is no need of softfp support for armv8, thus we may use the master or other branchs, if they are faster.

[Xreki]

Remove NOT APPLE in line 97, or add AND NOT ANDROID as this line.

[hedaoyuan]

Done.