On Mon, Mar 21, 2011 at 4:25 AM, Jim Huang jim.huang@linaro.org wrote:

Hello list,

Recently, Android team is working on integrating Linaro toolchain for Android and NDK.  According to the initial benchmark results[1], Linaro GCC is competitive comparing to Google toolchain.  In the meanwhile, we are trying to enable gcc-4.5 specific features such as Graphite and LTO (Link Time Optimization) in order to make the best choice for Android build system and NDK usage.  However, I encountered a problem about LTO and would like to ask help from toolchain WG.

Assuming Linaro Toolchain for Android is installed in directory /tmp/android-toolchain-eabi, you can obtain Google's toolchain benchmark suite by git:  # git clone git://android.git.kernel.org/toolchain/benchmark.git

You have to apply the attached patch in order to make benchmark suite work[2].  Then, change directory to skia:  # cd benchmark/skia And build skia bench with LTO enabled:  # ../scripts/bench.py --action=build --toolchain=/tmp/android-toolchain-eabi --add_cflags="-flto -user-linker-plugin"

The build process would be interrupted by gcc:

make -j4 --warn-undefined-variables -f ../scripts/build/main.mk TOOLCHAIN=/tmp/android-toolchain-eabi ADD_CFLAGS="-flto -user-linker-plugin" build CPP ARM obj/src/core/Sk64.o <= src/src/core/Sk64.cpp CPP ARM obj/src/core/SkAlphaRuns.o <= src/src/core/SkAlphaRuns.cpp CPP ARM obj/src/core/SkBitmap.o <= src/src/core/SkBitmap.cpp CPP ARM obj/src/core/SkBitmapProcShader.o <= src/src/core/SkBitmapProcShader.cpp CPP ARM obj/src/core/SkBitmapProcState.o <= src/src/core/SkBitmapProcState.cpp CPP ARM obj/src/core/SkBitmapProcState_matrixProcs.o <= src/src/core/SkBitmapProcState_matrixProcs.cpp src/src/core/SkBitmapProcShader.cpp: In function 'SkShader::CreateBitmapShader(SkBitmap const&, SkShader::TileMode, SkShader::TileMode, void*, unsigned int)': src/src/core/SkBitmapProcShader.cpp:243:13: warning: 'color' may be used uninitialized in this function CPP ARM obj/src/core/SkBitmapSampler.o <= src/src/core/SkBitmapSampler.cpp src/src/core/SkBitmapProcState_matrixProcs.cpp:530:1: sorry, unimplemented: gimple bytecode streams do not support machine specific builtin functions on this target

Hi Jim. This is being caused by the NEON intrinsics in SkBitmapProcState_matrixProcs.cpp such as the vdupq_n_s32() in decal_nofilter_scale(). If you wanted a first pass on LTO vs non-LTO then you could build SKIA without the NEON optimisations and see how it compares.

I'm afraid I don't know what the fix is. Anyone else?

-- Michael