Compiling GNURadio 3.7 with Clang 7 for ARM - The rough guide

TODO list:

• gnuradio/volk#222
• gnuradio/volk#221
• gnuradio/volk#220

You can cross compile and build on the pi. Builtlding on the pi takes longer but is sometimes useful.

Testing and pull requests very welcome!

Cross compiling

Setting up the toolchain

Warning: not for the faint of heart.

# Change to your liking
export SDKPATH=$HOME/src/rbpi3sdk

mkdir -p $SDKPATH

# http://releases.llvm.org/download.html
# I think 8.0.0 is available now
tar xf clang+llvm-7.0.0-x86_64-linux-gnu-ubuntu-16.04.tar.xz -C rbpi3sdk/prebuilt --strip-components=1

# binutils
tar xf binutils-2.31.tar.xz
cd binutils-2.31
./configure --prefix=$SDKPATH/prebuilt \
            --target=arm-linux-gnueabihf \
            --disable-nls \
            --with-sysroot=$SDKPATH/sysroot \
            --enable-gold=yes \
            --enable-interwork \
            --enable-multilib
make -j4 install

# Rsync sysroot from pi
# Install all the build dependencies on the Pi before.
# You can repeat this command after you install/remove extra packages on the pi.
rsync -rl --delete-after --safe-links pi@hostname.local:/{lib,usr} $SDKPATH/sysroot

# Need for pkg-config to correctly resolve dependencies.
cp arm-linux-gnueabihf-pkg-config $SDKPATH/prebuilt/bin

Cross GNURadio 3.8 (HEAD)

• IMPORTANT: gnuradio/gnuradio#2264 (add -pthread before -lrt)

cmake -DENABLE_INTERNAL_VOLK=OFF -DENABLE_GRC=OFF -DENABLE_PYTHON=OFF -DENABLE_GR_QTGUI=OFF \
        -DENABLE_GR_VOCODER=ON -DENABLE_GR_AUDIO=OFF -DENABLE_GR_WAVELET=OFF \
        -DENABLE_GR_DTV=OFF -DENABLE_DOXYGEN=OFF -DCMAKE_TOOLCHAIN_FILE=$SDKPATH/rbpi3.cmake ..

Cross Out-Of-Tree (OOT) module

# sometimes I have to run cmake twice, I get an error about GrTest the first time.
cmake -DENABLE_DOXYGEN=OFF -DENABLE_PYTHON=OFF -DCMAKE_TOOLCHAIN_FILE=$SDKPATH/rbpi3.cmake ..

On the Raspberry PI

Get the Clang for armhf here http://releases.llvm.org/download.html

# clang 7

cd /usr/local
tar xf ~/clang+llvm-7.0.0-armv7a-linux-gnueabihf.tar.xz

export PATH=/usr/local/clang+llvm-7.0.0-armv7a-linux-gnueabihf/bin:$PATH
export LD_LIBRARY_PATH=/usr/local/clang+llvm-7.0.0-armv7a-linux-gnueabihf/lib

# You might need to set LD_LIBRARY_PATH=/usr/local/lib if you are experimenting
# with multiple versions of libvolk and libfftw2
# ldd is your friend.

# careful to remember you did this if you need to build other stuff.
export CC=clang
export CXX=clang++

GNURadio

# Something like this...
cmake -DENABLE_INTERNAL_VOLK=OFF -DENABLE_GRC=OFF -DENABLE_PYTHON=OFF -DENABLE_GR_QTGUI=OFF \
        -DENABLE_GR_VOCODER=ON -DENABLE_GR_AUDIO=OFF -DENABLE_GR_WAVELET=OFF \
        -DENABLE_GR_DTV=OFF -DENABLE_DOXYGEN=OFF \
        -DCMAKE_C_FLAGS='-mcpu=cortex-a53 -march=armv7-a -mfpu=neon-fp-armv8 -mfloat-abi=hard' \
        -DCMAKE_TOOLCHAIN_FILE=$SDKPATH/rbpi3.cmake ..

make -j4 install

libvolk

git clone https://github.com/gnuradio/volk
cd volk
mkdir build
cd build

# remember to set CC and CXX
# on host
cmake -DCMAKE_ASM_FLAGS='-march=armv7-a' -DCMAKE_C_FLAGS='-march=armv7-a -mfpu=neon -mfloat-abi=hard' ..
make -j4 install

# cross
cmake -DCMAKE_ASM_FLAGS='-march=armv7-a' -DCMAKE_C_FLAGS='-march=armv7-a -mfpu=neon -mfloat-abi=hard' -DCMAKE_TOOLCHAIN_FILE=$SDKPATH/rbpi3.cmake ..

FFTW3 with neon

Why is my FFTW3 with neon slower than the raspbian one. Remember you can use export LD_LIBRARY_PATH=/usr/local to experiment with different versions.

# on host
CC=clang CXX=clang++ ./configure CFLAGS="-mcpu=cortex-a53 -march=armv7l -mfpu=neon-fp-armv8 -mfloat-abi=hard" --enable-float --enable-neon --enable-shared --enable-threads

# cross TODO