You will need p4fpga and p4c repository
git clone https://github.com/hanw/p4fpga.git
git clone https://github.com/p4lang/p4c.git
Create a soft-link to p4fpga source code in p4c
ln -s <path-to-p4fpga>/compiler extensions/p4fpga
Run bootstrap.sh in p4c
cd p4c
git submodule init
git submodule update
./bootstrap.sh
Build p4c with p4fpga backend
cd build
make -j8