Halide language experiments on RISC-V

This repository contains a number of examples written in Halide language which work on RISC-V CPU with RVV 0.7.1. Follow the steps below to reproduce the experiments or some of their parts.

NOTE: At this moment project relies on the Ahead-Of-Time (AOT) compilation of Halide kernels. However there are precompiled files for easy start.

Project uses OpenCV as a reference implementation for some algorithms. Also, we benchmark it to compare with Halide implemention. Fetch OpenCV source code by submodules update after clonning the repository.

git submodule update --init

Build and go

1. Download THead toolchain: Xuantie-900-gcc-linux-5.10.4-glibc-x86_64-V2.6.1-20220906.tar.gz (registration needed)

2. Clone Halide source code (no build required)

   git clone --depth 1 https://github.com/halide/Halide

3. Build a project for RISC-V CPU:

   export PATH=$HOME/Xuantie-900-gcc-linux-5.10.4-glibc-x86_64-V2.6.1/bin/:$PATH
   
   cmake \
       -DCMAKE_BUILD_TYPE=Release \
       -DCMAKE_TOOLCHAIN_FILE=$HOME/halide_riscv/riscv64-071.toolchain.cmake \
       -DHalide_INCLUDE_DIRS=$HOME/Halide/src/runtime \
       -S halide_riscv -B build_rv64
   
   cmake --build build_rv64 -j$(nproc --all)

4. Transfer build directory to the RISC-V board and run test_algo (accuracy tests) or perf_algo (performance tests).

   scp test_algo perf_algo libalgos.so opencv-prefix/src/opencv-build/lib/* sipeed@x.x.x.x:/home/sipeed/

   export LD_LIBRARY_PATH=./
   ./test_algo
   ./perf_algo

Performance results

HW: Sipeed Lichee RV Dock (Allwinner D1 aka XuanTie C906 CPU)

OS: 20211230_LicheeRV_debian_d1_hdmi_8723ds

BGR2Gray input: 1080x1920	Median time
Reference (interleaved)	37.80ms
OpenCV (interleaved), no RVV	32.18ms
Halide (interleaved)	30.78ms
Halide (planar)	6.65ms

Box filter input: 1080x1920 output: 1078x1918	Median time
OpenCV, no RVV	75.17ms
Halide	62.89ms

Histogram input: 1080x1920x3 output: 256x3	Median time
Reference	72.06ms
OpenCV, no RVV	57.35ms
Halide	92.44ms

Convolution FP32 input: 1x16x128x128 kernel: 32x16x3x3	Layout	Median time
OpenCV, no RVV	NCHW	829.13ms
Halide	NCHW	698.27ms
Halide	NHWC	418.95ms

Generate AOT kernels

If you want regenerate AOT artifacts or add new algorithms, build the project on x86:

1. Build LLVM from https://github.com/dkurt/llvm-rvv-071/tree/rvv-071

   cmake -DCMAKE_BUILD_TYPE=Release \
     -DLLVM_ENABLE_PROJECTS="clang;lld" \
     -DLLVM_TARGETS_TO_BUILD="RISCV" \
     -DLLVM_ENABLE_TERMINFO=OFF -DLLVM_ENABLE_ASSERTIONS=ON \
     -DLLVM_ENABLE_EH=ON -DLLVM_ENABLE_RTTI=ON -DLLVM_BUILD_32_BITS=OFF \
     -GNinja \
     -S llvm-project/llvm -B llvm-build
   
   cmake --build llvm-build -j4

2. Build Halide with the following patch (tested on revision https://github.com/halide/Halide/commit/7963cd4e3c23856b82567c99e0a3d16035ffe895):

   diff --git a/src/CodeGen_RISCV.cpp b/src/CodeGen_RISCV.cpp
   index ba9abe04d..454558d11 100644
   --- a/src/CodeGen_RISCV.cpp
   +++ b/src/CodeGen_RISCV.cpp
   @@ -151,6 +151,7 @@ string CodeGen_RISCV::mattrs() const {
               arch_flags += ",+zvl" + std::to_string(target.vector_bits) + "b";
           }
   #endif
   +        arch_flags += ",-zve64x";
       }
       return arch_flags;
   }
   diff --git a/src/autoschedulers/CMakeLists.txt b/src/autoschedulers/CMakeLists.txt
   index 9b88f0a66..10088bb9b 100644
   --- a/src/autoschedulers/CMakeLists.txt
   +++ b/src/autoschedulers/CMakeLists.txt
   @@ -24,6 +24,6 @@ endfunction()
   
   add_subdirectory(common)
   
   -add_subdirectory(adams2019)
   +# add_subdirectory(adams2019)
   add_subdirectory(li2018)
   add_subdirectory(mullapudi2016)

   export LLVM_ROOT=$HOME/llvm-build
   
   cmake -DLLVM_DIR=$LLVM_ROOT/lib/cmake/llvm \
       -DClang_DIR=$LLVM_ROOT/lib/cmake/clang \
       -DCMAKE_BUILD_TYPE=Release \
       -DWITH_TESTS=OFF \
       -DWITH_TUTORIALS=OFF \
       -DWITH_PYTHON_BINDINGS=OFF \
       -S Halide -B halide-build
   
   cmake --build halide-build -j4
   cmake --install halide-build --prefix halide-install

3. Build a project on x86

   export LD_LIBRARY_PATH=$HOME/halide-build/src/autoschedulers/mullapudi2016:$LD_LIBRARY_PATH
   
   cmake \
       -DCMAKE_BUILD_TYPE=Release \
       -DHalide_DIR=$HOME/halide-install/lib/cmake/Halide \
       -S halide_riscv -B build
   
   cmake --build build -j$(nproc --all)

4. Run perf_algo once and find the generated *.h and *.s files in the working directory.