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The Open Earth Compiler

Development repository for the Open Earth Compiler. The compiler implements a stencil dialect and transformations that lower stencil programs to efficient GPU code.

Publication

A detailed discussion of the Open Earth Compiler can be found here:

Domain-Specific Multi-Level IR Rewriting for GPU

Build Instructions

This setup assumes that you have built LLVM and MLIR in $BUILD_DIR and installed them to $PREFIX. To build and launch the tests, run

mkdir build && cd build
cmake -G Ninja .. -DMLIR_DIR=$PREFIX/lib/cmake/mlir -DLLVM_EXTERNAL_LIT=$BUILD_DIR/bin/llvm-lit
cmake --build . --target check-oec-opt

The ROCM_BACKEND_ENABLED flag enables the support for AMDGPU targets. It requires an LLVM build including lld and we need to set the path to lld using the following flag:

-DLLD_DIR=$PREFIX/lib/cmake/lld

To build the documentation from the TableGen description of the dialect operations, run

cmake --build . --target mlir-doc

Note: Make sure to pass -DLLVM_INSTALL_UTILS=ON when building LLVM with CMake in order to install FileCheck to the chosen installation prefix.

LLVM Build Instructions

The repository depends on a build of LLVM including MLIR. The Open Earth Compiler build has been tested with LLVM commit e59d336e75f4 using the following configuration:

cmake -G Ninja ../llvm -DLLVM_BUILD_EXAMPLES=OFF -DLLVM_TARGETS_TO_BUILD="host;NVPTX;AMDGPU" -DCMAKE_INSTALL_PREFIX=<install_root> -DLLVM_ENABLE_PROJECTS='mlir;lld' -DLLVM_OPTIMIZED_TABLEGEN=ON -DLLVM_ENABLE_OCAMLDOC=OFF -DLLVM_ENABLE_BINDINGS=OFF -DLLVM_INSTALL_UTILS=ON -DCMAKE_LINKER=<path_to_lld> -DLLVM_PARALLEL_LINK_JOBS=2

Note: Apply all patches found in the patch folder using git apply:

git apply ../stencil-dialect/patches/runtime.patch

Compiling an Example Stencil Program

The following command lowers the laplace example stencil to NVIDIA GPU code:

oec-opt --stencil-shape-inference --convert-stencil-to-std --cse --parallel-loop-tiling='parallel-loop-tile-sizes=128,1,1' --canonicalize --test-gpu-greedy-parallel-loop-mapping --convert-parallel-loops-to-gpu --canonicalize --lower-affine --convert-scf-to-std --stencil-kernel-to-cubin ../test/Examples/laplace.mlir > laplace_lowered.mlir

NOTE: Use the command line flag --stencil-kernel-to-hsaco for AMD GPUs.

The tools mlir-translate and llc then convert the lowered code to an assembly file and/or object file:

mlir-translate --mlir-to-llvmir laplace_lowered.mlir > laplace.bc
llc -O3 laplace.bc -o laplace.s
clang -c laplace.s -o laplace.o

The generated object then exports the following method:

void _mlir_ciface_laplace(MemRefType3D *input, MemRefType3D *output);