OliverScherf / mlir-emitc

MLIR EmitC dialect

MLIR EmitC

EmitC is a MLIR dialect to emit C++ code. The initial checked in code is forked from https://reviews.llvm.org/D76571.

DISCLAIMER: This is a research project and not intended for everyday use. The code is made available without any support. However, we welcome any kind of feedback via the issue tracker.

EmitC enables to convert operations from other MLIR dialects to EmitC ops and to translate those to C++.

Getting Started

Clone

git clone https://github.com/iml130/mlir-emitc.git
cd mlir-emitc
git submodule update --init

Build and Run

The setup assumes that you have built LLVM and MLIR in $BUILD_DIR and installed them to $PREFIX. You can use the build_tools/build_mlir.sh shell script to configure, build and install LLVM and MLIR.

Note: The hash of the latest tested LLVM version is given in build_tools/llvm_version.txt. Since MLIR evolves fast, it is possible that EmitC fails to build with a newer LLVM.

To build and launch the tests, run

mkdir build && cd build
cmake -G Ninja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ .. -DMLIR_DIR=$PREFIX/lib/cmake/mlir -DLLVM_EXTERNAL_LIT=$BUILD_DIR/bin/llvm-lit
cmake --build . --target check-emitc

Note: If you don't use build_tools/build_mlir.sh, make sure to pass -DLLVM_INSTALL_UTILS=ON when building LLVM with CMake in order to install FileCheck to the chosen installation prefix.

To additionally build and execute the unittests, run

cmake --build . --target MLIREmitCAllTests
./unittests/MLIREmitCAllTests

Supported Conversions and Translations

Conversions are supported for MLIR-HLO ops and some ops of the standard and SCF dialect. In addition, support for converting Tensor Operator Set Architecture (TOSA) dialect to EmitC is emerging. The emitc-opt tool enables conversions via the following options:

option
--convert-mhlo-region-ops-to-emitc	Convert MHLO operations containing regions to EmitC dialect.
--convert-mhlo-to-emitc	Convert from MHLO dialect to EmitC dialect.
--convert-std-to-emitc	Convert std dialect to EmitC dialect, replacing IndexCastOp and SplatOp.
--convert-tensor-to-emitc	Convert tensor dialect to EmitC dialect, replacing ExtractOp.
--convert-tosa-to-emitc	Convert TOSA dialect to EmitC dialect.

The currently supported MHLO ops are listed in the docs/mhlo-op-coverage.md document. Supported TOSA ops are listed in the docs/tosa-op-coverage.md document.

After converting to EmitC dialect, C++ code can be emitted using emitc-translate --mlir-to-cpp. For a restricted set of operations C code can be emitted using emitc-translate --mlir-to-c. Furthermore, emitc-translate has specific support for the option --forward-declare-variables.