MLIR-EmitC

Warning

The code provided in this repository is no longer maintained and superseded by code available in upstream MLIR.

Note

We encourage to use upstream MLIR lowering passes instead of the TOSA and StableHLO to EmitC conversions provided here. Lowering via multiple dialects and hence using different abstraction levels, allows to reuse different optimization passes. Furthermore, the generated C and C++ code depends on the standard libraries without requiring additional header files, whereas code generated with the the conversions in this repositories requires a header-only reference implementation. For missing features, we highly encourage to consider extending the upstream dialect and conversions.

MLIR-EmitC provides a way to translate ML models into C++ code. The repository contains scripts and tools to translate Keras and TensorFlow models into the TOSA and StableHLO dialect and to convert those to EmitC. The latter is used to generate calls to a reference implementation.

The EmitC dialect itself, as well as the C++ emitter, are part of MLIR core and are no longer provided via this repository.

The initial EmitC dialect and C++ emitter checked into this repository were 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.

Getting Started

Clone

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

Build and Run

There are two variants to build EmitC: As part of an LLVM/MLIR build (via the LLVM external projects mechanism) and against a pre-built LLVM/MLIR.

Building with pre-built LLVM/MLIR

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 MLIREmitCTests
./reference-implementation/unittests/MLIREmitCTests

Bulding as part of an LLVM/MLIR build

MLIR-EmitC can also be built as part of an LLVM/MLIR build, using the LLVM_EXTERNAL_PROJECTS mechanism (see https://llvm.org/docs/CMake.html).

To build and launch the tests, run

mkdir build && cd build
cmake -G Ninja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_BUILD_TYPE=Release -DEMITC_ENABLE_HLO=OFF -DLLVM_ENABLE_PROJECTS=mlir -DLLVM_EXTERNAL_PROJECTS="mlir-emitc" -DLLVM_EXTERNAL_MLIR_EMITC_SOURCE_DIR=`realpath ../` -DLLVM_TARGETS_TO_BUILD=host ${ROOT_PATH_TO_llvm-project}/llvm
cmake --build . --target check-emitc

Supported Conversions and Translations

Conversions are supported for StableHLO ops and some ops of the arith and Tensor dialect. In addition, support for converting Tensor Operator Set Architecture (TOSA) dialect to EmitC is emerging. The emitc-opt tool supports the following options:

option
--convert-func-to-emitc	Convert Func dialect to EmitC dialect
--convert-scf-to-emitc	Convert SCF dialect to EmitC dialect, maintaining structured control flow
--convert-stablehlo-region-ops-to-emitc	Convert StableHLO operations containing regions to EmitC dialect.
--convert-stablehlo-to-emitc	Convert from StableHLO dialect to EmitC dialect.
--convert-arith-to-emitc-ext	Convert arith dialect to EmitC dialect (extended).
--convert-tensor-to-emitc	Convert tensor dialect to EmitC dialect.
--convert-tosa-to-emitc	Convert TOSA dialect to EmitC dialect.
--insert-emitc-stablehlo-include	Insert an EmitC include for the StableHLO dialect.
--insert-emitc-arith-include	Insert an EmitC include for the arith dialect.
--insert-emitc-tensor-include	Insert an EmitC include for the tensor dialect.
--insert-emitc-tosa-include	Insert an EmitC include for the TOSA dialect.
--stablehlo-to-emitc-pipeline	Run the StableHLO to EmitC pipeline.
--arith-to-emitc-pipeline	Run the Arithmetic to EmitC pipeline.
--tensor-to-emitc-pipeline	Run the Tensor to EmitC pipeline.
--tosa-to-emitc-pipeline	Run the TOSA to EmitC pipeline.

The currently supported StableHLO ops are listed in the docs/stablehlo-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. Furthermore, emitc-translate has specific support to emit code with variables declared at top using --mlir-to-cpp --declare-variables-at-top.