Structured Additive Intermediate Representation (Sair)

An intermediate program representation, based on MLIR and designed to express implementation decisions on a program without losing the high-level structure of the code. It encodes implementation choices as attributes added on to existing operations (hence "additive" in the name).

Coding Guidelines

Follow Google C++ Style Guide whenever possible. Note that MLIR uses LLVM style that is often incompatible with Google style; only use LLVM style for MLIR overrides or CRTP hooks.

Follow MLIR testing guide. In particular, IR attributes, types and operations should be tested using textual IR format via FileCheck. Non-IR components should be tested with unit tests.

Build Instructions

Prerequisites:

• C++ compiler supporting C++17;
• git, cmake, ninja (or make)

Instructions:

First, fetch LLVM repository from git.

cd <llvm-path>
git clone https://github.com/llvm/llvm-project
cd llvm-project

Checkout the latest version of LLVM compatible with Sair, as specified in LLVM_VERSION in the repository.

VERSION=`cat <sair-path>/LLVM_VERSION`
git checkout $VERSION

(If MLIR, LLVM and relevant headers are already installed, skip this step).

Configure and compile LLVM with MLIR project enabled by following MLIR instructions. Make sure to set up the installation path. The following is only given as example:

mkdir build
cd build
cmake ../llvm -DLLVM_ENABLE_PROJECTS='mlir' \
  -DLLVM_TARGETS_TO_BUILD='host;NVPTX;AMDGPU' \
  -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_ENABLE_ASSERTIONS=On \
  -DLLVM_INCLUDE_Utils=On \
  -DCMAKE_INSTALL_PREFIX=<mlir-prefix> \
  -G Ninja  # Omit for "make" build.
ninja install -j <num_procs>  # make install -j <num_procs>

With MLIR installed, configure Sair.

cd <sair-path>
mkdir build
cd build
cmake .. \
  -DCMAKE_PREFIX_PATH=<mlir-prefix> \
  -DLLVM_EXTERNAL_LIT=<path-to-lit> \
  -G Ninja  # Omit for "make" build.

The LLVM_EXTERNAL_LIT line is necessary to configure LLVM's testing infrastructure to run Sair tests and can be omitted if one does not intend to run Sair tests. llvm-lit is often provided by system packages, or is available in the build path of LLVM since it is intended for use at build time. Therefore, <path-to-lit> can point to the system installation of llvm-lit, if any, or to <llvm-path>/build/bin/llvm-lit if LLVM was built from source.

One can now build and test Sair.

# To compile, run:
ninja sair-opt -j <num_procs>  # make sair-opt

# To check test (if Lit was configured), run:
ninja check-sair -j <num_procs>  # make check-sair

The compilation produces a single standalone statically-linked binary sair-opt that can be moved.