Fidelity MLIR Plugins

MLIR pass plugins for the Fidelity Framework. These plugins extend the MLIR lowering pipeline with transformations required by the Fidelity compilation model.

Each plugin is a shared library loaded via mlir-opt --load-pass-plugin=<plugin>.so.

Plugins

Plugin	Pass	Purpose
flat-closure-lowering	--resolve-closure-casts	Resolve closure-related type casts during LLVM lowering

Building

Requires MLIR/LLVM development headers (tested with LLVM 21).

cmake -B build -G Ninja
cmake --build build

The built plugins are placed in build/flat-closure-lowering/.

Usage

mlir-opt input.mlir \
  --load-pass-plugin=build/flat-closure-lowering/flat-closure-lowering.so \
  --resolve-closure-casts

Architecture

These plugins operate exclusively in the BackEnd of the Composer compilation pipeline. The MiddleEnd (Alex) emits target-agnostic MLIR using standard dialects. Plugins bridge the semantic gap between that representation and target-specific lowering requirements.

Plugins do not modify or depend on the MiddleEnd. They are loaded by the BackEnd's mlir-opt invocation at the appropriate pipeline position.

Known Issues

Arch Linux: MLIR cmake version mismatch

On Arch Linux, the mlir package may ship an MLIRConfig.cmake that hardcodes a stale LLVM version (e.g. 21.1.6 when LLVM 21.1.8 is installed). This causes cmake to fail with a version mismatch when MLIRConfig.cmake calls find_package(LLVM 21.1.6) against a newer LLVM.

Diagnosis: The error will mention an LLVM version that doesn't match your installed version:

Could not find a configuration file for package "LLVM" that is compatible
with requested version "21.1.6".

Fix: Correct the hardcoded version in MLIRConfig.cmake:

sudo sed -i 's/set(LLVM_VERSION 21.1.6)/set(LLVM_VERSION 21.1.8)/' /usr/lib/cmake/mlir/MLIRConfig.cmake

Adjust the version strings to match your actual installed LLVM version (llvm-config --version). This is a packaging bug — the MLIR and LLVM packages should agree on the version string.

License

Apache License 2.0