TheRock/compiler/amd-llvm/mlir/docs/ReleaseNotes.md

MLIR Release Notes

This document tries to provide some context about MLIR important changes in the context of LLVM releases. It is updated on a best effort basis.

At the moment the MLIR community does not qualify the LLVM release branch specifically, it is a snapshot of the MLIR development at the time of the release.

[TOC]

LLVM 21

GPU/NVVM Changes

• The default NVVM target architecture has been changed from sm_50 to sm_75. sm_75 is the oldest GPU variant compatible with the widest range of recent major CUDA Toolkit versions (11/12/13). This affects the NVVMTargetAttr, GpuNVVMAttachTarget pass, and the gpu-lower-to-nvvm-pipeline.

LLVM 20

All the MLIR runners other than mlir-cpu-runner have been removed, as their functionality has been merged into it, and it has been renamed to mlir-runner.

LLVM 18

Properties: beyond attributes

See LLVM 17 notes below. The Dialect option let usePropertiesForAttributes = 1; is now the default. You can set it to 0 to revert to the previous behavior. This will be removed in LLVM 19.

LLVM 17

See also the deprecations and refactoring doc.

Bytecode

MLIR now support a bytecode serialization with versionning compatibility allowing 2 ways compatibility scheme, and lazy-loading capabilities.

Properties: beyond attributes

This is a new mechanism to implement storage for operations without having to use attributes. You can opt-in to use Properties for ODS inherent attributes using let usePropertiesForAttributes = 1; in your dialect definition (the flag will be default in the next release). See slides and recording of the open meeting presentation for details.

Action: Tracing and Debugging MLIR-based Compilers

Action is a new mechanism to encapsulate any transformation of any granularity in a way that can be intercepted by the framework for debugging or tracing purposes, including skipping a transformation programmatically (think about “compiler fuel” or “debug counters” in LLVM). As such, “executing a pass” is an Action, so is “try to apply one canonicalization pattern”, or “tile this loop”.

slides and recording of the open meeting presentation for details.

Transform Dialect

See this EuroLLVM talk and the online tutorial.

Others

• There is now support for "distinct attributes".
• "Resources" (a way to store data outside the MLIR context) and "configuration" can now be serialized alongside the IR.