243f011577
Update MLIR's default SM to `sm_75`. This matches the behavior of offline compilation tools in the CUDA Toolkit (`nvcc`, `ptxas`, ...) and follows suit with 9fc5fd0ad689eed94f65b1d6d10f9c5642935e68. Additionally, `sm_75` is the oldest GPU variant compatible with the widest range of recent major CUDA Toolkit versions (11/12/13).
76 lines
2.9 KiB
Markdown
76 lines
2.9 KiB
Markdown
# MLIR Release Notes
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This document tries to provide some context about MLIR important changes in the
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context of LLVM releases. It is updated on a best effort basis.
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At the moment the MLIR community does not qualify the LLVM release branch
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specifically, it is a snapshot of the MLIR development at the time of the release.
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[TOC]
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## LLVM 21
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### GPU/NVVM Changes
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- The default NVVM target architecture has been changed from `sm_50` to `sm_75`.
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`sm_75` is the oldest GPU variant compatible with the widest range of recent
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major CUDA Toolkit versions (11/12/13). This affects the `NVVMTargetAttr`,
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`GpuNVVMAttachTarget` pass, and the `gpu-lower-to-nvvm-pipeline`.
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## LLVM 20
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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`.
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## LLVM 18
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### Properties: beyond attributes
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See LLVM 17 notes below. The Dialect option `let usePropertiesForAttributes = 1;` is
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now the default. You can set it to 0 to revert to the previous behavior. This will be
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removed in LLVM 19.
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## LLVM 17
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See also the [deprecations and refactoring](https://mlir.llvm.org/deprecation/) doc.
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### Bytecode
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MLIR now support a [bytecode serialization](https://mlir.llvm.org/docs/BytecodeFormat/)
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with versionning compatibility allowing 2 ways compatibility scheme, and lazy-loading
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capabilities.
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### Properties: beyond attributes
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This is a new mechanism to implement storage for operations without having to
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use attributes. You can opt-in to use Properties for ODS inherent attributes
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using `let usePropertiesForAttributes = 1;` in your dialect definition (the flag
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will be default in the next release). See
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[slides](https://mlir.llvm.org/OpenMeetings/2023-02-09-Properties.pdf) and
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[recording](https://youtu.be/7ofnlCFzlqg) of the open meeting presentation for
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details.
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### Action: Tracing and Debugging MLIR-based Compilers
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[Action](https://mlir.llvm.org/docs/ActionTracing/) is a new mechanism to
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encapsulate any transformation of any granularity in a way that can be
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intercepted by the framework for debugging or tracing purposes, including
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skipping a transformation programmatically (think about “compiler fuel” or
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“debug counters” in LLVM). As such, “executing a pass” is an Action, so is “try
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to apply one canonicalization pattern”, or “tile this loop”.
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[slides](https://mlir.llvm.org/OpenMeetings/2023-02-23-Actions.pdf) and
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[recording](https://youtu.be/ayQSyekVa3c) of the open meeting presentation for
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details.
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### Transform Dialect
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See this [EuroLLVM talk](https://www.youtube.com/watch?v=P4gUj3QtH_Y&t=1s) and
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[the online tutorial](https://mlir.llvm.org/docs/Tutorials/transform/).
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### Others
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- There is now support for
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"[distinct attributes](https://mlir.llvm.org/docs/Dialects/Builtin/#distinctattribute)".
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- "Resources" (a way to store data outside the MLIR context) and "configuration"
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can now be serialized alongside the IR.
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