[all-commits] [llvm/llvm-project] 7aa22f: [mlir][gpu] Add 'cluster_size' attribute to gpu.su...

[Andrea Faulds via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7aa22f013e24d20291aad745368ff907baa9dfa4
      https://github.com/llvm/llvm-project/commit/7aa22f013e24d20291aad745368ff907baa9dfa4
  Author: Andrea Faulds <andrea.faulds at amd.com>
  Date:   2024-08-20 (Tue, 20 Aug 2024)

  Changed paths:
    M mlir/include/mlir/Dialect/GPU/IR/GPUOps.td
    M mlir/lib/Conversion/GPUToNVVM/LowerGpuOpsToNVVMOps.cpp
    M mlir/lib/Conversion/GPUToSPIRV/GPUToSPIRV.cpp
    M mlir/lib/Dialect/GPU/IR/GPUDialect.cpp
    M mlir/lib/Dialect/GPU/Transforms/SubgroupReduceLowering.cpp
    M mlir/test/Dialect/GPU/canonicalize.mlir
    M mlir/test/Dialect/GPU/invalid.mlir
    M mlir/test/Dialect/GPU/subgroup-reduce-lowering.mlir

  Log Message:
  -----------
  [mlir][gpu] Add 'cluster_size' attribute to gpu.subgroup_reduce (#104851)

This enables performing several reductions in parallel, each smaller
than the size of the subgroup.

One potential application is flash attention with subgroup-wide matrix
multiplication and reduction combined in one kernel. The multiplication
operation requires a 2D matrix to be distributed over the lanes of the
subgroup, which then constrains the shape the following reduction can
have if we want to keep data in registers.



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