[all-commits] [llvm/llvm-project] c63125: [mlir] Fix block merging (#97697)

[Giuseppe Rossini via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c63125d4533a22a200c3b5b1efb8ac3ce4b1cb69
      https://github.com/llvm/llvm-project/commit/c63125d4533a22a200c3b5b1efb8ac3ce4b1cb69
  Author: Giuseppe Rossini <giuseppe.rossini at amd.com>
  Date:   2024-07-17 (Wed, 17 Jul 2024)

  Changed paths:
    M mlir/lib/Dialect/Bufferization/Transforms/BufferDeallocationSimplification.cpp
    M mlir/lib/Transforms/Utils/RegionUtils.cpp
    M mlir/test/Dialect/Bufferization/Transforms/OwnershipBasedBufferDeallocation/dealloc-branchop-interface.mlir
    M mlir/test/Dialect/Linalg/detensorize_entry_block.mlir
    M mlir/test/Dialect/Linalg/detensorize_if.mlir
    M mlir/test/Dialect/Linalg/detensorize_while.mlir
    M mlir/test/Dialect/Linalg/detensorize_while_impure_cf.mlir
    M mlir/test/Dialect/Linalg/detensorize_while_pure_cf.mlir
    M mlir/test/Transforms/canonicalize-block-merge.mlir
    M mlir/test/Transforms/canonicalize-dce.mlir
    M mlir/test/Transforms/make-isolated-from-above.mlir
    A mlir/test/Transforms/test-canonicalize-merge-large-blocks.mlir

  Log Message:
  -----------
  [mlir] Fix block merging (#97697)

With this PR I am trying to address:
https://github.com/llvm/llvm-project/issues/63230.

What changed:
- While merging identical blocks, don't add a block argument if it is
"identical" to another block argument. I.e., if the two block arguments
refer to the same `Value`. The operations operands in the block will
point to the argument we already inserted. This needs to happen to all
the arguments we pass to the different successors of the parent block
- After merged the blocks, get rid of "unnecessary" arguments. I.e., if
all the predecessors pass the same block argument, there is no need to
pass it as an argument.
- This last simplification clashed with
`BufferDeallocationSimplification`. The reason, I think, is that the two
simplifications are clashing. I.e., `BufferDeallocationSimplification`
contains an analysis based on the block structure. If we simplify the
block structure (by merging and/or dropping block arguments) the
analysis is invalid . The solution I found is to do a more prudent
simplification when running that pass.

**Note**: this a rework of #96871 . I ran all the integration tests
(`-DMLIR_INCLUDE_INTEGRATION_TESTS=ON`) and they passed.



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