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Andrzej Warzyński 541f33e075 [mlir][linalg] Prevent hoisting of transfer pairs in the presence of aliases (#145235 )

This patch adds additional checks to the hoisting logic to prevent hoisting of
`vector.transfer_read` / `vector.transfer_write` pairs when the underlying
memref has users that introduce aliases via operations implementing
`ViewLikeOpInterface`.

Note: This may conservatively block some valid hoisting opportunities and could
affect performance. However, as demonstrated by the included tests, the current
logic is too permissive and can lead to incorrect transformations.

If this change prevents hoisting in cases that are provably safe, please share
a minimal repro - I'm happy to explore ways to relax the check.

Special treatment is given to `memref.assume_alignment`, mainly to accommodate
recent updates in:

* https://github.com/llvm/llvm-project/pull/139521

Note that such special casing does not scale and should generally be avoided.
The current hoisting logic lacks robust alias analysis. While better support
would require more work, the broader semantics of `memref.assume_alignment`
remain somewhat unclear. It's possible this op may eventually be replaced with
the "alignment" attribute added in:

* https://github.com/llvm/llvm-project/pull/144344

2025-06-27 13:18:15 +01:00