[all-commits] [llvm/llvm-project] cf976b: [LoopInterchange] Add tests for the vectorization ...

[Ryotaro Kasuga via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: cf976bfdeba21405e1674c6dd09940773b2275ef
      https://github.com/llvm/llvm-project/commit/cf976bfdeba21405e1674c6dd09940773b2275ef
  Author: Ryotaro Kasuga <kasuga.ryotaro at fujitsu.com>
  Date:   2025-04-02 (Wed, 02 Apr 2025)

  Changed paths:
    A llvm/test/Transforms/LoopInterchange/profitability-vectorization-heuristic.ll

  Log Message:
  -----------
  [LoopInterchange] Add tests for the vectorization profitability (NFC) (#133665)

There is a problem with the current profitability check for
vectorization in LoopInterchange. There are both false positives and
false negatives. The former means that the heuristic may say that "an
exchange is necessary to vectorize the innermost loop" even though it's
already possible. The latter means that the heuristic may miss a case
where an exchange is necessary to vectorize the innermost loop. Note
that this is not a dependency analysis problem. This is caused by
incorrect handling of the dependency matrix in the profitability check,
so these problems can occur even if the analysis is accurate (no
overestimation).

This patch adds tests to clarify the cases that should be fixed. The
root cause of these cases is that the heuristic doesn't handle the
direction of a dependency correctly.



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