[all-commits] [llvm/llvm-project] f39409: [SLP] Scale extract cost of external uses with nul...

[Alexey Bataev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f394094f195b3d593336aab6b76ccd2b7b483e43
      https://github.com/llvm/llvm-project/commit/f394094f195b3d593336aab6b76ccd2b7b483e43
  Author: Alexey Bataev <a.bataev at outlook.com>
  Date:   2026-06-02 (Tue, 02 Jun 2026)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    M llvm/test/Transforms/SLPVectorizer/ARM/extract-cost-scale-nullptr-user.ll

  Log Message:
  -----------
  [SLP] Scale extract cost of external uses with nullptr user

The NCD pre-pass from #199962 only records extract blocks for external
uses that have a real user, so uses with a nullptr user were left
unscaled, making the loop in the report look profitable and get wrongly
vectorized. For a nullptr user vectorizeTree() places the extract right
after the vectorized instruction (entry block) and RAUWs the scalar, so
scale those extracts by the entry block frequency, restoring the
pre-#199962 behavior for that case.

Reviewers: 

Pull Request: https://github.com/llvm/llvm-project/pull/201193



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