[all-commits] [llvm/llvm-project] a8dab1: [AArch64] Add a subvector extract cost. (#121472)

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a8dab1aa036f248d551f7839360eb03fac4b7d96
      https://github.com/llvm/llvm-project/commit/a8dab1aa036f248d551f7839360eb03fac4b7d96
  Author: David Green <david.green at arm.com>
  Date:   2025-01-08 (Wed, 08 Jan 2025)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
    M llvm/test/Analysis/CostModel/AArch64/shuffle-extract.ll
    M llvm/test/Transforms/SLPVectorizer/AArch64/reduce-fadd.ll

  Log Message:
  -----------
  [AArch64] Add a subvector extract cost. (#121472)

These can generally be emitted using an ext instruction or mov from the
high half. The half half extracts can be free depending on the users,
but that is not handled here, just the basic costs. It originally
included all subvector extracts, but that was toned-down to just
half-vector extracts to try and help the mid end not breakup high/low
extracts without having the SLP vectorizer create a mess using other
shuffles.



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