[all-commits] [llvm/llvm-project] 5e77e2: [SLP]Treat 2-element FP reductions as always assoc...

[Alexey Bataev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5e77e2f8bc888b40753e5add3fa1bcf6e50d9b60
      https://github.com/llvm/llvm-project/commit/5e77e2f8bc888b40753e5add3fa1bcf6e50d9b60
  Author: Alexey Bataev <a.bataev at outlook.com>
  Date:   2026-09-11 (Fri, 11 Sep 2026)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    M llvm/test/Transforms/PhaseOrdering/X86/vector-reductions-logical.ll
    M llvm/test/Transforms/SLPVectorizer/AArch64/fmuladd-absorbed-copyable-sched-deps.ll
    M llvm/test/Transforms/SLPVectorizer/AArch64/lcssa-phi-extract-scale.ll
    M llvm/test/Transforms/SLPVectorizer/AArch64/reduce-fadd.ll
    M llvm/test/Transforms/SLPVectorizer/AArch64/vec3-reorder-reshuffle.ll
    M llvm/test/Transforms/SLPVectorizer/X86/crash_cmpop.ll
    M llvm/test/Transforms/SLPVectorizer/X86/dot-product.ll
    M llvm/test/Transforms/SLPVectorizer/X86/lookahead.ll
    M llvm/test/Transforms/SLPVectorizer/X86/phi-removed-on-operand-vectorization.ll
    M llvm/test/Transforms/SLPVectorizer/consecutive-access.ll
    M llvm/test/Transforms/SLPVectorizer/extractelement-insertpoint.ll

  Log Message:
  -----------
  [SLP]Treat 2-element FP reductions as always associative

A reduction of exactly 2 elements is a single operation, so no
reassociation is possible and the associativity check is not needed.
Emit vector.reduce.fadd/fmul with the reassoc flag for such
reductions even when the scalar operation lacks it, instead of
2 extracts + scalar operation.

Reviewers: bababuck, MrSidims

Pull Request: https://github.com/llvm/llvm-project/pull/222715



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