[all-commits] [llvm/llvm-project] 57aa7f: [X86] SimplifyDemandedVectorEltsForTargetNode - re...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 57aa7fa6ed64394ecd7d68fe34984b89778f319b
      https://github.com/llvm/llvm-project/commit/57aa7fa6ed64394ecd7d68fe34984b89778f319b
  Author: Simon Pilgrim <llvm-dev at redking.me.uk>
  Date:   2025-05-20 (Tue, 20 May 2025)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/and-or-setcc.ll
    M llvm/test/CodeGen/X86/extract-vselect-setcc.ll
    M llvm/test/CodeGen/X86/extractelement-fp.ll
    M llvm/test/CodeGen/X86/fcmp-logic.ll
    M llvm/test/CodeGen/X86/lzcnt-zext-cmp.ll
    M llvm/test/CodeGen/X86/pr40539.ll
    M llvm/test/CodeGen/X86/vector-reduce-fmax-nnan.ll
    M llvm/test/CodeGen/X86/vector-reduce-fmin-nnan.ll

  Log Message:
  -----------
  [X86] SimplifyDemandedVectorEltsForTargetNode - replace packed fcmp node with scalar fcmp node if only element0 is demanded (#140563)

These unnecessary vectorisation can appear due to fplogic opcodes only being available for 128-bit types - which can prevent folds that only work on the scalar source types and also lead to fcmp of garbage data in the upper elements.

Fixes #140534



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