[all-commits] [llvm/llvm-project] 765a5d: [X86] Pre-SSE42 v2i64 sgt lowering - check if repr...

[Simon Pilgrim via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 765a5d62bc59971d267a9effee2bfc0cee036182
      https://github.com/llvm/llvm-project/commit/765a5d62bc59971d267a9effee2bfc0cee036182
  Author: Simon Pilgrim <RKSimon at users.noreply.github.com>
  Date:   2024-03-01 (Fri, 01 Mar 2024)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelLowering.cpp
    M llvm/test/CodeGen/X86/vector-popcnt-128-ult-ugt.ll

  Log Message:
  -----------
  [X86] Pre-SSE42 v2i64 sgt lowering - check if representable as v2i32 (#83560)

Without PCMPGTQ, if the i64 elements are sign-extended enough to be representable as i32 then we can compare the lower i32 bits with PCMPGTD and splat the results into the upper elements.

Value tracking has meant we already get pretty close with this, but this allows us to remove a lot of unnecessary bit flipping.



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