[all-commits] [llvm/llvm-project] bf34b2: [profcheck] Add heuristical profile metadata for l...

[Jin Huang via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bf34b2e2df2ec55483ee678fc7c5c0fbfda35e98
      https://github.com/llvm/llvm-project/commit/bf34b2e2df2ec55483ee678fc7c5c0fbfda35e98
  Author: Jin Huang <jinhuang1102 at gmail.com>
  Date:   2025-10-08 (Wed, 08 Oct 2025)

  Changed paths:
    M llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
    M llvm/test/Transforms/AggressiveInstCombine/lower-table-based-cttz-basics.ll
    M llvm/test/Transforms/AggressiveInstCombine/lower-table-based-cttz-dereferencing-pointer.ll
    M llvm/test/Transforms/AggressiveInstCombine/lower-table-based-cttz-non-argument-value.ll
    M llvm/test/Transforms/AggressiveInstCombine/lower-table-based-cttz-zero-element.ll

  Log Message:
  -----------
  [profcheck] Add heuristical profile metadata for lowering table-based cttz. (#161898)

When lowering a `table-based cttz` calculation to the `llvm.cttz`
intrinsic, `AggressiveInstCombine` was not attaching profile metadata to
the newly generated `select` instruction.

This PR adds heuristic branch weights to the `select`. It uses a strong
100-to-1 probability favoring the `cttz` path over the zero-input case.
This allows later passes to optimize code layout and branch prediction.



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