[all-commits] [llvm/llvm-project] 889c28: [SimplfyCFG] Set `MD_prof` for `select` used for c...

[Mircea Trofin via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 889c289a409eea443cc5eba54d68cc6a3161be07
      https://github.com/llvm/llvm-project/commit/889c289a409eea443cc5eba54d68cc6a3161be07
  Author: Mircea Trofin <mtrofin at google.com>
  Date:   2025-09-12 (Fri, 12 Sep 2025)

  Changed paths:
    M llvm/lib/Transforms/Utils/SimplifyCFG.cpp
    M llvm/test/Transforms/SimplifyCFG/branch-fold-threshold.ll
    M llvm/test/Transforms/SimplifyCFG/branch-fold.ll
    M llvm/test/Transforms/SimplifyCFG/preserve-branchweights.ll

  Log Message:
  -----------
  [SimplfyCFG] Set `MD_prof` for `select` used for certain conditional simplifications (#154426)

There’s a pattern where a branch is conditioned on a conjunction or disjunction that ends up being modeled as a `select`​ where the first operand is set to `true`​ or the second to `false`​. If the branch has known branch weights, they can be copied to the `select`​. This is worth doing in case later the `select`​ gets transformed to something else (i.e. if we know the profile, we should propagate it).

Issue #147390



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