[all-commits] [llvm/llvm-project] 957952: [JumpThreading] Preserve profile metadata during s...

[Max Kazantsev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 957952dbf2f34ed552e8e1f8c35eed17eee2ea38
      https://github.com/llvm/llvm-project/commit/957952dbf2f34ed552e8e1f8c35eed17eee2ea38
  Author: Max Kazantsev <mkazantsev at azul.com>
  Date:   2023-01-09 (Mon, 09 Jan 2023)

  Changed paths:
    M llvm/lib/Transforms/Scalar/JumpThreading.cpp
    M llvm/test/Transforms/JumpThreading/select.ll

  Log Message:
  -----------
  [JumpThreading] Preserve profile metadata during select unfolding

Jump threading can replace select and unconditional branch with
conditional branch, but when doing so loses profile information.

This destructive transform can eventually lead to a performance
degradation due to folding of branches in
shouldFoldCondBranchesToCommonDestination as branch probabilities
are no longer known.

Patch by Roman Paukner!

Differential Revision: https://reviews.llvm.org/D138132
Reviewed By: mkazantsev