[all-commits] [llvm/llvm-project] 52a401: [JT] Preserve exisiting BPI/BFI during JumpThreading

[ebrevnov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 52a4018506e39f50d0c06ac5a1c987eb83b900c7
      https://github.com/llvm/llvm-project/commit/52a4018506e39f50d0c06ac5a1c987eb83b900c7
  Author: Evgeniy Brevnov <ybrevnov at azul.com>
  Date:   2022-11-17 (Thu, 17 Nov 2022)

  Changed paths:
    M llvm/include/llvm/Transforms/Scalar/JumpThreading.h
    M llvm/lib/Transforms/Scalar/JumpThreading.cpp
    M llvm/test/Transforms/JumpThreading/thread-prob-2.ll
    M llvm/test/Transforms/JumpThreading/thread-prob-3.ll
    M llvm/test/Transforms/JumpThreading/thread-prob-4.ll
    M llvm/test/Transforms/JumpThreading/thread-prob-5.ll
    M llvm/test/Transforms/JumpThreading/thread-prob-6.ll
    M llvm/test/Transforms/JumpThreading/threading_prof1.ll
    M llvm/test/Transforms/JumpThreading/threading_prof2.ll
    M llvm/test/Transforms/JumpThreading/threading_prof3.ll

  Log Message:
  -----------
  [JT] Preserve exisiting BPI/BFI during JumpThreading

Currently, JT creates and updates local instances of BPI\BFI. As a result global ones have to be invalidated if JT made any changes.
In fact, JT doesn't use any information from BPI/BFI for the sake of the transformation itself. It only creates BPI/BFI to keep them up to date. But since it updates local copies (besides cases when it updates profile metadata) it just waste of time.

Current patch is a rework of D124439. D124439 makes one step and replaces local copies with global ones retrieved through AnalysisPassManager. Here we do one more step and don't create BPI/BFI if the only reason of creation is to keep BPI/BFI up to date. Overall logic is the following. If there is cached BPI/BFI then update it along the transformations. If there is no existing BPI/BFI, then create it only if it is required to update profile metadata.

Please note if BPI/BFI exists on exit from JT (either cached or created) it is always up to date and no reason to invalidate it.

Differential Revision: https://reviews.llvm.org/D136827