[all-commits] [llvm/llvm-project] be1a23: Return "[LoopDeletion] Break backedge if we can pr...

[max-azul via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: be1a23203b1de655b8c7dac7549818d975a0cbbf
      https://github.com/llvm/llvm-project/commit/be1a23203b1de655b8c7dac7549818d975a0cbbf
  Author: Max Kazantsev <mkazantsev at azul.com>
  Date:   2021-05-26 (Wed, 26 May 2021)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LoopDeletion.cpp
    M llvm/test/Transforms/LoopDeletion/eval_first_iteration.ll
    M llvm/test/Transforms/LoopDeletion/zero-btc.ll

  Log Message:
  -----------
  Return "[LoopDeletion] Break backedge if we can prove that the loop is exited on 1st iteration" (try 2)

The patch was reverted due to compile time impact of contextual SCEV
queries. It also appeared that it introduced a miscompile on irreducible CFG.

Changes made:
1. isKnownPredicateAt is replaced with more lightweight isKnownPredicate;
2. Irreducible CFG in live code is now detected and excluded from processing.

Differential Revision: https://reviews.llvm.org/D102615