[all-commits] [llvm/llvm-project] 823098: [LoopSimplifyCFG] Prevent use-def dominance breach...

[Max Kazantsev via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 82309831c3ad922874221cfa47b7deda5607448e
      https://github.com/llvm/llvm-project/commit/82309831c3ad922874221cfa47b7deda5607448e
  Author: Max Kazantsev <mkazantsev at azul.com>
  Date:   2022-07-19 (Tue, 19 Jul 2022)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LoopSimplifyCFG.cpp
    M llvm/test/Transforms/LoopSimplifyCFG/pr56243.ll

  Log Message:
  -----------
  [LoopSimplifyCFG] Prevent use-def dominance breach by handling dead exits. PR56243

One of the transforms in LoopSimplifyCFG demands that the LCSSA form is
truly maintained for all values, tokens included, otherwise it may end up creating
a use that is not dominated by def (and Phi creation for tokens is impossible).
Detect this situation and prevent transform for it early.

Differential Revision: https://reviews.llvm.org/D129984
Reviewed By: efriedma