[all-commits] [llvm/llvm-project] 0afd10: [LoopPassManager] Assert that MemorySSA is preserv...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0afd10b4030dcca36c85f24942be8ea860df8d9e
      https://github.com/llvm/llvm-project/commit/0afd10b4030dcca36c85f24942be8ea860df8d9e
  Author: Nikita Popov <nikita.ppv at gmail.com>
  Date:   2021-08-20 (Fri, 20 Aug 2021)

  Changed paths:
    M llvm/lib/Transforms/Scalar/LoopPassManager.cpp
    A llvm/test/Other/loop-mssa-not-preserved.ll

  Log Message:
  -----------
  [LoopPassManager] Assert that MemorySSA is preserved if used

Currently it's possible to silently use a loop pass that does not
preserve MemorySSA in a loop-mssa pass manager, as we don't
statically know which loop passes preserve MemorySSA (as was the
case with the legacy pass manager).

However, we can at least add a check after the fact that if
MemorySSA is used, then it should also have been preserved.
Hopefully this will reduce confusion as seen in
https://bugs.llvm.org/show_bug.cgi?id=51020.

Differential Revision: https://reviews.llvm.org/D108399