[PATCH] D74574: [LoopRotate] Get and update MSSA only if available in legacy pass manager.

[Alina Sbirlea via Phabricator via llvm-commits]

asbirlea created this revision.
asbirlea added reviewers: dmgreen, fedor.sergeev, nikic.
Herald added subscribers: george.burgess.iv, hiraditya, Prazek.
Herald added a project: LLVM.

Potential fix for: https://bugs.llvm.org/show_bug.cgi?id=44889 and https://bugs.llvm.org/show_bug.cgi?id=44408

In the legacy pass manager, loop rotate need not compute MemorySSA when not being in the same loop pass manager with other loop passes.
There isn't currently a way to differentiate between the two cases, so this attempts to limit the usage in LoopRotate to only update MemorySSA when the analysis is already available.
The side-effect of this is that it will split the Loop pipeline.

This issue does not apply to the new pass manager, where we have a flag specifying if all loop passes in that loop pass manager preserve MemorySSA.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74574

Files:
  llvm/lib/Transforms/Scalar/LoopRotation.cpp
  llvm/test/Other/opt-O2-pipeline.ll
  llvm/test/Other/opt-O3-pipeline.ll
  llvm/test/Other/opt-Os-pipeline.ll
  llvm/test/Other/pass-pipelines.ll

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