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

[Florian Hahn via Phabricator via llvm-commits]

fhahn added a comment.

This workaround seems fine. I don't think there should be much interaction between LoopRotate and LICM/LoopUnswitch and running LoopRotate on all loops first should not really pessimism optimisations.



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Comment at: llvm/lib/Transforms/Scalar/LoopRotation.cpp:84
     AU.addRequired<TargetTransformInfoWrapperPass>();
-    if (EnableMSSALoopDependency) {
-      AU.addRequired<MemorySSAWrapperPass>();
+    if (EnableMSSALoopDependency)
       AU.addPreserved<MemorySSAWrapperPass>();
----------------
I think it would be good to add a comment that this will split the loop pipeline, to delay computing MemorySSA/skipping relatively costly updates?




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