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Only passes that preserve MemorySSA must mark it as preserved.

Authored by asbirlea on May 28 2019, 11:01 AM.



The method getLoopPassPreservedAnalyses should not mark MemorySSA as
preserved, because it's being called in a lot of passes that do not
preserve MemorySSA.
Instead, mark the MemorySSA analysis as preserved by each pass that does
preserve it.
These changes only affect the new pass mananger.

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asbirlea created this revision.May 28 2019, 11:01 AM
chandlerc accepted this revision.Jun 8 2019, 1:49 AM


Any chance you can add a test that shows one of the problems where verifying MemorySSA fails because we get a "preserved" copy after a loop pass that doesn't actually preserve it?

Fine to submit the patch whenever, and just try ta add a test case when its convenient.

This revision is now accepted and ready to land.Jun 8 2019, 1:49 AM
This revision was automatically updated to reflect the committed changes.

I wasn't yet able to reproduce this with opt -aa-pipeline=default -passes="default<O3>", only with clang -cc1 -O3 -fexperimental-new-pass-manager.
I'll keep working on getting a test, but I checked this in for now, since it's necessary to fix crashes for the combination of MemorySSA + NewPassManager.