[PATCH] D40480: MemorySSA backed Dead Store Elimination.

[Florian Hahn via Phabricator via llvm-commits]

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Hi!

I would be interested giving dead store elimination using MemorySSA another push. We've hit plenty DSE limitations especially together with `-ftrivial-auto-var-init` and I think modernizing DSE to use MemorySSA will help us to improve the situation.

@rnk, @dmgreen are you still interested in pushing for DSE + MSSA? Otherwise I would be happy to look into that. I think this patch is a great foundation and I think it be possible to break it up into a few distinct parts, starting with just replacing completely overwritten stores and adding additional cases as follow ups. I also have a few potential simplifications in mind I'd like to try. I rebased the patch and I tried to build SPEC2006/MultiSource tests, but it does not get very far without crashing. Again, my main goal would be to break it up into more manageable pieces :)

Looking a bit further ahead, I'd also like to lift the post-domination requirement for cases where we can prove that an overriding store on all paths to the exit/other reads.

Please let me know what you think!


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