[PATCH] D41812: [CVP] Replace incoming values from unreachable blocks with undef

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


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Comment at: llvm/trunk/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp:336
     // by a branch then do so now.
     ConstantFoldTerminator(BB);
 
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davide wrote:
> efriedma wrote:
> > This call invalidates the set of reachable blocks.
> hmmm, this is annoying.
> I can't think of an easy way of handling this case easily. Do you have something in your mind?
> If not, I'll revert the patch for now until I come up with a better idea.
> cc: @anna 
Maybe you could use an incrementally updated domtree to keep ReachableBlocks up-to-date?  Not sure how expensive that would be, though.

Alternatively, you could record dead edges, and postpone actually modifying the CFG until the end of the pass.  You lose a little optimization power that way, I guess, but it avoids any complicated incremental updates.


Repository:
  rL LLVM

https://reviews.llvm.org/D41812