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

[Davide Italiano via llvm-commits]

I'm currently not at a workstation where I have llvm checked out, can
somebody please revert this on my behalf?

Thanks,

--
Davide

On Tue, Jan 23, 2018 at 1:02 PM, Eli Friedman via Phabricator via
llvm-commits <llvm-commits at lists.llvm.org> wrote:
> efriedma added inline comments.
>
>
> ================
> Comment at: llvm/trunk/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp:336
>      // by a branch then do so now.
>      ConstantFoldTerminator(BB);
>
> ----------------
> 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
>
>
>
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-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare