[PATCH] D54827: [simplifycfg] Handle 3 sequential branches while the first two can infer the third one.

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

I've been looking at this:
rL347868 <https://reviews.llvm.org/rL347868>
rL347896 <https://reviews.llvm.org/rL347896>
rL348088 <https://reviews.llvm.org/rL348088>
...and I'm still not exactly sure how we should fix it, but I'm confident that what this patch is proposing is not the right answer. We don't want to create a dummy instruction only to analyze and delete it.
My best guess is that we can handle this case using a small enhancement to ValueTracking plus a minimal change to the callers in InstCombine and/or SimplifyCFG. These are hacks vs. a proper solution that uses a dominator tree and a more significant fix to CVP, but it's what we already do in both InstCombine and SimplifyCFG, so there's really no additional cost for optimizing simple cases like this.


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https://reviews.llvm.org/D54827