[PATCH] D68298: [GlobalOpt] Pass DTU to removeUnreachableBlocks instead of recomputing.

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

I suspect that this change caused a major compile-time performance regression in GlobalOpt. Doesn't this essentially break the laziness of `LookupDomTree()` and force DT construction even if it will not be needed?

As the `removeUnreachableBlocks()` call is (presumably) expected to never actually do something outside of manually constructed IR examples, this seems like a bad tradeoff. Ideally we would only fetch the DT here if it exists, but threading that through is likely not worthwhile.


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https://reviews.llvm.org/D68298