[PATCH] D70376: [LVI] Restructure caching

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

Unfortunately there is an additional complication here. Apparently the separate per-block storage of overdefined values is not just there to reduce memory usage, it is also necessary for the implementation of threadEdgeImpl: https://github.com/llvm/llvm-project/blob/8f183d9f3d13d66a679bd449b1f5d34942560028/llvm/lib/Analysis/LazyValueInfo.cpp#L264

This code needs to know which values are cached as overdefined for a given block, which would be highly inefficient (scan over all values) if we don't key by block first.

I'm not sure whether the threadEdgeImpl code can be dropped -- no tests fail if I do, but it's not like the commit that introduced this (https://github.com/llvm/llvm-project/commit/aa7f66ba6798ea946baa622b55679597dab60742) had any tests either...

Ideally we'd switch LVI to be based on PredicateInfo and thus avoid the need to track data per-block in the first place. Of course, this is not simple to do.


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https://reviews.llvm.org/D70376