[PATCH] D101553: [Loads] Ignore type test assume sequences inserted for devirtualization

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

Not a big fan of this -- this is effectively whitelisting a specific pattern, and doesn't generalize.

For this code, there are two limits of interest: The total number of instructions we look at, and the number of alias-analysis queries we perform. Currently we limit both through a small number of total instructions. However, the only expensive part, and what needs to be aggressively limited, is the number of alias analysis queries.

I think what we can do here is to have a relatively liberal upper limit on the number of scanned instructions (say 32), while having a tight limit on the number of AA queries or AA query candidates (say 4). This should make the code more resilient against additional bitcast/assume instructions in between, while still limiting compile-time impact.

Do you think something along those lines would address your motivation here?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D101553/new/

https://reviews.llvm.org/D101553