[PATCH] D101553: [Loads] Ignore type test assume sequences inserted for devirtualization
Nikita Popov via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 29 13:04:16 PDT 2021
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?
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https://reviews.llvm.org/D101553/new/
https://reviews.llvm.org/D101553
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