[PATCH] D147020: [AA] Add a tbaa-fence intrinsic.

[David Goldblatt via Phabricator via llvm-commits]

davidtgoldblatt added a comment.

> I think we do need to settle the question of whether "new" also needs to call this fence... if it does, we need to measure the compile-time/performance impact on existing code, and if it doesn't, we'll likely end up with two overlapping solutions for very similar issues.

I'm happy to run some tests; any particular benchmark you'd like to see? llvm-test-suite doesn't really use placement-new (which I think is the only place where this would be needed?).

I think that two similar-ish solutions may actually be correct; there's a real semantic difference: after a placement new, any prior stores to the memory is dead, while after a tbaa_fence, they're not. So this will necessarily be an over-conservative solution to fix the placement-new/tbaa issues.


Repository:
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  https://reviews.llvm.org/D147020/new/

https://reviews.llvm.org/D147020