[PATCH] D120033: [SCEV] Fully invalidate SCEVUnknown on RAUW

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

In D120033#3329890 <https://reviews.llvm.org/D120033#3329890>, @reames wrote:

> I don't think is quite right.  We can have SCEV forget all of it's memoized results, but we can't disallow a client hanging onto an expression containing a SCEVUnknown over a RAUW.  Given that, I think we need to explicitly forget, but keep the bit about changing the value pointer to the new value.

This is making the behavior the same as for erasing the value, so clients already need to deal with SCEVUnknown holding onto a nullptr (if they both cache it and inspect it that deeply).

Though I don't mind keeping the `setValPtr(New)`, that seems harmless.


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  https://reviews.llvm.org/D120033/new/

https://reviews.llvm.org/D120033