[PATCH] D34823: [PredicateInfo] Invalidate an OrderedBasicBlock when instruction in it is deleted.

[Xin Tong via Phabricator via llvm-commits]

trentxintong added a comment.

In https://reviews.llvm.org/D34823#795758, @dberlin wrote:

> Without a reason to do this specifically, it seems a waste of time
>
> None of this data is used after initial building, and all of these are destroyed after newgvn ends, so updating them doesn't seem to accomplish anything?


I was making the Instruction * in OrdereBasicBlock AssertingVH to make sure things are updated properly when instructions are deleted. If they are not, we are essentially holding a dangling pointer which could in worst case result in invalid dominance relationship being returned. Then i found NewGVN is breaking the rule, i.e. erasing an instruction without updating OrderedBasicBlock in OrderedInstruction.

I agree the way NewGVN is written now is ok even without updating the OrderedBasicBlock. Maybe we should not make Instruction * in OBB AssertingVH. Instead should give user the freedom to invalidate if necessary.


https://reviews.llvm.org/D34823