[PATCH] D11143: [RFC] Cross Block DSE

[Daniel Berlin]

dberlin added a comment.

Sigh, my review got drafted before, but submitted after you wrote
this, so it looks like a reply to this part.

You are right that you could hoist this check, IFF alias returns
must/mayalias in cases where getmodrefinfo returns mod.

Is this really guaranteed to be the case?

They are different properties, though modrefinfo is often implemented
with help from alias. In our world of synchronization instructions,
isn't it possible for ordering to cause something to not be aliased
with a store (which is about the abstract memory locations) but still
be modified by it (due to it being a release or whatever) ?

Or do we consider this aliasing in the AA interface to try to avoid
user confusion? :)

I haven't looked deeply enough to know if we truly have consistency
here. I know getModRefInfo performs checks on ordering, etc, before it
calls alias(), and i assumed those checks were actually necessary.
But, you know, not a lot of unit tests here :)


http://reviews.llvm.org/D11143