[PATCH] D42381: [DA] Correct size parameter from dependency analysis to AA

[Hal Finkel via Phabricator via llvm-commits]

hfinkel added a comment.

In https://reviews.llvm.org/D42381#1061379, @dmgreen wrote:

> > Does the fallback add anything?
>
> We need to detect things like this as mustalias (to find the flow dependence), not mayalias (confused):
>
>   for (int i = 0; i < n; i++) {
>     A[i + 2] = i;
>     ... = A[i];
>   
>
> Unless you mean just do the alias analysis like this:?
>
>   return AA->alias(GetUnderlyingObject(LocA.Ptr), MemoryLocation::UnknownSize, LocA.AATags, GetUnderlyingObject(LocB.Ptr), MemoryLocation::UnknownSize, LocB.AATags)
>


Just do:

  return AA->alias(LocA.Ptr, MemoryLocation::UnknownSize, LocA.AATags, LocB.Ptr, MemoryLocation::UnknownSize, LocB.AATags)

there's no need to call `GetUnderlyingObject` here explicitly. When you pass an unknown size, that's essentially what BasicAA is doing anyway (since it has no size information, AA can only look at the metadata and the underlying objects for aliasing information).


https://reviews.llvm.org/D42381