[PATCH] D136164: [MemorySSA] Use BatchAA for clobber walker

[Nikita Popov via Phabricator via llvm-commits]

nikic added a comment.

In D136164#3900876 <https://reviews.llvm.org/D136164#3900876>, @asbirlea wrote:

> It seems unnecessary to force all uses to instantiate and pass the BatchAA.
> Can this remain part of the ClobberWalkerBase instead? Default the calls to getClobberingMemoryAccess to instantiate a BatchAA internally and pass to the ClobberWalker.
> Then, there can be an additional API added to override the above behavior when useful (known as safe): either passing a given BatchAA like current patch, or, keeping a BatchAA in the ClobberWalker itself instead of the AA, and being able to "set" it to not re-initialize it on each call (and perhaps "reset" to reseting each time).
> What do you think?

We currently have 17 calls to getClobberingMemoryAccess() and if my analysis is right, I believe 15 of those can reuse the BatchAA instance in //some// way (though this patch mostly doesn't do it). Given this, I think it makes more sense to always require BatchAA -- it makes reuse opportunities more obvious, and is not a particularly large burden if reuse is not possible. I'd agree if it were the other way around and BatchAA reuse was not possible in most cases.


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