Minor update and ping.

I may not be the best to approve this change. Here are some high-level comments though.

[format]

I also cleaned up the usage of EnableLicmCap. It is only used in 2 places now, with no forced calls to getClobbering (the issue in MemorySSA requiring this is now resolved).
FWIW, I'm planning to replace this with an integer cap in a future patch (i.e. allow a limited number of calls to getClobbering, vs all or none like we have now).

Address comments.

Cleaned up after a series of MemorySSA updates, and rebased with ToT changes.

One nit, otherwise LGTM.

Thank you for the review!

Update setting of where to stop in getBlockingAccess:

• dropping the check for block since we may no longer be in the starting block after adding a paused path.
• adding a second StopAt access in walkToPhiOrClobber, only set when skipping self and for the same location.
• keeping paused path when the original StopAt is found.

Address comments.

Repurpose patch to refactor caching walker.

Ack, will hold off on checking this in until the follow-up use (walker) is finalized.

Address comments.

Thank you for the review!

Update MemorySSA when unswitching guard intrinsics.
And ping.

Based on the corresponding Phi updates, the MemoryPhi updates look correct.

Great catch, thank you for fixing this and for the additional tests.

MemorySSA is an analysis, all info is kept "on the side". It's standalone and no info is kept in BBs.
Some doc can be found here: http://releases.llvm.org/6.0.1/docs/MemorySSA.html

FWIW, long term DSE should ideally use MemorySSA instead of MemoryDependenceResults.
But this particular optimization has a high chance of being useful even then.

I have mixed feelings here because I understand Chris's point, but there are differences in this case which make this patch worth pushing forward IMO.

Let me re-purpose this patch:
Is there a point to having deleteValue()?
Is there a point to having the ref count (addRef, dropRef) for alias sets?

I agree with all your points! Thank you for following up.

clang-format. Thank you!

Gentle ping.

Test updated. Thank you for the review!

Rebase patch after resect changes.

Update pr35210.ll after recent upstream changes.

Thank you for the review!

Dropping this, since the issue is not resolvable in general AFAICT. Please see D51960.

Moving the MSSA after cloning earlier to avoid the ValueMap invalidation.
Adding another test.
And ping.

Final update before commit: changing a cast_or_null to dyn_cast_or_null for cloned instructions. LoopRotate can place Value in the map, as the clone of an instruction.