Thank you for the review!

Right, updated now.

Address comments.

Consider multiple edges between blocks. MemoryPhis have an entry for each edge in this case. Move all edges to the new phi to preserve number of edges equal to number of phi entries.

Format.

Format.

Address comments and remove movePhi API. There is a use case needing something move generic that I will send in a separate patch.

Address comments.

Some small comments, but otherwise lgtm.

Rebase after changes in SimpleLoopUnswitch and MemorySSA API changes.

Rebase and update after API change.

Rebase.

Rebase after checking in delete APIs.
Updated algorithm for updatePhisWhenAddingBBPred to consider any number of predecessors added for each block.
Updated cloneUseDef signature to use an LoopBlocksRPO.
Updated cloneUseDef to include an API with multiple VMaps, per the SimpleLoopUnswitch change.
Other cleanups.

Address comment. Thank you for the review!

LGTM.

Address comments.

nit: format.

Address comments.

LGTM.

Thank you for the review!

Add assert.

I'm not clear why my testing didn't catch this test, but the label change looks exactly like what D48202 would change.
Appoving without retesting to unblock this.

Address comments.

Thank you for the review!

Thank you for the review!

Fix nit.

Thank you for the review!

Address comments.

Rush edit.

Updated scev.ll to be fully parametric (vs updating one label). All other tests should use variables as well, but that can be a separate cleanup.

format.

Address comments and rebase.

Thank you for adding this!

Perhaps a more accurate description is "Invalidate ScEv in LoopSimplifyCFG" (when merging blocks).
LGTM.

LGTM.

Thank you for the comments!

Address comments.

This update is more a whole rewrite of the APIs.

Logic lgtm.

LG

LGTM. Looks like a clean simplification to me.

Cleanup and clang-format.

Some cleanup and clang-format.

Rebase and ping.

Update to use new API in dependent patch.

Update patch with the following:

• Fix a few bugs that were triggered by tests in SimpleLoopUnswitch
• Slightly modify current APIs and add a couple APIs motivated by SimpleLoopUnswitch
• Add APIs to delete blocks (SimpleLoopUnswitch modifies the CFG heavily) and MemoryPhi entries.

Thank you for the implementation patch!

Would be good if you can also add an implementation of this API (in a dependent patch).
I'm not entirely clear on the use yet, e.g. "BuffUseResult sameBuff" in your example is never used. An actual implementation would help with understanding and reviewing.

Rebase on dependent patch.

Rebase on dependent patch.

Address comments.

LGTM. Thanks for the change!

First concern is duplicating functionality already present in MemorySSA. I honestly don't understand everything well enough, so it's possible there are chunks that can be factored out from existing methods and the ones in this patch.

Uploaded D45300 and D45301 to give usage context.