[llvm] [MemorySSA] Handle MemoryDef optimized away during cloning (PR #117883)

[Nikita Popov via llvm-commits]

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@@ -276,7 +276,9 @@ class MemorySSAUpdater {
   // representation for. No other cases are supported.
   void cloneUsesAndDefs(BasicBlock *BB, BasicBlock *NewBB,
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nikic wrote:

Done. Also converted the whole comment into doxygen format.

https://github.com/llvm/llvm-project/pull/117883