[llvm] [MemorySSA] Make getPreviousDef iterative to avoid stack overflow (PR #205159)

[Alina Sbirlea via llvm-commits]

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alinas wrote:

Do you need to create the predecessor vector in the StackFrame or could you just store a pred_iterator (`pred_begin(CurBB)`)? I don't think there are any changes that will invalidate the iterator, and you count use it below at new line :175. 

https://github.com/llvm/llvm-project/pull/205159