[flang] [llvm] [mlir] [Flang]Fix for changed code at the end of AllocaIP. (PR #92430)

[Tom Eccles via llvm-commits]

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tblah wrote:

What I meant by this was that the initial bug you seemed to be fixing was that the state kept around in the AllocaIP was becoming invalidated and needed to be carefully updated or not relied upon at particular points in the code.

I wonder if this is not something that should be stored as persistent state at all, instead always getting the block start or end (before the terminator) afresh like in the changes you have made here.

https://github.com/llvm/llvm-project/pull/92430