[llvm] [SROA] Fix assertion failure when promoting self-referential load/store (PR #208826)

[Krisitan Erik Olsen via llvm-commits]

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Kristianerik wrote:

The original minimal test I had didn't correctly reproduce the crash.  The unknown-offset getelementptr load is required to trigger propagateStoredValuesToLoads, which is the code path with the bug. I've updated the test to use the original reproducer structure (minus the target triple and @main function) which does crash without the fix. Verified locally in both directions.

https://github.com/llvm/llvm-project/pull/208826