[llvm] [RDA] Fix getGlobalUses() to account for redefinitions (PR #78178)

[Sam Parker via llvm-commits]

https://github.com/sparker-arm commented:

Thanks for fixing this, the patch looks okay to me. Unfortunately, testing this analysis is a bit of pain... I'm struggling to think of way to do this in the context of LowOverheadLoops.

https://github.com/llvm/llvm-project/pull/78178