[llvm] [InstCombine] Simplify the pointer operand of store if writing to null is UB (PR #127979)

[Nikita Popov via llvm-commits]

nikic wrote:

> Before merging with the code in visitLoadInst, I need to investigate if the one-use check is necessary:

I think it's only needed for the first transform, but not the second...

https://github.com/llvm/llvm-project/pull/127979