[llvm] [InstCombine] Do not fold gep operand into phi unless not poison (PR #115901)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

I don't think this is the right fix. As far as I can tell this is just a bug in the flag intersection, because we end up ignoring the flags on the first instruction. Would doing this fix the issue?

`GEPNoWrapFlags NW = FirstInst->getNoWrapFlags()`

https://github.com/llvm/llvm-project/pull/115901