When reassociating GEPs, we can only keep inbounds if both original
GEPs were inbounds, and their offsets have the same sign. For the
sake of simplicity, I only handle the case where both offsets are
non-negative here.
It would probably be fine to just not preserve inbounds at all here,
but as I don't see a compile-time impact for adding the
isKnownNonNegative() calls I went with this more conservative
approach.
Fixes https://github.com/llvm/llvm-project/issues/44206.
Differential Revision: https://reviews.llvm.org/D126687
36cbdaa163