[llvm] [CaptureTracking] Don't require offset to stay the same (PR #201106)

[Nikita Popov via llvm-commits]

nikic wrote:

> LGTM. I've been wondering though, when is MustPreserveOffset meant to be true (and be preserved)?

I think mainly DecomposeGEPExpression (which needs to know the offset from the base) and isKnownNonZero().

https://github.com/llvm/llvm-project/pull/201106