[llvm] [LAA] Use computeConstantDifference() (PR #103725)

[Nikita Popov via llvm-commits]

nikic wrote:

> The two uses I can find of this interface in LAA are in sortPtrAccesses, and isConsecutiveAccess.

Note that this API is also used by SLP. That's the use that's actually compile-time sensitive.

> For the former, another way to frame this (in SCEV) would be to find the underlying base pointer (which must be the same for the difference to be defined), and then compute each offset against that.

I don't think this part would work, as the difference to the base pointer may be variable (as the base pointer is the base outside all loops etc).

https://github.com/llvm/llvm-project/pull/103725