[llvm] [NaryReassociate] Fix crash from pointer width / index width confusion (PR #125923)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Given that this is working with SE, it would be better to use APIs like SE.getTypeSizeInBits or SE.getEffectiveSCEVType.

https://github.com/llvm/llvm-project/pull/125923