[llvm] CallPromotionUtils: Correctly use IndexSize when determining the bit width of pointer offsets. (PR #119483)

[Jessica Clarke via llvm-commits]

https://github.com/jrtc27 approved this pull request.

This looks good to me. If the buildbot is unhappy again with the modified version we should make sure to actually reproduce the issue (I can have a go another day if needed).

https://github.com/llvm/llvm-project/pull/119483