[llvm] [TypePromotion] Do not zero-extend getelementptr indexes since signed (PR #134281)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

This should match the original intent of the function, as per comment. We don't seem to bother with sign-extending here, but can change this to sext instead of bailing out, if needed.

https://github.com/llvm/llvm-project/pull/134281