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

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

@davemgreen Is there any particular reason why we do not run isTriviallyDead here in TypePromotion, as happens in other parts in CodeGen? We convert an unused trunc to a used zext in the snippet in https://github.com/llvm/llvm-project/issues/133928. This would impact 22 tests primarily among AArch64 and RISCV, so I'd like this to be confirmed before adding it.

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