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

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

> Hi - I would guess that we usually assume that trivial instructions have already been removed in anything that wasn't a hand-written (or reduced) test case, and that the snippet for https://github.com/llvm/llvm-project/issues/133928 would just need to be larger if it had to include extra uses for the trivial instructions - the original problem would remain just in a different form. I don't think it would be an issue if you wanted to add it, but I doubt it would be super useful in the entire pass pipeline.

That makes sense, although perhaps some earlier pruning in TypePromotion could alleviate a bit of work in CGP, which is scheduled to run next and recursively deletes trivially dead instructions.

> I think in practice all gep indices will be canonicalized to ptrsize so this is probably OK. Can you update the // Ignore GEPs because ... comment before the gep, and add a testcase from https://github.com/llvm/llvm-project/issues/133928 with a comment explaining what is going on?

Updated, thanks!

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