correct signedness of pmadd arguments

[folkertdev]

No description provided.

[rustbot]

r? @sayantn

rustbot has assigned @sayantn.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[sayantn]

It doesn't really matter when linking to LLVM intrinsics (LLVM only had i8, the signedness is determined by the operation). But we can do this just for the sake of our understanding. Will it be possible for you to check for other such inconsistencies? I believe there should be a lot more of them

[folkertdev]

These I just found looking at rust-lang/miri#4705, I don't currently want to spend the time to look for more cases really.

[sayantn]

Ok np, should I merge this then?

[folkertdev]

Yes, if you think it looks good.