[llvm] [DAG] Fold (vt trunc (extload (vt x))) -> (vt load x) (PR #75229)

[Jay Foad via llvm-commits]

jayfoad wrote:

> There's some major AMDGPU codegen changes (especially kernel-args.ll), I don't know if this is OK, or whether it was relying on any particular behavior.

The only changes are for ancient subtargets that I have no interest in. Maybe Matt does.

https://github.com/llvm/llvm-project/pull/75229