[llvm] [GlobalISel] Enhance iPTR type support in SDAG patterns (PR #111503)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> > This is just a bug, the vector index type is separate from the pointer type
> 
> @arsenm if this is a bug it's already buried too deep.
> 

The default implementation happens to use the address space 0 pointer type, that's not very deep.

> So each target that has vectors implemented in SDAG must overwrite default interface and whole SDAG implementation to enable vector patterns in GlobalISel. 

I think we should just remove the SDTCisPtrTy constraint from the vector nodes. It's simply not correct. If we wanted to, we could have a parallel mechanism for the vector index type 

https://github.com/llvm/llvm-project/pull/111503