Module `Ast.Element_to_GP`

Constraint tying vector element width to GP register width for INS and UMOV.

B/H/S elements use W (32-bit GP)
D elements use X (64-bit GP)

type (_, _) t =

| B : ([ `B ], [ `W ]) t
| H : ([ `H ], [ `W ]) t
| S : ([ `S ], [ `W ]) t
| D : ([ `D ], [ `X ]) t