Definition psub (p: aptr) (n: ptrofs) : aptr :=
match p with
| Gl id ofs => Gl id (Ptrofs.sub ofs n)
| Stk ofs => Stk (Ptrofs.sub ofs n)
| _ => p
end.

Lemma psub_sound:
forall b ofs p delta,
pmatch b ofs p ->
pmatch b (Ptrofs.sub ofs delta) (psub p delta).