Section SOUNDNESS.
Variable ge: genv.
Variable sp: block.
Variables m m': mem.
Hypothesis PERM: forall b ofs k p, Mem.perm m b ofs k p -> Mem.perm m' b ofs k p.

Lemma val_sub_lessdef:
forall v1 v1' v2 v2',
Val.lessdef v1 v1' -> Val.lessdef v2 v2' -> Val.lessdef (Val.sub v1 v2) (Val.sub v1' v2').