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 needs_of_shift_sound:
forall v v' s nv,
vagree v v' (needs_of_shift s nv) ->
vagree (eval_shift s v) (eval_shift s v') nv.