Definition bmatch (m: mem) (b: block) (ab: ablock) : Prop :=
  smatch m b ab.(ab_summary) /\
  forall chunk ofs v, Mem.load chunk m b ofs = Some v -> vmatch v (ablock_load chunk ab ofs).

Lemma chunk_compat_true: forall c c', chunk_compat c c' = true -> size_chunk c = size_chunk c' /\ align_chunk c <= align_chunk c' /\ type_of_chunk c = type_of_chunk c'.