Inductive match_stack: list Mach.stackframe -> Prop :=
  | match_stack_nil:
      match_stack nil
  | match_stack_cons: forall fb sp ra c s f tf tc,
      Genv.find_funct_ptr ge fb = Some (Internal f) ->
      transl_code_at_pc ge ra fb f c false tf tc ->
      sp <> Vundef ->
      match_stack s ->
      match_stack (Stackframe fb sp ra c :: s).Inductive match_stack: list Mach.stackframe -> Prop :=
  | match_stack_nil:
      match_stack nil
  | match_stack_cons: forall fb sp ra c s f tf tc,
      Genv.find_funct_ptr ge fb = Some (Internal f) ->
      transl_code_at_pc ge ra fb f c false tf tc ->
      sp <> Vundef ->
      match_stack s ->
      match_stack (Stackframe fb sp ra c :: s).Inductive match_stack: list Mach.stackframe -> Prop :=
  | match_stack_nil:
      match_stack nil
  | match_stack_cons: forall fb sp ra c s f tf tc,
      Genv.find_funct_ptr ge fb = Some (Internal f) ->
      transl_code_at_pc ge ra fb f c false tf tc ->
      sp <> Vundef ->
      match_stack s ->
      match_stack (Stackframe fb sp ra c :: s).

Lemma parent_ra_def: forall s, match_stack s -> parent_ra s <> Vundef.