Definition eval_extcond (xc: extcond) (rs: regset) : option bool :=
  match xc with
  | Cond_base c =>
      eval_testcond c rs
  | Cond_and c1 c2 =>
      match eval_testcond c1 rs, eval_testcond c2 rs with
      | Some b1, Some b2 => Some (b1 && b2)
      | _, _ => None
      end
  | Cond_or c1 c2 =>
      match eval_testcond c1 rs, eval_testcond c2 rs with
      | Some b1, Some b2 => Some (b1 || b2)
      | _, _ => None
      end
  end.Definition swap_floats {A: Type} (c: comparison) (n1 n2: A) : A :=
  match c with
  | Clt | Cle => n2
  | Ceq | Cne | Cgt | Cge => n1
  end.

Lemma testcond_for_neg_float_comparison_correct: forall c n1 n2 rs, eval_extcond (testcond_for_condition (Cnotcompf c)) (nextinstr (compare_floats (Vfloat (swap_floats c n1 n2)) (Vfloat (swap_floats c n2 n1)) rs)) = Some(negb(Float.cmp c n1 n2)).