Proof with eauto 10 with reg_renamings val_renamings.
intros.
unfold compare_floats;
destruct v1; inversion Hval_obs; subst;
destruct v2; inversion Hval_obs'; subst...
Qed.

Lemma val_obs_testcond:
forall f c rs rs'
(Hrs_ren: regset_ren f rs rs'),
val_obs f (Val.of_optbool (eval_testcond c rs))
(Val.of_optbool (eval_testcond c rs')).