Proof with eauto 10 using val_erasure_cmpu with regs_erasure val_erasure.
intros.
unfold compare_floats32.
destruct v1,v2; inv Hval_erasure; inv Hval_erasure2; simpl;
eauto 6 with regs_erasure val_erasure;
try destruct v1'; try destruct v2';
eauto 6 with regs_erasure val_erasure;
unfold Val.of_bool;
repeat rewrite if_negb;
repeat match goal with
| [|- context[match ?Expr with | _ => _ end]] =>
destruct Expr eqn:?
end...
Qed.
Hint Transparent undef_regs: regs_erasure.

(* TODO: move this to the right place*)
Lemma get_reg_erasure:
forall rs rs' r
(Hregs_erasure: regs_erasure rs rs')
(Hundef: rs r <> Vundef),
rs r = rs' r.