Admitted.

Lemma hybrid_thread_diagram:
forall (U0 : list nat) (st1 : C1) (m1 : mem) (st1' : C1) (m1' : mem),
machine_semantics.thread_step (HCSem Sems Semt hb1 U) genv U0 st1 m1 st1' m1' ->
forall cd (st2 : C2) (mu : meminj) (m2 : mem),
concur_match cd mu st1 m1 st2 m2 ->
exists (st2' : C2) (m2' : mem) cd' (mu' : meminj),
concur_match cd' mu' st1' m1' st2' m2' /\
(machine_semantics_lemmas.thread_step_plus
(HCSem Sems Semt hb2 U) genv U0 st2 m2 st2' m2' \/
machine_semantics_lemmas.thread_step_star
(HCSem Sems Semt hb2 U) genv U0 st2 m2 st2' m2'
/\ option_compiler_order cd' cd).