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Diffstat (limited to 'scheduling/postpass_lib/ForwardSimulationBlock.v')
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diff --git a/scheduling/postpass_lib/ForwardSimulationBlock.v b/scheduling/postpass_lib/ForwardSimulationBlock.v new file mode 100644 index 00000000..cc6ecdd8 --- /dev/null +++ b/scheduling/postpass_lib/ForwardSimulationBlock.v @@ -0,0 +1,387 @@ +(* *************************************************************) +(* *) +(* The Compcert verified compiler *) +(* *) +(* Sylvain Boulmé Grenoble-INP, VERIMAG *) +(* David Monniaux CNRS, VERIMAG *) +(* Cyril Six Kalray *) +(* *) +(* Copyright Kalray. Copyright VERIMAG. All rights reserved. *) +(* This file is distributed under the terms of the INRIA *) +(* Non-Commercial License Agreement. *) +(* *) +(* *************************************************************) + +(*** + +Auxiliary lemmas on starN and forward_simulation +in order to prove the forward simulation of Mach -> Machblock. + +***) + +Require Import Relations. +Require Import Wellfounded. +Require Import Coqlib. +Require Import Events. +Require Import Globalenvs. +Require Import Smallstep. +Require Import Lia. + +Local Open Scope nat_scope. + + +(** Auxiliary lemma on starN *) +Section starN_lemma. + +Variable L: semantics. + +Local Hint Resolve starN_refl starN_step Eapp_assoc: core. + +Lemma starN_split n s t s': + starN (step L) (globalenv L) n s t s' -> + forall m k, n=m+k -> + exists (t1 t2:trace) s0, starN (step L) (globalenv L) m s t1 s0 /\ starN (step L) (globalenv L) k s0 t2 s' /\ t=t1**t2. +Proof. + induction 1; cbn. + + intros m k H; assert (X: m=0); try lia. + assert (X0: k=0); try lia. + subst; repeat (eapply ex_intro); intuition eauto. + + intros m; destruct m as [| m']; cbn. + - intros k H2; subst; repeat (eapply ex_intro); intuition eauto. + - intros k H2. inversion H2. + exploit (IHstarN m' k); eauto. intro. + destruct H3 as (t5 & t6 & s0 & H5 & H6 & H7). + repeat (eapply ex_intro). + instantiate (1 := t6); instantiate (1 := t1 ** t5); instantiate (1 := s0). + intuition eauto. subst. auto. +Qed. + +Lemma starN_tailstep n s t1 s': + starN (step L) (globalenv L) n s t1 s' -> + forall (t t2:trace) s'', + Step L s' t2 s'' -> t = t1 ** t2 -> starN (step L) (globalenv L) (S n) s t s''. +Proof. + induction 1; cbn. + + intros t t1 s0; autorewrite with trace_rewrite. + intros; subst; eapply starN_step; eauto. + autorewrite with trace_rewrite; auto. + + intros. eapply starN_step; eauto. + intros; subst; autorewrite with trace_rewrite; auto. +Qed. + +End starN_lemma. + + + +(** General scheme from a "match_states" relation *) + +Section ForwardSimuBlock_REL. + +Variable L1 L2: semantics. + + +(** Hypothèses de la preuve *) + +Variable dist_end_block: state L1 -> nat. + +Hypothesis simu_mid_block: + forall s1 t s1', Step L1 s1 t s1' -> (dist_end_block s1)<>0 -> t = E0 /\ dist_end_block s1=S (dist_end_block s1'). + +Hypothesis public_preserved: + forall id, Senv.public_symbol (symbolenv L2) id = Senv.public_symbol (symbolenv L1) id. + +Variable match_states: state L1 -> state L2 -> Prop. + +Hypothesis match_initial_states: + forall s1, initial_state L1 s1 -> exists s2, match_states s1 s2 /\ initial_state L2 s2. + +Hypothesis match_final_states: + forall s1 s2 r, final_state L1 s1 r -> match_states s1 s2 -> final_state L2 s2 r. + +Hypothesis final_states_end_block: + forall s1 t s1' r, Step L1 s1 t s1' -> final_state L1 s1' r -> dist_end_block s1 = 0. + +Hypothesis simu_end_block: + forall s1 t s1' s2, starN (step L1) (globalenv L1) (S (dist_end_block s1)) s1 t s1' -> match_states s1 s2 -> exists s2', Step L2 s2 t s2' /\ match_states s1' s2'. + + +(** Introduction d'une sémantique par bloc sur L1 appelée "memoL1" *) + +Local Hint Resolve starN_refl starN_step: core. + +Definition follows_in_block (head current: state L1): Prop := + dist_end_block head >= dist_end_block current + /\ starN (step L1) (globalenv L1) (minus (dist_end_block head) (dist_end_block current)) head E0 current. + +Lemma follows_in_block_step (head previous next: state L1): + forall t, follows_in_block head previous -> Step L1 previous t next -> (dist_end_block previous)<>0 -> follows_in_block head next. +Proof. + intros t [H1 H2] H3 H4. + destruct (simu_mid_block _ _ _ H3 H4) as [H5 H6]; subst. + constructor 1. + + lia. + + replace (dist_end_block head - dist_end_block next) with (S (dist_end_block head - dist_end_block previous)). + - eapply starN_tailstep; eauto. + - lia. +Qed. + +Lemma follows_in_block_init (head current: state L1): + forall t, Step L1 head t current -> (dist_end_block head)<>0 -> follows_in_block head current. +Proof. + intros t H3 H4. + destruct (simu_mid_block _ _ _ H3 H4) as [H5 H6]; subst. + constructor 1. + + lia. + + replace (dist_end_block head - dist_end_block current) with 1. + - eapply starN_tailstep; eauto. + - lia. +Qed. + + +Record memostate := { + real: state L1; + memorized: option (state L1); + memo_star: forall head, memorized = Some head -> follows_in_block head real; + memo_final: forall r, final_state L1 real r -> memorized = None +}. + +Definition head (s: memostate): state L1 := + match memorized s with + | None => real s + | Some s' => s' + end. + +Lemma head_followed (s: memostate): follows_in_block (head s) (real s). +Proof. + destruct s as [rs ms Hs]. cbn. + destruct ms as [ms|]; unfold head; cbn; auto. + constructor 1. + lia. + replace (dist_end_block rs - dist_end_block rs)%nat with O. + + apply starN_refl; auto. + + lia. +Qed. + +Inductive is_well_memorized (s s': memostate): Prop := + | StartBloc: + dist_end_block (real s) <> O -> + memorized s = None -> + memorized s' = Some (real s) -> + is_well_memorized s s' + | MidBloc: + dist_end_block (real s) <> O -> + memorized s <> None -> + memorized s' = memorized s -> + is_well_memorized s s' + | ExitBloc: + dist_end_block (real s) = O -> + memorized s' = None -> + is_well_memorized s s'. + +Local Hint Resolve StartBloc MidBloc ExitBloc: core. + +Definition memoL1 := {| + state := memostate; + genvtype := genvtype L1; + step := fun ge s t s' => + step L1 ge (real s) t (real s') + /\ is_well_memorized s s' ; + initial_state := fun s => initial_state L1 (real s) /\ memorized s = None; + final_state := fun s r => final_state L1 (real s) r; + globalenv:= globalenv L1; + symbolenv:= symbolenv L1 +|}. + + +(** Preuve des 2 forward simulations: L1 -> memoL1 et memoL1 -> L2 *) + +Lemma discr_dist_end s: + {dist_end_block s = O} + {dist_end_block s <> O}. +Proof. + destruct (dist_end_block s); cbn; intuition. +Qed. + +Lemma memo_simulation_step: + forall s1 t s1', Step L1 s1 t s1' -> + forall s2, s1 = (real s2) -> exists s2', Step memoL1 s2 t s2' /\ s1' = (real s2'). +Proof. + intros s1 t s1' H1 [rs2 ms2 Hmoi] H2. cbn in H2; subst. + destruct (discr_dist_end rs2) as [H3 | H3]. + + refine (ex_intro _ {|real:=s1'; memorized:=None |} _); cbn. + intuition. + + destruct ms2 as [s|]. + - refine (ex_intro _ {|real:=s1'; memorized:=Some s |} _); cbn. + intuition. + - refine (ex_intro _ {|real:=s1'; memorized:=Some rs2 |} _); cbn. + intuition. + Unshelve. + * intros; discriminate. + * intros; auto. + * intros head X; injection X; clear X; intros; subst. + eapply follows_in_block_step; eauto. + * intros r X; erewrite final_states_end_block in H3; intuition eauto. + * intros head X; injection X; clear X; intros; subst. + eapply follows_in_block_init; eauto. + * intros r X; erewrite final_states_end_block in H3; intuition eauto. +Qed. + +Lemma forward_memo_simulation_1: forward_simulation L1 memoL1. +Proof. + apply forward_simulation_step with (match_states:=fun s1 s2 => s1 = (real s2)); auto. + + intros s1 H; eapply ex_intro with (x:={|real:=s1; memorized:=None |}); cbn. + intuition. + + intros; subst; auto. + + intros; exploit memo_simulation_step; eauto. + Unshelve. + * intros; discriminate. + * auto. +Qed. + +Lemma forward_memo_simulation_2: forward_simulation memoL1 L2. +Proof. + unfold memoL1; cbn. + apply forward_simulation_opt with (measure:=fun s => dist_end_block (real s)) (match_states:=fun s1 s2 => match_states (head s1) s2); cbn; auto. + + intros s1 [H0 H1]; destruct (match_initial_states (real s1) H0). + unfold head; rewrite H1. + intuition eauto. + + intros s1 s2 r X H0; unfold head in X. + erewrite memo_final in X; eauto. + + intros s1 t s1' [H1 H2] s2 H; subst. + destruct H2 as [ H0 H2 H3 | H0 H2 H3 | H0 H2]. + - (* StartBloc *) + constructor 2. destruct (simu_mid_block (real s1) t (real s1')) as [H5 H4]; auto. + unfold head in * |- *. rewrite H2 in H. rewrite H3. rewrite H4. intuition. + - (* MidBloc *) + constructor 2. destruct (simu_mid_block (real s1) t (real s1')) as [H5 H4]; auto. + unfold head in * |- *. rewrite H3. rewrite H4. intuition. + destruct (memorized s1); cbn; auto. tauto. + - (* EndBloc *) + constructor 1. + destruct (simu_end_block (head s1) t (real s1') s2) as (s2' & H3 & H4); auto. + * destruct (head_followed s1) as [H4 H3]. + replace (dist_end_block (head s1) - dist_end_block (real s1)) with (dist_end_block (head s1)) in H3; try lia. + eapply starN_tailstep; eauto. + * unfold head; rewrite H2; cbn. intuition eauto. +Qed. + +Lemma forward_simulation_block_rel: forward_simulation L1 L2. +Proof. + eapply compose_forward_simulations. + eapply forward_memo_simulation_1. + apply forward_memo_simulation_2. +Qed. + + +End ForwardSimuBlock_REL. + + + +(* An instance of the previous scheme, when there is a translation from L1 states to L2 states + +Here, we do not require that the sequence of S2 states does exactly match the sequence of L1 states by trans_state. +This is because the exact matching is broken in Machblock on "goto" instruction (due to the find_label). + +However, the Machblock state after a goto remains "equivalent" to the trans_state of the Mach state in the sense of "equiv_on_next_step" below... + +*) + + +Section ForwardSimuBlock_TRANS. + +Variable L1 L2: semantics. + +Variable trans_state: state L1 -> state L2. + +Definition equiv_on_next_step (P Q: Prop) s2_a s2_b: Prop := + (P -> (forall t s', Step L2 s2_a t s' <-> Step L2 s2_b t s')) /\ (Q -> (forall r, (final_state L2 s2_a r) <-> (final_state L2 s2_b r))). + +Definition match_states s1 s2: Prop := + equiv_on_next_step (exists t s1', Step L1 s1 t s1') (exists r, final_state L1 s1 r) s2 (trans_state s1). + +Lemma match_states_trans_state s1: match_states s1 (trans_state s1). +Proof. + unfold match_states, equiv_on_next_step. intuition. +Qed. + +Variable dist_end_block: state L1 -> nat. + +Hypothesis simu_mid_block: + forall s1 t s1', Step L1 s1 t s1' -> (dist_end_block s1)<>0 -> t = E0 /\ dist_end_block s1=S (dist_end_block s1'). + +Hypothesis public_preserved: + forall id, Senv.public_symbol (symbolenv L2) id = Senv.public_symbol (symbolenv L1) id. + +Hypothesis match_initial_states: + forall s1, initial_state L1 s1 -> exists s2, match_states s1 s2 /\ initial_state L2 s2. + +Hypothesis match_final_states: + forall s1 r, final_state L1 s1 r -> final_state L2 (trans_state s1) r. + +Hypothesis final_states_end_block: + forall s1 t s1' r, Step L1 s1 t s1' -> final_state L1 s1' r -> dist_end_block s1 = 0. + +Hypothesis simu_end_block: + forall s1 t s1', starN (step L1) (globalenv L1) (S (dist_end_block s1)) s1 t s1' -> exists s2', Step L2 (trans_state s1) t s2' /\ match_states s1' s2'. + +Lemma forward_simulation_block_trans: forward_simulation L1 L2. +Proof. + eapply forward_simulation_block_rel with (dist_end_block:=dist_end_block) (match_states:=match_states); try tauto. + + (* final_states *) intros s1 s2 r H1 [H2 H3]. rewrite H3; eauto. + + (* simu_end_block *) + intros s1 t s1' s2 H1 [H2a H2b]. exploit simu_end_block; eauto. + intros (s2' & H3 & H4); econstructor 1; intuition eauto. + rewrite H2a; auto. + inversion_clear H1. eauto. +Qed. + +End ForwardSimuBlock_TRANS. + + +(* another version with a relation [trans_state_R] instead of a function [trans_state] *) +Section ForwardSimuBlock_TRANS_R. + +Variable L1 L2: semantics. + +Variable trans_state_R: state L1 -> state L2 -> Prop. + +Definition match_states_R s1 s2: Prop := + exists s2', trans_state_R s1 s2' /\ equiv_on_next_step _ (exists t s1', Step L1 s1 t s1') (exists r, final_state L1 s1 r) s2 s2'. + +Lemma match_states_trans_state_R s1 s2: trans_state_R s1 s2 -> match_states_R s1 s2. +Proof. + unfold match_states, equiv_on_next_step. firstorder. +Qed. + +Variable dist_end_block: state L1 -> nat. + +Hypothesis simu_mid_block: + forall s1 t s1', Step L1 s1 t s1' -> (dist_end_block s1)<>0 -> t = E0 /\ dist_end_block s1=S (dist_end_block s1'). + +Hypothesis public_preserved: + forall id, Senv.public_symbol (symbolenv L2) id = Senv.public_symbol (symbolenv L1) id. + +Hypothesis match_initial_states: + forall s1, initial_state L1 s1 -> exists s2, match_states_R s1 s2 /\ initial_state L2 s2. + +Hypothesis match_final_states: + forall s1 s2 r, final_state L1 s1 r -> trans_state_R s1 s2 -> final_state L2 s2 r. + +Hypothesis final_states_end_block: + forall s1 t s1' r, Step L1 s1 t s1' -> final_state L1 s1' r -> dist_end_block s1 = 0. + +Hypothesis simu_end_block: + forall s1 t s1' s2, starN (step L1) (globalenv L1) (S (dist_end_block s1)) s1 t s1' -> trans_state_R s1 s2 -> exists s2', Step L2 s2 t s2' /\ match_states_R s1' s2'. + +Lemma forward_simulation_block_trans_R: forward_simulation L1 L2. +Proof. + eapply forward_simulation_block_rel with (dist_end_block:=dist_end_block) (match_states:=match_states_R); try tauto. + + (* final_states *) intros s1 s2 r H1 (s2' & H2 & H3 & H4). rewrite H4; eauto. + + (* simu_end_block *) + intros s1 t s1' s2 H1 (s2' & H2 & H2a & H2b). exploit simu_end_block; eauto. + intros (x & Hx & (y & H3 & H4 & H5)). repeat (econstructor; eauto). + rewrite H2a; eauto. + inversion_clear H1. eauto. +Qed. + +End ForwardSimuBlock_TRANS_R. + |