Merge pull request #93 from AbsInt/separate-compilation

This pull request implements "approach A" to separate compilation in CompCert from the paper

Lightweight verification of separate compilation
by Jeehoon Kang, Yoonseung Kim, Chung-Kil Hur, Derek Dreyer, Viktor Vafeiadis,
POPL 2016, pages 178-190

In a nutshell, semantic preservation is still stated and proved in terms of a whole C program and a whole assembly program. However, the whole C program can be the result of syntactic linking of several C compilation units, each unit being separated compiled by CompCert to produce assembly unit, and these assembly units being linked together to produce the whole assembly program.

This way, the statement of semantic preservation and its proof now take into account the fact that each compilation unit is compiled separately, knowing only a fragment of the whole program (i.e. the current compilation unit) rather than the whole program.

1 files changed, 34 insertions, 58 deletions

diff --git a/backend/Stackingproof.v b/backend/Stackingproof.v
index 8becb773..a76fdbba 100644
--- a/backend/Stackingproof.v
+++ b/backend/Stackingproof.v
@@ -14,26 +14,22 @@
 
 (** This file proves semantic preservation for the [Stacking] pass. *)
 
-Require Import Coqlib.
-Require Import Errors.
-Require Import AST.
-Require Import Integers.
-Require Import Values.
-Require Import Op.
-Require Import Memory.
-Require Import Events.
-Require Import Globalenvs.
-Require Import Smallstep.
-Require Import Locations.
-Require Import LTL.
-Require Import Linear.
-Require Import Lineartyping.
-Require Import Mach.
-Require Import Bounds.
-Require Import Conventions.
-Require Import Stacklayout.
+Require Import Coqlib Errors.
+Require Import Integers AST Linking.
+Require Import Values Memory Events Globalenvs Smallstep.
+Require Import LTL Op Locations Linear Mach.
+Require Import Bounds Conventions Stacklayout Lineartyping.
 Require Import Stacking.
 
+Definition match_prog (p: Linear.program) (tp: Mach.program) :=
+  match_program (fun _ f tf => transf_fundef f = OK tf) eq p tp.
+
+Lemma transf_program_match:
+  forall p tp, transf_program p = OK tp -> match_prog p tp.
+Proof.
+  intros. eapply match_transform_partial_program; eauto.
+Qed.
+
 (** * Properties of frame offsets *)
 
 Lemma typesize_typesize:
@@ -61,11 +57,10 @@ Let step := Mach.step return_address_offset.
 
 Variable prog: Linear.program.
 Variable tprog: Mach.program.
-Hypothesis TRANSF: transf_program prog = OK tprog.
+Hypothesis TRANSF: match_prog prog tprog.
 Let ge := Genv.globalenv prog.
 Let tge := Genv.globalenv tprog.
 
-
 Section FRAME_PROPERTIES.
 
 Variable f: Linear.function.
@@ -2261,44 +2256,26 @@ Qed.
 (** Preservation / translation of global symbols and functions. *)
 
 Lemma symbols_preserved:
-  forall id, Genv.find_symbol tge id = Genv.find_symbol ge id.
-Proof.
-  intros. unfold ge, tge.
-  apply Genv.find_symbol_transf_partial with transf_fundef.
-  exact TRANSF.
-Qed.
+  forall (s: ident), Genv.find_symbol tge s = Genv.find_symbol ge s.
+Proof (Genv.find_symbol_match TRANSF).
 
-Lemma public_preserved:
-  forall id, Genv.public_symbol tge id = Genv.public_symbol ge id.
-Proof.
-  intros. unfold ge, tge.
-  apply Genv.public_symbol_transf_partial with transf_fundef.
-  exact TRANSF.
-Qed.
-
-Lemma varinfo_preserved:
-  forall b, Genv.find_var_info tge b = Genv.find_var_info ge b.
-Proof.
-  intros. unfold ge, tge.
-  apply Genv.find_var_info_transf_partial with transf_fundef.
-  exact TRANSF.
-Qed.
+Lemma senv_preserved:
+  Senv.equiv ge tge.
+Proof (Genv.senv_match TRANSF).
 
 Lemma functions_translated:
   forall v f,
   Genv.find_funct ge v = Some f ->
   exists tf,
   Genv.find_funct tge v = Some tf /\ transf_fundef f = OK tf.
-Proof
-  (Genv.find_funct_transf_partial transf_fundef _ TRANSF).
+Proof (Genv.find_funct_transf_partial TRANSF).
 
 Lemma function_ptr_translated:
-  forall v f,
-  Genv.find_funct_ptr ge v = Some f ->
+  forall b f,
+  Genv.find_funct_ptr ge b = Some f ->
   exists tf,
-  Genv.find_funct_ptr tge v = Some tf /\ transf_fundef f = OK tf.
-Proof
-  (Genv.find_funct_ptr_transf_partial transf_fundef _ TRANSF).
+  Genv.find_funct_ptr tge b = Some tf /\ transf_fundef f = OK tf.
+Proof (Genv.find_funct_ptr_transf_partial TRANSF).
 
 Lemma sig_preserved:
   forall f tf, transf_fundef f = OK tf -> Mach.funsig tf = Linear.funsig f.
@@ -2749,8 +2726,7 @@ Proof.
   econstructor; split.
   apply plus_one. econstructor; eauto.
   eapply eval_builtin_args_preserved with (ge1 := ge); eauto. exact symbols_preserved.
-  eapply external_call_symbols_preserved. eauto.
-  exact symbols_preserved. exact public_preserved. exact varinfo_preserved.
+  eapply external_call_symbols_preserved; eauto. apply senv_preserved.
   econstructor; eauto with coqlib.
   eapply match_stack_change_extcall; eauto.
   apply Plt_Ple. change (Mem.valid_block m sp0). eapply agree_valid_linear; eauto.
@@ -2858,8 +2834,7 @@ Proof.
   intros [j' [res' [m1' [A [B [C [D [E [F G]]]]]]]]].
   econstructor; split.
   apply plus_one. eapply exec_function_external; eauto.
-  eapply external_call_symbols_preserved'; eauto.
-  exact symbols_preserved. exact public_preserved. exact varinfo_preserved.
+  eapply external_call_symbols_preserved'; eauto. apply senv_preserved.
   econstructor; eauto.
   apply match_stacks_change_bounds with (Mem.nextblock m) (Mem.nextblock m'0).
   inv H0; inv A. eapply match_stack_change_extcall; eauto. apply Ple_refl. apply Ple_refl.
@@ -2884,8 +2859,8 @@ Proof.
   exploit function_ptr_translated; eauto. intros [tf [FIND TR]].
   econstructor; split.
   econstructor.
-  eapply Genv.init_mem_transf_partial; eauto.
-  rewrite (transform_partial_program_main _ _ TRANSF).
+  eapply (Genv.init_mem_transf_partial TRANSF); eauto.
+  rewrite (match_program_main TRANSF).
   rewrite symbols_preserved. eauto.
   econstructor; eauto.
   eapply Genv.initmem_inject; eauto.
@@ -2913,9 +2888,10 @@ Qed.
 Lemma wt_prog:
   forall i fd, In (i, Gfun fd) prog.(prog_defs) -> wt_fundef fd.
 Proof.
-  intros. exploit transform_partial_program_succeeds; eauto.
-  intros [tfd TF]. destruct fd; simpl in *.
-- monadInv TF. unfold transf_function in EQ.
+  intros.
+  exploit list_forall2_in_left. eexact (proj1 TRANSF). eauto.
+  intros ([i' g] & P & Q & R). simpl in *. inv R. destruct fd; simpl in *.
+- monadInv H2. unfold transf_function in EQ.
   destruct (wt_function f). auto. discriminate.
 - auto.
 Qed.
@@ -2925,7 +2901,7 @@ Theorem transf_program_correct:
 Proof.
   set (ms := fun s s' => wt_state s /\ match_states s s').
   eapply forward_simulation_plus with (match_states := ms).
-- exact public_preserved.
+- apply senv_preserved.
 - intros. exploit transf_initial_states; eauto. intros [st2 [A B]].
   exists st2; split; auto. split; auto.
   apply wt_initial_state with (prog := prog); auto. exact wt_prog.