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, 25 insertions, 36 deletions

diff --git a/backend/Linearizeproof.v b/backend/Linearizeproof.v
index 65258b2d..16717365 100644
--- a/backend/Linearizeproof.v
+++ b/backend/Linearizeproof.v
@@ -13,32 +13,29 @@
 (** Correctness proof for code linearization *)
 
 Require Import FSets.
-Require Import Coqlib.
-Require Import Maps.
-Require Import Ordered.
-Require Import Lattice.
-Require Import AST.
-Require Import Integers.
-Require Import Values.
-Require Import Memory.
-Require Import Events.
-Require Import Globalenvs.
-Require Import Errors.
-Require Import Smallstep.
-Require Import Op.
-Require Import Locations.
-Require Import LTL.
-Require Import Linear.
+Require Import Coqlib Maps Ordered Errors Lattice Kildall Integers.
+Require Import AST Linking.
+Require Import Values Memory Events Globalenvs Smallstep.
+Require Import Op Locations LTL Linear.
 Require Import Linearize.
 
 Module NodesetFacts := FSetFacts.Facts(Nodeset).
 
+Definition match_prog (p: LTL.program) (tp: Linear.program) :=
+  match_program (fun ctx 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.
+
 Section LINEARIZATION.
 
 Variable prog: LTL.program.
 Variable tprog: Linear.program.
 
-Hypothesis TRANSF: transf_program prog = OK tprog.
+Hypothesis TRANSF: match_prog prog tprog.
 
 Let ge := Genv.globalenv prog.
 Let tge := Genv.globalenv tprog.
@@ -48,28 +45,23 @@ Lemma functions_translated:
   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 ->
   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).
+Proof (Genv.find_funct_ptr_transf_partial TRANSF).
 
 Lemma symbols_preserved:
   forall id,
   Genv.find_symbol tge id = Genv.find_symbol ge id.
-Proof (Genv.find_symbol_transf_partial transf_fundef _ TRANSF).
-
-Lemma public_preserved:
-  forall id,
-  Genv.public_symbol tge id = Genv.public_symbol ge id.
-Proof (Genv.public_symbol_transf_partial transf_fundef _ TRANSF).
+Proof (Genv.find_symbol_transf_partial TRANSF).
 
-Lemma varinfo_preserved:
-  forall b, Genv.find_var_info tge b = Genv.find_var_info ge b.
-Proof (Genv.find_var_info_transf_partial transf_fundef _ TRANSF).
+Lemma senv_preserved:
+  Senv.equiv ge tge.
+Proof (Genv.senv_transf_partial TRANSF).
 
 Lemma sig_preserved:
   forall f tf,
@@ -645,8 +637,7 @@ Proof.
   left; econstructor; split. simpl.
   apply plus_one. eapply exec_Lbuiltin; 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.
 
   (* Lbranch *)
@@ -703,8 +694,7 @@ Proof.
   (* external function *)
   monadInv H8. left; 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.
 
   (* return *)
@@ -721,10 +711,9 @@ Proof.
   intros. inversion H.
   exploit function_ptr_translated; eauto. intros [tf [A B]].
   exists (Callstate nil tf (Locmap.init Vundef) m0); split.
-  econstructor; eauto. eapply Genv.init_mem_transf_partial; eauto.
-  replace (prog_main tprog) with (prog_main prog).
+  econstructor; eauto. eapply (Genv.init_mem_transf_partial TRANSF); eauto.
+  rewrite (match_program_main TRANSF).
   rewrite symbols_preserved. eauto.
-  symmetry. apply (transform_partial_program_main transf_fundef _ TRANSF).
   rewrite <- H3. apply sig_preserved. auto.
   constructor. constructor. auto.
 Qed.
@@ -740,7 +729,7 @@ Theorem transf_program_correct:
   forward_simulation (LTL.semantics prog) (Linear.semantics tprog).
 Proof.
   eapply forward_simulation_star.
-  eexact public_preserved.
+  apply senv_preserved.
   eexact transf_initial_states.
   eexact transf_final_states.
   eexact transf_step_correct.