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, 26 insertions, 32 deletions

diff --git a/backend/Tunnelingproof.v b/backend/Tunnelingproof.v
index 22f0521e..4f1f8143 100644
--- a/backend/Tunnelingproof.v
+++ b/backend/Tunnelingproof.v
@@ -12,20 +12,21 @@
 
 (** Correctness proof for the branch tunneling optimization. *)
 
-Require Import Coqlib.
-Require Import Maps.
-Require Import UnionFind.
-Require Import AST.
-Require Import Values.
-Require Import Memory.
-Require Import Events.
-Require Import Globalenvs.
-Require Import Smallstep.
-Require Import Op.
-Require Import Locations.
-Require Import LTL.
+Require Import Coqlib Maps UnionFind.
+Require Import AST Linking.
+Require Import Values Memory Events Globalenvs Smallstep.
+Require Import Op Locations LTL.
 Require Import Tunneling.
 
+Definition match_prog (p tp: program) :=
+  match_program (fun ctx f tf => tf = tunnel_fundef f) eq p tp.
+
+Lemma transf_program_match:
+  forall p, match_prog p (tunnel_program p).
+Proof.
+  intros. eapply match_transform_program; eauto.
+Qed.
+
 (** * Properties of the branch map computed using union-find. *)
 
 (** A variant of [record_goto] that also incrementally computes a measure [f: node -> nat]
@@ -138,8 +139,8 @@ Qed.
 
 Section PRESERVATION.
 
-Variable prog: program.
-Let tprog := tunnel_program prog.
+Variables prog tprog: program.
+Hypothesis TRANSL: match_prog prog tprog.
 Let ge := Genv.globalenv prog.
 Let tge := Genv.globalenv tprog.
 
@@ -147,27 +148,22 @@ Lemma functions_translated:
   forall v f,
   Genv.find_funct ge v = Some f ->
   Genv.find_funct tge v = Some (tunnel_fundef f).
-Proof (@Genv.find_funct_transf _ _ _ tunnel_fundef prog).
+Proof (Genv.find_funct_transf TRANSL).
 
 Lemma function_ptr_translated:
   forall v f,
   Genv.find_funct_ptr ge v = Some f ->
   Genv.find_funct_ptr tge v = Some (tunnel_fundef f).
-Proof (@Genv.find_funct_ptr_transf _ _ _ tunnel_fundef prog).
+Proof (Genv.find_funct_ptr_transf TRANSL).
 
 Lemma symbols_preserved:
   forall id,
   Genv.find_symbol tge id = Genv.find_symbol ge id.
-Proof (@Genv.find_symbol_transf _ _ _ tunnel_fundef prog).
-
-Lemma public_preserved:
-  forall id,
-  Genv.public_symbol tge id = Genv.public_symbol ge id.
-Proof (@Genv.public_symbol_transf _ _ _ tunnel_fundef prog).
+Proof (Genv.find_symbol_transf TRANSL).
 
-Lemma varinfo_preserved:
-  forall b, Genv.find_var_info tge b = Genv.find_var_info ge b.
-Proof (@Genv.find_var_info_transf _ _ _ tunnel_fundef prog).
+Lemma senv_preserved:
+  Senv.equiv ge tge.
+Proof (Genv.senv_transf TRANSL).
 
 Lemma sig_preserved:
   forall f, funsig (tunnel_fundef f) = funsig f.
@@ -340,8 +336,7 @@ Proof.
   left; simpl; econstructor; split.
   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. apply senv_preserved. eauto.
   econstructor; eauto.
 
   (* Lbranch (preserved) *)
@@ -372,8 +367,7 @@ Proof.
   (* external function *)
   left; simpl; econstructor; split.
   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.
   simpl. econstructor; eauto.
   (* return *)
   inv H3. inv H1.
@@ -389,8 +383,8 @@ Proof.
   intros. inversion H.
   exists (Callstate nil (tunnel_fundef f) (Locmap.init Vundef) m0); split.
   econstructor; eauto.
-  apply Genv.init_mem_transf; auto.
-  change (prog_main tprog) with (prog_main prog).
+  apply (Genv.init_mem_transf TRANSL); auto.
+  rewrite (match_program_main TRANSL).
   rewrite symbols_preserved. eauto.
   apply function_ptr_translated; auto.
   rewrite <- H3. apply sig_preserved.
@@ -408,7 +402,7 @@ Theorem transf_program_correct:
   forward_simulation (LTL.semantics prog) (LTL.semantics tprog).
 Proof.
   eapply forward_simulation_opt.
-  eexact public_preserved.
+  apply senv_preserved.
   eexact transf_initial_states.
   eexact transf_final_states.
   eexact tunnel_step_correct.