From 10941819e09e2f9090e7fe39301a0b9026a0eba0 Mon Sep 17 00:00:00 2001
From: Xavier Leroy <xavier.leroy@inria.fr>
Date: Wed, 5 Nov 2014 14:36:14 +0100
Subject: Verification of the Unusedglob pass (removal of unreferenced static
 global definitions).  Assorted changes to ia32/Op.v.  PowerPC and ARM need
 updating.

---
 backend/Unusedglob.v | 141 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 backend/Unusedglob.v

(limited to 'backend/Unusedglob.v')

diff --git a/backend/Unusedglob.v b/backend/Unusedglob.v
new file mode 100644
index 00000000..55a093a4
--- /dev/null
+++ b/backend/Unusedglob.v
@@ -0,0 +1,141 @@
+(* *********************************************************************)
+(*                                                                     *)
+(*              The Compcert verified compiler                         *)
+(*                                                                     *)
+(*          Xavier Leroy, INRIA Paris-Rocquencourt                     *)
+(*                                                                     *)
+(*  Copyright Institut National de Recherche en Informatique et en     *)
+(*  Automatique.  All rights reserved.  This file is distributed       *)
+(*  under the terms of the INRIA Non-Commercial License Agreement.     *)
+(*                                                                     *)
+(* *********************************************************************)
+
+(** Elimination of unreferenced static definitions *)
+
+Require Import FSets.
+Require Import Coqlib.
+Require Import Ordered.
+Require Import Maps.
+Require Import Iteration.
+Require Import AST.
+Require Import Errors.
+Require Import Op.
+Require Import Registers.
+Require Import RTL.
+
+Local Open Scope string_scope.
+
+(** * Determination of global identifiers that are referenced *)
+
+(** The working set *)
+
+Module IS := FSetAVL.Make(OrderedPositive).
+
+Record workset := mk_workset {
+  w_seen :> IS.t;
+  w_todo: list ident
+}.
+
+Definition add_workset (id: ident) (w: workset) : workset :=
+  if IS.mem id w.(w_seen)
+  then w
+  else {| w_seen := IS.add id w.(w_seen); w_todo := id :: w.(w_todo) |}.
+
+Fixpoint addlist_workset (l: list ident) (w: workset) : workset :=
+  match l with
+  | nil => w
+  | id :: l' => addlist_workset l' (add_workset id w)
+  end.
+
+(** Global symbols referenced in a function or variable definition *)
+
+Definition ref_instruction (i: instruction) : list ident :=
+  match i with
+  | Inop _ => nil
+  | Iop op _ _ _ => globals_operation op
+  | Iload _ addr _ _ _ => globals_addressing addr
+  | Istore _ addr _ _ _ => globals_addressing addr
+  | Icall _ (inl r) _ _ _ => nil
+  | Icall _ (inr id) _ _ _ => id :: nil
+  | Itailcall _ (inl r) _ => nil
+  | Itailcall _ (inr id) _ => id :: nil
+  | Ibuiltin ef _ _ _ => globals_external ef
+  | Icond cond _ _ _ => nil
+  | Ijumptable _ _ => nil
+  | Ireturn _ => nil
+  end.
+
+Definition add_ref_instruction (w: workset) (pc: node) (i: instruction) : workset :=
+  addlist_workset (ref_instruction i) w.
+
+Definition add_ref_function (f: function) (w: workset): workset :=
+  PTree.fold add_ref_instruction f.(fn_code) w.
+
+Definition add_ref_init_data (w: workset) (i: init_data) : workset :=
+  match i with
+  | Init_addrof id _ => add_workset id w
+  | _ => w
+  end.
+
+Definition add_ref_globvar (gv: globvar unit) (w: workset): workset :=
+  List.fold_left add_ref_init_data gv.(gvar_init) w.
+
+Definition prog_map : Type := PTree.t (globdef fundef unit).
+
+Definition add_ref_definition (pm: prog_map) (id: ident) (w: workset): workset :=
+  match pm!id with
+  | None => w
+  | Some (Gfun (Internal f)) => add_ref_function f w
+  | Some (Gfun (External ef)) => addlist_workset (globals_external ef) w
+  | Some (Gvar gv) => add_ref_globvar gv w
+  end.
+
+(** Traversal of the dependency graph. *)
+
+Definition iter_step (pm: prog_map) (w: workset) : IS.t + workset :=
+  match w.(w_todo) with
+  | nil =>
+      inl _ w.(w_seen)
+  | id :: rem =>
+      inr _ (add_ref_definition pm id {| w_seen := w.(w_seen); w_todo := rem |})
+  end.
+
+Definition initial_workset (p: program): workset :=
+  add_workset p.(prog_main)
+    (List.fold_left (fun w id => add_workset id w)
+                    p.(prog_public)
+                    {| w_seen := IS.empty; w_todo := nil |}).
+
+Definition add_def_prog_map (pm: prog_map) (id_df: ident * globdef fundef unit) : prog_map :=
+  PTree.set (fst id_df) (snd id_df) pm.
+
+Definition program_map (p: program) : prog_map :=
+  List.fold_left add_def_prog_map p.(prog_defs) (PTree.empty _).
+
+Definition used_globals (p: program) : option IS.t :=
+  let pm := program_map p in
+  PrimIter.iterate _ _ (iter_step pm) (initial_workset p).
+
+(** * Elimination of unreferenced global definitions *)
+
+(** We also eliminate multiple definitions of the same global name, keeping ony
+  the last definition (in program definition order). *)
+
+Fixpoint filter_globdefs (used: IS.t) (accu defs: list (ident * globdef fundef unit)) :=
+  match defs with
+  | nil => accu
+  | (id, gd) :: defs' =>
+      if IS.mem id used
+      then filter_globdefs (IS.remove id used) ((id, gd) :: accu) defs'
+      else filter_globdefs used accu defs'
+  end.
+
+Definition transform_program (p: program) : res program :=
+  match used_globals p with
+  | None => Error (msg "Unusedglob: analysis failed")
+  | Some used =>
+      OK {| prog_defs := filter_globdefs used nil (List.rev p.(prog_defs));
+            prog_public := p.(prog_public);
+            prog_main := p.(prog_main) |}
+  end.
+
-- 
cgit