From 0053b1aa1d26da5d1f995a603b127daf799c2da9 Mon Sep 17 00:00:00 2001
From: xleroy <xleroy@fca1b0fc-160b-0410-b1d3-a4f43f01ea2e>
Date: Mon, 21 May 2012 16:26:30 +0000
Subject: Merge of the newmem branch: - Revised memory model with Max and Cur
 permissions, but without bounds - Constant propagation of 'const' globals -
 Function inlining at RTL level - (Unprovable) elimination of unreferenced
 static definitions

git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1899 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e
---
 backend/Unusedglob.ml | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 backend/Unusedglob.ml

(limited to 'backend/Unusedglob.ml')

diff --git a/backend/Unusedglob.ml b/backend/Unusedglob.ml
new file mode 100644
index 0000000..4139678
--- /dev/null
+++ b/backend/Unusedglob.ml
@@ -0,0 +1,91 @@
+(* *********************************************************************)
+(*                                                                     *)
+(*              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.     *)
+(*                                                                     *)
+(* *********************************************************************)
+
+(* Removing unused definitions of static functions and global variables *)
+
+open Camlcoq
+open Maps
+open AST
+open Asm
+open Unusedglob1
+
+module IdentSet = Set.Make(struct type t = ident let compare = compare end)
+
+(* The set of globals referenced from a function definition *)
+
+let add_referenced_instr rf i =
+  List.fold_right IdentSet.add (referenced_instr i) rf
+
+let referenced_function f =
+  List.fold_left add_referenced_instr IdentSet.empty (code_of_function f)
+
+let referenced_fundef = function
+  | Internal f -> referenced_function f
+  | External ef -> IdentSet.empty
+
+(* The set of globals referenced from a variable definition (initialization) *)
+
+let add_referenced_init_data rf = function
+  | Init_addrof(id, ofs) -> IdentSet.add id rf
+  | _ -> rf
+
+let referenced_globvar gv =
+  List.fold_left add_referenced_init_data IdentSet.empty gv.gvar_init
+
+(* The map global |-> set of globals it references *)
+
+let use_map p =
+  List.fold_left (fun m (id, gv) -> PTree.set id (referenced_globvar gv) m)
+  (List.fold_left (fun m (id, fd) -> PTree.set id (referenced_fundef fd) m)
+   PTree.empty p.prog_funct) p.prog_vars
+
+(* Worklist algorithm computing the set of used globals *)
+
+let rec used_idents usemap used wrk =
+  match wrk with
+  | [] -> used
+  | id :: wrk ->
+      if IdentSet.mem id used then used_idents usemap used wrk else
+        match PTree.get id usemap with
+        | None -> used_idents usemap used wrk
+        | Some s -> used_idents usemap (IdentSet.add id used)
+                                       (IdentSet.fold (fun id l -> id::l) s wrk)
+
+(* The worklist is initially populated with all nonstatic globals *)
+
+let add_nonstatic wrk id =
+  if C2C.atom_is_static id then wrk else id :: wrk
+
+let initial_worklist p =
+  List.fold_left (fun wrk (id, gv) -> add_nonstatic wrk id)
+   (List.fold_left (fun wrk (id, fd) -> add_nonstatic wrk id)
+     [] p.prog_funct) p.prog_vars
+
+(* Eliminate unused definitions *)
+
+let rec filter used = function
+  | [] -> []
+  | (id, def) :: rem ->
+      if IdentSet.mem id used
+      then (id, def) :: filter used rem
+      else filter used rem
+
+let filter_prog used p =
+  { prog_funct = filter used p.prog_funct;
+    prog_main = p.prog_main;
+    prog_vars = filter used p.prog_vars }
+
+(* Entry point *)
+
+let transf_program p =
+  filter_prog (used_idents (use_map p) IdentSet.empty (initial_worklist p)) p
+
-- 
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