[pph] Do not emit the same decl more than once in the symbol table

gcc/cp/pph-streamer-out.c

 /* Routines for writing PPH data.
    Copyright (C) 2011 Free Software Foundation, Inc.
    Contributed by Diego Novillo <dnovillo@google.com>.
 
    This file is part of GCC.
 
    GCC is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 3, or (at your option)
    any later version.
@@ skipping 25 matching lines @@
 /* FIXME pph.  This holds the FILE handle for the current PPH file
    that we are writing.  It is necessary because the LTO callbacks do
    not allow passing a FILE handle to them.  */
 static FILE *current_pph_file = NULL;
 
 /* List of declarations to register with the middle end.  This is
    collected as the compiler instantiates symbols and functions.  Once
    we finish parsing the header file, this array is written out to the
    PPH image.  This way, the reader will be able to instantiate these
    symbols in the same order that they were instantiated originally.  */
-static VEC(tree,heap) *decls_to_register = NULL;
+typedef struct decls_to_register_t {
+  /* Table of all the declarations to register in declaration order.  */
+  VEC(tree,heap) *v;
+
+  /* Set of declarations to register used to avoid adding duplicate
+     entries to the table.  */
+  struct pointer_set_t *m;
+} decls_to_register_t;
+
+static decls_to_register_t decls_to_register = { NULL, NULL };
 
 /* Callback for packing value fields in ASTs.  BP is the bitpack·
    we are packing into.  EXPR is the tree to pack.  */
 
 void
 pph_pack_value_fields (struct bitpack_d *bp, tree expr)
 {
   if (TYPE_P (expr))
     {
       bp_pack_value (bp, TYPE_LANG_FLAG_0 (expr), 1);
@@ skipping 1172 matching lines @@
    original header files and out of PPH images.
 
    REF_P is as in pph_out_tree.  */
 
 static void
 pph_out_symtab (pph_stream *stream, bool ref_p)
 {
   tree decl;
   unsigned i;
 
-  pph_out_uint (stream, VEC_length (tree, decls_to_register));
-  FOR_EACH_VEC_ELT (tree, decls_to_register, i, decl)
+  pph_out_uint (stream, VEC_length (tree, decls_to_register.v));
+  FOR_EACH_VEC_ELT (tree, decls_to_register.v, i, decl)
     if (TREE_CODE (decl) == FUNCTION_DECL && DECL_STRUCT_FUNCTION (decl))
       {
         if (DECL_SAVED_TREE (decl))
           pph_out_symtab_marker (stream, PPH_SYMTAB_FUNCTION_BODY);
         else
           pph_out_symtab_marker (stream, PPH_SYMTAB_FUNCTION);
         pph_out_struct_function (stream, DECL_STRUCT_FUNCTION (decl), ref_p);
       }
     else
       {
         pph_out_symtab_marker (stream, PPH_SYMTAB_DECL);
         pph_out_tree (stream, decl, ref_p);
       }
 
-  VEC_free (tree, heap, decls_to_register);
+  if (decls_to_register.m)
+    {
+      VEC_free (tree, heap, decls_to_register.v);
+      pointer_set_destroy (decls_to_register.m);
+      decls_to_register.m = NULL;
+    }
 }
 
 
 /* Write PPH output symbols and IDENTS_USED to STREAM as an object.  */
 
 static void
 pph_write_file_contents (pph_stream *stream, cpp_idents_used *idents_used)
 {·
   /* Emit all the identifiers and symbols in the global namespace.  */
   pph_out_identifiers (stream, idents_used);
+
+  /* Emit the bindings for the global namespace.  */
   pph_out_scope_chain (stream, scope_chain, false);
   if (flag_pph_dump_tree)
     pph_dump_namespace (pph_logfile, global_namespace);
 
   /* Emit other global state kept by the parser.  FIXME pph, these
      globals should be fields in struct cp_parser.  */
   pph_out_tree (stream, keyed_classes, false);
   pph_out_tree_vec (stream, unemitted_tinfo_decls, false);
   pph_out_tree (stream, static_aggregates, false);
 
@@ skipping 382 matching lines @@
 }
 
 
 /* Add DECL to the list of symbols that need to be registered with the
    middle end when reading current_pph_stream.  */
 
 void
 pph_add_decl_to_register (tree decl)
 {
   if (decl)
-    VEC_safe_push (tree, heap, decls_to_register, decl);
+    {
+      if (decls_to_register.m == NULL)
+        decls_to_register.m = pointer_set_create ();
+
+      if (!pointer_set_insert (decls_to_register.m, decl))
+        VEC_safe_push (tree, heap, decls_to_register.v, decl);
+    }
 }