cgraph.h (const_value_known_p): Replace by ...

	* cgraph.h (const_value_known_p): Replace by ...
	(ctor_for_folding): .. this one.
	* cgraphunit.c (process_function_and_variable_attributes): Use it.
	* lto-cgraph.c (compute_ltrans_boundary): Use ctor_for_folding.
	* expr.c (expand_expr_real_1): Likewise.
	(string_constant): Likewise.
	* tree-ssa-loop-ivcanon.c (constant_after_peeling): Likewise.
	* ipa.c (process_references): Likewise.
	(symtab_remove_unreachable_nodes): Likewise.
	* ipa-inline-analysis.c (param_change_prob): Likewise.
	* gimple-fold.c (canonicalize_constructor_val): Likewise.
	(get_base_constructor): Likwise.
	* varpool.c (varpool_remove_node): Likewise.
	(varpool_remove_initializer): LIkewise.
	(dump_varpool_node): LIkwise.
	(const_value_known_p): Rewrite to ...
	(ctor_for_folding): ... this one.

	* lto-partition.c (add_references_to_partition): Use
	ctor_for_folding.

	* gcc.dg/tree-ssa/attr-alias-2.c: New testcase.

From-SVN: r200211

14 files changed, 224 insertions, 112 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8b6bc6f..b2c2ee7 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,23 @@
+2013-06-19  Jan Hubicka  <jh@suse.cz>
+
+	* cgraph.h (const_value_known_p): Replace by ...
+	(ctor_for_folding): .. this one.
+	* cgraphunit.c (process_function_and_variable_attributes): Use it.
+	* lto-cgraph.c (compute_ltrans_boundary): Use ctor_for_folding.
+	* expr.c (expand_expr_real_1): Likewise.
+	(string_constant): Likewise.
+	* tree-ssa-loop-ivcanon.c (constant_after_peeling): Likewise.
+	* ipa.c (process_references): Likewise.
+	(symtab_remove_unreachable_nodes): Likewise.
+	* ipa-inline-analysis.c (param_change_prob): Likewise.
+	* gimple-fold.c (canonicalize_constructor_val): Likewise.
+	(get_base_constructor): Likwise.
+	* varpool.c (varpool_remove_node): Likewise.
+	(varpool_remove_initializer): LIkewise.
+	(dump_varpool_node): LIkwise.
+	(const_value_known_p): Rewrite to ...
+	(ctor_for_folding): ... this one.
+
 2013-06-19  Jakub Jelinek  <jakub@redhat.com>
 
 	PR driver/57651
diff --git a/gcc/cgraph.h b/gcc/cgraph.h
index 6259189..ef2a2a0 100644
--- a/gcc/cgraph.h
+++ b/gcc/cgraph.h
@@ -797,7 +797,7 @@ void varpool_analyze_node (struct varpool_node *);
 struct varpool_node * varpool_extra_name_alias (tree, tree);
 struct varpool_node * varpool_create_variable_alias (tree, tree);
 void varpool_reset_queue (void);
-bool const_value_known_p (tree);
+tree ctor_for_folding (tree);
 bool varpool_for_node_and_aliases (struct varpool_node *,
 		                   bool (*) (struct varpool_node *, void *),
 			           void *, bool);
diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index 51365eb..731a0e9 100644
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -762,8 +762,7 @@ process_function_and_variable_attributes (struct cgraph_node *first,
     {
       tree decl = vnode->symbol.decl;
       if (DECL_EXTERNAL (decl)
-	  && DECL_INITIAL (decl)
-	  && const_value_known_p (decl))
+	  && DECL_INITIAL (decl))
 	varpool_finalize_decl (decl);
       if (DECL_PRESERVE_P (decl))
 	vnode->symbol.force_output = true;
diff --git a/gcc/expr.c b/gcc/expr.c
index 2a7824b..bce96c9 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -9698,6 +9698,7 @@ expand_expr_real_1 (tree exp, rtx target, enum machine_mode tmode,
       {
 	tree array = treeop0;
 	tree index = treeop1;
+        tree init;
 
 	/* Fold an expression like: "foo"[2].
 	   This is not done in fold so it won't happen inside &.
@@ -9744,76 +9745,72 @@ expand_expr_real_1 (tree exp, rtx target, enum machine_mode tmode,
 		 && modifier != EXPAND_INITIALIZER
 		 && modifier != EXPAND_MEMORY
 		 && TREE_READONLY (array) && ! TREE_SIDE_EFFECTS (array)
-		 && TREE_CODE (array) == VAR_DECL && DECL_INITIAL (array)
-		 && TREE_CODE (DECL_INITIAL (array)) != ERROR_MARK
-		 && const_value_known_p (array))
+		 && TREE_CODE (index) == INTEGER_CST
+		 && (TREE_CODE (array) == VAR_DECL
+		     || TREE_CODE (array) == CONST_DECL)
+		 && (init = ctor_for_folding (array)) != error_mark_node)
 	  {
-	    if (TREE_CODE (index) == INTEGER_CST)
+	    if (TREE_CODE (init) == CONSTRUCTOR)
 	      {
-		tree init = DECL_INITIAL (array);
+		unsigned HOST_WIDE_INT ix;
+		tree field, value;
 
-		if (TREE_CODE (init) == CONSTRUCTOR)
-		  {
-		    unsigned HOST_WIDE_INT ix;
-		    tree field, value;
+		FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (init), ix,
+					  field, value)
+		  if (tree_int_cst_equal (field, index))
+		    {
+		      if (TREE_SIDE_EFFECTS (value))
+			break;
 
-		    FOR_EACH_CONSTRUCTOR_ELT (CONSTRUCTOR_ELTS (init), ix,
-					      field, value)
-		      if (tree_int_cst_equal (field, index))
+		      if (TREE_CODE (value) == CONSTRUCTOR)
 			{
-			  if (TREE_SIDE_EFFECTS (value))
+			  /* If VALUE is a CONSTRUCTOR, this
+			     optimization is only useful if
+			     this doesn't store the CONSTRUCTOR
+			     into memory.  If it does, it is more
+			     efficient to just load the data from
+			     the array directly.  */
+			  rtx ret = expand_constructor (value, target,
+							modifier, true);
+			  if (ret == NULL_RTX)
 			    break;
-
-			  if (TREE_CODE (value) == CONSTRUCTOR)
-			    {
-			      /* If VALUE is a CONSTRUCTOR, this
-				 optimization is only useful if
-				 this doesn't store the CONSTRUCTOR
-				 into memory.  If it does, it is more
-				 efficient to just load the data from
-				 the array directly.  */
-			      rtx ret = expand_constructor (value, target,
-							    modifier, true);
-			      if (ret == NULL_RTX)
-				break;
-			    }
-
-			  return expand_expr (fold (value), target, tmode,
-					      modifier);
 			}
-		  }
-		else if(TREE_CODE (init) == STRING_CST)
+
+		      return expand_expr (fold (value), target, tmode,
+					  modifier);
+		    }
+	      }
+	    else if(TREE_CODE (init) == STRING_CST)
+	      {
+		tree index1 = index;
+		tree low_bound = array_ref_low_bound (exp);
+		index1 = fold_convert_loc (loc, sizetype,
+					   treeop1);
+
+		/* Optimize the special-case of a zero lower bound.
+
+		   We convert the low_bound to sizetype to avoid some problems
+		   with constant folding.  (E.g. suppose the lower bound is 1,
+		   and its mode is QI.  Without the conversion,l (ARRAY
+		   +(INDEX-(unsigned char)1)) becomes ((ARRAY+(-(unsigned char)1))
+		   +INDEX), which becomes (ARRAY+255+INDEX).  Opps!)  */
+
+		if (! integer_zerop (low_bound))
+		  index1 = size_diffop_loc (loc, index1,
+					fold_convert_loc (loc, sizetype,
+							  low_bound));
+
+		if (0 > compare_tree_int (index1,
+					  TREE_STRING_LENGTH (init)))
 		  {
-		    tree index1 = index;
-		    tree low_bound = array_ref_low_bound (exp);
-		    index1 = fold_convert_loc (loc, sizetype,
-					       treeop1);
-
-		    /* Optimize the special-case of a zero lower bound.
-
-		       We convert the low_bound to sizetype to avoid some problems
-		       with constant folding.  (E.g. suppose the lower bound is 1,
-		       and its mode is QI.  Without the conversion,l (ARRAY
-		       +(INDEX-(unsigned char)1)) becomes ((ARRAY+(-(unsigned char)1))
-		       +INDEX), which becomes (ARRAY+255+INDEX).  Opps!)  */
-
-		    if (! integer_zerop (low_bound))
-		      index1 = size_diffop_loc (loc, index1,
-					    fold_convert_loc (loc, sizetype,
-							      low_bound));
-
-		    if (0 > compare_tree_int (index1,
-					      TREE_STRING_LENGTH (init)))
-		      {
-			tree type = TREE_TYPE (TREE_TYPE (init));
-			enum machine_mode mode = TYPE_MODE (type);
-
-			if (GET_MODE_CLASS (mode) == MODE_INT
-			    && GET_MODE_SIZE (mode) == 1)
-			  return gen_int_mode (TREE_STRING_POINTER (init)
-					       [TREE_INT_CST_LOW (index1)],
-					       mode);
-		      }
+		    tree type = TREE_TYPE (TREE_TYPE (init));
+		    enum machine_mode mode = TYPE_MODE (type);
+
+		    if (GET_MODE_CLASS (mode) == MODE_INT
+			&& GET_MODE_SIZE (mode) == 1)
+		      return gen_int_mode (TREE_STRING_POINTER (init)
+					   [TREE_INT_CST_LOW (index1)],
+					   mode);
 		  }
 	      }
 	  }
@@ -10676,17 +10673,18 @@ string_constant (tree arg, tree *ptr_offset)
 	   || TREE_CODE (array) == CONST_DECL)
     {
       int length;
+      tree init = ctor_for_folding (array);
 
       /* Variables initialized to string literals can be handled too.  */
-      if (!const_value_known_p (array)
-	  || !DECL_INITIAL (array)
-	  || TREE_CODE (DECL_INITIAL (array)) != STRING_CST)
+      if (init == error_mark_node
+	  || !init
+	  || TREE_CODE (init) != STRING_CST)
 	return 0;
 
       /* Avoid const char foo[4] = "abcde";  */
       if (DECL_SIZE_UNIT (array) == NULL_TREE
 	  || TREE_CODE (DECL_SIZE_UNIT (array)) != INTEGER_CST
-	  || (length = TREE_STRING_LENGTH (DECL_INITIAL (array))) <= 0
+	  || (length = TREE_STRING_LENGTH (init)) <= 0
 	  || compare_tree_int (DECL_SIZE_UNIT (array), length) < 0)
 	return 0;
 
@@ -10699,7 +10697,7 @@ string_constant (tree arg, tree *ptr_offset)
 	return 0;
 
       *ptr_offset = offset;
-      return DECL_INITIAL (array);
+      return init;
     }
 
   return 0;
diff --git a/gcc/gimple-fold.c b/gcc/gimple-fold.c
index 60fca6b..b6d22b3 100644
--- a/gcc/gimple-fold.c
+++ b/gcc/gimple-fold.c
@@ -192,9 +192,9 @@ canonicalize_constructor_val (tree cval, tree from_decl)
 tree
 get_symbol_constant_value (tree sym)
 {
-  if (const_value_known_p (sym))
+  tree val = ctor_for_folding (sym);
+  if (val != error_mark_node)
     {
-      tree val = DECL_INITIAL (sym);
       if (val)
 	{
 	  val = canonicalize_constructor_val (unshare_expr (val), sym);
@@ -2695,19 +2695,18 @@ get_base_constructor (tree base, HOST_WIDE_INT *bit_offset,
   switch (TREE_CODE (base))
     {
     case VAR_DECL:
-      if (!const_value_known_p (base))
-	return NULL_TREE;
-
-      /* Fallthru.  */
     case CONST_DECL:
-      if (!DECL_INITIAL (base)
-	  && (TREE_STATIC (base) || DECL_EXTERNAL (base)))
-        return error_mark_node;
-      /* Do not return an error_mark_node DECL_INITIAL.  LTO uses this
-         as special marker (_not_ zero ...) for its own purposes.  */
-      if (DECL_INITIAL (base) == error_mark_node)
-	return NULL_TREE;
-      return DECL_INITIAL (base);
+      {
+	tree init = ctor_for_folding (base);
+
+	/* Our semantic is exact oposite of ctor_for_folding;
+	   NULL means unknown, while error_mark_node is 0.  */
+	if (init == error_mark_node)
+	  return NULL_TREE;
+	if (!init)
+	  return error_mark_node;
+	return init;
+      }
 
     case ARRAY_REF:
     case COMPONENT_REF:
diff --git a/gcc/ipa-inline-analysis.c b/gcc/ipa-inline-analysis.c
index a25f517..9a36292 100644
--- a/gcc/ipa-inline-analysis.c
+++ b/gcc/ipa-inline-analysis.c
@@ -2106,8 +2106,9 @@ param_change_prob (gimple stmt, int i)
       struct record_modified_bb_info info;
       bitmap_iterator bi;
       unsigned index;
+      tree init = ctor_for_folding (base);
 
-      if (const_value_known_p (base))
+      if (init != error_mark_node)
 	return 0;
       if (!bb->frequency)
 	return REG_BR_PROB_BASE;
diff --git a/gcc/ipa.c b/gcc/ipa.c
index 0f2a5c8..7c0d495 100644
--- a/gcc/ipa.c
+++ b/gcc/ipa.c
@@ -145,7 +145,9 @@ process_references (struct ipa_ref_list *list,
 		     constant folding.  Keep references alive so partitioning
 		     knows about potential references.  */
 		  || (TREE_CODE (node->symbol.decl) == VAR_DECL
-		      && flag_wpa && const_value_known_p (node->symbol.decl)))))
+		      && flag_wpa
+		      && ctor_for_folding (node->symbol.decl)
+		         != error_mark_node))))
 	pointer_set_insert (reachable, node);
       enqueue_node ((symtab_node) node, first, reachable);
     }
@@ -400,6 +402,7 @@ symtab_remove_unreachable_nodes (bool before_inlining_p, FILE *file)
 	}
       else if (!pointer_set_contains (reachable, vnode))
         {
+	  tree init;
 	  if (vnode->symbol.definition)
 	    {
 	      if (file)
@@ -411,8 +414,10 @@ symtab_remove_unreachable_nodes (bool before_inlining_p, FILE *file)
 	  vnode->symbol.aux = NULL;
 
 	  /* Keep body if it may be useful for constant folding.  */
-	  if (!const_value_known_p (vnode->symbol.decl))
+	  if ((init = ctor_for_folding (vnode->symbol.decl)) == error_mark_node)
 	    varpool_remove_initializer (vnode);
+	  else
+	    DECL_INITIAL (vnode->symbol.decl) = init;
 	  ipa_remove_all_references (&vnode->symbol.ref_list);
 	}
       else
diff --git a/gcc/lto-cgraph.c b/gcc/lto-cgraph.c
index e3f8880..2122f70 100644
--- a/gcc/lto-cgraph.c
+++ b/gcc/lto-cgraph.c
@@ -766,10 +766,9 @@ compute_ltrans_boundary (lto_symtab_encoder_t in_encoder)
       symtab_node node = lto_symtab_encoder_deref (encoder, i);
       if (varpool_node *vnode = dyn_cast <varpool_node> (node))
 	{
-	  if (DECL_INITIAL (vnode->symbol.decl)
-	      && !lto_symtab_encoder_encode_initializer_p (encoder,
-							   vnode)
-	      && const_value_known_p (vnode->symbol.decl))
+	  if (!lto_symtab_encoder_encode_initializer_p (encoder,
+							vnode)
+	      && ctor_for_folding (vnode->symbol.decl) != error_mark_node)
 	    {
 	      lto_set_symtab_encoder_encode_initializer (encoder, vnode);
 	      add_references (encoder, &vnode->symbol.ref_list);
diff --git a/gcc/lto/ChangeLog b/gcc/lto/ChangeLog
index aeda657..2723678 100644
--- a/gcc/lto/ChangeLog
+++ b/gcc/lto/ChangeLog
@@ -1,3 +1,8 @@
+2013-06-19  Jan Hubicka  <jh@suse.cz>
+
+	* lto-partition.c (add_references_to_partition): Use
+	ctor_for_folding.
+
 2013-06-18  Richard Biener  <rguenther@suse.de>
 
 	* lto.c (lto_register_var_decl_in_symtab): Pass in cache index
diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c
index 6f45380..ffc8da3 100644
--- a/gcc/lto/lto-partition.c
+++ b/gcc/lto/lto-partition.c
@@ -146,7 +146,7 @@ add_references_to_partition (ltrans_partition part, symtab_node node)
        Recursively look into the initializers of the constant variable and add
        references, too.  */
     else if (is_a <varpool_node> (ref->referred)
-	     && const_value_known_p (ref->referred->symbol.decl)
+	     && ctor_for_folding (ref->referred->symbol.decl) != error_mark_node
 	     && !lto_symtab_encoder_in_partition_p (part->encoder, ref->referred))
       {
 	if (!part->initializers_visited)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f731837..baae9b9 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-06-19  Jan Hubicka  <jh@suse.cz>
+
+	* gcc.dg/tree-ssa/attr-alias-2.c: New testcase.
+
 2013-06-19  Balaji V. Iyer  <balaji.v.iyer@intel.com>
 
        * c-c++-common/cilk-plus/AN/builtin_fn_custom.c: Replaced all the
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/attr-alias-2.c b/gcc/testsuite/gcc.dg/tree-ssa/attr-alias-2.c
new file mode 100644
index 0000000..50623a4
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/attr-alias-2.c
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+/* { dg-require-alias "" } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+static int a=4;
+static int b __attribute__ ((alias("a")));
+main()
+{
+   return b+a;
+}
+/* { dg-final { scan-tree-dump "return 8" "optimized" } } */
+/* { dg-do compile } */
+/* { dg-require-alias "" } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+static int a=4;
+static int b __attribute__ ((alias("a")));
+main()
+{
+   return b+a;
+}
+/* { dg-final { scan-tree-dump "return 8" "optimized" } } */
+/* { dg-do compile } */
+/* { dg-require-alias "" } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+static int a=4;
+static int b __attribute__ ((alias("a")));
+main()
+{
+   return b+a;
+}
+/* { dg-final { scan-tree-dump "return 8" "optimized" } } */
diff --git a/gcc/tree-ssa-loop-ivcanon.c b/gcc/tree-ssa-loop-ivcanon.c
index 45774e6..91cf8c1 100644
--- a/gcc/tree-ssa-loop-ivcanon.c
+++ b/gcc/tree-ssa-loop-ivcanon.c
@@ -174,7 +174,7 @@ constant_after_peeling (tree op, gimple stmt, struct loop *loop)
       while (handled_component_p (base))
 	base = TREE_OPERAND (base, 0);
       if ((DECL_P (base)
-	   && const_value_known_p (base))
+	   && ctor_for_folding (base) != error_mark_node)
 	  || CONSTANT_CLASS_P (base))
 	{
 	  /* If so, see if we understand all the indices.  */
diff --git a/gcc/varpool.c b/gcc/varpool.c
index 80e98b3..b426757 100644
--- a/gcc/varpool.c
+++ b/gcc/varpool.c
@@ -66,12 +66,15 @@ void
 varpool_remove_node (struct varpool_node *node)
 {
   symtab_unregister_node ((symtab_node)node);
+  tree init;
 
   /* Because we remove references from external functions before final compilation,
      we may end up removing useful constructors.
      FIXME: We probably want to trace boundaries better.  */
-  if (!const_value_known_p (node->symbol.decl))
+  if ((init = ctor_for_folding (node->symbol.decl)) == error_mark_node)
     varpool_remove_initializer (node);
+  else
+    DECL_INITIAL (node->symbol.decl) = init;
   ggc_free (node);
 }
 
@@ -109,7 +112,7 @@ dump_varpool_node (FILE *f, struct varpool_node *node)
     fprintf (f, " output");
   if (TREE_READONLY (node->symbol.decl))
     fprintf (f, " read-only");
-  if (const_value_known_p (node->symbol.decl))
+  if (ctor_for_folding (node->symbol.decl) != error_mark_node)
     fprintf (f, " const-value-known");
   fprintf (f, "\n");
 }
@@ -144,44 +147,93 @@ varpool_node_for_asm (tree asmname)
 }
 
 /* Return if DECL is constant and its initial value is known (so we can do
-   constant folding using DECL_INITIAL (decl)).  */
+   constant folding using DECL_INITIAL (decl)).
+   Return ERROR_MARK_NODE when value is unknown.  */
 
-bool
-const_value_known_p (tree decl)
+tree
+ctor_for_folding (tree decl)
 {
+  struct varpool_node *node, *real_node;
+  tree real_decl;
+
   if (TREE_CODE (decl) != VAR_DECL
-      &&TREE_CODE (decl) != CONST_DECL)
-    return false;
+      && TREE_CODE (decl) != CONST_DECL)
+    return error_mark_node;
 
   if (TREE_CODE (decl) == CONST_DECL
       || DECL_IN_CONSTANT_POOL (decl))
-    return true;
+    return DECL_INITIAL (decl);
+
+  if (TREE_THIS_VOLATILE (decl))
+    return error_mark_node;
+
+  /* Do not care about automatic variables.  Those are never initialized
+     anyway, because gimplifier exapnds the code*/
+  if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
+    {
+      gcc_assert (!TREE_PUBLIC (decl));
+      return error_mark_node;
+    }
 
   gcc_assert (TREE_CODE (decl) == VAR_DECL);
 
-  if (!TREE_READONLY (decl) || TREE_THIS_VOLATILE (decl))
-    return false;
+  node = varpool_get_node (decl);
+  if (node)
+    {
+      real_node = varpool_variable_node (node);
+      real_decl = real_node->symbol.decl;
+    }
+  else
+    real_decl = decl;
+
+  /* See if we are dealing with alias.
+     In most cases alias is just alternative symbol pointing to a given
+     constructor.  This allows us to use interposition rules of DECL
+     constructor of REAL_NODE.  However weakrefs are special by being just
+     alternative name of their target (if defined).  */
+  if (decl != real_decl)
+    {
+      gcc_assert (!DECL_INITIAL (decl)
+		  || DECL_INITIAL (decl) == error_mark_node);
+      if (lookup_attribute ("weakref", DECL_ATTRIBUTES (decl)))
+	{
+	  node = varpool_alias_target (node);
+	  decl = node->symbol.decl;
+	}
+    }
 
-  /* Gimplifier takes away constructors of local vars  */
-  if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
-    return DECL_INITIAL (decl) != NULL;
+  /* Vtables are defined by their types and must match no matter of interposition
+     rules.  */
+  if (DECL_VIRTUAL_P (real_decl))
+    {
+      gcc_checking_assert (TREE_READONLY (real_decl));
+      return DECL_INITIAL (real_decl);
+    }
+
+  /* If thre is no constructor, we have nothing to do.  */
+  if (DECL_INITIAL (real_decl) == error_mark_node)
+    return error_mark_node;
 
-  gcc_assert (TREE_STATIC (decl) || DECL_EXTERNAL (decl));
+  /* Non-readonly alias of readonly variable is also de-facto readonly,
+     because the variable itself is in readonly section.  
+     We also honnor READONLY flag on alias assuming that user knows
+     what he is doing.  */
+  if (!TREE_READONLY (decl) && !TREE_READONLY (real_decl))
+    return error_mark_node;
 
   /* Variables declared 'const' without an initializer
      have zero as the initializer if they may not be
      overridden at link or run time.  */
-  if (!DECL_INITIAL (decl)
-      && (DECL_EXTERNAL (decl)
-	  || decl_replaceable_p (decl)))
-    return false;
+  if (!DECL_INITIAL (real_decl)
+      && (DECL_EXTERNAL (decl) || decl_replaceable_p (decl)))
+    return error_mark_node;
 
   /* Variables declared `const' with an initializer are considered
      to not be overwritable with different initializer by default. 
 
      ??? Previously we behaved so for scalar variables but not for array
      accesses.  */
-  return true;
+  return DECL_INITIAL (real_decl);
 }
 
 /* Add the variable DECL to the varpool.