tree-ssa-ccp.c (maybe_fold_stmt_indirect): Do not mess with TREE_THIS_VOLATILE on shared nodes.

2008-08-20  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-ccp.c (maybe_fold_stmt_indirect): Do not mess
	with TREE_THIS_VOLATILE on shared nodes.
	(fold_stmt_r): Likewise.

	* gcc.c-torture/compile/20080820-1.c: New testcase.

From-SVN: r139325

gcc/ChangeLog

+2008-08-20  Richard Guenther  <rguenther@suse.de>
+
+	* tree-ssa-ccp.c (maybe_fold_stmt_indirect): Do not mess
+	with TREE_THIS_VOLATILE on shared nodes.
+	(fold_stmt_r): Likewise.
+
 2008-08-20  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/37171

gcc/testsuite/ChangeLog

+2008-08-20  Richard Guenther  <rguenther@suse.de>
+
+	* gcc.c-torture/compile/20080820-1.c: New testcase.
+
 2008-08-20  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/37171

gcc/testsuite/gcc.c-torture/compile/20080820-1.c

+extern unsigned long volatile jiffies;
+void do_timer(void)
+{
+  (*(unsigned long *)&jiffies)++;
+}

gcc/tree-ssa-ccp.c

@@ -2118,7 +2118,11 @@ maybe_fold_stmt_indirect (tree expr, tree base, tree offset)
 					  TREE_TYPE (expr));
       if (t)
 	{
-	  TREE_THIS_VOLATILE (t) = volatile_p;
+	  /* Preserve volatileness of the original expression.
+	     We can end up with a plain decl here which is shared
+	     and we shouldn't mess with its flags.  */
+	  if (!SSA_VAR_P (t))
+	    TREE_THIS_VOLATILE (t) = volatile_p;
 	  return t;
 	}
     }
@@ -2404,8 +2408,11 @@ fold_stmt_r (tree *expr_p, int *walk_subtrees, void *data)
 
   if (t)
     {
-      /* Preserve volatileness of the original expression.  */
-      TREE_THIS_VOLATILE (t) = volatile_p;
+      /* Preserve volatileness of the original expression.
+	 We can end up with a plain decl here which is shared
+	 and we shouldn't mess with its flags.  */
+      if (!SSA_VAR_P (t))
+	TREE_THIS_VOLATILE (t) = volatile_p;
       *expr_p = t;
       *changed_p = true;
     }