c-common.c (c_get_alias_set): Fix support for poitners and references.

	* c-common.c (c_get_alias_set): Fix support for poitners and
	references.

Co-Authored-By: Mark Mitchell <mark@codesourcery.com>

From-SVN: r28768

1 files changed, 33 insertions, 3 deletions

diff --git a/gcc/c-common.c b/gcc/c-common.c
index 137d1d3d9f3..d194be625e4 100644
--- a/gcc/c-common.c
+++ b/gcc/c-common.c
@@ -3401,11 +3401,41 @@ c_get_alias_set (t)
        whose type is the same as one of the fields, recursively, but
        we don't yet make any use of that information.)  */
     TYPE_ALIAS_SET (type) = 0;
+  else if (TREE_CODE (type) == POINTER_TYPE
+	   || TREE_CODE (type) == REFERENCE_TYPE)
+    {
+      tree t;
+
+      /* Unfortunately, there is no canonical form of a pointer type.
+	 In particular, if we have `typedef int I', then `int *', and
+	 `I *' are different types.  So, we have to pick a canonical
+	 representative.  We do this below.
+	 
+	 Note that this approach is actually more conservative that it
+	 needs to be.  In particular, `const int *' and `int *' should
+	 be in different alias sets, but this approach puts them in
+	 the same alias set.  */
+
+      t = TYPE_MAIN_VARIANT (TREE_TYPE (type));
+      t = ((TREE_CODE (type) == POINTER_TYPE)
+	   ? build_pointer_type (t) : build_reference_type (t));
+      if (t != type)
+	TYPE_ALIAS_SET (type) = c_get_alias_set (t);
+    }
 
   if (!TYPE_ALIAS_SET_KNOWN_P (type)) 
-    /* TYPE is something we haven't seen before.  Put it in a new
-       alias set.  */
-    TYPE_ALIAS_SET (type) = new_alias_set ();
+    {
+      /* Types that are not allocated on the permanent obstack are not
+	 placed in the type hash table.  Thus, there can be multiple
+	 copies of identical types in local scopes.  In the long run,
+	 all types should be permanent.  */
+      if (! TREE_PERMANENT (type))
+	TYPE_ALIAS_SET (type) = 0;
+      else
+	/* TYPE is something we haven't seen before.  Put it in a new
+	   alias set.  */
+	TYPE_ALIAS_SET (type) = new_alias_set ();
+    }
 
   return TYPE_ALIAS_SET (type);
 }