C++ alias analysis improvement.

2002-03-06  Dan Nicolaescu  <dann@ics.uci.edu>
            Daniel Berlin  <dan@dberlin.org>

        C++ alias analysis improvement.
	* alias.c (record_component_aliases): Record aliases for base
        classes too.
	* cp/cp-lang.c (ok_to_generate_alias_set_for_type): New function.
	(cxx_get_alias_set): Use it.

Co-Authored-By: Daniel Berlin <dberlin@dberlin.org>

From-SVN: r50587

gcc/ChangeLog

+2002-03-11  Dan Nicolaescu  <dann@ics.uci.edu>
+	    Daniel Berlin  <dan@dberlin.org>
+
+	C++ alias analysis improvement.
+	* alias.c (record_component_aliases): Record aliases for base 
+	classes too.
+
 2002-03-11  Ulrich Weigand  <uweigand@de.ibm.com>
 
 	* config/s390/s390.h (REG_ALLOC_ORDER): Add missing register.

gcc/alias.c

@@ -679,6 +679,17 @@ record_component_aliases (type)
     case RECORD_TYPE:
     case UNION_TYPE:
     case QUAL_UNION_TYPE:
+      /* Recursively record aliases for the base classes, if there are any */
+      if (TYPE_BINFO (type) != NULL && TYPE_BINFO_BASETYPES (type) != NULL)
+        {
+          int i;
+          for (i = 0; i < TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (type)); i++)
+            {
+              tree binfo = TREE_VEC_ELT (TYPE_BINFO_BASETYPES (type), i);
+              record_alias_subset (superset,
+				   get_alias_set (BINFO_TYPE (binfo)));
+            }
+        }
       for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
 	if (TREE_CODE (field) == FIELD_DECL && ! DECL_NONADDRESSABLE_P (field))
 	  record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));

gcc/cp/ChangeLog

+2002-03-11  Dan Nicolaescu  <dann@ics.uci.edu>
+	    Daniel Berlin  <dan@dberlin.org>
+
+	* cp-lang.c (ok_to_generate_alias_set_for_type): New function.
+	(cxx_get_alias_set): Use it.
+
 2002-03-10  Kaveh R. Ghazi  <ghazi@caip.rutgers.edu>
 
 	* cp-tree.h (stabilize_expr): Prototype.

gcc/cp/cp-lang.c

@@ -29,6 +29,7 @@ Boston, MA 02111-1307, USA.  */
 #include "langhooks-def.h"
 
 static HOST_WIDE_INT cxx_get_alias_set PARAMS ((tree));
+static bool ok_to_generate_alias_set_for_type PARAMS ((tree));
 
 #undef LANG_HOOKS_NAME
 #define LANG_HOOKS_NAME "GNU C++"
@@ -99,15 +100,66 @@ static HOST_WIDE_INT cxx_get_alias_set PARAMS ((tree));
 /* Each front end provides its own hooks, for toplev.c.  */
 const struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
 
+/* Check if a C++ type is safe for aliasing.
+   Return TRUE if T safe for aliasing FALSE otherwise.  */
+
+static bool
+ok_to_generate_alias_set_for_type (t)
+     tree t;
+{
+  if (TYPE_PTRMEMFUNC_P (t))
+    return true;
+  if (AGGREGATE_TYPE_P (t))
+    {
+      if ((TREE_CODE (t) == RECORD_TYPE) || (TREE_CODE (t) == UNION_TYPE))
+	{
+	  tree fields;
+	  /* PODs are safe.  */
+	  if (! CLASSTYPE_NON_POD_P(t))
+	    return true;
+	  /* Classes with virtual baseclasses are not.  */
+	  if (TYPE_USES_VIRTUAL_BASECLASSES (t))
+	    return false;
+	  /* Recursively check the base classes.  */
+	  if (TYPE_BINFO (t) != NULL && TYPE_BINFO_BASETYPES (t) != NULL)
+	    {
+	      int i;
+	      for (i = 0; i < TREE_VEC_LENGTH (TYPE_BINFO_BASETYPES (t)); i++)
+		{
+		  tree binfo = TREE_VEC_ELT (TYPE_BINFO_BASETYPES (t), i);
+		  if (!ok_to_generate_alias_set_for_type (BINFO_TYPE (binfo)))
+		    return false;
+		}
+	    }
+	  /* Check all the fields.  */
+	  for (fields = TYPE_FIELDS (t); fields; fields = TREE_CHAIN (fields))
+	    {
+	      if (TREE_CODE (fields) != FIELD_DECL)
+		continue;
+	      if (! ok_to_generate_alias_set_for_type (TREE_TYPE (fields)))
+		return false;
+	    }
+	  return true;
+	}
+      else if (TREE_CODE (t) == ARRAY_TYPE)
+	return ok_to_generate_alias_set_for_type (TREE_TYPE (t));
+      else
+	/* This should never happen, we dealt with all the aggregate
+	   types that can appear in C++ above.  */
+	abort ();
+    }
+  else
+    return true;
+}
+
 /* Special routine to get the alias set for C++.  */
 
 static HOST_WIDE_INT
 cxx_get_alias_set (t)
      tree t;
 {
-  /* It's not yet safe to use alias sets for classes in C++ because
-     the TYPE_FIELDs list for a class doesn't mention base classes.  */
-  if (AGGREGATE_TYPE_P (t))
+  /* It's not yet safe to use alias sets for classes in C++.  */
+  if (!ok_to_generate_alias_set_for_type(t))
     return 0;
 
   return c_common_get_alias_set (t);