re PR middle-end/17526 (libcpp is miscompiled with -fno-pcc-struct-return -O2)

        PR middle-end/17526
        * tree-gimple.c (is_gimple_mem_rhs): Also require a val for
        aggregate types that are not BLKmode.

From-SVN: r89915

gcc/ChangeLog

+2004-10-31  Jason Merrill  <jason@redhat.com>
+
+	PR middle-end/17526
+	* tree-gimple.c (is_gimple_mem_rhs): Also require a val for
+	aggregate types that are not BLKmode.
+
 2004-10-30  Ziemowit Laski  <zlaski@apple.com>
 
 	* c-common.h (objc_lookup_ivar): Add second parameter to

gcc/tree-gimple.c

@@ -111,9 +111,12 @@ is_gimple_reg_rhs (tree t)
 bool
 is_gimple_mem_rhs (tree t)
 {
-  /* If we're dealing with a renamable type, either source or dest
-     must be a renamed variable.  */
-  if (is_gimple_reg_type (TREE_TYPE (t)))
+  /* If we're dealing with a renamable type, either source or dest must be
+     a renamed variable.  Also force a temporary if the type doesn't need
+     to be stored in memory, since it's cheap and prevents erroneous
+     tailcalls (PR 17526).  */
+  if (is_gimple_reg_type (TREE_TYPE (t))
+      || TYPE_MODE (TREE_TYPE (t)) != BLKmode)
     return is_gimple_val (t);
   else
     return is_gimple_formal_tmp_rhs (t);