re PR middle-end/26004 (gcc errors on valid code [SVO])

        PR c/26004
        * gimplify.c (gimplify_modify_expr_rhs): Don't do return slot opt if
        the target was declared 'register'.

From-SVN: r111947

gcc/ChangeLog

+2006-03-10  Jason Merrill  <jason@redhat.com>
+
+	PR c/26004
+	* gimplify.c (gimplify_modify_expr_rhs): Don't do return slot opt if 
+	the target was declared 'register'.
+
 2006-03-10  Adam Nemet  <anemet@caviumnetworks.com>
 
 	* genpreds.c (write_insn_constraint_len): Change definition of

gcc/gimplify.c

@@ -3295,7 +3295,8 @@ gimplify_modify_expr_rhs (tree *expr_p, tree *from_p, tree *to_p, tree *pre_p,
 		     && needs_to_live_in_memory (*to_p))
 	      /* It's OK to use the return slot directly unless it's an NRV. */
 	      use_target = true;
-	    else if (is_gimple_reg_type (TREE_TYPE (*to_p)))
+	    else if (is_gimple_reg_type (TREE_TYPE (*to_p))
+		     || (DECL_P (*to_p) && DECL_REGISTER (*to_p)))
 	      /* Don't force regs into memory.  */
 	      use_target = false;
 	    else if (TREE_CODE (*to_p) == VAR_DECL

gcc/testsuite/gcc.dg/pr26004.c

+/* PR c/26004 */
+/* Bug: the return slot optimization was taking the address of s_3,
+   causing an error. */
+
+struct s_3 { short s[3]; } z_3, s_3;
+struct s_3 add_struct_3 (struct s_3 s){}
+wack_struct_3 (void)
+{
+  int i; register struct s_3 u = z_3;
+  u = add_struct_3 (u);
+}