Implement the Named Return Value optimization.

        * c-common.h (RETURN_NULLIFIED_P): New macro.
        * c-semantics.c (genrtl_return_stmt): Check it.
        * cp-tree.h (struct cp_language_function): Add x_return_value.
        (current_function_return_value): Now a macro.
        * decl.c: Don't define it.
        (define_label, finish_case_label): Don't clear it.
        (init_decl_processing): Don't register it with GC.
        * semantics.c (genrtl_finish_function): Don't check it for
        no_return_label.  Copy the RTL from the return value to
        current_function_return_value and walk, calling...
        (nullify_returns_r): ...this new fn.
        * typeck.c (check_return_expr): Set current_function_return_value.

        * expr.c (clear_storage): Set TREE_NOTHROW on the decl for memset.
        (emit_block_move): Likewise.

From-SVN: r43445

1 files changed, 7 insertions, 1 deletions

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 5da11ee..9910624 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -863,6 +863,7 @@ struct cp_language_function
   tree x_eh_spec_block;
   tree x_in_charge_parm;
   tree x_vtt_parm;
+  tree x_return_value;
 
   tree *x_vcalls_possible_p;
 
@@ -953,7 +954,12 @@ struct cp_language_function
 
 #define in_function_try_handler cp_function_chain->in_function_try_handler
 
-extern tree current_function_return_value;
+/* Expression always returned from function, or error_mark_node
+   otherwise, for use by the automatic named return value optimization.  */
+
+#define current_function_return_value \
+  (cp_function_chain->x_return_value)
+
 extern tree global_namespace;
 
 #define ansi_opname(CODE) \