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, 9 insertions, 1 deletions

diff --git a/gcc/c-semantics.c b/gcc/c-semantics.c
index 6a963a9..eca64ba 100644
--- a/gcc/c-semantics.c
+++ b/gcc/c-semantics.c
@@ -460,7 +460,15 @@ void
 genrtl_return_stmt (stmt)
      tree stmt;
 {
-  tree expr = RETURN_EXPR (stmt);
+  tree expr;
+
+  /* If RETURN_NULLIFIED_P is set, the frontend has arranged to set up
+     the return value separately, so just return the return value
+     itself.  This is used for the C++ named return value optimization.  */
+  if (RETURN_NULLIFIED_P (stmt))
+    expr = DECL_RESULT (current_function_decl);
+  else
+    expr = RETURN_EXPR (stmt);
 
   emit_line_note (input_filename, lineno);
   if (!expr)