2 files changed, 11 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog
index c11a4a4b67..8cafa060ed 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Sep 30 15:47:13 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm_args.c (vm_caller_setup_arg_block): bypass Symbol#to_proc
+	  call to optimize symbol block passing.
+
 Wed Sep 30 01:34:34 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* parse.y (parser_free): fix memory leak at syntax error when
diff --git a/vm_args.c b/vm_args.c
index bc336dd395..1ed98b5a4c 100644
--- a/vm_args.c
+++ b/vm_args.c
@@ -776,7 +776,12 @@ vm_caller_setup_arg_block(const rb_thread_t *th, rb_control_frame_t *reg_cfp,
 
 	proc = *(--reg_cfp->sp);
 
-	if (proc != Qnil) {
+	if (SYMBOL_P(proc) && rb_method_basic_definition_p(rb_cSymbol, idTo_proc)) {
+	    calling->blockptr = RUBY_VM_GET_BLOCK_PTR_IN_CFP(reg_cfp);
+	    calling->blockptr->iseq = (rb_iseq_t *)IFUNC_NEW(rb_sym_proc_call, SYM2ID(proc), 0);
+	    calling->blockptr->proc = 0;
+	}
+	else if (!NIL_P(proc)) {
 	    if (!rb_obj_is_proc(proc)) {
 		VALUE b;
 		b = rb_check_convert_type(proc, T_DATA, "Proc", "to_proc");