[es6] Tail calls support.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 7f976940b5a2213e505c3af0005405d9efb1dc8b..03f73f06487c8f30db3561e72eee37a782156f22 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -2002,8 +2002,11 @@ void CallICStub::Generate(MacroAssembler* masm) {
 
   __ bind(&call_function);
   __ Set(rax, argc);
-  __ Jump(masm->isolate()->builtins()->CallFunction(convert_mode()),
-          RelocInfo::CODE_TARGET);
+  Handle<Code> call_function_builtin =
+      tail_call_mode() == TailCallMode::kDisallow
+          ? masm->isolate()->builtins()->CallFunction(convert_mode())
+          : masm->isolate()->builtins()->TailCallFunction(convert_mode());
+  __ Jump(call_function_builtin, RelocInfo::CODE_TARGET);
 
   __ bind(&extra_checks_or_miss);
   Label uninitialized, miss, not_allocation_site;