[es6] Tail calls support.

src/x64/macro-assembler-x64.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_X64_MACRO_ASSEMBLER_X64_H_
 #define V8_X64_MACRO_ASSEMBLER_X64_H_
 
 #include "src/assembler.h"
 #include "src/bailout-reason.h"
 #include "src/base/flags.h"
@@ skipping 347 matching lines @@
   void InitializeRootRegister() {
     ExternalReference roots_array_start =
         ExternalReference::roots_array_start(isolate());
     Move(kRootRegister, roots_array_start);
     addp(kRootRegister, Immediate(kRootRegisterBias));
   }
 
   // ---------------------------------------------------------------------------
   // JavaScript invokes
 
+  void DropCurrentJSFrame(Register args, Register scratch1, Register scratch2,

[Benedikt Meurer, 2016/01/21 05:20:49]

Nit: The name is a bit misleading, since this not only drops the "current JS
frame", but might also remove the arguments adaptor frame. I don't have a great
suggestion yet, tho.

[Igor Sheludko, 2016/01/21 14:37:08]

PrepareForTailCall is a better name. Done.

+                          Register scratch3);
+
   // Invoke the JavaScript function code by either calling or jumping.
   void InvokeFunctionCode(Register function, Register new_target,
                           const ParameterCount& expected,
                           const ParameterCount& actual, InvokeFlag flag,
                           const CallWrapper& call_wrapper);
 
   void FloodFunctionIfStepping(Register fun, Register new_target,
                                const ParameterCount& expected,
                                const ParameterCount& actual);
 
@@ skipping 1362 matching lines @@
   }                                                                          \
   masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_