[es6] Tail calls support.

src/x64/builtins-x64.cc

 // 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 2026 matching lines @@
   {
     __ CompareRoot(rdx, Heap::kUndefinedValueRootIndex);
     __ j(equal, masm->isolate()->builtins()->Call(), RelocInfo::CODE_TARGET);
     __ Jump(masm->isolate()->builtins()->Construct(), RelocInfo::CODE_TARGET);
   }
 }
 
 
 // static
 void Builtins::Generate_CallFunction(MacroAssembler* masm,
-                                     ConvertReceiverMode mode) {
+                                     ConvertReceiverMode mode,
+                                     TailCallMode tail_call_mode) {
   // ----------- S t a t e -------------
   //  -- rax : the number of arguments (not including the receiver)
   //  -- rdi : the function to call (checked to be a JSFunction)
   // -----------------------------------
   StackArgumentsAccessor args(rsp, rax);
   __ AssertFunction(rdi);
 
   // ES6 section 9.2.1 [[Call]] ( thisArgument, argumentsList)
   // Check that the function is not a "classConstructor".
   Label class_constructor;
@@ skipping 75 matching lines @@
   }
   __ bind(&done_convert);
 
   // ----------- S t a t e -------------
   //  -- rax : the number of arguments (not including the receiver)
   //  -- rdx : the shared function info.
   //  -- rdi : the function to call (checked to be a JSFunction)
   //  -- rsi : the function context.
   // -----------------------------------
 
+  if (tail_call_mode == TailCallMode::kAllow) {
+    __ DropCurrentJSFrame(rax, rbx, rcx, r8);

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

We need to check whether the debugger is active, and if so don't eliminate the
frame(s), but do a normal call. See Yang's tail call+debugger document for
background.

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

Done.

+  }
+
   __ LoadSharedFunctionInfoSpecialField(
       rbx, rdx, SharedFunctionInfo::kFormalParameterCountOffset);
   ParameterCount actual(rax);
   ParameterCount expected(rbx);
 
   __ InvokeFunctionCode(rdi, no_reg, expected, actual, JUMP_FUNCTION,
                         CheckDebugStepCallWrapper());
 
   // The function is a "classConstructor", need to raise an exception.
   __ bind(&class_constructor);
@@ skipping 462 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64