diff --git a/src/x64/builtins-x64.cc b/src/x64/builtins-x64.cc
new file mode 100644
index 0000000..35eddc4
--- /dev/null
+++ b/src/x64/builtins-x64.cc
@@ -0,0 +1,1280 @@
+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "v8.h"
+#include "codegen-inl.h"
+#include "macro-assembler.h"
+
+namespace v8 {
+namespace internal {
+
+#define __ ACCESS_MASM(masm)
+
+void Builtins::Generate_Adaptor(MacroAssembler* masm, CFunctionId id) {
+  // TODO(428): Don't pass the function in a static variable.
+  ExternalReference passed = ExternalReference::builtin_passed_function();
+  __ movq(kScratchRegister, passed.address(), RelocInfo::EXTERNAL_REFERENCE);
+  __ movq(Operand(kScratchRegister, 0), rdi);
+
+  // The actual argument count has already been loaded into register
+  // rax, but JumpToRuntime expects rax to contain the number of
+  // arguments including the receiver.
+  __ incq(rax);
+  __ JumpToRuntime(ExternalReference(id), 1);
+}
+
+
+static void EnterArgumentsAdaptorFrame(MacroAssembler* masm) {
+  __ push(rbp);
+  __ movq(rbp, rsp);
+
+  // Store the arguments adaptor context sentinel.
+  __ push(Immediate(Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR)));
+
+  // Push the function on the stack.
+  __ push(rdi);
+
+  // Preserve the number of arguments on the stack. Must preserve both
+  // rax and rbx because these registers are used when copying the
+  // arguments and the receiver.
+  __ Integer32ToSmi(rcx, rax);
+  __ push(rcx);
+}
+
+
+static void LeaveArgumentsAdaptorFrame(MacroAssembler* masm) {
+  // Retrieve the number of arguments from the stack. Number is a Smi.
+  __ movq(rbx, Operand(rbp, ArgumentsAdaptorFrameConstants::kLengthOffset));
+
+  // Leave the frame.
+  __ movq(rsp, rbp);
+  __ pop(rbp);
+
+  // Remove caller arguments from the stack.
+  // rbx holds a Smi, so we convery to dword offset by multiplying by 4.
+  // TODO(smi): Find a way to abstract indexing by a smi.
+  ASSERT_EQ(kSmiTagSize, 1 && kSmiTag == 0);
+  ASSERT_EQ(kPointerSize, (1 << kSmiTagSize) * 4);
+  // TODO(smi): Find way to abstract indexing by a smi.
+  __ pop(rcx);
+  // 1 * kPointerSize is offset of receiver.
+  __ lea(rsp, Operand(rsp, rbx, times_half_pointer_size, 1 * kPointerSize));
+  __ push(rcx);
+}
+
+
+void Builtins::Generate_ArgumentsAdaptorTrampoline(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- rax : actual number of arguments
+  //  -- rbx : expected number of arguments
+  //  -- rdx : code entry to call
+  // -----------------------------------
+
+  Label invoke, dont_adapt_arguments;
+  __ IncrementCounter(&Counters::arguments_adaptors, 1);
+
+  Label enough, too_few;
+  __ cmpq(rax, rbx);
+  __ j(less, &too_few);
+  __ cmpq(rbx, Immediate(SharedFunctionInfo::kDontAdaptArgumentsSentinel));
+  __ j(equal, &dont_adapt_arguments);
+
+  {  // Enough parameters: Actual >= expected.
+    __ bind(&enough);
+    EnterArgumentsAdaptorFrame(masm);
+
+    // Copy receiver and all expected arguments.
+    const int offset = StandardFrameConstants::kCallerSPOffset;
+    __ lea(rax, Operand(rbp, rax, times_pointer_size, offset));
+    __ movq(rcx, Immediate(-1));  // account for receiver
+
+    Label copy;
+    __ bind(&copy);
+    __ incq(rcx);
+    __ push(Operand(rax, 0));
+    __ subq(rax, Immediate(kPointerSize));
+    __ cmpq(rcx, rbx);
+    __ j(less, &copy);
+    __ jmp(&invoke);
+  }
+
+  {  // Too few parameters: Actual < expected.
+    __ bind(&too_few);
+    EnterArgumentsAdaptorFrame(masm);
+
+    // Copy receiver and all actual arguments.
+    const int offset = StandardFrameConstants::kCallerSPOffset;
+    __ lea(rdi, Operand(rbp, rax, times_pointer_size, offset));
+    __ movq(rcx, Immediate(-1));  // account for receiver
+
+    Label copy;
+    __ bind(&copy);
+    __ incq(rcx);
+    __ push(Operand(rdi, 0));
+    __ subq(rdi, Immediate(kPointerSize));
+    __ cmpq(rcx, rax);
+    __ j(less, &copy);
+
+    // Fill remaining expected arguments with undefined values.
+    Label fill;
+    __ LoadRoot(kScratchRegister, Heap::kUndefinedValueRootIndex);
+    __ bind(&fill);
+    __ incq(rcx);
+    __ push(kScratchRegister);
+    __ cmpq(rcx, rbx);
+    __ j(less, &fill);
+
+    // Restore function pointer.
+    __ movq(rdi, Operand(rbp, JavaScriptFrameConstants::kFunctionOffset));
+  }
+
+  // Call the entry point.
+  __ bind(&invoke);
+  __ call(rdx);
+
+  // Leave frame and return.
+  LeaveArgumentsAdaptorFrame(masm);
+  __ ret(0);
+
+  // -------------------------------------------
+  // Dont adapt arguments.
+  // -------------------------------------------
+  __ bind(&dont_adapt_arguments);
+  __ jmp(rdx);
+}
+
+
+void Builtins::Generate_FunctionCall(MacroAssembler* masm) {
+  // Stack Layout:
+  // rsp: return address
+  //  +1: Argument n
+  //  +2: Argument n-1
+  //  ...
+  //  +n: Argument 1 = receiver
+  //  +n+1: Argument 0 = function to call
+  //
+  // rax contains the number of arguments, n, not counting the function.
+  //
+  // 1. Make sure we have at least one argument.
+  { Label done;
+    __ testq(rax, rax);
+    __ j(not_zero, &done);
+    __ pop(rbx);
+    __ Push(Factory::undefined_value());
+    __ push(rbx);
+    __ incq(rax);
+    __ bind(&done);
+  }
+
+  // 2. Get the function to call from the stack.
+  { Label done, non_function, function;
+    // The function to call is at position n+1 on the stack.
+    __ movq(rdi, Operand(rsp, rax, times_pointer_size, +1 * kPointerSize));
+    __ JumpIfSmi(rdi, &non_function);
+    __ CmpObjectType(rdi, JS_FUNCTION_TYPE, rcx);
+    __ j(equal, &function);
+
+    // Non-function called: Clear the function to force exception.
+    __ bind(&non_function);
+    __ xor_(rdi, rdi);
+    __ jmp(&done);
+
+    // Function called: Change context eagerly to get the right global object.
+    __ bind(&function);
+    __ movq(rsi, FieldOperand(rdi, JSFunction::kContextOffset));
+
+    __ bind(&done);
+  }
+
+  // 3. Make sure first argument is an object; convert if necessary.
+  { Label call_to_object, use_global_receiver, patch_receiver, done;
+    __ movq(rbx, Operand(rsp, rax, times_pointer_size, 0));
+
+    __ JumpIfSmi(rbx, &call_to_object);
+
+    __ CompareRoot(rbx, Heap::kNullValueRootIndex);
+    __ j(equal, &use_global_receiver);
+    __ CompareRoot(rbx, Heap::kUndefinedValueRootIndex);
+    __ j(equal, &use_global_receiver);
+
+    __ CmpObjectType(rbx, FIRST_JS_OBJECT_TYPE, rcx);
+    __ j(below, &call_to_object);
+    __ CmpInstanceType(rcx, LAST_JS_OBJECT_TYPE);
+    __ j(below_equal, &done);
+
+    __ bind(&call_to_object);
+    __ EnterInternalFrame();  // preserves rax, rbx, rdi
+
+    // Store the arguments count on the stack (smi tagged).
+    __ Integer32ToSmi(rax, rax);
+    __ push(rax);
+
+    __ push(rdi);  // save edi across the call
+    __ push(rbx);
+    __ InvokeBuiltin(Builtins::TO_OBJECT, CALL_FUNCTION);
+    __ movq(rbx, rax);
+    __ pop(rdi);  // restore edi after the call
+
+    // Get the arguments count and untag it.
+    __ pop(rax);
+    __ SmiToInteger32(rax, rax);
+
+    __ LeaveInternalFrame();
+    __ jmp(&patch_receiver);
+
+    // Use the global receiver object from the called function as the receiver.
+    __ bind(&use_global_receiver);
+    const int kGlobalIndex =
+        Context::kHeaderSize + Context::GLOBAL_INDEX * kPointerSize;
+    __ movq(rbx, FieldOperand(rsi, kGlobalIndex));
+    __ movq(rbx, FieldOperand(rbx, GlobalObject::kGlobalReceiverOffset));
+
+    __ bind(&patch_receiver);
+    __ movq(Operand(rsp, rax, times_pointer_size, 0), rbx);
+
+    __ bind(&done);
+  }
+
+  // 4. Shift stuff one slot down the stack.
+  { Label loop;
+    __ lea(rcx, Operand(rax, +1));  // +1 ~ copy receiver too
+    __ bind(&loop);
+    __ movq(rbx, Operand(rsp, rcx, times_pointer_size, 0));
+    __ movq(Operand(rsp, rcx, times_pointer_size, 1 * kPointerSize), rbx);
+    __ decq(rcx);
+    __ j(not_zero, &loop);
+  }
+
+  // 5. Remove TOS (copy of last arguments), but keep return address.
+  __ pop(rbx);
+  __ pop(rcx);
+  __ push(rbx);
+  __ decq(rax);
+
+  // 6. Check that function really was a function and get the code to
+  //    call from the function and check that the number of expected
+  //    arguments matches what we're providing.
+  { Label invoke, trampoline;
+    __ testq(rdi, rdi);
+    __ j(not_zero, &invoke);
+    __ xor_(rbx, rbx);
+    __ GetBuiltinEntry(rdx, Builtins::CALL_NON_FUNCTION);
+    __ bind(&trampoline);
+    __ Jump(Handle<Code>(builtin(ArgumentsAdaptorTrampoline)),
+            RelocInfo::CODE_TARGET);
+
+    __ bind(&invoke);
+    __ movq(rdx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
+    __ movsxlq(rbx,
+           FieldOperand(rdx, SharedFunctionInfo::kFormalParameterCountOffset));
+    __ movq(rdx, FieldOperand(rdx, SharedFunctionInfo::kCodeOffset));
+    __ lea(rdx, FieldOperand(rdx, Code::kHeaderSize));
+    __ cmpq(rax, rbx);
+    __ j(not_equal, &trampoline);
+  }
+
+  // 7. Jump (tail-call) to the code in register edx without checking arguments.
+  ParameterCount expected(0);
+  __ InvokeCode(rdx, expected, expected, JUMP_FUNCTION);
+}
+
+
+void Builtins::Generate_FunctionApply(MacroAssembler* masm) {
+  // Stack at entry:
+  //    rsp: return address
+  //  rsp+8: arguments
+  // rsp+16: receiver ("this")
+  // rsp+24: function
+  __ EnterInternalFrame();
+  // Stack frame:
+  //    rbp: Old base pointer
+  // rbp[1]: return address
+  // rbp[2]: function arguments
+  // rbp[3]: receiver
+  // rbp[4]: function
+  static const int kArgumentsOffset = 2 * kPointerSize;
+  static const int kReceiverOffset = 3 * kPointerSize;
+  static const int kFunctionOffset = 4 * kPointerSize;
+  __ push(Operand(rbp, kFunctionOffset));
+  __ push(Operand(rbp, kArgumentsOffset));
+  __ InvokeBuiltin(Builtins::APPLY_PREPARE, CALL_FUNCTION);
+
+  if (FLAG_check_stack) {
+    // We need to catch preemptions right here, otherwise an unlucky preemption
+    // could show up as a failed apply.
+    Label retry_preemption;
+    Label no_preemption;
+    __ bind(&retry_preemption);
+    ExternalReference stack_guard_limit =
+        ExternalReference::address_of_stack_guard_limit();
+    __ movq(kScratchRegister, stack_guard_limit);
+    __ movq(rcx, rsp);
+    __ subq(rcx, Operand(kScratchRegister, 0));
+    // rcx contains the difference between the stack limit and the stack top.
+    // We use it below to check that there is enough room for the arguments.
+    __ j(above, &no_preemption);
+
+    // Preemption!
+    // Because runtime functions always remove the receiver from the stack, we
+    // have to fake one to avoid underflowing the stack.
+    __ push(rax);
+    __ push(Immediate(Smi::FromInt(0)));
+
+    // Do call to runtime routine.
+    __ CallRuntime(Runtime::kStackGuard, 1);
+    __ pop(rax);
+    __ jmp(&retry_preemption);
+
+    __ bind(&no_preemption);
+
+    Label okay;
+    // Make rdx the space we need for the array when it is unrolled onto the
+    // stack.
+    __ PositiveSmiTimesPowerOfTwoToInteger64(rdx, rax, kPointerSizeLog2);
+    __ cmpq(rcx, rdx);
+    __ j(greater, &okay);
+
+    // Too bad: Out of stack space.
+    __ push(Operand(rbp, kFunctionOffset));
+    __ push(rax);
+    __ InvokeBuiltin(Builtins::APPLY_OVERFLOW, CALL_FUNCTION);
+    __ bind(&okay);
+  }
+
+  // Push current index and limit.
+  const int kLimitOffset =
+      StandardFrameConstants::kExpressionsOffset - 1 * kPointerSize;
+  const int kIndexOffset = kLimitOffset - 1 * kPointerSize;
+  __ push(rax);  // limit
+  __ push(Immediate(0));  // index
+
+  // Change context eagerly to get the right global object if
+  // necessary.
+  __ movq(rdi, Operand(rbp, kFunctionOffset));
+  __ movq(rsi, FieldOperand(rdi, JSFunction::kContextOffset));
+
+  // Compute the receiver.
+  Label call_to_object, use_global_receiver, push_receiver;
+  __ movq(rbx, Operand(rbp, kReceiverOffset));
+  __ JumpIfSmi(rbx, &call_to_object);
+  __ CompareRoot(rbx, Heap::kNullValueRootIndex);
+  __ j(equal, &use_global_receiver);
+  __ CompareRoot(rbx, Heap::kUndefinedValueRootIndex);
+  __ j(equal, &use_global_receiver);
+
+  // If given receiver is already a JavaScript object then there's no
+  // reason for converting it.
+  __ CmpObjectType(rbx, FIRST_JS_OBJECT_TYPE, rcx);
+  __ j(below, &call_to_object);
+  __ CmpInstanceType(rcx, LAST_JS_OBJECT_TYPE);
+  __ j(below_equal, &push_receiver);
+
+  // Convert the receiver to an object.
+  __ bind(&call_to_object);
+  __ push(rbx);
+  __ InvokeBuiltin(Builtins::TO_OBJECT, CALL_FUNCTION);
+  __ movq(rbx, rax);
+  __ jmp(&push_receiver);
+
+  // Use the current global receiver object as the receiver.
+  __ bind(&use_global_receiver);
+  const int kGlobalOffset =
+      Context::kHeaderSize + Context::GLOBAL_INDEX * kPointerSize;
+  __ movq(rbx, FieldOperand(rsi, kGlobalOffset));
+  __ movq(rbx, FieldOperand(rbx, GlobalObject::kGlobalReceiverOffset));
+
+  // Push the receiver.
+  __ bind(&push_receiver);
+  __ push(rbx);
+
+  // Copy all arguments from the array to the stack.
+  Label entry, loop;
+  __ movq(rax, Operand(rbp, kIndexOffset));
+  __ jmp(&entry);
+  __ bind(&loop);
+  __ movq(rcx, Operand(rbp, kArgumentsOffset));  // load arguments
+  __ push(rcx);
+  __ push(rax);
+
+  // Use inline caching to speed up access to arguments.
+  Handle<Code> ic(Builtins::builtin(Builtins::KeyedLoadIC_Initialize));
+  __ Call(ic, RelocInfo::CODE_TARGET);
+  // It is important that we do not have a test instruction after the
+  // call.  A test instruction after the call is used to indicate that
+  // we have generated an inline version of the keyed load.  In this
+  // case, we know that we are not generating a test instruction next.
+
+  // Remove IC arguments from the stack and push the nth argument.
+  __ addq(rsp, Immediate(2 * kPointerSize));
+  __ push(rax);
+
+  // Update the index on the stack and in register rax.
+  __ movq(rax, Operand(rbp, kIndexOffset));
+  __ addq(rax, Immediate(Smi::FromInt(1)));
+  __ movq(Operand(rbp, kIndexOffset), rax);
+
+  __ bind(&entry);
+  __ cmpq(rax, Operand(rbp, kLimitOffset));
+  __ j(not_equal, &loop);
+
+  // Invoke the function.
+  ParameterCount actual(rax);
+  __ SmiToInteger32(rax, rax);
+  __ movq(rdi, Operand(rbp, kFunctionOffset));
+  __ InvokeFunction(rdi, actual, CALL_FUNCTION);
+
+  __ LeaveInternalFrame();
+  __ ret(3 * kPointerSize);  // remove function, receiver, and arguments
+}
+
+
+// Load the built-in Array function from the current context.
+static void GenerateLoadArrayFunction(MacroAssembler* masm, Register result) {
+  // Load the global context.
+  __ movq(result, Operand(rsi, Context::SlotOffset(Context::GLOBAL_INDEX)));
+  __ movq(result, FieldOperand(result, GlobalObject::kGlobalContextOffset));
+  // Load the Array function from the global context.
+  __ movq(result,
+          Operand(result, Context::SlotOffset(Context::ARRAY_FUNCTION_INDEX)));
+}
+
+
+// Number of empty elements to allocate for an empty array.
+static const int kPreallocatedArrayElements = 4;
+
+
+// Allocate an empty JSArray. The allocated array is put into the result
+// register. If the parameter initial_capacity is larger than zero an elements
+// backing store is allocated with this size and filled with the hole values.
+// Otherwise the elements backing store is set to the empty FixedArray.
+static void AllocateEmptyJSArray(MacroAssembler* masm,
+                                 Register array_function,
+                                 Register result,
+                                 Register scratch1,
+                                 Register scratch2,
+                                 Register scratch3,
+                                 int initial_capacity,
+                                 Label* gc_required) {
+  ASSERT(initial_capacity >= 0);
+
+  // Load the initial map from the array function.
+  __ movq(scratch1, FieldOperand(array_function,
+                                 JSFunction::kPrototypeOrInitialMapOffset));
+
+  // Allocate the JSArray object together with space for a fixed array with the
+  // requested elements.
+  int size = JSArray::kSize;
+  if (initial_capacity > 0) {
+    size += FixedArray::SizeFor(initial_capacity);
+  }
+  __ AllocateInNewSpace(size,
+                        result,
+                        scratch2,
+                        scratch3,
+                        gc_required,
+                        TAG_OBJECT);
+
+  // Allocated the JSArray. Now initialize the fields except for the elements
+  // array.
+  // result: JSObject
+  // scratch1: initial map
+  // scratch2: start of next object
+  __ movq(FieldOperand(result, JSObject::kMapOffset), scratch1);
+  __ Move(FieldOperand(result, JSArray::kPropertiesOffset),
+          Factory::empty_fixed_array());
+  // Field JSArray::kElementsOffset is initialized later.
+  __ movq(FieldOperand(result, JSArray::kLengthOffset), Immediate(0));
+
+  // If no storage is requested for the elements array just set the empty
+  // fixed array.
+  if (initial_capacity == 0) {
+    __ Move(FieldOperand(result, JSArray::kElementsOffset),
+            Factory::empty_fixed_array());
+    return;
+  }
+
+  // Calculate the location of the elements array and set elements array member
+  // of the JSArray.
+  // result: JSObject
+  // scratch2: start of next object
+  __ lea(scratch1, Operand(result, JSArray::kSize));
+  __ movq(FieldOperand(result, JSArray::kElementsOffset), scratch1);
+
+  // Initialize the FixedArray and fill it with holes. FixedArray length is not
+  // stored as a smi.
+  // result: JSObject
+  // scratch1: elements array
+  // scratch2: start of next object
+  __ Move(FieldOperand(scratch1, JSObject::kMapOffset),
+          Factory::fixed_array_map());
+  __ movq(FieldOperand(scratch1, Array::kLengthOffset),
+          Immediate(initial_capacity));
+
+  // Fill the FixedArray with the hole value. Inline the code if short.
+  // Reconsider loop unfolding if kPreallocatedArrayElements gets changed.
+  static const int kLoopUnfoldLimit = 4;
+  ASSERT(kPreallocatedArrayElements <= kLoopUnfoldLimit);
+  __ Move(scratch3, Factory::the_hole_value());
+  if (initial_capacity <= kLoopUnfoldLimit) {
+    // Use a scratch register here to have only one reloc info when unfolding
+    // the loop.
+    for (int i = 0; i < initial_capacity; i++) {
+      __ movq(FieldOperand(scratch1,
+                           FixedArray::kHeaderSize + i * kPointerSize),
+              scratch3);
+    }
+  } else {
+    Label loop, entry;
+    __ jmp(&entry);
+    __ bind(&loop);
+    __ movq(Operand(scratch1, 0), scratch3);
+    __ addq(scratch1, Immediate(kPointerSize));
+    __ bind(&entry);
+    __ cmpq(scratch1, scratch2);
+    __ j(below, &loop);
+  }
+}
+
+
+// Allocate a JSArray with the number of elements stored in a register. The
+// register array_function holds the built-in Array function and the register
+// array_size holds the size of the array as a smi. The allocated array is put
+// into the result register and beginning and end of the FixedArray elements
+// storage is put into registers elements_array and elements_array_end  (see
+// below for when that is not the case). If the parameter fill_with_holes is
+// true the allocated elements backing store is filled with the hole values
+// otherwise it is left uninitialized. When the backing store is filled the
+// register elements_array is scratched.
+static void AllocateJSArray(MacroAssembler* masm,
+                            Register array_function,  // Array function.
+                            Register array_size,  // As a smi.
+                            Register result,
+                            Register elements_array,
+                            Register elements_array_end,
+                            Register scratch,
+                            bool fill_with_hole,
+                            Label* gc_required) {
+  Label not_empty, allocated;
+
+  // Load the initial map from the array function.
+  __ movq(elements_array,
+          FieldOperand(array_function,
+                       JSFunction::kPrototypeOrInitialMapOffset));
+
+  // Check whether an empty sized array is requested.
+  __ testq(array_size, array_size);
+  __ j(not_zero, &not_empty);
+
+  // If an empty array is requested allocate a small elements array anyway. This
+  // keeps the code below free of special casing for the empty array.
+  int size = JSArray::kSize + FixedArray::SizeFor(kPreallocatedArrayElements);
+  __ AllocateInNewSpace(size,
+                        result,
+                        elements_array_end,
+                        scratch,
+                        gc_required,
+                        TAG_OBJECT);
+  __ jmp(&allocated);
+
+  // Allocate the JSArray object together with space for a FixedArray with the
+  // requested elements.
+  __ bind(&not_empty);
+  ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
+  __ AllocateInNewSpace(JSArray::kSize + FixedArray::kHeaderSize,
+                        times_half_pointer_size,  // array_size is a smi.
+                        array_size,
+                        result,
+                        elements_array_end,
+                        scratch,
+                        gc_required,
+                        TAG_OBJECT);
+
+  // Allocated the JSArray. Now initialize the fields except for the elements
+  // array.
+  // result: JSObject
+  // elements_array: initial map
+  // elements_array_end: start of next object
+  // array_size: size of array (smi)
+  __ bind(&allocated);
+  __ movq(FieldOperand(result, JSObject::kMapOffset), elements_array);
+  __ Move(elements_array, Factory::empty_fixed_array());
+  __ movq(FieldOperand(result, JSArray::kPropertiesOffset), elements_array);
+  // Field JSArray::kElementsOffset is initialized later.
+  __ movq(FieldOperand(result, JSArray::kLengthOffset), array_size);
+
+  // Calculate the location of the elements array and set elements array member
+  // of the JSArray.
+  // result: JSObject
+  // elements_array_end: start of next object
+  // array_size: size of array (smi)
+  __ lea(elements_array, Operand(result, JSArray::kSize));
+  __ movq(FieldOperand(result, JSArray::kElementsOffset), elements_array);
+
+  // Initialize the fixed array. FixedArray length is not stored as a smi.
+  // result: JSObject
+  // elements_array: elements array
+  // elements_array_end: start of next object
+  // array_size: size of array (smi)
+  ASSERT(kSmiTag == 0);
+  __ SmiToInteger64(array_size, array_size);
+  __ Move(FieldOperand(elements_array, JSObject::kMapOffset),
+          Factory::fixed_array_map());
+  Label not_empty_2, fill_array;
+  __ testq(array_size, array_size);
+  __ j(not_zero, &not_empty_2);
+  // Length of the FixedArray is the number of pre-allocated elements even
+  // though the actual JSArray has length 0.
+  __ movq(FieldOperand(elements_array, Array::kLengthOffset),
+          Immediate(kPreallocatedArrayElements));
+  __ jmp(&fill_array);
+  __ bind(&not_empty_2);
+  // For non-empty JSArrays the length of the FixedArray and the JSArray is the
+  // same.
+  __ movq(FieldOperand(elements_array, Array::kLengthOffset), array_size);
+
+  // Fill the allocated FixedArray with the hole value if requested.
+  // result: JSObject
+  // elements_array: elements array
+  // elements_array_end: start of next object
+  __ bind(&fill_array);
+  if (fill_with_hole) {
+    Label loop, entry;
+    __ Move(scratch, Factory::the_hole_value());
+    __ lea(elements_array, Operand(elements_array,
+                                   FixedArray::kHeaderSize - kHeapObjectTag));
+    __ jmp(&entry);
+    __ bind(&loop);
+    __ movq(Operand(elements_array, 0), scratch);
+    __ addq(elements_array, Immediate(kPointerSize));
+    __ bind(&entry);
+    __ cmpq(elements_array, elements_array_end);
+    __ j(below, &loop);
+  }
+}
+
+
+// Create a new array for the built-in Array function. This function allocates
+// the JSArray object and the FixedArray elements array and initializes these.
+// If the Array cannot be constructed in native code the runtime is called. This
+// function assumes the following state:
+//   rdi: constructor (built-in Array function)
+//   rax: argc
+//   rsp[0]: return address
+//   rsp[8]: last argument
+// This function is used for both construct and normal calls of Array. The only
+// difference between handling a construct call and a normal call is that for a
+// construct call the constructor function in rdi needs to be preserved for
+// entering the generic code. In both cases argc in rax needs to be preserved.
+// Both registers are preserved by this code so no need to differentiate between
+// a construct call and a normal call.
+static void ArrayNativeCode(MacroAssembler* masm,
+                            Label *call_generic_code) {
+  Label argc_one_or_more, argc_two_or_more;
+
+  // Check for array construction with zero arguments.
+  __ testq(rax, rax);
+  __ j(not_zero, &argc_one_or_more);
+
+  // Handle construction of an empty array.
+  AllocateEmptyJSArray(masm,
+                       rdi,
+                       rbx,
+                       rcx,
+                       rdx,
+                       r8,
+                       kPreallocatedArrayElements,
+                       call_generic_code);
+  __ IncrementCounter(&Counters::array_function_native, 1);
+  __ movq(rax, rbx);
+  __ ret(kPointerSize);
+
+  // Check for one argument. Bail out if argument is not smi or if it is
+  // negative.
+  __ bind(&argc_one_or_more);
+  __ cmpq(rax, Immediate(1));
+  __ j(not_equal, &argc_two_or_more);
+  __ movq(rdx, Operand(rsp, kPointerSize));  // Get the argument from the stack.
+  Condition not_positive_smi = __ CheckNotPositiveSmi(rdx);
+  __ j(not_positive_smi, call_generic_code);
+
+  // Handle construction of an empty array of a certain size. Bail out if size
+  // is to large to actually allocate an elements array.
+  __ JumpIfSmiGreaterEqualsConstant(rdx,
+                                    JSObject::kInitialMaxFastElementArray,
+                                    call_generic_code);
+
+  // rax: argc
+  // rdx: array_size (smi)
+  // rdi: constructor
+  // esp[0]: return address
+  // esp[8]: argument
+  AllocateJSArray(masm,
+                  rdi,
+                  rdx,
+                  rbx,
+                  rcx,
+                  r8,
+                  r9,
+                  true,
+                  call_generic_code);
+  __ IncrementCounter(&Counters::array_function_native, 1);
+  __ movq(rax, rbx);
+  __ ret(2 * kPointerSize);
+
+  // Handle construction of an array from a list of arguments.
+  __ bind(&argc_two_or_more);
+  __ movq(rdx, rax);
+  __ Integer32ToSmi(rdx, rdx);  // Convet argc to a smi.
+  // rax: argc
+  // rdx: array_size (smi)
+  // rdi: constructor
+  // esp[0] : return address
+  // esp[8] : last argument
+  AllocateJSArray(masm,
+                  rdi,
+                  rdx,
+                  rbx,
+                  rcx,
+                  r8,
+                  r9,
+                  false,
+                  call_generic_code);
+  __ IncrementCounter(&Counters::array_function_native, 1);
+
+  // rax: argc
+  // rbx: JSArray
+  // rcx: elements_array
+  // r8: elements_array_end (untagged)
+  // esp[0]: return address
+  // esp[8]: last argument
+
+  // Location of the last argument
+  __ lea(r9, Operand(rsp, kPointerSize));
+
+  // Location of the first array element (Parameter fill_with_holes to
+  // AllocateJSArrayis false, so the FixedArray is returned in rcx).
+  __ lea(rdx, Operand(rcx, FixedArray::kHeaderSize - kHeapObjectTag));
+
+  // rax: argc
+  // rbx: JSArray
+  // rdx: location of the first array element
+  // r9: location of the last argument
+  // esp[0]: return address
+  // esp[8]: last argument
+  Label loop, entry;
+  __ movq(rcx, rax);
+  __ jmp(&entry);
+  __ bind(&loop);
+  __ movq(kScratchRegister, Operand(r9, rcx, times_pointer_size, 0));
+  __ movq(Operand(rdx, 0), kScratchRegister);
+  __ addq(rdx, Immediate(kPointerSize));
+  __ bind(&entry);
+  __ decq(rcx);
+  __ j(greater_equal, &loop);
+
+  // Remove caller arguments from the stack and return.
+  // rax: argc
+  // rbx: JSArray
+  // esp[0]: return address
+  // esp[8]: last argument
+  __ pop(rcx);
+  __ lea(rsp, Operand(rsp, rax, times_pointer_size, 1 * kPointerSize));
+  __ push(rcx);
+  __ movq(rax, rbx);
+  __ ret(0);
+}
+
+
+void Builtins::Generate_ArrayCode(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- rax : argc
+  //  -- rsp[0] : return address
+  //  -- rsp[8] : last argument
+  // -----------------------------------
+  Label generic_array_code;
+
+  // Get the Array function.
+  GenerateLoadArrayFunction(masm, rdi);
+
+  if (FLAG_debug_code) {
+    // Initial map for the builtin Array function shoud be a map.
+    __ movq(rbx, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
+    // Will both indicate a NULL and a Smi.
+    ASSERT(kSmiTag == 0);
+    Condition not_smi = __ CheckNotSmi(rbx);
+    __ Assert(not_smi, "Unexpected initial map for Array function");
+    __ CmpObjectType(rbx, MAP_TYPE, rcx);
+    __ Assert(equal, "Unexpected initial map for Array function");
+  }
+
+  // Run the native code for the Array function called as a normal function.
+  ArrayNativeCode(masm, &generic_array_code);
+
+  // Jump to the generic array code in case the specialized code cannot handle
+  // the construction.
+  __ bind(&generic_array_code);
+  Code* code = Builtins::builtin(Builtins::ArrayCodeGeneric);
+  Handle<Code> array_code(code);
+  __ Jump(array_code, RelocInfo::CODE_TARGET);
+}
+
+
+void Builtins::Generate_ArrayConstructCode(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- rax : argc
+  //  -- rdi : constructor
+  //  -- rsp[0] : return address
+  //  -- rsp[8] : last argument
+  // -----------------------------------
+  Label generic_constructor;
+
+  if (FLAG_debug_code) {
+    // The array construct code is only set for the builtin Array function which
+    // does always have a map.
+    GenerateLoadArrayFunction(masm, rbx);
+    __ cmpq(rdi, rbx);
+    __ Assert(equal, "Unexpected Array function");
+    // Initial map for the builtin Array function should be a map.
+    __ movq(rbx, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
+    // Will both indicate a NULL and a Smi.
+    ASSERT(kSmiTag == 0);
+    Condition not_smi = __ CheckNotSmi(rbx);
+    __ Assert(not_smi, "Unexpected initial map for Array function");
+    __ CmpObjectType(rbx, MAP_TYPE, rcx);
+    __ Assert(equal, "Unexpected initial map for Array function");
+  }
+
+  // Run the native code for the Array function called as constructor.
+  ArrayNativeCode(masm, &generic_constructor);
+
+  // Jump to the generic construct code in case the specialized code cannot
+  // handle the construction.
+  __ bind(&generic_constructor);
+  Code* code = Builtins::builtin(Builtins::JSConstructStubGeneric);
+  Handle<Code> generic_construct_stub(code);
+  __ Jump(generic_construct_stub, RelocInfo::CODE_TARGET);
+}
+
+
+void Builtins::Generate_JSConstructCall(MacroAssembler* masm) {
+  // ----------- S t a t e -------------
+  //  -- rax: number of arguments
+  //  -- rdi: constructor function
+  // -----------------------------------
+
+  Label non_function_call;
+  // Check that function is not a smi.
+  __ JumpIfSmi(rdi, &non_function_call);
+  // Check that function is a JSFunction.
+  __ CmpObjectType(rdi, JS_FUNCTION_TYPE, rcx);
+  __ j(not_equal, &non_function_call);
+
+  // Jump to the function-specific construct stub.
+  __ movq(rbx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
+  __ movq(rbx, FieldOperand(rbx, SharedFunctionInfo::kConstructStubOffset));
+  __ lea(rbx, FieldOperand(rbx, Code::kHeaderSize));
+  __ jmp(rbx);
+
+  // edi: called object
+  // eax: number of arguments
+  __ bind(&non_function_call);
+
+  // Set expected number of arguments to zero (not changing eax).
+  __ movq(rbx, Immediate(0));
+  __ GetBuiltinEntry(rdx, Builtins::CALL_NON_FUNCTION_AS_CONSTRUCTOR);
+  __ Jump(Handle<Code>(builtin(ArgumentsAdaptorTrampoline)),
+          RelocInfo::CODE_TARGET);
+}
+
+
+void Builtins::Generate_JSConstructStubGeneric(MacroAssembler* masm) {
+    // Enter a construct frame.
+  __ EnterConstructFrame();
+
+  // Store a smi-tagged arguments count on the stack.
+  __ Integer32ToSmi(rax, rax);
+  __ push(rax);
+
+  // Push the function to invoke on the stack.
+  __ push(rdi);
+
+  // Try to allocate the object without transitioning into C code. If any of the
+  // preconditions is not met, the code bails out to the runtime call.
+  Label rt_call, allocated;
+  if (FLAG_inline_new) {
+    Label undo_allocation;
+
+#ifdef ENABLE_DEBUGGER_SUPPORT
+    ExternalReference debug_step_in_fp =
+        ExternalReference::debug_step_in_fp_address();
+    __ movq(kScratchRegister, debug_step_in_fp);
+    __ cmpq(Operand(kScratchRegister, 0), Immediate(0));
+    __ j(not_equal, &rt_call);
+#endif
+
+    // Verified that the constructor is a JSFunction.
+    // Load the initial map and verify that it is in fact a map.
+    // rdi: constructor
+    __ movq(rax, FieldOperand(rdi, JSFunction::kPrototypeOrInitialMapOffset));
+    // Will both indicate a NULL and a Smi
+    ASSERT(kSmiTag == 0);
+    __ JumpIfSmi(rax, &rt_call);
+    // rdi: constructor
+    // rax: initial map (if proven valid below)
+    __ CmpObjectType(rax, MAP_TYPE, rbx);
+    __ j(not_equal, &rt_call);
+
+    // Check that the constructor is not constructing a JSFunction (see comments
+    // in Runtime_NewObject in runtime.cc). In which case the initial map's
+    // instance type would be JS_FUNCTION_TYPE.
+    // rdi: constructor
+    // rax: initial map
+    __ CmpInstanceType(rax, JS_FUNCTION_TYPE);
+    __ j(equal, &rt_call);
+
+    // Now allocate the JSObject on the heap.
+    __ movzxbq(rdi, FieldOperand(rax, Map::kInstanceSizeOffset));
+    __ shl(rdi, Immediate(kPointerSizeLog2));
+    // rdi: size of new object
+    __ AllocateInNewSpace(rdi,
+                          rbx,
+                          rdi,
+                          no_reg,
+                          &rt_call,
+                          NO_ALLOCATION_FLAGS);
+    // Allocated the JSObject, now initialize the fields.
+    // rax: initial map
+    // rbx: JSObject (not HeapObject tagged - the actual address).
+    // rdi: start of next object
+    __ movq(Operand(rbx, JSObject::kMapOffset), rax);
+    __ LoadRoot(rcx, Heap::kEmptyFixedArrayRootIndex);
+    __ movq(Operand(rbx, JSObject::kPropertiesOffset), rcx);
+    __ movq(Operand(rbx, JSObject::kElementsOffset), rcx);
+    // Set extra fields in the newly allocated object.
+    // rax: initial map
+    // rbx: JSObject
+    // rdi: start of next object
+    { Label loop, entry;
+      __ LoadRoot(rdx, Heap::kUndefinedValueRootIndex);
+      __ lea(rcx, Operand(rbx, JSObject::kHeaderSize));
+      __ jmp(&entry);
+      __ bind(&loop);
+      __ movq(Operand(rcx, 0), rdx);
+      __ addq(rcx, Immediate(kPointerSize));
+      __ bind(&entry);
+      __ cmpq(rcx, rdi);
+      __ j(less, &loop);
+    }
+
+    // Add the object tag to make the JSObject real, so that we can continue and
+    // jump into the continuation code at any time from now on. Any failures
+    // need to undo the allocation, so that the heap is in a consistent state
+    // and verifiable.
+    // rax: initial map
+    // rbx: JSObject
+    // rdi: start of next object
+    __ or_(rbx, Immediate(kHeapObjectTag));
+
+    // Check if a non-empty properties array is needed.
+    // Allocate and initialize a FixedArray if it is.
+    // rax: initial map
+    // rbx: JSObject
+    // rdi: start of next object
+    // Calculate total properties described map.
+    __ movzxbq(rdx, FieldOperand(rax, Map::kUnusedPropertyFieldsOffset));
+    __ movzxbq(rcx, FieldOperand(rax, Map::kPreAllocatedPropertyFieldsOffset));
+    __ addq(rdx, rcx);
+    // Calculate unused properties past the end of the in-object properties.
+    __ movzxbq(rcx, FieldOperand(rax, Map::kInObjectPropertiesOffset));
+    __ subq(rdx, rcx);
+    // Done if no extra properties are to be allocated.
+    __ j(zero, &allocated);
+    __ Assert(positive, "Property allocation count failed.");
+
+    // Scale the number of elements by pointer size and add the header for
+    // FixedArrays to the start of the next object calculation from above.
+    // rbx: JSObject
+    // rdi: start of next object (will be start of FixedArray)
+    // rdx: number of elements in properties array
+    __ AllocateInNewSpace(FixedArray::kHeaderSize,
+                          times_pointer_size,
+                          rdx,
+                          rdi,
+                          rax,
+                          no_reg,
+                          &undo_allocation,
+                          RESULT_CONTAINS_TOP);
+
+    // Initialize the FixedArray.
+    // rbx: JSObject
+    // rdi: FixedArray
+    // rdx: number of elements
+    // rax: start of next object
+    __ LoadRoot(rcx, Heap::kFixedArrayMapRootIndex);
+    __ movq(Operand(rdi, JSObject::kMapOffset), rcx);  // setup the map
+    __ movl(Operand(rdi, FixedArray::kLengthOffset), rdx);  // and length
+
+    // Initialize the fields to undefined.
+    // rbx: JSObject
+    // rdi: FixedArray
+    // rax: start of next object
+    // rdx: number of elements
+    { Label loop, entry;
+      __ LoadRoot(rdx, Heap::kUndefinedValueRootIndex);
+      __ lea(rcx, Operand(rdi, FixedArray::kHeaderSize));
+      __ jmp(&entry);
+      __ bind(&loop);
+      __ movq(Operand(rcx, 0), rdx);
+      __ addq(rcx, Immediate(kPointerSize));
+      __ bind(&entry);
+      __ cmpq(rcx, rax);
+      __ j(below, &loop);
+    }
+
+    // Store the initialized FixedArray into the properties field of
+    // the JSObject
+    // rbx: JSObject
+    // rdi: FixedArray
+    __ or_(rdi, Immediate(kHeapObjectTag));  // add the heap tag
+    __ movq(FieldOperand(rbx, JSObject::kPropertiesOffset), rdi);
+
+
+    // Continue with JSObject being successfully allocated
+    // rbx: JSObject
+    __ jmp(&allocated);
+
+    // Undo the setting of the new top so that the heap is verifiable. For
+    // example, the map's unused properties potentially do not match the
+    // allocated objects unused properties.
+    // rbx: JSObject (previous new top)
+    __ bind(&undo_allocation);
+    __ UndoAllocationInNewSpace(rbx);
+  }
+
+  // Allocate the new receiver object using the runtime call.
+  // rdi: function (constructor)
+  __ bind(&rt_call);
+  // Must restore rdi (constructor) before calling runtime.
+  __ movq(rdi, Operand(rsp, 0));
+  __ push(rdi);
+  __ CallRuntime(Runtime::kNewObject, 1);
+  __ movq(rbx, rax);  // store result in rbx
+
+  // New object allocated.
+  // rbx: newly allocated object
+  __ bind(&allocated);
+  // Retrieve the function from the stack.
+  __ pop(rdi);
+
+  // Retrieve smi-tagged arguments count from the stack.
+  __ movq(rax, Operand(rsp, 0));
+  __ SmiToInteger32(rax, rax);
+
+  // Push the allocated receiver to the stack. We need two copies
+  // because we may have to return the original one and the calling
+  // conventions dictate that the called function pops the receiver.
+  __ push(rbx);
+  __ push(rbx);
+
+  // Setup pointer to last argument.
+  __ lea(rbx, Operand(rbp, StandardFrameConstants::kCallerSPOffset));
+
+  // Copy arguments and receiver to the expression stack.
+  Label loop, entry;
+  __ movq(rcx, rax);
+  __ jmp(&entry);
+  __ bind(&loop);
+  __ push(Operand(rbx, rcx, times_pointer_size, 0));
+  __ bind(&entry);
+  __ decq(rcx);
+  __ j(greater_equal, &loop);
+
+  // Call the function.
+  ParameterCount actual(rax);
+  __ InvokeFunction(rdi, actual, CALL_FUNCTION);
+
+  // Restore context from the frame.
+  __ movq(rsi, Operand(rbp, StandardFrameConstants::kContextOffset));
+
+  // If the result is an object (in the ECMA sense), we should get rid
+  // of the receiver and use the result; see ECMA-262 section 13.2.2-7
+  // on page 74.
+  Label use_receiver, exit;
+  // If the result is a smi, it is *not* an object in the ECMA sense.
+  __ JumpIfSmi(rax, &use_receiver);
+
+  // If the type of the result (stored in its map) is less than
+  // FIRST_JS_OBJECT_TYPE, it is not an object in the ECMA sense.
+  __ CmpObjectType(rax, FIRST_JS_OBJECT_TYPE, rcx);
+  __ j(above_equal, &exit);
+
+  // Throw away the result of the constructor invocation and use the
+  // on-stack receiver as the result.
+  __ bind(&use_receiver);
+  __ movq(rax, Operand(rsp, 0));
+
+  // Restore the arguments count and leave the construct frame.
+  __ bind(&exit);
+  __ movq(rbx, Operand(rsp, kPointerSize));  // get arguments count
+  __ LeaveConstructFrame();
+
+  // Remove caller arguments from the stack and return.
+  ASSERT(kSmiTagSize == 1 && kSmiTag == 0);
+  // TODO(smi): Find a way to abstract indexing by a smi.
+  __ pop(rcx);
+  // 1 * kPointerSize is offset of receiver.
+  __ lea(rsp, Operand(rsp, rbx, times_half_pointer_size, 1 * kPointerSize));
+  __ push(rcx);
+  __ IncrementCounter(&Counters::constructed_objects, 1);
+  __ ret(0);
+}
+
+
+static void Generate_JSEntryTrampolineHelper(MacroAssembler* masm,
+                                             bool is_construct) {
+  // Expects five C++ function parameters.
+  // - Address entry (ignored)
+  // - JSFunction* function (
+  // - Object* receiver
+  // - int argc
+  // - Object*** argv
+  // (see Handle::Invoke in execution.cc).
+
+  // Platform specific argument handling. After this, the stack contains
+  // an internal frame and the pushed function and receiver, and
+  // register rax and rbx holds the argument count and argument array,
+  // while rdi holds the function pointer and rsi the context.
+#ifdef _WIN64
+  // MSVC parameters in:
+  // rcx : entry (ignored)
+  // rdx : function
+  // r8 : receiver
+  // r9 : argc
+  // [rsp+0x20] : argv
+
+  // Clear the context before we push it when entering the JS frame.
+  __ xor_(rsi, rsi);
+  __ EnterInternalFrame();
+
+  // Load the function context into rsi.
+  __ movq(rsi, FieldOperand(rdx, JSFunction::kContextOffset));
+
+  // Push the function and the receiver onto the stack.
+  __ push(rdx);
+  __ push(r8);
+
+  // Load the number of arguments and setup pointer to the arguments.
+  __ movq(rax, r9);
+  // Load the previous frame pointer to access C argument on stack
+  __ movq(kScratchRegister, Operand(rbp, 0));
+  __ movq(rbx, Operand(kScratchRegister, EntryFrameConstants::kArgvOffset));
+  // Load the function pointer into rdi.
+  __ movq(rdi, rdx);
+#else  // !defined(_WIN64)
+  // GCC parameters in:
+  // rdi : entry (ignored)
+  // rsi : function
+  // rdx : receiver
+  // rcx : argc
+  // r8  : argv
+
+  __ movq(rdi, rsi);
+  // rdi : function
+
+  // Clear the context before we push it when entering the JS frame.
+  __ xor_(rsi, rsi);
+  // Enter an internal frame.
+  __ EnterInternalFrame();
+
+  // Push the function and receiver and setup the context.
+  __ push(rdi);
+  __ push(rdx);
+  __ movq(rsi, FieldOperand(rdi, JSFunction::kContextOffset));
+
+  // Load the number of arguments and setup pointer to the arguments.
+  __ movq(rax, rcx);
+  __ movq(rbx, r8);
+#endif  // _WIN64
+
+  // Set up the roots register.
+  ExternalReference roots_address = ExternalReference::roots_address();
+  __ movq(r13, roots_address);
+
+  // Current stack contents:
+  // [rsp + 2 * kPointerSize ... ]: Internal frame
+  // [rsp + kPointerSize]         : function
+  // [rsp]                        : receiver
+  // Current register contents:
+  // rax : argc
+  // rbx : argv
+  // rsi : context
+  // rdi : function
+
+  // Copy arguments to the stack in a loop.
+  // Register rbx points to array of pointers to handle locations.
+  // Push the values of these handles.
+  Label loop, entry;
+  __ xor_(rcx, rcx);  // Set loop variable to 0.
+  __ jmp(&entry);
+  __ bind(&loop);
+  __ movq(kScratchRegister, Operand(rbx, rcx, times_pointer_size, 0));
+  __ push(Operand(kScratchRegister, 0));  // dereference handle
+  __ addq(rcx, Immediate(1));
+  __ bind(&entry);
+  __ cmpq(rcx, rax);
+  __ j(not_equal, &loop);
+
+  // Invoke the code.
+  if (is_construct) {
+    // Expects rdi to hold function pointer.
+    __ Call(Handle<Code>(Builtins::builtin(Builtins::JSConstructCall)),
+            RelocInfo::CODE_TARGET);
+  } else {
+    ParameterCount actual(rax);
+    // Function must be in rdi.
+    __ InvokeFunction(rdi, actual, CALL_FUNCTION);
+  }
+
+  // Exit the JS frame. Notice that this also removes the empty
+  // context and the function left on the stack by the code
+  // invocation.
+  __ LeaveInternalFrame();
+  // TODO(X64): Is argument correct? Is there a receiver to remove?
+  __ ret(1 * kPointerSize);  // remove receiver
+}
+
+
+void Builtins::Generate_JSEntryTrampoline(MacroAssembler* masm) {
+  Generate_JSEntryTrampolineHelper(masm, false);
+}
+
+
+void Builtins::Generate_JSConstructEntryTrampoline(MacroAssembler* masm) {
+  Generate_JSEntryTrampolineHelper(masm, true);
+}
+
+} }  // namespace v8::internal