Partial revert of rest parameter desugaring.

src/full-codegen/x64/full-codegen-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/ast/scopes.h"
 #include "src/code-factory.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 231 matching lines @@
     SetVar(this_function_var, rdi, rbx, rcx);
   }
 
   // Possibly set up a local binding to the new target value.
   Variable* new_target_var = scope()->new_target_var();
   if (new_target_var != nullptr) {
     Comment cmnt(masm_, "[ new.target");
     SetVar(new_target_var, rdx, rbx, rcx);
   }
 
+  // Possibly allocate RestParameters
+  int rest_index;
+  Variable* rest_param = scope()->rest_parameter(&rest_index);
+  if (rest_param) {
+    Comment cmnt(masm_, "[ Allocate rest parameter array");
+
+    int num_parameters = info->scope()->num_parameters();
+    int offset = num_parameters * kPointerSize;
+
+    __ leap(rdx,
+            Operand(rbp, StandardFrameConstants::kCallerSPOffset + offset));
+    __ Push(rdx);
+    __ Push(Smi::FromInt(num_parameters));
+    __ Push(Smi::FromInt(rest_index));
+    __ Push(Smi::FromInt(language_mode()));
+    function_in_register = false;
+
+    RestParamAccessStub stub(isolate());
+    __ CallStub(&stub);
+
+    SetVar(rest_param, rax, rbx, rdx);
+  }
+
   // Possibly allocate an arguments object.
   Variable* arguments = scope()->arguments();
   if (arguments != NULL) {
     // Arguments object must be allocated after the context object, in
     // case the "arguments" or ".arguments" variables are in the context.
     Comment cmnt(masm_, "[ Allocate arguments object");
     DCHECK(rdi.is(ArgumentsAccessNewDescriptor::function()));
     if (!function_in_register) {
       __ movp(rdi, Operand(rbp, JavaScriptFrameConstants::kFunctionOffset));
     }
@@ skipping 4510 matching lines @@
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64