Reland "In-object double fields unboxing (for 64-bit only)."

src/arm64/lithium-arm64.cc

 // Copyright 2013 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.
 
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/arm64/lithium-codegen-arm64.h"
 #include "src/hydrogen-osr.h"
@@ skipping 2382 matching lines @@
 LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   // TODO(jbramley): It might be beneficial to allow value to be a constant in
   // some cases. x64 makes use of this with FLAG_track_fields, for example.
 
   LOperand* object = UseRegister(instr->object());
   LOperand* value;
   LOperand* temp0 = NULL;
   LOperand* temp1 = NULL;
 
   if (instr->access().IsExternalMemory() ||
-      instr->field_representation().IsDouble()) {
+      (!FLAG_unbox_double_fields && instr->field_representation().IsDouble())) {
     value = UseRegister(instr->value());
   } else if (instr->NeedsWriteBarrier()) {
     value = UseRegisterAndClobber(instr->value());
     temp0 = TempRegister();
     temp1 = TempRegister();
   } else if (instr->NeedsWriteBarrierForMap()) {
     value = UseRegister(instr->value());
     temp0 = TempRegister();
     temp1 = TempRegister();
   } else {
@@ skipping 330 matching lines @@
     HAllocateBlockContext* instr) {
   LOperand* context = UseFixed(instr->context(), cp);
   LOperand* function = UseRegisterAtStart(instr->function());
   LAllocateBlockContext* result =
       new(zone()) LAllocateBlockContext(context, function);
   return MarkAsCall(DefineFixed(result, cp), instr);
 }
 
 
 } }  // namespace v8::internal