In background compilation make a copy of Field in order to freeze its state

runtime/vm/intermediate_language_arm.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/compiler.h"
@@ skipping 1592 matching lines @@
       locs()->temp(locs()->temp_count() - 1).reg() : kNoRegister;
 
   Label ok, fail_label;
 
   Label* deopt = compiler->is_optimizing() ?
       compiler->AddDeoptStub(deopt_id(), ICData::kDeoptGuardField) : NULL;
 
   Label* fail = (deopt != NULL) ? deopt : &fail_label;
 
   if (emit_full_guard) {
-    __ LoadObject(field_reg, Field::ZoneHandle(field().raw()));
+    __ LoadObject(field_reg, Field::ZoneHandle(field().Original()));
 
     FieldAddress field_cid_operand(field_reg, Field::guarded_cid_offset());
     FieldAddress field_nullability_operand(
         field_reg, Field::is_nullable_offset());
 
     if (value_cid == kDynamicCid) {
       LoadValueCid(compiler, value_cid_reg, value_reg);
       __ ldrh(IP, field_cid_operand);
       __ cmp(value_cid_reg, Operand(IP));
       __ b(&ok, EQ);
@@ skipping 126 matching lines @@
   const Register value_reg = locs()->in(0).reg();
 
   if (!compiler->is_optimizing() ||
       (field().guarded_list_length() == Field::kUnknownFixedLength)) {
     const Register field_reg = locs()->temp(0).reg();
     const Register offset_reg = locs()->temp(1).reg();
     const Register length_reg = locs()->temp(2).reg();
 
     Label ok;
 
-    __ LoadObject(field_reg, Field::ZoneHandle(field().raw()));
+    __ LoadObject(field_reg, Field::ZoneHandle(field().Original()));
 
     __ ldrsb(offset_reg, FieldAddress(field_reg,
         Field::guarded_list_length_in_object_offset_offset()));
     __ ldr(length_reg, FieldAddress(field_reg,
         Field::guarded_list_length_offset()));
 
     __ tst(offset_reg, Operand(offset_reg));
     __ b(&ok, MI);
 
     // Load the length from the value. GuardFieldClass already verified that
@@ skipping 336 matching lines @@
       // Value input is a writable register and should be manually preserved
       // across allocation slow-path.
       locs()->live_registers()->Add(locs()->in(1), kTagged);
     }
 
     Label store_pointer;
     Label store_double;
     Label store_float32x4;
     Label store_float64x2;
 
-    __ LoadObject(temp, Field::ZoneHandle(field().raw()));
+    __ LoadObject(temp, *field().OriginalAsHandle(compiler->zone()));

[siva, 2016/02/25 23:38:32]

__ LoadObject(temp, Field::ZoneHandle(compiler->zone(), field().Original()));

[srdjan, 2016/02/26 00:40:42]

Done.

 
     __ ldrh(temp2, FieldAddress(temp, Field::is_nullable_offset()));
     __ CompareImmediate(temp2, kNullCid);
     __ b(&store_pointer, EQ);
 
     __ ldrb(temp2, FieldAddress(temp, Field::kind_bits_offset()));
     __ tst(temp2, Operand(1 << Field::kUnboxingCandidateBit));
     __ b(&store_pointer, EQ);
 
     __ ldrh(temp2, FieldAddress(temp, Field::guarded_cid_offset()));
@@ skipping 119 matching lines @@
                                               : Location::RequiresRegister());
   locs->set_temp(0, Location::RequiresRegister());
   return locs;
 }
 
 
 void StoreStaticFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   const Register value = locs()->in(0).reg();
   const Register temp = locs()->temp(0).reg();
 
-  __ LoadObject(temp, field());
+  __ LoadObject(temp, *field().OriginalAsHandle(compiler->zone()));

[siva, 2016/02/25 23:38:32]

Ditto.

   if (this->value()->NeedsStoreBuffer()) {
     __ StoreIntoObject(temp,
                        FieldAddress(temp, Field::static_value_offset()),
                        value,
                        CanValueBeSmi());
   } else {
     __ StoreIntoObjectNoBarrier(
         temp, FieldAddress(temp, Field::static_value_offset()), value);
   }
 }
@@ skipping 201 matching lines @@
   if (IsPotentialUnboxedLoad()) {
     const DRegister value = EvenDRegisterOf(locs()->temp(0).fpu_reg());
     const Register temp = locs()->temp(1).reg();
     const Register temp2 = locs()->temp(2).reg();
 
     Label load_pointer;
     Label load_double;
     Label load_float32x4;
     Label load_float64x2;
 
-    __ LoadObject(result_reg, Field::ZoneHandle(field()->raw()));
+    __ LoadObject(result_reg, Field::ZoneHandle(field()->Original()));
 
     FieldAddress field_cid_operand(result_reg, Field::guarded_cid_offset());
     FieldAddress field_nullability_operand(result_reg,
                                            Field::is_nullable_offset());
 
     __ ldrh(temp, field_nullability_operand);
     __ CompareImmediate(temp, kNullCid);
     __ b(&load_pointer, EQ);
 
     __ ldrh(temp, field_cid_operand);
@@ skipping 4333 matching lines @@
                                 1,
                                 locs());
   __ Drop(1);
   __ Pop(result);
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM