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

runtime/vm/intermediate_language_arm64.cc

 // Copyright (c) 2014, 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_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/compiler.h"
 #include "vm/dart_entry.h"
 #include "vm/flow_graph.h"
 #include "vm/flow_graph_compiler.h"
 #include "vm/flow_graph_range_analysis.h"
 #include "vm/locations.h"
 #include "vm/object_store.h"
 #include "vm/parser.h"
 #include "vm/simulator.h"
 #include "vm/stack_frame.h"
 #include "vm/stub_code.h"
 #include "vm/symbols.h"
 
 #define __ compiler->assembler()->
+#define Z (compiler->zone())
 
 namespace dart {
 
 // Generic summary for call instructions that have all arguments pushed
 // on the stack and return the result in a fixed register R0.
 LocationSummary* Instruction::MakeCallSummary(Zone* zone) {
   LocationSummary* result = new(zone) LocationSummary(
       zone, 0, 0, LocationSummary::kCall);
   result->set_out(0, Location::RegisterLocation(R0));
   return result;
@@ skipping 1426 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(), kUnsignedWord);
     FieldAddress field_nullability_operand(
         field_reg, Field::is_nullable_offset(), kUnsignedWord);
 
     if (value_cid == kDynamicCid) {
       LoadValueCid(compiler, value_cid_reg, value_reg);
       Label skip_length_check;
       __ ldr(TMP, field_cid_operand, kUnsignedWord);
@@ skipping 123 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()));
 
     __ ldr(offset_reg,
            FieldAddress(field_reg,
                         Field::guarded_list_length_in_object_offset_offset()),
            kByte);
     __ ldr(length_reg, FieldAddress(field_reg,
         Field::guarded_list_length_offset()));
 
     __ tst(offset_reg, Operand(offset_reg));
     __ b(&ok, MI);
@@ skipping 205 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::ZoneHandle(Z, field().Original()));
 
     __ LoadFieldFromOffset(temp2, temp, Field::is_nullable_offset(),
                            kUnsignedWord);
     __ CompareImmediate(temp2, kNullCid);
     __ b(&store_pointer, EQ);
 
     __ LoadFromOffset(
         temp2, temp, Field::kind_bits_offset() - kHeapObjectTag,
         kUnsignedByte);
     __ tsti(temp2, Immediate(1 << Field::kUnboxingCandidateBit));
@@ skipping 117 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::ZoneHandle(Z, field().Original()));
   if (this->value()->NeedsStoreBuffer()) {
     __ StoreIntoObjectOffset(
         temp, Field::static_value_offset(), value, CanValueBeSmi());
   } else {
     __ StoreIntoObjectOffsetNoBarrier(temp,
                                       Field::static_value_offset(),
                                       value);
   }
 }
 
@@ skipping 191 matching lines @@
   Label done;
   const Register result_reg = locs()->out(0).reg();
   if (IsPotentialUnboxedLoad()) {
     const Register temp = locs()->temp(0).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(), kUnsignedWord);
     FieldAddress field_nullability_operand(
         result_reg, Field::is_nullable_offset(), kUnsignedWord);
 
     __ ldr(temp, field_nullability_operand, kUnsignedWord);
     __ CompareImmediate(temp, kNullCid);
     __ b(&load_pointer, EQ);
 
@@ skipping 3380 matching lines @@
                                 1,
                                 locs());
   __ Drop(1);
   __ Pop(result);
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64