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

runtime/vm/intermediate_language_mips.cc

Index: runtime/vm/intermediate_language_mips.cc
diff --git a/runtime/vm/intermediate_language_mips.cc b/runtime/vm/intermediate_language_mips.cc
index 9401634a26442b10c1212a5b59d734227477719b..f4b80321d69d84a879dbc9e2c59b2d9c4b24f802 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -21,6 +21,7 @@
 #include "vm/symbols.h"
 
 #define __ compiler->assembler()->
+#define Z (compiler->zone())
 
 namespace dart {
 
@@ -1641,7 +1642,7 @@ void GuardFieldClassInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   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(
@@ -1786,7 +1787,7 @@ void GuardFieldLengthInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 
     Label ok;
 
-    __ LoadObject(field_reg, Field::ZoneHandle(field().raw()));
+    __ LoadObject(field_reg, Field::ZoneHandle(field().Original()));
 
     __ lb(CMPRES1, FieldAddress(field_reg,
         Field::guarded_list_length_in_object_offset_offset()));
@@ -2001,7 +2002,7 @@ void StoreInstanceFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     Label store_pointer;
     Label store_double;
 
-    __ LoadObject(temp, Field::ZoneHandle(field().raw()));
+    __ LoadObject(temp, Field::ZoneHandle(Z, field().Original()));
 
     __ lhu(temp2, FieldAddress(temp, Field::is_nullable_offset()));
     __ BranchEqual(temp2, Immediate(kNullCid), &store_pointer);
@@ -2107,7 +2108,7 @@ void StoreStaticFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Register value = locs()->in(0).reg();
   Register temp = locs()->temp(0).reg();
 
-  __ LoadObject(temp, field());
+  __ LoadObject(temp, Field::ZoneHandle(Z, field().Original()));
   if (this->value()->NeedsStoreBuffer()) {
     __ StoreIntoObject(temp,
                        FieldAddress(temp, Field::static_value_offset()),
@@ -2317,7 +2318,7 @@ void LoadFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     Label load_pointer;
     Label load_double;
 
-    __ 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,