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

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index 111215fd561354f9c267a645e7191cacfa3ec87a..ec108a80cd809b4443fc46d752c15181663882e4 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -20,6 +20,7 @@
 #include "vm/symbols.h"
 
 #define __ compiler->assembler()->
+#define Z (compiler->zone())
 
 namespace dart {
 
@@ -1483,7 +1484,7 @@ 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(
@@ -1617,7 +1618,7 @@ void GuardFieldLengthInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 
     Label ok;
 
-    __ LoadObject(field_reg, Field::ZoneHandle(field().raw()));
+    __ LoadObject(field_reg, Field::ZoneHandle(field().Original()));
 
     __ movsxb(offset_reg, FieldAddress(field_reg,
         Field::guarded_list_length_in_object_offset_offset()));
@@ -1855,7 +1856,7 @@ void StoreInstanceFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     Label store_float32x4;
     Label store_float64x2;
 
-    __ LoadObject(temp, Field::ZoneHandle(field().raw()));
+    __ LoadObject(temp, Field::ZoneHandle(Z, field().Original()));
 
     __ cmpl(FieldAddress(temp, Field::is_nullable_offset()),
             Immediate(kNullCid));
@@ -1997,7 +1998,7 @@ 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()),
@@ -2215,7 +2216,7 @@ void LoadFieldInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     Label load_float32x4;
     Label load_float64x2;
 
-    __ LoadObject(result, Field::ZoneHandle(field()->raw()));
+    __ LoadObject(result, Field::ZoneHandle(field()->Original()));
 
     __ cmpl(FieldAddress(result, Field::is_nullable_offset()),
             Immediate(kNullCid));