VM: Fix race between background compiler and guarded cid update.

runtime/vm/compiler.cc

 // Copyright (c) 2012, 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/compiler.h"
 
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
 #include "vm/block_scheduler.h"
@@ skipping 478 matching lines @@
 // Returns true if any of disabling fields is inside the guarded_fields.
 // The number of guarded_fields and disabling-fields is expected to be small
 // (less than 5).
 static bool CheckDisablingFields(
     Thread* thread,
     const ZoneGrowableArray<const Field*>& guarded_fields) {
   Isolate* isolate = thread->isolate();
   Zone* zone = thread->zone();
   Field& field = Field::Handle(zone, isolate->GetDisablingField());
   while (!field.IsNull()) {
+    ASSERT(field.IsOriginal());
     for (intptr_t i = 0; i < guarded_fields.length(); i++) {
-      if (guarded_fields.At(i)->raw() == field.raw()) {
+      if (guarded_fields.At(i)->Original() == field.raw()) {
         return true;
       }
     }
     // Get next field.
     field = isolate->GetDisablingField();
   }
   return false;
 }
 
 
@@ skipping 128 matching lines @@
     }
 
     if (code_was_installed) {
       // The generated code was compiled under certain assumptions about
       // class hierarchy and field types. Register these dependencies
       // to ensure that the code will be deoptimized if they are violated.
       thread()->cha()->RegisterDependencies(code);
 
       const ZoneGrowableArray<const Field*>& guarded_fields =
           *flow_graph->parsed_function().guarded_fields();
+      Field& field = Field::Handle();
       for (intptr_t i = 0; i < guarded_fields.length(); i++) {
-        const Field* field = guarded_fields[i];
-        field->RegisterDependentCode(code);
+        field = guarded_fields[i]->Original();
+        field.RegisterDependentCode(code);
       }
     }
   } else {  // not optimized.
     if (function.ic_data_array() == Array::null()) {
       function.SaveICDataMap(
           graph_compiler->deopt_id_to_ic_data(),
           Array::Handle(zone, graph_compiler->edge_counters_array()));
     }
     function.set_unoptimized_code(code);
     function.AttachCode(code);
@@ skipping 1523 matching lines @@
 
 
 bool BackgroundCompiler::IsDisabled() {
   UNREACHABLE();
   return true;
 }
 
 #endif  // DART_PRECOMPILED_RUNTIME
 
 }  // namespace dart