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

runtime/vm/jit_optimizer.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/jit_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 2899 matching lines @@
 
 void JitOptimizer::VisitStoreInstanceField(
     StoreInstanceFieldInstr* instr) {
   if (instr->IsUnboxedStore()) {
     ASSERT(instr->is_potential_unboxed_initialization_);
     // Determine if this field should be unboxed based on the usage of getter
     // and setter functions: The heuristic requires that the setter has a
     // usage count of at least 1/kGetterSetterRatio of the getter usage count.
     // This is to avoid unboxing fields where the setter is never or rarely
     // executed.
-    const Field& field = Field::ZoneHandle(Z, instr->field().Original());
+    const Field& field = instr->field();
     const String& field_name = String::Handle(Z, field.name());
-    const Class& owner = Class::Handle(Z, field.Owner());
+    const Class& owner =
+        Class::Handle(Z, Field::Handle(Z, field.Original()).Owner());
     const Function& getter =
         Function::Handle(Z, owner.LookupGetterFunction(field_name));
     const Function& setter =
         Function::Handle(Z, owner.LookupSetterFunction(field_name));
     bool unboxed_field = false;
     if (!getter.IsNull() && !setter.IsNull()) {
       if (field.is_double_initialized()) {
         unboxed_field = true;
       } else if ((setter.usage_counter() > 0) &&
                  ((FLAG_getter_setter_ratio * setter.usage_counter()) >=
@@ skipping 14 matching lines @@
       }
       if (FLAG_trace_optimization || FLAG_trace_field_guards) {
         THR_Print("Disabling unboxing of %s\n", field.ToCString());
         if (!setter.IsNull()) {
           OS::Print("  setter usage count: %" Pd "\n", setter.usage_counter());
         }
         if (!getter.IsNull()) {
           OS::Print("  getter usage count: %" Pd "\n", getter.usage_counter());
         }
       }
+      ASSERT(field.IsOriginal());
       field.set_is_unboxing_candidate(false);
       field.DeoptimizeDependentCode();
     } else {
       flow_graph()->parsed_function().AddToGuardedFields(&field);
     }
   }
 }
 
 
 void JitOptimizer::VisitAllocateContext(AllocateContextInstr* instr) {
@@ skipping 114 matching lines @@
 
   // Discard the environment from the original instruction because the store
   // can't deoptimize.
   instr->RemoveEnvironment();
   ReplaceCall(instr, store);
   return true;
 }
 
 
 }  // namespace dart