VM: Allow configuring use_field_guards on the per-isolate basis and include it into snapshot featur…

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.
 #ifndef DART_PRECOMPILED_RUNTIME
 #include "vm/jit_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/branch_optimizer.h"
 #include "vm/cha.h"
 #include "vm/compiler.h"
@@ skipping 1787 matching lines @@
   const String& field_name =
       String::Handle(Z, Field::NameFromSetter(instr->function_name()));
   const Field& field = Field::ZoneHandle(Z, GetField(class_id, field_name));
   ASSERT(!field.IsNull());
 
   if (flow_graph()->InstanceCallNeedsClassCheck(instr,
                                                 RawFunction::kImplicitSetter)) {
     AddReceiverCheck(instr);
   }
   if (field.guarded_cid() != kDynamicCid) {
-    ASSERT(FLAG_use_field_guards);
+    ASSERT(I->use_field_guards());
     InsertBefore(
         instr, new (Z) GuardFieldClassInstr(new (Z) Value(instr->ArgumentAt(1)),
                                             field, instr->deopt_id()),
         instr->env(), FlowGraph::kEffect);
   }
 
   if (field.needs_length_check()) {
-    ASSERT(FLAG_use_field_guards);
+    ASSERT(I->use_field_guards());
     InsertBefore(instr, new (Z) GuardFieldLengthInstr(
                             new (Z) Value(instr->ArgumentAt(1)), field,
                             instr->deopt_id()),
                  instr->env(), FlowGraph::kEffect);
   }
 
   // Field guard was detached.
   StoreInstanceFieldInstr* store = new (Z)
       StoreInstanceFieldInstr(field, new (Z) Value(instr->ArgumentAt(0)),
                               new (Z) Value(instr->ArgumentAt(1)),
                               kEmitStoreBarrier, instr->token_pos());
 
   if (store->IsUnboxedStore()) {
     flow_graph()->parsed_function().AddToGuardedFields(&field);
   }
 
   // Discard the environment from the original instruction because the store
   // can't deoptimize.
   instr->RemoveEnvironment();
   ReplaceCall(instr, store);
   return true;
 }
 
 
 }  // namespace dart
 #endif  // DART_PRECOMPILED_RUNTIME