Minor cleanups to use null_array(), null_object() and null_string() handles.

runtime/vm/flow_graph_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/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
@@ skipping 2093 matching lines @@
   switch (view_cid) {
     case kTypedDataInt8ArrayCid:
     case kTypedDataUint8ArrayCid:
     case kTypedDataUint8ClampedArrayCid:
     case kExternalTypedDataUint8ArrayCid:
     case kExternalTypedDataUint8ClampedArrayCid:
     case kTypedDataInt16ArrayCid:
     case kTypedDataUint16ArrayCid: {
       // Check that value is always smi.
       value_check = ICData::New(Function::Handle(),
-                                String::Handle(),
+                                Object::null_string(),
                                 Object::null_array(),
                                 Isolate::kNoDeoptId,
                                 1);
       value_check.AddReceiverCheck(kSmiCid, Function::Handle());
       break;
     }
     case kTypedDataInt32ArrayCid:
     case kTypedDataUint32ArrayCid:
       // We don't have ICData for the value stored, so we optimistically assume
       // smis first. If we ever deoptimized here, we require to unbox the value
       // before storing to handle the mint case, too.
       if (call->ic_data()->deopt_reason() == kDeoptUnknown) {
         value_check = ICData::New(Function::Handle(),
-                                  String::Handle(),
+                                  Object::null_string(),
                                   Object::null_array(),  // Dummy args. descr.
                                   Isolate::kNoDeoptId,
                                   1);
         value_check.AddReceiverCheck(kSmiCid, Function::Handle());
       }
       break;
     case kTypedDataFloat32ArrayCid:
     case kTypedDataFloat64ArrayCid: {
       // Check that value is always double.
       value_check = ICData::New(Function::Handle(),
-                                String::Handle(),
+                                Object::null_string(),
                                 Object::null_array(),  // Dummy args. descr.
                                 Isolate::kNoDeoptId,
                                 1);
       value_check.AddReceiverCheck(kDoubleCid, Function::Handle());
       break;
     }
     case kTypedDataFloat32x4ArrayCid: {
       // Check that value is always Float32x4.
       value_check = ICData::New(Function::Handle(),
-                                String::Handle(),
+                                Object::null_string(),
                                 Object::null_array(),  // Dummy args. descr.
                                 Isolate::kNoDeoptId,
                                 1);
       value_check.AddReceiverCheck(kFloat32x4Cid, Function::Handle());
       break;
     }
     default:
       // Array cids are already checked in the caller.
       UNREACHABLE();
   }
@@ skipping 4417 matching lines @@
 
   // Insert materializations at environment uses.
   const Class& cls = Class::Handle(alloc->constructor().Owner());
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, cls, *fields);
   }
 }
 
 
 }  // namespace dart