VM: Fix performance regression introduced by r28408.

runtime/vm/flow_graph_builder.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/flow_graph_builder.h"
 
 #include "lib/invocation_mirror.h"
 #include "vm/ast_printer.h"
 #include "vm/bit_vector.h"
 #include "vm/code_descriptors.h"
@@ skipping 3094 matching lines @@
 
 
 // StoreInstanceFieldNode does not return result.
 void ValueGraphVisitor::VisitStoreInstanceFieldNode(
     StoreInstanceFieldNode* node) {
   UNIMPLEMENTED();
 }
 
 
 void EffectGraphVisitor::VisitLoadStaticFieldNode(LoadStaticFieldNode* node) {
+  if (node->field().is_const()) {
+    ASSERT(node->field().value() != Object::sentinel().raw());
+    ASSERT(node->field().value() != Object::transition_sentinel().raw());
+    Definition* result =
+        new ConstantInstr(Instance::ZoneHandle(node->field().value()));
+    return ReturnDefinition(result);
+  }
   Value* field_value = Bind(new ConstantInstr(node->field()));
   LoadStaticFieldInstr* load = new LoadStaticFieldInstr(field_value);
   ReturnDefinition(load);
 }
 
 
 Definition* EffectGraphVisitor::BuildStoreStaticField(
   StoreStaticFieldNode* node, bool result_is_needed) {
   ValueGraphVisitor for_value(owner(), temp_index());
   node->value()->Visit(&for_value);
@@ skipping 715 matching lines @@
   intptr_t len = OS::SNPrint(NULL, 0, kFormat, function_name, reason) + 1;
   char* chars = Isolate::Current()->current_zone()->Alloc<char>(len);
   OS::SNPrint(chars, len, kFormat, function_name, reason);
   const Error& error = Error::Handle(
       LanguageError::New(String::Handle(String::New(chars))));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 
 }  // namespace dart