Avoid linear search for function lookup.

runtime/vm/object.h

 // 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.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 931 matching lines @@
   intptr_t FindFieldIndex(const Field& field) const;
   RawField* FieldFromIndex(intptr_t idx) const;
 
   // Returns an array of all fields of this class and its superclasses indexed
   // by offset in words.
   RawArray* OffsetToFieldMap() const;
 
   // Returns true if non-static fields are defined.
   bool HasInstanceFields() const;
 
+  // TODO(koda): Avoid VM service indexing into this array; unite w/ hash table.
   RawArray* functions() const { return raw_ptr()->functions_; }
   void SetFunctions(const Array& value) const;
   void AddFunction(const Function& function) const;
   intptr_t FindFunctionIndex(const Function& function) const;
   RawFunction* FunctionFromIndex(intptr_t idx) const;
   intptr_t FindImplicitClosureFunctionIndex(const Function& needle) const;
   RawFunction* ImplicitClosureFunctionFromIndex(intptr_t idx) const;
 
   RawGrowableObjectArray* closures() const {
     return raw_ptr()->closure_functions_;
@@ skipping 242 matching lines @@
   RawObject* canonical_types() const;
 
   RawArray* invocation_dispatcher_cache() const;
   void set_invocation_dispatcher_cache(const Array& cache) const;
   RawFunction* CreateInvocationDispatcher(const String& target_name,
                                           const Array& args_desc,
                                           RawFunction::Kind kind) const;
 
   void CalculateFieldOffsets() const;
 
+  // functions_hash_table is in use iff there are at least this many functions.
+  static const intptr_t kFunctionLookupHashTreshold = 16;
+
   // Initial value for the cached number of type arguments.
   static const intptr_t kUnknownNumTypeArguments = -1;
 
   int16_t num_type_arguments() const {
     return raw_ptr()->num_type_arguments_;
   }
   void set_num_type_arguments(intptr_t value) const;
 
   int16_t num_own_type_arguments() const {
     return raw_ptr()->num_own_type_arguments_;
@@ skipping 6089 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_