Avoid numerous type allocations by caching the canonical type of a class, which

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 1016 matching lines @@
     }
     set_type_arguments_field_offset_in_words(value);
   }
   void set_type_arguments_field_offset_in_words(intptr_t value) const {
     StoreNonPointer(&raw_ptr()->type_arguments_field_offset_in_words_, value);
   }
   static intptr_t type_arguments_field_offset_in_words_offset() {
     return OFFSET_OF(RawClass, type_arguments_field_offset_in_words_);
   }
 
-  RawType* CanonicalType() const {
-    if ((NumTypeArguments() == 0) && !IsSignatureClass()) {
-      return reinterpret_cast<RawType*>(raw_ptr()->canonical_types_);
-    }
-    return reinterpret_cast<RawType*>(Object::null());
-  }
+  // Returns the canonical type of this class, i.e. the canonical type whose
+  // type class is this class and whose type arguments are the uninstantiated
+  // type parameters declared by this class if it is generic, e.g. Map<K, V>.

[srdjan, 2015/08/21 05:02:21]

Add comment: returns Type::null() if ...

[regis, 2015/08/21 15:38:22]

Done.

+  RawType* CanonicalType() const;
+  void SetCanonicalType(const Type& type) const;
+
   static intptr_t canonical_types_offset() {
     return OFFSET_OF(RawClass, canonical_types_);
   }
 
   // The super type of this class, Object type if not explicitly specified.
   // Note that the super type may be bounded, as in this example:
   // class C<T> extends S<T> { }; class S<T extends num> { };
   RawAbstractType* super_type() const { return raw_ptr()->super_type_; }
   void set_super_type(const AbstractType& value) const;
   static intptr_t super_type_offset() {
@@ skipping 133 matching lines @@
   RawFunction* LookupSetterFunction(const String& name) const;
   RawFunction* LookupFunctionAtToken(intptr_t token_pos) const;
   RawField* LookupInstanceField(const String& name) const;
   RawField* LookupStaticField(const String& name) const;
   RawField* LookupField(const String& name) const;
 
   RawLibraryPrefix* LookupLibraryPrefix(const String& name) const;
 
   void InsertCanonicalConstant(intptr_t index, const Instance& constant) const;
 
-  intptr_t NumCanonicalTypes() const;
   intptr_t FindCanonicalTypeIndex(const Type& needle) const;
   RawType* CanonicalTypeFromIndex(intptr_t idx) const;
 
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawClass));
   }
 
   bool is_implemented() const {
     return ImplementedBit::decode(raw_ptr()->state_bits_);
   }
@@ skipping 6831 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_