Shrink some fields and add some bounds checks.

runtime/vm/raw_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_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/atomic.h"
 #include "vm/globals.h"
@@ skipping 595 matching lines @@
   RawObject* canonical_types_;  // An array of canonicalized types of this class
                                 // or the canonical type.
   RawArray* invocation_dispatcher_cache_;  // Cache for dispatcher functions.
   RawArray* cha_codes_;  // CHA optimized codes.
   RawCode* allocation_stub_;  // Stub code for allocation of instances.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->allocation_stub_);
   }
 
   cpp_vtable handle_vtable_;
-  int32_t id_;  // Class Id, also index in the class table.
   int32_t token_pos_;
   int32_t instance_size_in_words_;  // Size if fixed len or 0 if variable len.
   int32_t type_arguments_field_offset_in_words_;  // Offset of type args fld.
   int32_t next_field_offset_in_words_;  // Offset of the next instance field.
+  uint16_t id_;  // Class Id, also index in the class table.

[rmacnak, 2015/06/02 21:04:11]

Limited by object header

   int16_t num_type_arguments_;  // Number of type arguments in flatten vector.
   int16_t num_own_type_arguments_;  // Number of non-overlapping type arguments.
   uint16_t num_native_fields_;  // Number of native fields in class.
   uint16_t state_bits_;
 
   friend class Instance;
   friend class Object;
   friend class RawInstance;
   friend class RawInstructions;
   friend class SnapshotReader;
@@ skipping 277 matching lines @@
   RawGrowableObjectArray* metadata_;  // Metadata on classes, methods etc.
   RawArray* anonymous_classes_;  // Classes containing top-level elements.
   RawArray* imports_;            // List of Namespaces imported without prefix.
   RawArray* exports_;            // List of re-exported Namespaces.
   RawArray* loaded_scripts_;     // Array of scripts loaded in this library.
   RawInstance* load_error_;      // Error iff load_state_ == kLoadError.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->load_error_);
   }
 
-  int32_t index_;               // Library id number.
-  int32_t num_imports_;         // Number of entries in imports_.
-  int32_t num_anonymous_;       // Number of entries in anonymous_classes_.
   Dart_NativeEntryResolver native_entry_resolver_;  // Resolves natives.
   Dart_NativeEntrySymbol native_entry_symbol_resolver_;
+  uint16_t index_;              // Library id number.

[rmacnak, 2015/06/02 21:04:11]

Limited by number of classes

+  uint16_t num_imports_;        // Number of entries in imports_.
+  uint16_t num_anonymous_;      // Number of entries in anonymous_classes_.
+  int8_t load_state_;           // Of type LibraryState.
   bool corelib_imported_;
   bool is_dart_scheme_;
-  bool debuggable_;              // True if debugger can stop in library.
-  int8_t load_state_;            // Of type LibraryState.
+  bool debuggable_;             // True if debugger can stop in library.
 
   friend class Isolate;
 };
 
 
 class RawNamespace : public RawObject {
   RAW_HEAP_OBJECT_IMPLEMENTATION(Namespace);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->library_);
@@ skipping 455 matching lines @@
 
   RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->name_); }
   RawString* name_;               // Library prefix name.
   RawArray* imports_;             // Libraries imported with this prefix.
   RawLibrary* importer_;          // Library which declares this prefix.
   RawArray* dependent_code_;      // Code that refers to deferred, unloaded
                                   // library prefix.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->dependent_code_);
   }
-  int32_t num_imports_;          // Number of library entries in libraries_.
+  int16_t num_imports_;          // Number of library entries in libraries_.
   bool is_deferred_load_;
   bool is_loaded_;
 };
 
 
 class RawAbstractType : public RawInstance {
  protected:
   enum TypeState {
     kAllocated,  // Initial state.
     kResolved,  // Type class and type arguments resolved.
@@ skipping 45 matching lines @@
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(TypeParameter);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->parameterized_class_);
   }
   RawClass* parameterized_class_;
   RawString* name_;
   RawAbstractType* bound_;  // ObjectType if no explicit bound specified.
   RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->bound_); }
-  int32_t index_;
   int32_t token_pos_;
+  int16_t index_;

[rmacnak, 2015/06/02 21:04:11]

Limited by num_type_arguments_ in RawClass

   int8_t type_state_;
 };
 
 
 class RawBoundedType : public RawAbstractType {
  private:
   RAW_HEAP_OBJECT_IMPLEMENTATION(BoundedType);
 
   RawObject** from() {
     return reinterpret_cast<RawObject**>(&ptr()->type_);
@@ skipping 656 matching lines @@
   COMPILE_ASSERT(kExternalTypedDataInt8ArrayCid ==
                  kTypedDataInt8ArrayViewCid + 15);
   COMPILE_ASSERT(kByteBufferCid == kExternalTypedDataInt8ArrayCid + 14);
   COMPILE_ASSERT(kNullCid == kByteBufferCid + 1);
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_