Restore back pointer from Instructions to Code

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 3696 matching lines @@
   friend class Class;
   friend class Object;
   friend class RawObjectPool;
 };
 
 
 class Instructions : public Object {
  public:
   intptr_t size() const { return raw_ptr()->size_; }  // Excludes HeaderSize().
 
+  RawCode* code() const {
+    // This should only be accessed when jitting.
+    // TODO(johnmccutchan): Remove code back pointer.
+    ASSERT(!Dart::IsRunningPrecompiledCode());
+    return raw_ptr()->code_;
+  }
+
   uword EntryPoint() const {
     return reinterpret_cast<uword>(raw_ptr()) + HeaderSize();
   }
 
   static const intptr_t kMaxElements = (kMaxInt32 -
                                         (sizeof(RawInstructions) +
                                          sizeof(RawObject) +
                                          (2 * OS::kMaxPreferredCodeAlignment)));
 
   static intptr_t InstanceSize() {
@@ skipping 18 matching lines @@
   static RawInstructions* FromEntryPoint(uword entry_point) {
     return reinterpret_cast<RawInstructions*>(
         entry_point - HeaderSize() + kHeapObjectTag);
   }
 
  private:
   void set_size(intptr_t size) const {
     StoreNonPointer(&raw_ptr()->size_, size);
   }
 
+  void set_code(RawCode* code) const {
+    StorePointer(&raw_ptr()->code_, code);
+  }
+
   // New is a private method as RawInstruction and RawCode objects should
   // only be created using the Code::FinalizeCode method. This method creates
   // the RawInstruction and RawCode objects, sets up the pointer offsets
   // and links the two in a GC safe manner.
   static RawInstructions* New(intptr_t size);
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(Instructions, Object);
   friend class Class;
   friend class Code;
   friend class InstructionsWriter;
@@ skipping 4358 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_