VM: Clean up and fix bugs in instructions patterns

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 3607 matching lines @@
   static intptr_t InstanceSize(intptr_t len) {
     // Ensure that variable length data is not adding to the object length.
     ASSERT(sizeof(RawObjectPool) == (sizeof(RawObject) + (2 * kWordSize)));
     ASSERT(0 <= len && len <= kMaxElements);
     return RoundedAllocationSize(
         sizeof(RawObjectPool) + (len * kBytesPerElement));
   }
 
   static RawObjectPool* New(intptr_t len);
 
+  // Returns the pool index from the offset relative to a tagged RawObjectPool*,
+  // adjusting for the tag-bit.
   static intptr_t IndexFromOffset(intptr_t offset) {
     return (offset + kHeapObjectTag - data_offset()) / kBytesPerElement;
   }
 
+  static intptr_t OffsetFromIndex(intptr_t index) {
+    return element_offset(index) - kHeapObjectTag;
+  }
+
   void DebugPrint() const;
 
  private:
   RawObjectPool::Entry const* EntryAddr(intptr_t index) const {
     ASSERT((index >= 0) && (index < Length()));
     return &raw_ptr()->data()[index];
   }
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(ObjectPool, Object);
   friend class Class;
@@ skipping 4396 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_