More compact string representation on 64 bit.

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 95288b1e1407513aceb2514fe2abea4016cd6c76..488739cfbf2f115848aa9a7b095500405043f7be 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -266,21 +266,11 @@ class RawObject {
     kVMHeapObjectBit = 2,
     kRememberedBit = 3,
     kReservedTagPos = 4,  // kReservedBit{100K,1M,10M}
-#if defined(ARCH_IS_32_BIT)
     kReservedTagSize = 4,
     kSizeTagPos = kReservedTagPos + kReservedTagSize,  // = 8
     kSizeTagSize = 8,
     kClassIdTagPos = kSizeTagPos + kSizeTagSize,  // = 16
     kClassIdTagSize = 16,
-#elif defined(ARCH_IS_64_BIT)
-    kReservedTagSize = 12,
-    kSizeTagPos = kReservedTagPos + kReservedTagSize,  // = 16
-    kSizeTagSize = 16,
-    kClassIdTagPos = kSizeTagPos + kSizeTagSize,  // = 32
-    kClassIdTagSize = 32,
-#else
-#error Unexpected architecture word size
-#endif
   };
 
   COMPILE_ASSERT(kClassIdTagSize == (sizeof(classid_t) * kBitsPerByte));
@@ -614,6 +604,7 @@ class RawObject {
   friend class RawExternalTypedData;
   friend class RawInstructions;
   friend class RawInstance;
+  friend class RawString;
   friend class RawTypedData;
   friend class Scavenger;
   friend class ScavengerVisitor;
@@ -1863,10 +1854,20 @@ class RawString : public RawInstance {
  protected:
   RawObject** from() { return reinterpret_cast<RawObject**>(&ptr()->length_); }
   RawSmi* length_;
+#if !defined(HASH_IN_OBJECT_HEADER)
   RawSmi* hash_;
   RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->hash_); }
+#else
+  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->length_); }
+#endif
 
+ private:
   friend class Library;
+  friend class OneByteStringSerializationCluster;
+  friend class TwoByteStringSerializationCluster;
+  friend class OneByteStringDeserializationCluster;
+  friend class TwoByteStringDeserializationCluster;
+  friend class RODataSerializationCluster;
 };
 
 
@@ -2453,6 +2454,7 @@ inline intptr_t RawObject::NumberOfTypedDataClasses() {
   return (kNullCid - kTypedDataInt8ArrayCid);
 }
 
+
 }  // namespace dart
 
 #endif  // RUNTIME_VM_RAW_OBJECT_H_