diff -r 000000000000 -r a61af66fc99e src/share/vm/utilities/sizes.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/share/vm/utilities/sizes.hpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,144 @@
+/*
+ * Copyright 2000-2004 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// The following two classes are used to represent 'sizes' and 'offsets' in the VM;
+// they serve as 'unit' types. ByteSize is used for sizes measured in bytes, while
+// WordSize is used for sizes measured in machine words (i.e., 32bit or 64bit words
+// depending on platform).
+//
+// The classes are defined with friend functions operating on them instead of member
+// functions so that they (the classes) can be re-#define'd to int types in optimized
+// mode. This allows full type checking and maximum safety in debug mode, and full
+// optimizations (constant folding) and zero overhead (time and space wise) in the
+// optimized build (some compilers do not optimize one-element value classes but
+// instead create an object in memory - thus the overhead may be significant).
+//
+// Note: 1) DO NOT add new overloaded friend functions that do not have a unique function
+//          function name but require signature types for resolution. This will not work
+//          in optimized mode as both, ByteSize and WordSize are mapped to the same type
+//          and thus the distinction would not be possible anymore (=> compiler errors).
+//
+//       2) DO NOT add non-static member functions as they cannot be mapped so something
+//          compilable in the optimized build. Static member functions could be added
+//          but require a corresponding class definition in the optimized build.
+//
+// These classes should help doing a transition from (currently) word-size based offsets
+// to byte-size based offsets in the VM (this will be important if we desire to pack
+// objects more densely in the VM for 64bit machines). Such a transition should proceed
+// in two steps to minimize the risk of introducing hard-to-find bugs:
+//
+// a) first transition the whole VM into a form where all sizes are strongly typed
+// b) change all WordSize's to ByteSize's where desired and fix the compilation errors
+
+
+#ifdef ASSERT
+
+class ByteSize VALUE_OBJ_CLASS_SPEC {
+ private:
+  int _size;
+
+  // Note: This constructor must be private to avoid implicit conversions!
+  ByteSize(int size)                                  { _size = size; }
+
+ public:
+  // constructors
+  inline friend ByteSize in_ByteSize(int size);
+
+  // accessors
+  inline friend int in_bytes(ByteSize x);
+
+  // operators
+  friend ByteSize operator + (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) + in_bytes(y)); }
+  friend ByteSize operator - (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) - in_bytes(y)); }
+  friend ByteSize operator * (ByteSize x, int      y) { return ByteSize(in_bytes(x) * y          ); }
+
+  // comparison
+  friend bool operator == (ByteSize x, ByteSize y)    { return in_bytes(x) == in_bytes(y); }
+  friend bool operator != (ByteSize x, ByteSize y)    { return in_bytes(x) != in_bytes(y); }
+  friend bool operator <  (ByteSize x, ByteSize y)    { return in_bytes(x) <  in_bytes(y); }
+  friend bool operator <= (ByteSize x, ByteSize y)    { return in_bytes(x) <= in_bytes(y); }
+  friend bool operator >  (ByteSize x, ByteSize y)    { return in_bytes(x) >  in_bytes(y); }
+  friend bool operator >= (ByteSize x, ByteSize y)    { return in_bytes(x) >= in_bytes(y); }
+};
+
+inline ByteSize in_ByteSize(int size) { return ByteSize(size); }
+inline int      in_bytes(ByteSize x)  { return x._size; }
+
+
+class WordSize VALUE_OBJ_CLASS_SPEC {
+ private:
+  int _size;
+
+  // Note: This constructor must be private to avoid implicit conversions!
+  WordSize(int size)                                  { _size = size; }
+
+ public:
+  // constructors
+  inline friend WordSize in_WordSize(int size);
+
+  // accessors
+  inline friend int in_words(WordSize x);
+
+  // operators
+  friend WordSize operator + (WordSize x, WordSize y) { return WordSize(in_words(x) + in_words(y)); }
+  friend WordSize operator - (WordSize x, WordSize y) { return WordSize(in_words(x) - in_words(y)); }
+  friend WordSize operator * (WordSize x, int      y) { return WordSize(in_words(x) * y          ); }
+
+  // comparison
+  friend bool operator == (WordSize x, WordSize y)    { return in_words(x) == in_words(y); }
+  friend bool operator != (WordSize x, WordSize y)    { return in_words(x) != in_words(y); }
+  friend bool operator <  (WordSize x, WordSize y)    { return in_words(x) <  in_words(y); }
+  friend bool operator <= (WordSize x, WordSize y)    { return in_words(x) <= in_words(y); }
+  friend bool operator >  (WordSize x, WordSize y)    { return in_words(x) >  in_words(y); }
+  friend bool operator >= (WordSize x, WordSize y)    { return in_words(x) >= in_words(y); }
+};
+
+inline WordSize in_WordSize(int size) { return WordSize(size); }
+inline int      in_words(WordSize x)  { return x._size; }
+
+
+#else // ASSERT
+
+// The following definitions must match the corresponding friend declarations
+// in the Byte/WordSize classes if they are typedef'ed to be int. This will
+// be the case in optimized mode to ensure zero overhead for these types.
+//
+// Note: If a compiler does not inline these function calls away, one may
+//       want to use #define's to make sure full optimization (constant
+//       folding in particular) is possible.
+
+typedef int ByteSize;
+inline ByteSize in_ByteSize(int size)                 { return size; }
+inline int      in_bytes   (ByteSize x)               { return x; }
+
+typedef int WordSize;
+inline WordSize in_WordSize(int size)                 { return size; }
+inline int      in_words   (WordSize x)               { return x; }
+
+#endif // ASSERT
+
+
+// Use the following #define to get C++ field member offsets
+
+#define byte_offset_of(klass,field)   in_ByteSize((int)offset_of(klass, field))