duke@435: /*
stefank@2314:  * Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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duke@435:  */
duke@435: 
stefank@2314: #ifndef SHARE_VM_UTILITIES_SIZES_HPP
stefank@2314: #define SHARE_VM_UTILITIES_SIZES_HPP
stefank@2314: 
stefank@2314: #include "memory/allocation.hpp"
stefank@2314: #include "utilities/globalDefinitions.hpp"
stefank@2314: 
duke@435: // The following two classes are used to represent 'sizes' and 'offsets' in the VM;
duke@435: // they serve as 'unit' types. ByteSize is used for sizes measured in bytes, while
duke@435: // WordSize is used for sizes measured in machine words (i.e., 32bit or 64bit words
duke@435: // depending on platform).
duke@435: //
duke@435: // The classes are defined with friend functions operating on them instead of member
duke@435: // functions so that they (the classes) can be re-#define'd to int types in optimized
duke@435: // mode. This allows full type checking and maximum safety in debug mode, and full
duke@435: // optimizations (constant folding) and zero overhead (time and space wise) in the
duke@435: // optimized build (some compilers do not optimize one-element value classes but
duke@435: // instead create an object in memory - thus the overhead may be significant).
duke@435: //
duke@435: // Note: 1) DO NOT add new overloaded friend functions that do not have a unique function
duke@435: //          function name but require signature types for resolution. This will not work
duke@435: //          in optimized mode as both, ByteSize and WordSize are mapped to the same type
duke@435: //          and thus the distinction would not be possible anymore (=> compiler errors).
duke@435: //
duke@435: //       2) DO NOT add non-static member functions as they cannot be mapped so something
duke@435: //          compilable in the optimized build. Static member functions could be added
duke@435: //          but require a corresponding class definition in the optimized build.
duke@435: //
duke@435: // These classes should help doing a transition from (currently) word-size based offsets
duke@435: // to byte-size based offsets in the VM (this will be important if we desire to pack
duke@435: // objects more densely in the VM for 64bit machines). Such a transition should proceed
duke@435: // in two steps to minimize the risk of introducing hard-to-find bugs:
duke@435: //
duke@435: // a) first transition the whole VM into a form where all sizes are strongly typed
duke@435: // b) change all WordSize's to ByteSize's where desired and fix the compilation errors
duke@435: 
duke@435: 
duke@435: #ifdef ASSERT
duke@435: 
duke@435: class ByteSize VALUE_OBJ_CLASS_SPEC {
duke@435:  private:
duke@435:   int _size;
duke@435: 
duke@435:   // Note: This constructor must be private to avoid implicit conversions!
duke@435:   ByteSize(int size)                                  { _size = size; }
duke@435: 
duke@435:  public:
duke@435:   // constructors
duke@435:   inline friend ByteSize in_ByteSize(int size);
duke@435: 
duke@435:   // accessors
duke@435:   inline friend int in_bytes(ByteSize x);
duke@435: 
duke@435:   // operators
duke@435:   friend ByteSize operator + (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) + in_bytes(y)); }
duke@435:   friend ByteSize operator - (ByteSize x, ByteSize y) { return ByteSize(in_bytes(x) - in_bytes(y)); }
duke@435:   friend ByteSize operator * (ByteSize x, int      y) { return ByteSize(in_bytes(x) * y          ); }
duke@435: 
duke@435:   // comparison
duke@435:   friend bool operator == (ByteSize x, ByteSize y)    { return in_bytes(x) == in_bytes(y); }
duke@435:   friend bool operator != (ByteSize x, ByteSize y)    { return in_bytes(x) != in_bytes(y); }
duke@435:   friend bool operator <  (ByteSize x, ByteSize y)    { return in_bytes(x) <  in_bytes(y); }
duke@435:   friend bool operator <= (ByteSize x, ByteSize y)    { return in_bytes(x) <= in_bytes(y); }
duke@435:   friend bool operator >  (ByteSize x, ByteSize y)    { return in_bytes(x) >  in_bytes(y); }
duke@435:   friend bool operator >= (ByteSize x, ByteSize y)    { return in_bytes(x) >= in_bytes(y); }
duke@435: };
duke@435: 
duke@435: inline ByteSize in_ByteSize(int size) { return ByteSize(size); }
duke@435: inline int      in_bytes(ByteSize x)  { return x._size; }
duke@435: 
duke@435: 
duke@435: class WordSize VALUE_OBJ_CLASS_SPEC {
duke@435:  private:
duke@435:   int _size;
duke@435: 
duke@435:   // Note: This constructor must be private to avoid implicit conversions!
duke@435:   WordSize(int size)                                  { _size = size; }
duke@435: 
duke@435:  public:
duke@435:   // constructors
duke@435:   inline friend WordSize in_WordSize(int size);
duke@435: 
duke@435:   // accessors
duke@435:   inline friend int in_words(WordSize x);
duke@435: 
duke@435:   // operators
duke@435:   friend WordSize operator + (WordSize x, WordSize y) { return WordSize(in_words(x) + in_words(y)); }
duke@435:   friend WordSize operator - (WordSize x, WordSize y) { return WordSize(in_words(x) - in_words(y)); }
duke@435:   friend WordSize operator * (WordSize x, int      y) { return WordSize(in_words(x) * y          ); }
duke@435: 
duke@435:   // comparison
duke@435:   friend bool operator == (WordSize x, WordSize y)    { return in_words(x) == in_words(y); }
duke@435:   friend bool operator != (WordSize x, WordSize y)    { return in_words(x) != in_words(y); }
duke@435:   friend bool operator <  (WordSize x, WordSize y)    { return in_words(x) <  in_words(y); }
duke@435:   friend bool operator <= (WordSize x, WordSize y)    { return in_words(x) <= in_words(y); }
duke@435:   friend bool operator >  (WordSize x, WordSize y)    { return in_words(x) >  in_words(y); }
duke@435:   friend bool operator >= (WordSize x, WordSize y)    { return in_words(x) >= in_words(y); }
duke@435: };
duke@435: 
duke@435: inline WordSize in_WordSize(int size) { return WordSize(size); }
duke@435: inline int      in_words(WordSize x)  { return x._size; }
duke@435: 
duke@435: 
duke@435: #else // ASSERT
duke@435: 
duke@435: // The following definitions must match the corresponding friend declarations
duke@435: // in the Byte/WordSize classes if they are typedef'ed to be int. This will
duke@435: // be the case in optimized mode to ensure zero overhead for these types.
duke@435: //
duke@435: // Note: If a compiler does not inline these function calls away, one may
duke@435: //       want to use #define's to make sure full optimization (constant
duke@435: //       folding in particular) is possible.
duke@435: 
duke@435: typedef int ByteSize;
duke@435: inline ByteSize in_ByteSize(int size)                 { return size; }
duke@435: inline int      in_bytes   (ByteSize x)               { return x; }
duke@435: 
duke@435: typedef int WordSize;
duke@435: inline WordSize in_WordSize(int size)                 { return size; }
duke@435: inline int      in_words   (WordSize x)               { return x; }
duke@435: 
duke@435: #endif // ASSERT
duke@435: 
duke@435: 
duke@435: // Use the following #define to get C++ field member offsets
duke@435: 
duke@435: #define byte_offset_of(klass,field)   in_ByteSize((int)offset_of(klass, field))
stefank@2314: 
stefank@2314: #endif // SHARE_VM_UTILITIES_SIZES_HPP