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      1 /*
      2  * Copyright (C) 2008 Apple Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  *
      8  * 1.  Redistributions of source code must retain the above copyright
      9  *     notice, this list of conditions and the following disclaimer.
     10  * 2.  Redistributions in binary form must reproduce the above copyright
     11  *     notice, this list of conditions and the following disclaimer in the
     12  *     documentation and/or other materials provided with the distribution.
     13  * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
     14  *     its contributors may be used to endorse or promote products derived
     15  *     from this software without specific prior written permission.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
     18  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     19  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     20  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     21  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     22  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     23  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
     24  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     26  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #ifndef Label_h
     30 #define Label_h
     31 
     32 #include "CodeBlock.h"
     33 #include "Instruction.h"
     34 #include <wtf/Assertions.h>
     35 #include <wtf/Vector.h>
     36 #include <limits.h>
     37 
     38 namespace JSC {
     39 
     40     class Label {
     41     public:
     42         explicit Label(CodeBlock* codeBlock)
     43             : m_refCount(0)
     44             , m_location(invalidLocation)
     45             , m_codeBlock(codeBlock)
     46         {
     47         }
     48 
     49         void setLocation(unsigned location)
     50         {
     51             m_location = location;
     52 
     53             unsigned size = m_unresolvedJumps.size();
     54             for (unsigned i = 0; i < size; ++i)
     55                 m_codeBlock->instructions()[m_unresolvedJumps[i].second].u.operand = m_location - m_unresolvedJumps[i].first;
     56         }
     57 
     58         int bind(int opcode, int offset) const
     59         {
     60             if (m_location == invalidLocation) {
     61                 m_unresolvedJumps.append(std::make_pair(opcode, offset));
     62                 return 0;
     63             }
     64             return m_location - opcode;
     65         }
     66 
     67         void ref() { ++m_refCount; }
     68         void deref()
     69         {
     70             --m_refCount;
     71             ASSERT(m_refCount >= 0);
     72         }
     73         int refCount() const { return m_refCount; }
     74 
     75         bool isForward() const { return m_location == invalidLocation; }
     76 
     77     private:
     78         typedef Vector<std::pair<int, int>, 8> JumpVector;
     79 
     80         static const unsigned invalidLocation = UINT_MAX;
     81 
     82         int m_refCount;
     83         unsigned m_location;
     84         CodeBlock* m_codeBlock;
     85         mutable JumpVector m_unresolvedJumps;
     86     };
     87 
     88 } // namespace JSC
     89 
     90 #endif // Label_h
     91