1  /*
 2   * Copyright (C) 2013, 2015 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   * 1. Redistributions of source code must retain the above copyright
 8   *    notice, this list of conditions and the following disclaimer.
 9   * 2. Redistributions in binary form must reproduce the above copyright
10   *    notice, this list of conditions and the following disclaimer in the
11   *    documentation and/or other materials provided with the distribution.
12   *
13   * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
14   * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15   * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16   * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
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18   * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19   * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21   * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23   * THE POSSIBILITY OF SUCH DAMAGE.
24   */
25  
26  #pragma once
27  
28  #include "BytecodeLivenessAnalysis.h"
29  #include "Operands.h"
30  #include <wtf/FastBitVector.h>
31  
32  namespace JSC {
33  
34  class BytecodeLivenessAnalysis;
35  class CodeBlock;
36  
37  // Note: Full bytecode liveness does not track any information about the liveness of temps.
38  // If you want tmp liveness for a checkpoint ask tmpLivenessForCheckpoint.
39  class FullBytecodeLiveness {
40      WTF_MAKE_FAST_ALLOCATED;
41  public:
42      const FastBitVector& getLiveness(BytecodeIndex bytecodeIndex, LivenessCalculationPoint point) const
43      {
44          // We don't have to worry about overflowing into the next bytecodeoffset in our vectors because we
45          // static assert that bytecode length is greater than the number of checkpoints in BytecodeStructs.h
46          switch (point) {
47          case LivenessCalculationPoint::BeforeUse:
48              return m_usesBefore[toIndex(bytecodeIndex)];
49          case LivenessCalculationPoint::AfterUse:
50              return m_usesAfter[toIndex(bytecodeIndex)];
51          }
52          RELEASE_ASSERT_NOT_REACHED();
53      }
54      
55      bool virtualRegisterIsLive(VirtualRegister reg, BytecodeIndex bytecodeIndex, LivenessCalculationPoint point) const
56      {
57          return virtualRegisterIsAlwaysLive(reg) || virtualRegisterThatIsNotAlwaysLiveIsLive(getLiveness(bytecodeIndex, point), reg);
58      }
59      
60  private:
61      friend class BytecodeLivenessAnalysis;
62      
63      static size_t toIndex(BytecodeIndex bytecodeIndex) { return bytecodeIndex.offset() + bytecodeIndex.checkpoint(); }
64  
65      // FIXME: Use FastBitVector's view mechanism to make them compact.
66      // https://bugs.webkit.org/show_bug.cgi?id=204427
67      Vector<FastBitVector, 0, UnsafeVectorOverflow> m_usesBefore;
68      Vector<FastBitVector, 0, UnsafeVectorOverflow> m_usesAfter;
69  };
70  
71  } // namespace JSC