dfg/DFGValueStrength.h

   1 /*
   2  * Copyright (C) 2014, 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. ``AS IS'' AND ANY
  14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef DFGValueStrength_h
  27 #define DFGValueStrength_h
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include <wtf/PrintStream.h>
  32
  33 namespace JSC { namespace DFG {
  34
  35 enum ValueStrength {
  36     // The value has been used for optimization and it arose through inference. We don't want the
  37     // fact that we optimized the code to result in the GC keeping this value alive unnecessarily,
  38     // so we'd rather kill the code and recompile than keep the object alive longer.
  39     WeakValue,
  40
  41     // The code will keep this value alive. This is true of constants that were present in the
  42     // source. String constants tend to be strong.
  43     StrongValue
  44 };
  45
  46 inline ValueStrength merge(ValueStrength a, ValueStrength b)
  47 {
  48     switch (a) {
  49     case WeakValue:
  50         return b;
  51     case StrongValue:
  52         return StrongValue;
  53     }
  54     RELEASE_ASSERT_NOT_REACHED();
  55
  56     return WeakValue;
  57 }
  58
  59 } } // namespace JSC::DFG
  60
  61 namespace WTF {
  62
  63 void printInternal(PrintStream&, JSC::DFG::ValueStrength);
  64
  65 } // namespace WTF
  66
  67 #endif // ENABLE(DFG_JIT)
  68
  69 #endif // DFGValueStrength_h
  70