dfg/DFGLazyJSValue.h

   1 /*
   2  * Copyright (C) 2013 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,
  18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef DFGLazyJSValue_h
  27 #define DFGLazyJSValue_h
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "JSCJSValue.h"
  32 #include <wtf/text/StringImpl.h>
  33
  34 namespace JSC { namespace DFG {
  35
  36 // Represents either a JSValue, or for JSValues that require allocation in the heap,
  37 // it tells you everything you'd need to know in order to allocate it.
  38
  39 enum LazinessKind {
  40     KnownValue,
  41     SingleCharacterString,
  42     KnownStringImpl
  43 };
  44
  45 class LazyJSValue {
  46 public:
  47     LazyJSValue(JSValue value = JSValue())
  48         : m_kind(KnownValue)
  49     {
  50         u.value = JSValue::encode(value);
  51     }
  52
  53     static LazyJSValue singleCharacterString(UChar character)
  54     {
  55         LazyJSValue result;
  56         result.m_kind = SingleCharacterString;
  57         result.u.character = character;
  58         return result;
  59     }
  60
  61     static LazyJSValue knownStringImpl(StringImpl* string)
  62     {
  63         LazyJSValue result;
  64         result.m_kind = KnownStringImpl;
  65         result.u.stringImpl = string;
  66         return result;
  67     }
  68
  69     JSValue tryGetValue() const
  70     {
  71         if (m_kind == KnownValue)
  72             return value();
  73         return JSValue();
  74     }
  75
  76     JSValue getValue(VM&) const;
  77
  78     JSValue value() const
  79     {
  80         ASSERT(m_kind == KnownValue);
  81         return JSValue::decode(u.value);
  82     }
  83
  84     UChar character() const
  85     {
  86         ASSERT(m_kind == SingleCharacterString);
  87         return u.character;
  88     }
  89
  90     StringImpl* stringImpl() const
  91     {
  92         ASSERT(m_kind == KnownStringImpl);
  93         return u.stringImpl;
  94     }
  95
  96     TriState strictEqual(const LazyJSValue& other) const;
  97
  98     unsigned switchLookupValue() const
  99     {
 100         // NB. Not every kind of JSValue will be able to give you a switch lookup
 101         // value, and this method will assert, or do bad things, if you use it
 102         // for a kind of value that can't.
 103         switch (m_kind) {
 104         case KnownValue:
 105             return value().asInt32();
 106         case SingleCharacterString:
 107             return character();
 108         default:
 109             RELEASE_ASSERT_NOT_REACHED();
 110             return 0;
 111         }
 112     }
 113
 114     void dump(PrintStream&) const;
 115     void dumpInContext(PrintStream&, DumpContext*) const;
 116
 117 private:
 118     union {
 119         EncodedJSValue value;
 120         UChar character;
 121         StringImpl* stringImpl;
 122     } u;
 123     LazinessKind m_kind;
 124 };
 125
 126 } } // namespace JSC::DFG
 127
 128 #endif // ENABLE(DFG_JIT)
 129
 130 #endif // DFGLazyJSValue_h
 131