bytecode/DFGExitProfile.h

   1 /*
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   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
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   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
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  19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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  23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #ifndef DFGExitProfile_h
  27 #define DFGExitProfile_h
  28
  29 #if ENABLE(DFG_JIT)
  30
  31 #include "ConcurrentJITLock.h"
  32 #include "ExitKind.h"
  33 #include "ExitingJITType.h"
  34 #include <wtf/HashSet.h>
  35 #include <wtf/Vector.h>
  36
  37 namespace JSC { namespace DFG {
  38
  39 class FrequentExitSite {
  40 public:
  41     FrequentExitSite()
  42         : m_bytecodeOffset(0) // 0 = empty value
  43         , m_kind(ExitKindUnset)
  44         , m_jitType(ExitFromAnything)
  45     {
  46     }
  47
  48     FrequentExitSite(WTF::HashTableDeletedValueType)
  49         : m_bytecodeOffset(1) // 1 = deleted value
  50         , m_kind(ExitKindUnset)
  51         , m_jitType(ExitFromAnything)
  52     {
  53     }
  54
  55     explicit FrequentExitSite(unsigned bytecodeOffset, ExitKind kind, ExitingJITType jitType = ExitFromAnything)
  56         : m_bytecodeOffset(bytecodeOffset)
  57         , m_kind(kind)
  58         , m_jitType(jitType)
  59     {
  60         if (m_kind == ArgumentsEscaped) {
  61             // Count this one globally. It doesn't matter where in the code block the arguments excaped;
  62             // the fact that they did is not associated with any particular instruction.
  63             m_bytecodeOffset = 0;
  64         }
  65     }
  66
  67     // Use this constructor if you wish for the exit site to be counted globally within its
  68     // code block.
  69     explicit FrequentExitSite(ExitKind kind, ExitingJITType jitType = ExitFromAnything)
  70         : m_bytecodeOffset(0)
  71         , m_kind(kind)
  72         , m_jitType(jitType)
  73     {
  74     }
  75
  76     bool operator!() const
  77     {
  78         return m_kind == ExitKindUnset;
  79     }
  80
  81     bool operator==(const FrequentExitSite& other) const
  82     {
  83         return m_bytecodeOffset == other.m_bytecodeOffset
  84             && m_kind == other.m_kind
  85             && m_jitType == other.m_jitType;
  86     }
  87
  88     bool subsumes(const FrequentExitSite& other) const
  89     {
  90         if (m_bytecodeOffset != other.m_bytecodeOffset)
  91             return false;
  92         if (m_kind != other.m_kind)
  93             return false;
  94         if (m_jitType == ExitFromAnything)
  95             return true;
  96         return m_jitType == other.m_jitType;
  97     }
  98
  99     unsigned hash() const
 100     {
 101         return WTF::intHash(m_bytecodeOffset) + m_kind + m_jitType * 7;
 102     }
 103
 104     unsigned bytecodeOffset() const { return m_bytecodeOffset; }
 105     ExitKind kind() const { return m_kind; }
 106     ExitingJITType jitType() const { return m_jitType; }
 107
 108     FrequentExitSite withJITType(ExitingJITType jitType) const
 109     {
 110         FrequentExitSite result = *this;
 111         result.m_jitType = jitType;
 112         return result;
 113     }
 114
 115     bool isHashTableDeletedValue() const
 116     {
 117         return m_kind == ExitKindUnset && m_bytecodeOffset;
 118     }
 119
 120 private:
 121     unsigned m_bytecodeOffset;
 122     ExitKind m_kind;
 123     ExitingJITType m_jitType;
 124 };
 125
 126 struct FrequentExitSiteHash {
 127     static unsigned hash(const FrequentExitSite& key) { return key.hash(); }
 128     static bool equal(const FrequentExitSite& a, const FrequentExitSite& b) { return a == b; }
 129     static const bool safeToCompareToEmptyOrDeleted = true;
 130 };
 131
 132 } } // namespace JSC::DFG
 133
 134
 135 namespace WTF {
 136
 137 template<typename T> struct DefaultHash;
 138 template<> struct DefaultHash<JSC::DFG::FrequentExitSite> {
 139     typedef JSC::DFG::FrequentExitSiteHash Hash;
 140 };
 141
 142 template<typename T> struct HashTraits;
 143 template<> struct HashTraits<JSC::DFG::FrequentExitSite> : SimpleClassHashTraits<JSC::DFG::FrequentExitSite> { };
 144
 145 } // namespace WTF
 146
 147 namespace JSC { namespace DFG {
 148
 149 class QueryableExitProfile;
 150
 151 class ExitProfile {
 152 public:
 153     ExitProfile();
 154     ~ExitProfile();
 155
 156     // Add a new frequent exit site. Return true if this is a new one, or false
 157     // if we already knew about it. This is an O(n) operation, because it errs
 158     // on the side of keeping the data structure compact. Also, this will only
 159     // be called a fixed number of times per recompilation. Recompilation is
 160     // rare to begin with, and implies doing O(n) operations on the CodeBlock
 161     // anyway.
 162     bool add(const ConcurrentJITLocker&, const FrequentExitSite&);
 163
 164     // Get the frequent exit sites for a bytecode index. This is O(n), and is
 165     // meant to only be used from debugging/profiling code.
 166     Vector<FrequentExitSite> exitSitesFor(unsigned bytecodeIndex);
 167
 168     // This is O(n) and should be called on less-frequently executed code paths
 169     // in the compiler. It should be strictly cheaper than building a
 170     // QueryableExitProfile, if you really expect this to be called infrequently
 171     // and you believe that there are few exit sites.
 172     bool hasExitSite(const ConcurrentJITLocker&, const FrequentExitSite&) const;
 173     bool hasExitSite(const ConcurrentJITLocker& locker, ExitKind kind) const
 174     {
 175         return hasExitSite(locker, FrequentExitSite(kind));
 176     }
 177     bool hasExitSite(const ConcurrentJITLocker& locker, unsigned bytecodeIndex, ExitKind kind) const
 178     {
 179         return hasExitSite(locker, FrequentExitSite(bytecodeIndex, kind));
 180     }
 181
 182 private:
 183     friend class QueryableExitProfile;
 184
 185     std::unique_ptr<Vector<FrequentExitSite>> m_frequentExitSites;
 186 };
 187
 188 class QueryableExitProfile {
 189 public:
 190     QueryableExitProfile();
 191     ~QueryableExitProfile();
 192
 193     void initialize(const ConcurrentJITLocker&, const ExitProfile&);
 194
 195     bool hasExitSite(const FrequentExitSite& site) const
 196     {
 197         if (site.jitType() == ExitFromAnything) {
 198             return hasExitSite(site.withJITType(ExitFromDFG))
 199                 || hasExitSite(site.withJITType(ExitFromFTL));
 200         }
 201         return m_frequentExitSites.find(site) != m_frequentExitSites.end();
 202     }
 203
 204     bool hasExitSite(ExitKind kind) const
 205     {
 206         return hasExitSite(FrequentExitSite(kind));
 207     }
 208
 209     bool hasExitSite(unsigned bytecodeIndex, ExitKind kind) const
 210     {
 211         return hasExitSite(FrequentExitSite(bytecodeIndex, kind));
 212     }
 213 private:
 214     HashSet<FrequentExitSite> m_frequentExitSites;
 215 };
 216
 217 } } // namespace JSC::DFG
 218
 219 #endif // ENABLE(DFG_JIT)
 220
 221 #endif // DFGExitProfile_h