bytecode/ValueProfile.h

   1 /*
   2  * Copyright (C) 2011, 2012, 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  *
   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 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 ValueProfile_h
  30 #define ValueProfile_h
  31
  32 #include "ConcurrentJITLock.h"
  33 #include "Heap.h"
  34 #include "JSArray.h"
  35 #include "SpeculatedType.h"
  36 #include "Structure.h"
  37 #include "WriteBarrier.h"
  38 #include <wtf/PrintStream.h>
  39 #include <wtf/StringPrintStream.h>
  40
  41 namespace JSC {
  42
  43 template<unsigned numberOfBucketsArgument>
  44 struct ValueProfileBase {
  45     static const unsigned numberOfBuckets = numberOfBucketsArgument;
  46     static const unsigned numberOfSpecFailBuckets = 1;
  47     static const unsigned bucketIndexMask = numberOfBuckets - 1;
  48     static const unsigned totalNumberOfBuckets = numberOfBuckets + numberOfSpecFailBuckets;
  49
  50     ValueProfileBase()
  51         : m_bytecodeOffset(-1)
  52         , m_prediction(SpecNone)
  53         , m_numberOfSamplesInPrediction(0)
  54     {
  55         for (unsigned i = 0; i < totalNumberOfBuckets; ++i)
  56             m_buckets[i] = JSValue::encode(JSValue());
  57     }
  58
  59     ValueProfileBase(int bytecodeOffset)
  60         : m_bytecodeOffset(bytecodeOffset)
  61         , m_prediction(SpecNone)
  62         , m_numberOfSamplesInPrediction(0)
  63     {
  64         for (unsigned i = 0; i < totalNumberOfBuckets; ++i)
  65             m_buckets[i] = JSValue::encode(JSValue());
  66     }
  67
  68     EncodedJSValue* specFailBucket(unsigned i)
  69     {
  70         ASSERT(numberOfBuckets + i < totalNumberOfBuckets);
  71         return m_buckets + numberOfBuckets + i;
  72     }
  73
  74     const ClassInfo* classInfo(unsigned bucket) const
  75     {
  76         JSValue value = JSValue::decode(m_buckets[bucket]);
  77         if (!!value) {
  78             if (!value.isCell())
  79                 return 0;
  80             return value.asCell()->structure()->classInfo();
  81         }
  82         return 0;
  83     }
  84
  85     unsigned numberOfSamples() const
  86     {
  87         unsigned result = 0;
  88         for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
  89             if (!!JSValue::decode(m_buckets[i]))
  90                 result++;
  91         }
  92         return result;
  93     }
  94
  95     unsigned totalNumberOfSamples() const
  96     {
  97         return numberOfSamples() + m_numberOfSamplesInPrediction;
  98     }
  99
 100     bool isLive() const
 101     {
 102         for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
 103             if (!!JSValue::decode(m_buckets[i]))
 104                 return true;
 105         }
 106         return false;
 107     }
 108
 109     CString briefDescription(const ConcurrentJITLocker& locker)
 110     {
 111         computeUpdatedPrediction(locker);
 112
 113         StringPrintStream out;
 114         out.print("predicting ", SpeculationDump(m_prediction));
 115         return out.toCString();
 116     }
 117
 118     void dump(PrintStream& out)
 119     {
 120         out.print("samples = ", totalNumberOfSamples(), " prediction = ", SpeculationDump(m_prediction));
 121         bool first = true;
 122         for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
 123             JSValue value = JSValue::decode(m_buckets[i]);
 124             if (!!value) {
 125                 if (first) {
 126                     out.printf(": ");
 127                     first = false;
 128                 } else
 129                     out.printf(", ");
 130                 out.print(value);
 131             }
 132         }
 133     }
 134
 135     // Updates the prediction and returns the new one. Never call this from any thread
 136     // that isn't executing the code.
 137     SpeculatedType computeUpdatedPrediction(const ConcurrentJITLocker&)
 138     {
 139         for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
 140             JSValue value = JSValue::decode(m_buckets[i]);
 141             if (!value)
 142                 continue;
 143
 144             m_numberOfSamplesInPrediction++;
 145             mergeSpeculation(m_prediction, speculationFromValue(value));
 146
 147             m_buckets[i] = JSValue::encode(JSValue());
 148         }
 149
 150         return m_prediction;
 151     }
 152
 153     int m_bytecodeOffset; // -1 for prologue
 154
 155     SpeculatedType m_prediction;
 156     unsigned m_numberOfSamplesInPrediction;
 157
 158     EncodedJSValue m_buckets[totalNumberOfBuckets];
 159 };
 160
 161 struct MinimalValueProfile : public ValueProfileBase<0> {
 162     MinimalValueProfile(): ValueProfileBase<0>() { }
 163     MinimalValueProfile(int bytecodeOffset): ValueProfileBase<0>(bytecodeOffset) { }
 164 };
 165
 166 template<unsigned logNumberOfBucketsArgument>
 167 struct ValueProfileWithLogNumberOfBuckets : public ValueProfileBase<1 << logNumberOfBucketsArgument> {
 168     static const unsigned logNumberOfBuckets = logNumberOfBucketsArgument;
 169
 170     ValueProfileWithLogNumberOfBuckets()
 171         : ValueProfileBase<1 << logNumberOfBucketsArgument>()
 172     {
 173     }
 174     ValueProfileWithLogNumberOfBuckets(int bytecodeOffset)
 175         : ValueProfileBase<1 << logNumberOfBucketsArgument>(bytecodeOffset)
 176     {
 177     }
 178 };
 179
 180 struct ValueProfile : public ValueProfileWithLogNumberOfBuckets<0> {
 181     ValueProfile(): ValueProfileWithLogNumberOfBuckets<0>() { }
 182     ValueProfile(int bytecodeOffset): ValueProfileWithLogNumberOfBuckets<0>(bytecodeOffset) { }
 183 };
 184
 185 template<typename T>
 186 inline int getValueProfileBytecodeOffset(T* valueProfile)
 187 {
 188     return valueProfile->m_bytecodeOffset;
 189 }
 190
 191 // This is a mini value profile to catch pathologies. It is a counter that gets
 192 // incremented when we take the slow path on any instruction.
 193 struct RareCaseProfile {
 194     RareCaseProfile(int bytecodeOffset)
 195         : m_bytecodeOffset(bytecodeOffset)
 196         , m_counter(0)
 197     {
 198     }
 199
 200     int m_bytecodeOffset;
 201     uint32_t m_counter;
 202 };
 203
 204 inline int getRareCaseProfileBytecodeOffset(RareCaseProfile* rareCaseProfile)
 205 {
 206     return rareCaseProfile->m_bytecodeOffset;
 207 }
 208
 209 } // namespace JSC
 210
 211 #endif // ValueProfile_h
 212