ValueProfile.h   [plain text]

/*
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 *     notice, this list of conditions and the following disclaimer.
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#ifndef ValueProfile_h
#define ValueProfile_h

#include "ConcurrentJITLock.h"
#include "Heap.h"
#include "JSArray.h"
#include "SpeculatedType.h"
#include "Structure.h"
#include "TagRegistersMode.h"
#include "WriteBarrier.h"
#include <wtf/PrintStream.h>
#include <wtf/StringPrintStream.h>

namespace JSC {

class CCallHelpers;

template<unsigned numberOfBucketsArgument>
struct ValueProfileBase {
    static const unsigned numberOfBuckets = numberOfBucketsArgument;
    static const unsigned numberOfSpecFailBuckets = 1;
    static const unsigned bucketIndexMask = numberOfBuckets - 1;
    static const unsigned totalNumberOfBuckets = numberOfBuckets + numberOfSpecFailBuckets;
    
    ValueProfileBase()
        : m_bytecodeOffset(-1)
        , m_prediction(SpecNone)
        , m_numberOfSamplesInPrediction(0)
    {
        for (unsigned i = 0; i < totalNumberOfBuckets; ++i)
            m_buckets[i] = JSValue::encode(JSValue());
    }
    
    ValueProfileBase(int bytecodeOffset)
        : m_bytecodeOffset(bytecodeOffset)
        , m_prediction(SpecNone)
        , m_numberOfSamplesInPrediction(0)
    {
        for (unsigned i = 0; i < totalNumberOfBuckets; ++i)
            m_buckets[i] = JSValue::encode(JSValue());
    }
    
    EncodedJSValue* specFailBucket(unsigned i)
    {
        ASSERT(numberOfBuckets + i < totalNumberOfBuckets);
        return m_buckets + numberOfBuckets + i;
    }
    
    const ClassInfo* classInfo(unsigned bucket) const
    {
        JSValue value = JSValue::decode(m_buckets[bucket]);
        if (!!value) {
            if (!value.isCell())
                return 0;
            return value.asCell()->structure()->classInfo();
        }
        return 0;
    }
    
    unsigned numberOfSamples() const
    {
        unsigned result = 0;
        for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
            if (!!JSValue::decode(m_buckets[i]))
                result++;
        }
        return result;
    }
    
    unsigned totalNumberOfSamples() const
    {
        return numberOfSamples() + m_numberOfSamplesInPrediction;
    }
    
    bool isLive() const
    {
        for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
            if (!!JSValue::decode(m_buckets[i]))
                return true;
        }
        return false;
    }
    
    CString briefDescription(const ConcurrentJITLocker& locker)
    {
        computeUpdatedPrediction(locker);
        
        StringPrintStream out;
        out.print("predicting ", SpeculationDump(m_prediction));
        return out.toCString();
    }
    
    void dump(PrintStream& out)
    {
        out.print("samples = ", totalNumberOfSamples(), " prediction = ", SpeculationDump(m_prediction));
        bool first = true;
        for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
            JSValue value = JSValue::decode(m_buckets[i]);
            if (!!value) {
                if (first) {
                    out.printf(": ");
                    first = false;
                } else
                    out.printf(", ");
                out.print(value);
            }
        }
    }
    
    // Updates the prediction and returns the new one. Never call this from any thread
    // that isn't executing the code.
    SpeculatedType computeUpdatedPrediction(const ConcurrentJITLocker&)
    {
        for (unsigned i = 0; i < totalNumberOfBuckets; ++i) {
            JSValue value = JSValue::decode(m_buckets[i]);
            if (!value)
                continue;
            
            m_numberOfSamplesInPrediction++;
            mergeSpeculation(m_prediction, speculationFromValue(value));
            
            m_buckets[i] = JSValue::encode(JSValue());
        }
        
        return m_prediction;
    }
    
    int m_bytecodeOffset; // -1 for prologue
    
    SpeculatedType m_prediction;
    unsigned m_numberOfSamplesInPrediction;
    
    EncodedJSValue m_buckets[totalNumberOfBuckets];
};

struct MinimalValueProfile : public ValueProfileBase<0> {
    MinimalValueProfile(): ValueProfileBase<0>() { }
    MinimalValueProfile(int bytecodeOffset): ValueProfileBase<0>(bytecodeOffset) { }
};

template<unsigned logNumberOfBucketsArgument>
struct ValueProfileWithLogNumberOfBuckets : public ValueProfileBase<1 << logNumberOfBucketsArgument> {
    static const unsigned logNumberOfBuckets = logNumberOfBucketsArgument;
    
    ValueProfileWithLogNumberOfBuckets()
        : ValueProfileBase<1 << logNumberOfBucketsArgument>()
    {
    }
    ValueProfileWithLogNumberOfBuckets(int bytecodeOffset)
        : ValueProfileBase<1 << logNumberOfBucketsArgument>(bytecodeOffset)
    {
    }
};

struct ValueProfile : public ValueProfileWithLogNumberOfBuckets<0> {
    ValueProfile(): ValueProfileWithLogNumberOfBuckets<0>() { }
    ValueProfile(int bytecodeOffset): ValueProfileWithLogNumberOfBuckets<0>(bytecodeOffset) { }
};

template<typename T>
inline int getValueProfileBytecodeOffset(T* valueProfile)
{
    return valueProfile->m_bytecodeOffset;
}

// This is a mini value profile to catch pathologies. It is a counter that gets
// incremented when we take the slow path on any instruction.
struct RareCaseProfile {
    RareCaseProfile(int bytecodeOffset)
        : m_bytecodeOffset(bytecodeOffset)
        , m_counter(0)
    {
    }
    
    int m_bytecodeOffset;
    uint32_t m_counter;
};

inline int getRareCaseProfileBytecodeOffset(RareCaseProfile* rareCaseProfile)
{
    return rareCaseProfile->m_bytecodeOffset;
}

struct ResultProfile {
private:
    static const int numberOfFlagBits = 5;

public:
    ResultProfile(int bytecodeOffset)
        : m_bytecodeOffsetAndFlags(bytecodeOffset << numberOfFlagBits)
    {
        ASSERT(((bytecodeOffset << numberOfFlagBits) >> numberOfFlagBits) == bytecodeOffset);
    }

    enum ObservedResults {
        NonNegZeroDouble = 1 << 0,
        NegZeroDouble    = 1 << 1,
        NonNumber        = 1 << 2,
        Int32Overflow    = 1 << 3,
        Int52Overflow    = 1 << 4,
    };

    int bytecodeOffset() const { return m_bytecodeOffsetAndFlags >> numberOfFlagBits; }
    unsigned specialFastPathCount() const { return m_specialFastPathCount; }

    bool didObserveNonInt32() const { return hasBits(NonNegZeroDouble | NegZeroDouble | NonNumber); }
    bool didObserveDouble() const { return hasBits(NonNegZeroDouble | NegZeroDouble); }
    bool didObserveNonNegZeroDouble() const { return hasBits(NonNegZeroDouble); }
    bool didObserveNegZeroDouble() const { return hasBits(NegZeroDouble); }
    bool didObserveNonNumber() const { return hasBits(NonNumber); }
    bool didObserveInt32Overflow() const { return hasBits(Int32Overflow); }
    bool didObserveInt52Overflow() const { return hasBits(Int52Overflow); }

    void setObservedNonNegZeroDouble() { setBit(NonNegZeroDouble); }
    void setObservedNegZeroDouble() { setBit(NegZeroDouble); }
    void setObservedNonNumber() { setBit(NonNumber); }
    void setObservedInt32Overflow() { setBit(Int32Overflow); }
    void setObservedInt52Overflow() { setBit(Int52Overflow); }

    void* addressOfFlags() { return &m_bytecodeOffsetAndFlags; }
    void* addressOfSpecialFastPathCount() { return &m_specialFastPathCount; }
    
    void detectNumericness(JSValue value)
    {
        if (value.isInt32())
            return;
        if (value.isNumber()) {
            m_bytecodeOffsetAndFlags |= Int32Overflow | Int52Overflow | NonNegZeroDouble | NegZeroDouble;
            return;
        }
        m_bytecodeOffsetAndFlags |= NonNumber;
    }

#if ENABLE(JIT)    
    // Sets (Int32Overflow | Int52Overflow | NonNegZeroDouble | NegZeroDouble) if it sees a
    // double. Sets NonNumber if it sees a non-number.
    void emitDetectNumericness(CCallHelpers&, JSValueRegs, TagRegistersMode = HaveTagRegisters);
    
    // Sets (Int32Overflow | Int52Overflow | NonNegZeroDouble | NegZeroDouble).
    void emitSetDouble(CCallHelpers&);
    
    // Sets NonNumber.
    void emitSetNonNumber(CCallHelpers&);
#endif // ENABLE(JIT)

private:
    bool hasBits(int mask) const { return m_bytecodeOffsetAndFlags & mask; }
    void setBit(int mask) { m_bytecodeOffsetAndFlags |= mask; }

    int m_bytecodeOffsetAndFlags;
    unsigned m_specialFastPathCount { 0 };
};

inline int getResultProfileBytecodeOffset(ResultProfile* profile)
{
    return profile->bytecodeOffset();
}

} // namespace JSC

namespace WTF {

void printInternal(PrintStream&, const JSC::ResultProfile&);

} // namespace WTF

#endif // ValueProfile_h