Source/JavaScriptCore/bytecode/ArrayProfile.h

/*
 * Copyright (C) 2012-2018 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#pragma once

#include "ConcurrentJSLock.h"
#include "Structure.h"
#include <wtf/SegmentedVector.h>

namespace JSC {

class CodeBlock;
class LLIntOffsetsExtractor;

// This is a bitfield where each bit represents an type of array access that we have seen.
// There are 19 indexing types that use the lower bits.
// There are 9 typed array types taking the bits 16 to 25.
typedef unsigned ArrayModes;

// The possible IndexingTypes are limited within (0 - 16, 21, 23, 25).
// This is because CoW types only appear for JSArrays.
static_assert(CopyOnWriteArrayWithInt32 == 21, "");
static_assert(CopyOnWriteArrayWithDouble == 23, "");
static_assert(CopyOnWriteArrayWithContiguous == 25, "");
const ArrayModes CopyOnWriteArrayWithInt32ArrayMode = 1 << CopyOnWriteArrayWithInt32;
const ArrayModes CopyOnWriteArrayWithDoubleArrayMode = 1 << CopyOnWriteArrayWithDouble;
const ArrayModes CopyOnWriteArrayWithContiguousArrayMode = 1 << CopyOnWriteArrayWithContiguous;

const ArrayModes Int8ArrayMode = 1 << 16;
const ArrayModes Int16ArrayMode = 1 << 17;
const ArrayModes Int32ArrayMode = 1 << 18;
const ArrayModes Uint8ArrayMode = 1 << 19;
const ArrayModes Uint8ClampedArrayMode = 1 << 20; // 21 - 25 are used for CoW arrays.
const ArrayModes Uint16ArrayMode = 1 << 26;
const ArrayModes Uint32ArrayMode = 1 << 27;
const ArrayModes Float32ArrayMode = 1 << 28;
const ArrayModes Float64ArrayMode = 1 << 29;

JS_EXPORT_PRIVATE extern const ArrayModes typedArrayModes[NumberOfTypedArrayTypesExcludingDataView];

constexpr ArrayModes asArrayModesIgnoringTypedArrays(IndexingType indexingMode)
{
    return static_cast<unsigned>(1) << static_cast<unsigned>(indexingMode);
}

#define ALL_TYPED_ARRAY_MODES \
    (Int8ArrayMode            \
    | Int16ArrayMode          \
    | Int32ArrayMode          \
    | Uint8ArrayMode          \
    | Uint8ClampedArrayMode   \
    | Uint16ArrayMode         \
    | Uint32ArrayMode         \
    | Float32ArrayMode        \
    | Float64ArrayMode        \
    )

#define ALL_NON_ARRAY_ARRAY_MODES                       \
    (asArrayModesIgnoringTypedArrays(NonArray)                             \
    | asArrayModesIgnoringTypedArrays(NonArrayWithInt32)                   \
    | asArrayModesIgnoringTypedArrays(NonArrayWithDouble)                  \
    | asArrayModesIgnoringTypedArrays(NonArrayWithContiguous)              \
    | asArrayModesIgnoringTypedArrays(NonArrayWithArrayStorage)            \
    | asArrayModesIgnoringTypedArrays(NonArrayWithSlowPutArrayStorage)     \
    | ALL_TYPED_ARRAY_MODES)

#define ALL_COPY_ON_WRITE_ARRAY_MODES                   \
    (CopyOnWriteArrayWithInt32ArrayMode                 \
    | CopyOnWriteArrayWithDoubleArrayMode               \
    | CopyOnWriteArrayWithContiguousArrayMode)

#define ALL_WRITABLE_ARRAY_ARRAY_MODES                  \
    (asArrayModesIgnoringTypedArrays(ArrayClass)                           \
    | asArrayModesIgnoringTypedArrays(ArrayWithUndecided)                  \
    | asArrayModesIgnoringTypedArrays(ArrayWithInt32)                      \
    | asArrayModesIgnoringTypedArrays(ArrayWithDouble)                     \
    | asArrayModesIgnoringTypedArrays(ArrayWithContiguous)                 \
    | asArrayModesIgnoringTypedArrays(ArrayWithArrayStorage)               \
    | asArrayModesIgnoringTypedArrays(ArrayWithSlowPutArrayStorage))

#define ALL_ARRAY_ARRAY_MODES                           \
    (ALL_WRITABLE_ARRAY_ARRAY_MODES                     \
    | ALL_COPY_ON_WRITE_ARRAY_MODES)

#define ALL_ARRAY_MODES (ALL_NON_ARRAY_ARRAY_MODES | ALL_ARRAY_ARRAY_MODES)

inline ArrayModes arrayModesFromStructure(Structure* structure)
{
    JSType type = structure->typeInfo().type();
    if (isTypedArrayType(type))
        return typedArrayModes[type - FirstTypedArrayType];
    return asArrayModesIgnoringTypedArrays(structure->indexingMode());
}

void dumpArrayModes(PrintStream&, ArrayModes);
MAKE_PRINT_ADAPTOR(ArrayModesDump, ArrayModes, dumpArrayModes);

inline bool mergeArrayModes(ArrayModes& left, ArrayModes right)
{
    ArrayModes newModes = left | right;
    if (newModes == left)
        return false;
    left = newModes;
    return true;
}

inline bool arrayModesAreClearOrTop(ArrayModes modes)
{
    return !modes || modes == ALL_ARRAY_MODES;
}

// Checks if proven is a subset of expected.
inline bool arrayModesAlreadyChecked(ArrayModes proven, ArrayModes expected)
{
    return (expected | proven) == expected;
}

inline bool arrayModesIncludeIgnoringTypedArrays(ArrayModes arrayModes, IndexingType shape)
{
    ArrayModes modes = asArrayModesIgnoringTypedArrays(NonArray | shape) | asArrayModesIgnoringTypedArrays(ArrayClass | shape);
    if (hasInt32(shape) || hasDouble(shape) || hasContiguous(shape))
        modes |= asArrayModesIgnoringTypedArrays(ArrayClass | shape | CopyOnWrite);
    return !!(arrayModes & modes);
}

inline bool shouldUseSlowPutArrayStorage(ArrayModes arrayModes)
{
    return arrayModesIncludeIgnoringTypedArrays(arrayModes, SlowPutArrayStorageShape);
}

inline bool shouldUseFastArrayStorage(ArrayModes arrayModes)
{
    return arrayModesIncludeIgnoringTypedArrays(arrayModes, ArrayStorageShape);
}

inline bool shouldUseContiguous(ArrayModes arrayModes)
{
    return arrayModesIncludeIgnoringTypedArrays(arrayModes, ContiguousShape);
}

inline bool shouldUseDouble(ArrayModes arrayModes)
{
    return arrayModesIncludeIgnoringTypedArrays(arrayModes, DoubleShape);
}

inline bool shouldUseInt32(ArrayModes arrayModes)
{
    return arrayModesIncludeIgnoringTypedArrays(arrayModes, Int32Shape);
}

inline bool hasSeenArray(ArrayModes arrayModes)
{
    return arrayModes & ALL_ARRAY_ARRAY_MODES;
}

inline bool hasSeenNonArray(ArrayModes arrayModes)
{
    return arrayModes & ALL_NON_ARRAY_ARRAY_MODES;
}

inline bool hasSeenWritableArray(ArrayModes arrayModes)
{
    return arrayModes & ALL_WRITABLE_ARRAY_ARRAY_MODES;
}

inline bool hasSeenCopyOnWriteArray(ArrayModes arrayModes)
{
    return arrayModes & ALL_COPY_ON_WRITE_ARRAY_MODES;
}

class ArrayProfile {
    friend class CodeBlock;

public:
    ArrayProfile()
        : ArrayProfile(std::numeric_limits<unsigned>::max())
    {
    }
    
    explicit ArrayProfile(unsigned bytecodeOffset)
        : m_bytecodeOffset(bytecodeOffset)
        , m_mayInterceptIndexedAccesses(false)
        , m_usesOriginalArrayStructures(true)
        , m_didPerformFirstRunPruning(false)
    {
    }
    
    unsigned bytecodeOffset() const { return m_bytecodeOffset; }
    
    StructureID* addressOfLastSeenStructureID() { return &m_lastSeenStructureID; }
    ArrayModes* addressOfArrayModes() { return &m_observedArrayModes; }
    bool* addressOfMayStoreToHole() { return &m_mayStoreToHole; }

    void setOutOfBounds() { m_outOfBounds = true; }
    bool* addressOfOutOfBounds() { return &m_outOfBounds; }
    
    void observeStructure(Structure* structure)
    {
        m_lastSeenStructureID = structure->id();
    }

    void computeUpdatedPrediction(const ConcurrentJSLocker&, CodeBlock*);
    void computeUpdatedPrediction(const ConcurrentJSLocker&, CodeBlock*, Structure* lastSeenStructure);
    
    void observeArrayMode(ArrayModes mode) { m_observedArrayModes |= mode; }
    void observeIndexedRead(VM&, JSCell*, unsigned index);

    ArrayModes observedArrayModes(const ConcurrentJSLocker&) const { return m_observedArrayModes; }
    bool mayInterceptIndexedAccesses(const ConcurrentJSLocker&) const { return m_mayInterceptIndexedAccesses; }
    
    bool mayStoreToHole(const ConcurrentJSLocker&) const { return m_mayStoreToHole; }
    bool outOfBounds(const ConcurrentJSLocker&) const { return m_outOfBounds; }
    
    bool usesOriginalArrayStructures(const ConcurrentJSLocker&) const { return m_usesOriginalArrayStructures; }

    CString briefDescription(const ConcurrentJSLocker&, CodeBlock*);
    CString briefDescriptionWithoutUpdating(const ConcurrentJSLocker&);
    
#if !ASSERT_DISABLED
    inline bool isValid() const { return m_typeName == s_typeName; }
#endif

private:
    friend class LLIntOffsetsExtractor;
    
    static Structure* polymorphicStructure() { return static_cast<Structure*>(reinterpret_cast<void*>(1)); }
    
    unsigned m_bytecodeOffset;
    StructureID m_lastSeenStructureID { 0 };
    bool m_mayStoreToHole { false }; // This flag may become overloaded to indicate other special cases that were encountered during array access, as it depends on indexing type. Since we currently have basically just one indexing type (two variants of ArrayStorage), this flag for now just means exactly what its name implies.
    bool m_outOfBounds { false };
    bool m_mayInterceptIndexedAccesses : 1;
    bool m_usesOriginalArrayStructures : 1;
    bool m_didPerformFirstRunPruning : 1;
    ArrayModes m_observedArrayModes { 0 };

#if !ASSERT_DISABLED
    static const char* const s_typeName;
    const char* m_typeName { s_typeName };
#endif
};

typedef SegmentedVector<ArrayProfile, 4> ArrayProfileVector;

} // namespace JSC