Source/JavaScriptCore/bytecode/MetadataTable.h

/*
 * Copyright (C) 2018-2024 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
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 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include <JavaScriptCore/Instruction.h>
#include <JavaScriptCore/Opcode.h>
#include <JavaScriptCore/UnlinkedMetadataTable.h>
#include <JavaScriptCore/ValueProfile.h>
#include <wtf/RefCounted.h>
#include <wtf/TZoneMalloc.h>

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

namespace JSC {

class CodeBlock;

// MetadataTable has a bit strange memory layout for LLInt optimization.
// [ValueProfile][UnlinkedMetadataTable::LinkingData][MetadataTableOffsets][MetadataContent]
//                                                   ^
//                 The pointer of MetadataTable points at this address.
class MetadataTable {
    WTF_MAKE_TZONE_ALLOCATED(MetadataTable);
    WTF_MAKE_NONCOPYABLE(MetadataTable);
    friend class LLIntOffsetsExtractor;
    friend class UnlinkedMetadataTable;
public:
    ~MetadataTable();

    template<typename Metadata>
    ALWAYS_INLINE Metadata* get()
    {
        auto opcodeID = Metadata::opcodeID;
        ASSERT(opcodeID < NUMBER_OF_BYTECODE_WITH_METADATA);
        uintptr_t ptr = std::bit_cast<uintptr_t>(getWithoutAligning(opcodeID));
        ptr = roundUpToMultipleOf(alignof(Metadata), ptr);
        return std::bit_cast<Metadata*>(ptr);
    }

    template<typename Op, typename Functor>
    ALWAYS_INLINE void forEach(const Functor& func)
    {
        auto* metadata = get<typename Op::Metadata>();
        auto* end = std::bit_cast<typename Op::Metadata*>(getWithoutAligning(Op::opcodeID + 1));
        for (; metadata < end; ++metadata)
            func(*metadata);
    }

    template<typename Functor>
    ALWAYS_INLINE void forEachValueProfile(const Functor& func)
    {
        // We could do a checked multiply here but if it overflows we'd just not look at any value profiles so it's probably not worth it.
        int lastValueProfileOffset = -unlinkedMetadata()->m_numValueProfiles;
        for (int i = -1; i >= lastValueProfileOffset; --i)
            func(valueProfilesEnd()[i]);
    }

    ValueProfile* valueProfilesEnd()
    {
        return reinterpret_cast_ptr<ValueProfile*>(&linkingData());
    }

    ValueProfile& valueProfileForOffset(unsigned profileOffset)
    {
        ASSERT(profileOffset <= unlinkedMetadata()->m_numValueProfiles);
        return valueProfilesEnd()[-static_cast<ptrdiff_t>(profileOffset)];
    }

    size_t sizeInBytesForGC();

    void ref()
    {
        ++linkingData().refCount;
    }

    void deref()
    {
        if (!--linkingData().refCount) {
            // Setting refCount to 1 here prevents double delete within the destructor but not from another thread
            // since such a thread could have ref'ed this object long after it had been deleted. This is consistent
            // with ThreadSafeRefCounted.h, see webkit.org/b/201576 for the reasoning.
            linkingData().refCount = 1;

            MetadataTable::destroy(this);
            return;
        }
    }

    unsigned refCount() const
    {
        return linkingData().refCount;
    }

    unsigned hasOneRef() const
    {
        return refCount() == 1;
    }

    template <typename Opcode>
    uintptr_t offsetInMetadataTable(const Opcode& opcode)
    {
        uintptr_t baseTypeOffset = is32Bit() ? offsetTable32()[Opcode::opcodeID] : offsetTable16()[Opcode::opcodeID];
        baseTypeOffset = roundUpToMultipleOf(alignof(typename Opcode::Metadata), baseTypeOffset);
        return baseTypeOffset + sizeof(typename Opcode::Metadata) * opcode.m_metadataID;
    }

    void validate() const;

    RefPtr<UnlinkedMetadataTable> unlinkedMetadata() const { return linkingData().unlinkedMetadata.copyRef(); }

    SUPPRESS_ASAN bool isDestroyed() const
    {
        uintptr_t unlinkedMetadataPtr = *std::bit_cast<uintptr_t*>(&linkingData().unlinkedMetadata);
        return !unlinkedMetadataPtr;
    }

private:
    MetadataTable(UnlinkedMetadataTable&);

    UnlinkedMetadataTable::Offset16* offsetTable16() const { return std::bit_cast<UnlinkedMetadataTable::Offset16*>(this); }
    UnlinkedMetadataTable::Offset32* offsetTable32() const { return std::bit_cast<UnlinkedMetadataTable::Offset32*>(std::bit_cast<uint8_t*>(this) + UnlinkedMetadataTable::s_offset16TableSize); }

    size_t totalSize() const
    {
        return unlinkedMetadata()->m_numValueProfiles * sizeof(ValueProfile) + sizeof(UnlinkedMetadataTable::LinkingData) + getOffset(UnlinkedMetadataTable::s_offsetTableEntries - 1);
    }

    UnlinkedMetadataTable::LinkingData& linkingData() const
    {
        return *std::bit_cast<UnlinkedMetadataTable::LinkingData*>((std::bit_cast<uint8_t*>(this) - sizeof(UnlinkedMetadataTable::LinkingData)));
    }

    void* buffer() { return this; }

    // Offset of zero means that the 16 bit table is not in use.
    bool is32Bit() const { return !offsetTable16()[0]; }

    ALWAYS_INLINE unsigned getOffset(unsigned i) const
    {
        unsigned offset = offsetTable16()[i];
        if (offset)
            return offset;
        return offsetTable32()[i];
    }

    ALWAYS_INLINE uint8_t* getWithoutAligning(unsigned i)
    {
        return std::bit_cast<uint8_t*>(this) + getOffset(i);
    }

    static void destroy(MetadataTable*);
};

} // namespace JSC

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END