qqmljsoptimizations_p.h

// Copyright (C) 2024 The Qt Company Ltd.

// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only WITH Qt-GPL-exception-1.0

// Qt-Security score:significant

#ifndef QQMLJSOPTIMIZATIONS_P_H

#define QQMLJSOPTIMIZATIONS_P_H

//

//  W A R N I N G

//  -------------

//

// This file is not part of the Qt API.  It exists purely as an

// implementation detail.  This header file may change from version to

// version without notice, or even be removed.

//

// We mean it.

#include <private/qqmljscompilepass_p.h>

QT_BEGIN_NAMESPACE

class Q_QMLCOMPILER_EXPORT QQmlJSOptimizations : public QQmlJSCompilePass

public:

    using Conversions = QSet<int>;

    QQmlJSOptimizations(const QV4::Compiler::JSUnitGenerator *unitGenerator,

                        const QQmlJSTypeResolver *typeResolver, QQmlJSLogger *logger,

                        const BasicBlocks &basicBlocks, const InstructionAnnotations &annotations,

                        QList<ObjectOrArrayDefinition> objectAndArrayDefinitions)

        : QQmlJSCompilePass(unitGenerator, typeResolver, logger, basicBlocks, annotations),

          m_objectAndArrayDefinitions{ std::move(objectAndArrayDefinitions) }

    ~QQmlJSOptimizations() = default;

    BlocksAndAnnotations run(const Function *function);

private:

    struct RegisterAccess

        // Content written by this instruction, or contents merged/converted into this register.

        QList<QQmlJSRegisterContent> trackedTypes;

        // Instructions that genuinely consume the *value* this write produced (never renames/copies

        // of it), keyed by instruction offset, with the exact content each one reads it as.

        // Tracked by content identity, so this follows the value across register renames rather

        // than being tied to one register slot.

        // Drives the write's required output type (see QQmlJSTypeResolver::adjustTrackedType) and

        // whether it can be moved into its single use site (see canMove).

        QHash<int, QQmlJSRegisterContent> typeReaders;

        // Reads of this write's *specific register slot* while it's still the reaching definition

        // (i.e. before any later write overwrites that register), keyed by instruction offset,

        // together with the type-conversion instructions crossed between the write and each read.

        // Drives which type conversions are actually needed in codegen (see liveConversions in

        // adjustTypes) and, combined with typeReaders, whether a store is conversion-free enough to

        // move.

        QHash<int, Conversions> registerReadersAndConversions;

        // Register slot written to by this instruction.

        int trackedRegister;

};

    QV4::Moth::ByteCodeHandler::Verdict startInstruction(QV4::Moth::Instr::Type) override

        return ProcessInstruction;

    void endInstruction(QV4::Moth::Instr::Type) override { }

    void populateBasicBlocks();

    void populateReaderLocationsTrackedTypes();

    void populateReaderLocationsReadersAndConversions();

    void adjustTypes();

    bool canMove(int instructionOffset, const RegisterAccess &access) const;

    void removeReadsFromErasedInstructions(const QFlatMap<int, InstructionAnnotation>::const_iterator &it);

    void removeDeadStoresUntilStable();

    bool eraseDeadStore(const InstructionAnnotations::iterator &it, bool &erasedReaders);

    QHash<int, RegisterAccess> m_readerLocations;

    QList<ObjectOrArrayDefinition> m_objectAndArrayDefinitions;

};

QT_END_NAMESPACE

#endif // QQMLJSOPTIMIZATIONS_P_H