Source/JavaScriptCore/ftl/FTLSlowPathCallKey.h

/*
 * Copyright (C) 2013-2021 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
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#pragma once

#if ENABLE(FTL_JIT)

#include "HashableRegisterSet.h"
#include "MacroAssemblerCodeRef.h"

namespace JSC { namespace FTL {

// This is used for creating some sanity in slow-path calls out of the FTL's inline
// caches. The idea is that we don't want all of the register save/restore stuff to
// be generated at each IC site. Instead, the IC slow path call site will just save
// the registers needed for the arguments. It will arrange for there to be enough
// space on top of stack to save the remaining registers and the return PC. Then it
// will call a shared thunk that will save the remaining registers. That thunk needs
// to know the stack offset at which things get saved along with the call target.

// Note that the offset is *not including* the return PC that would be pushed on X86.

class SlowPathCallKey {
public:
    SlowPathCallKey()
        : m_offset(0)
    {
    }
    
    SlowPathCallKey(
        const RegisterSet& set, FunctionPtr<CFunctionPtrTag> callTarget, const RegisterSet& argumentRegisters,
        ptrdiff_t offset, int32_t indirectOffset)
        : m_usedRegisters(set)
        , m_callTarget(callTarget.retagged<OperationPtrTag>())
        , m_argumentRegisters(argumentRegisters)
        , m_offset(offset)
        , m_indirectOffset(indirectOffset)
    {
    }
    
    const RegisterSet& usedRegisters() const { return m_usedRegisters; }
    FunctionPtr<OperationPtrTag> callTarget() const { return m_callTarget; }
    const RegisterSet& argumentRegisters() const { return m_argumentRegisters; }
    ptrdiff_t offset() const { return m_offset; }
    int32_t indirectOffset() const { return m_indirectOffset; }
    
    SlowPathCallKey withCallTarget(FunctionPtr<CFunctionPtrTag> callTarget)
    {
        return SlowPathCallKey(usedRegisters(), callTarget, argumentRegisters(), offset(), indirectOffset());
    }
    
    void dump(PrintStream&) const;
    
    enum EmptyValueTag { EmptyValue };
    enum DeletedValueTag { DeletedValue };
    
    SlowPathCallKey(EmptyValueTag)
        : m_usedRegisters(HashableRegisterSet::EmptyValue)
    {
    }
    
    SlowPathCallKey(DeletedValueTag)
        : m_usedRegisters(HashableRegisterSet::DeletedValue)
    {
    }
    
    bool isEmptyValue() const { return m_usedRegisters.isEmptyValue(); }
    bool isDeletedValue() const { return m_usedRegisters.isDeletedValue(); }
    
    bool operator==(const SlowPathCallKey& other) const
    {
        return m_usedRegisters == other.m_usedRegisters
            && m_callTarget == other.m_callTarget
            && m_offset == other.m_offset
            && m_indirectOffset == other.m_indirectOffset;
    }
    unsigned hash() const
    {
        return m_usedRegisters.hash() + PtrHash<void*>::hash(m_callTarget.executableAddress()) + m_offset + m_indirectOffset;
    }

private:
    HashableRegisterSet m_usedRegisters;
    FunctionPtr<OperationPtrTag> m_callTarget;
    RegisterSet m_argumentRegisters;
    ptrdiff_t m_offset { 0 };
    int32_t m_indirectOffset { 0 };
};

struct SlowPathCallKeyHash {
    static unsigned hash(const SlowPathCallKey& key) { return key.hash(); }
    static bool equal(const SlowPathCallKey& a, const SlowPathCallKey& b) { return a == b; }
    static constexpr bool safeToCompareToEmptyOrDeleted = false;
};

} } // namespace JSC::FTL

namespace WTF {

template<typename T> struct DefaultHash;
template<> struct DefaultHash<JSC::FTL::SlowPathCallKey> : JSC::FTL::SlowPathCallKeyHash { };

template<typename T> struct HashTraits;
template<> struct HashTraits<JSC::FTL::SlowPathCallKey> : public CustomHashTraits<JSC::FTL::SlowPathCallKey> { };

} // namespace WTF

#endif // ENABLE(FTL_JIT)