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80 lines
3.0 KiB
C++
80 lines
3.0 KiB
C++
// SPDX-License-Identifier: MIT
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#pragma once
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#include <FEXCore/Utils/LogManager.h>
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#include <cstdint>
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namespace FEXCore::Utils {
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/**
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* @brief Casts a class's member function pointer to a raw pointer that we can JIT
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*
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* Has additional validation to ensure we aren't casting a class member that is invalid
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*/
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template <typename PointerToMemberType>
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class MemberFunctionToPointerCast final {
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public:
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MemberFunctionToPointerCast(PointerToMemberType Function) {
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memcpy(&PMF, &Function, sizeof(PMF));
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}
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uintptr_t GetConvertedPointer() const {
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#ifdef _M_X86_64
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// Itanium C++ ABI (https://itanium-cxx-abi.github.io/cxx-abi/abi.html#member-function-pointers)
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// Low bit of ptr specifies if this Member function pointer is virtual or not
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// Throw an assert if we were trying to cast a virtual member
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LOGMAN_THROW_AA_FMT((PMF.ptr & 1) == 0, "C++ Pointer-To-Member representation didn't have low bit set to 0. Are you trying to cast a virtual member?");
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#elif defined(_M_ARM_64)
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// C++ ABI for the Arm 64-bit Architecture (IHI 0059E)
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// 4.2.1 Representation of pointer to member function
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// Differs from Itanium specification
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LOGMAN_THROW_AA_FMT(PMF.adj == 0, "C++ Pointer-To-Member representation didn't have adj == 0. Are you trying to cast a virtual member?");
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#else
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#error Don't know how to cast Member to function here. Likely just Itanium
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#endif
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return PMF.ptr;
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}
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// Gets the vtable entry position of a virtual member function.
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size_t GetVTableOffset() const {
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#ifdef _M_X86_64
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// Itanium C++ ABI (https://itanium-cxx-abi.github.io/cxx-abi/abi.html#member-function-pointers)
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// Low bit of ptr specifies if this Member function pointer is virtual or not
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// Throw an assert if we are not loading a virtual member.
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LOGMAN_THROW_AA_FMT((PMF.ptr & 1) == 1, "C++ Pointer-To-Member representation didn't have low bit set to 1. This cast only works for virtual members.");
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return PMF.ptr & ~1ULL;
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#elif defined(_M_ARM_64)
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// C++ ABI for the Arm 64-bit Architecture (IHI 0059E)
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// 4.2.1 Representation of pointer to member function
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// Differs from Itanium specification
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LOGMAN_THROW_AA_FMT((PMF.adj & 1) == 1, "C++ Pointer-To-Member representation didn't have adj == 1. This cast only works for virtual members.");
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return PMF.ptr;
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#else
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#error Don't know how to cast Member to function here. Likely just Itanium
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#endif
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}
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// Gets the pointer to the vtable entry for the object passed it.
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template<typename Class>
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uintptr_t GetVTableEntry(Class *VirtualClass) const {
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// VTable is always stored at the beginning of a class object.
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uintptr_t *VTable = *reinterpret_cast<uintptr_t**>(VirtualClass);
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size_t Offset = GetVTableOffset() / sizeof(void*);
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return VTable[Offset];
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}
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private:
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struct PointerToMember {
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uintptr_t ptr;
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uintptr_t adj;
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};
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PointerToMember PMF;
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// Ensure the representation of PointerToMember matches
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static_assert(sizeof(PMF) == sizeof(PointerToMemberType));
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};
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}
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