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#include "CPU.h"
#include <stdexcept>
#include <iostream>
#include <iomanip>
#include <bitset>
#include <stdlib.h>
#include <array>
#include <cassert>
#include "Exceptions.h"
#include "InstructionModifierLookup.h"
static const Instruction s_EmptyInstruction{};
CPU::CPU(std::shared_ptr<Bus>& bus) : m_Bus(bus), m_IsHalted(false), m_Context({m_Instruction, m_InstructionPointer, m_Flags, m_Registers, m_Bus, m_IsHalted}) {
m_InstructionPointer = 0x00008000;
for(int i = 0; i < 8; i++) {
m_Registers[i] = 0;
}
for(int i = 0; i < 8; i++) {
m_SegmentRegisters[i] = 0;
}
}
void CPU::Step() {
FetchDecode();
Execute();
}
void CPU::Dump() {
std::cout << "--TRACE-- ";
std::cout << std::endl;
for(uint8_t i = 0; i < 8; i++)
{
std::cout << x86::Register2Str((x86::Register)i) << ": " << m_Registers[i] << " | ";
}
std::cout << std::endl;
std::bitset<32> flags(m_Flags);
std::cout << "IP: " << std::hex << m_InstructionPointer << " | FLAGS: " << flags;
std::cout << std::endl;
}
void CPU::Reset() {
for(uint8_t i = 0; i < 8; i++)
{
m_Registers[i] = 0;
m_SegmentRegisters[i] = 0;
}
m_InstructionPointer = 0x8000;
m_Flags = 0;
std::cout << "[CPU] State Flushed!" << std::endl;
m_IsHalted = false;
m_Instruction = s_EmptyInstruction;
}
CPUStatus CPU::GetStatus() {
return (CPUStatus){.m_Registers = m_Registers, .m_IP = m_InstructionPointer, .m_Instruction = m_Instruction};
}
void CPU::FetchDecode() {
m_Instruction = s_EmptyInstruction;
uint8_t opcode_raw = m_Bus->AccessX<uint8_t>(m_InstructionPointer);
Opcode opcode = static_cast<Opcode>(opcode_raw);
auto& instruction_table = GetInstructionTable();
if(instruction_table[opcode_raw].m_Executor == nullptr) {
std::cout << "Encoding: " << opcode_raw << std::endl;
std::string exception = "[CPU] [FetchDecode] Opcode is not in instruction table! Opcode_raw: " + std::to_string(opcode_raw);
throw CPUException(exception);
}
auto& instruction = instruction_table[opcode_raw];
uint8_t encoding_mask = 0b00001111;
uint8_t encoding = instruction.m_Encoding & encoding_mask;
uint8_t immediate = instruction.m_Encoding & ~encoding_mask;
m_Instruction.m_Opcode = opcode;
switch(encoding) {
case OI:
if (immediate == I32) {
m_Instruction.m_Operand1 = m_Bus->AccessX<uint32_t>(m_InstructionPointer + 1);
m_Instruction.m_Length = 5;
} else if (immediate == I16) {
m_Instruction.m_Operand1 = m_Bus->AccessX<uint16_t>(m_InstructionPointer + 1);
m_Instruction.m_Length = 3;
} else if (immediate == I8) {
m_Instruction.m_Operand1 = m_Bus->AccessX<uint8_t>(m_InstructionPointer + 1);
m_Instruction.m_Length = 2;
} else {
throw CPUException("[CPU] [FetchDecode] OI instruction encoding only supports imm8,imm16,imm32.");
}
break;
case ZO:
m_Instruction.m_Length = 1;
break;
case RM:
case MR: {
uint8_t modrm = m_Bus->AccessX<uint8_t>(m_InstructionPointer + 1);
m_Instruction.m_ModRM = x86::ProcessMODRM(modrm);
m_Instruction.m_Length = 2;
FetchModRMFields(modrm);
if (m_Instruction.m_ModRM.m_SIB) {
uint8_t sib = m_Bus->AccessX<uint8_t>(m_InstructionPointer + m_Instruction.m_Length);
m_Instruction.m_Length += 1;
m_Instruction.m_SIB = x86::ProcessSIB(sib);
}
break;
}
default:
throw CPUException("[CPU] [FetchDecode] Encoding was not found!");
}
m_Instruction.m_Func = instruction.m_Executor;
m_InstructionPointer += m_Instruction.m_Length;
}
void CPU::Execute() {
if(m_Instruction.m_Func != nullptr)
{
m_Instruction.m_Func(m_Context);
return;
}
throw std::runtime_error("[CPU] [Execute] m_Func is nullptr!");
}
void CPU::FetchModRMFields(uint8_t modrm) {
assert(m_Instruction.m_Length != 0); // FetchDecode() must set m_Length before calling FetchModRMFields()
auto modrm_table = GetMod32Table();
modrm_table[modrm](m_Context);
}
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