Initial Commit

src/CPU.cpp

@@ -0,0 +1,69 @@
+#include "CPU.h"
+
+#include <stdexcept>
+#include <iostream>
+#include <iomanip>
+#include <stdlib.h>
+#include <array>
+
+CPU::CPU(std::shared_ptr<Bus> bus) : m_Bus(bus), m_Context({m_Instruction, m_InstructionPointer, m_Flags, m_Registers, m_Bus}){
+  m_InstructionPointer = 0x00008000;
+
+  for(int i = 0; i < 16; i++)
+  {
+    m_Registers[i] = 0;
+  }
+}
+
+void CPU::Step(){
+  FetchDecode();
+  Execute();
+}
+
+void CPU::FetchDecode(){
+  std::cout << "Fetching instruction: " << std::hex << m_InstructionPointer << std::endl;
+  m_InstructionRaw = m_Bus->AccessX<uint64_t>(m_InstructionPointer); // Slice of 8 bytes.
+
+  std::cout << "Context window fetched: " << std::hex <<  m_InstructionRaw << std::endl; // Start Decode Instruction
+  uint64_t first_byte = m_InstructionRaw & 0xFF;
+  std::cout << "Decoded first byte: " << std::hex << first_byte << std::endl;
+  Opcode opcode = static_cast<Opcode>(first_byte);
+
+  if(first_byte >= 0xB8 && first_byte <= 0xBF)
+  {
+    m_Instruction.m_Operand1 = first_byte - 0xB8;
+    opcode = Opcode::MOV_R_IMM32;
+  }
+    
+  switch(opcode){
+  case Opcode::NOP:    m_Instruction.m_Length = 1;    break;
+  case Opcode::HLT:    m_Instruction.m_Length = 1;    break;
+  case Opcode::MOV_R_IMM32:
+    m_Instruction.m_Operand2 = m_Bus->AccessX<uint32_t>(m_InstructionPointer + 1);
+    m_Instruction.m_Length = 5;
+    break;
+  case Opcode::ADD_RM32_R32:
+    m_Instruction.m_Operand1 = m_Bus->AccessX<uint8_t>(m_InstructionPointer + 1);
+    m_Instruction.m_Operand2 = m_Bus->AccessX<uint32_t>(m_InstructionPointer + 2);
+    m_Instruction.m_Length = 6;
+    break;
+  default:
+    std::runtime_error("Decode encountered unexpected opcode.");
+    break;
+  }
+
+  m_Instruction.m_Opcode = opcode;
+  m_InstructionPointer += m_Instruction.m_Length;
+}
+
+void CPU::Execute(){
+  std::cout << "Executing... \n";
+  uint8_t opcode_value = static_cast<uint8_t>(m_Instruction.m_Opcode);
+  auto& exec_table = GetExecutorTable();
+  if(exec_table[opcode_value])
+  {
+    exec_table[opcode_value](m_Context);
+    return;
+  }
+  throw std::runtime_error("Opcode not found!");
+}