initial commitHEADmaster

1 files changed, 142 insertions, 0 deletions

diff --git a/src/CPU.cpp b/src/CPU.cpp
new file mode 100644
index 0000000..dd03a19
--- /dev/null
+++ b/src/CPU.cpp
@@ -0,0 +1,142 @@
+#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);
+}