Initial Commit

2026-02-04 12:52:42 +01:00
commit 4671a62ddf
15 changed files with 430 additions and 0 deletions
--- a/src/ExecutorCases.cpp
+++ b/src/ExecutorCases.cpp
@@ -0,0 +1,104 @@
+#include "ExecutorCases.h"
+
+#include "Instruction.h"
+#include "Bus.h"
+
+#include <bitset>
+#include <iostream>
+
+CPUContext::CPUContext(Instruction& i, uint64_t& ip, uint64_t& flags, uint64_t* reg, std::shared_ptr<Bus>& bus) : m_Instruction(i), m_InstructionPointer(ip), m_Flags(flags), m_Registers(reg), m_Bus(bus) { }
+
+CPUContext::~CPUContext() = default;
+
+// NO SIB SUPPORT YET
+ModRM process_modrm(uint8_t modrm){
+  uint8_t mod_mask = 0b11000000;
+  uint8_t reg_mask = 0b00111000;
+  uint8_t rm_mask = 0b00000111;
+  
+  uint8_t mod = modrm & mod_mask;
+  uint8_t reg = (modrm & reg_mask) >> 3;
+  uint8_t rm = modrm & rm_mask;
+
+  ModRMState state = ModRMState::INVALID;
+  
+  switch(mod) {
+  case 0b00000000:
+    state = ModRMState::LR;
+    break;
+  case 0b01000000:
+    state = ModRMState::LR_DISP8;
+    break;
+  case 0b10000000:
+    state = ModRMState::LR_DISP32;
+    break;
+  case 0b11000000:
+    state = ModRMState::R;
+    break;
+  default:
+    throw std::runtime_error("Mod R/M does not support non-register operands right now!");
+  }
+  return {.m_State = state, .m_Reg = reg, .m_Rm = rm};  
+}
+
+namespace executor_cases {
+  void Nop(CPUContext& cc){
+    std::cout << "No op" << std::endl;
+  }
+
+  void Hlt(CPUContext& cc){
+    std::cout << "Program halted!" << std::endl;
+    exit(0);
+  }
+
+  void Mov_r32_imm32(CPUContext& cc){
+    cc.m_Registers[cc.m_Instruction.m_Operand1] = cc.m_Instruction.m_Operand2;
+    std::cout << "Contents of " << x86::Register2Str((x86::Register)cc.m_Instruction.m_Operand1) << " changed to " << cc.m_Registers[cc.m_Instruction.m_Operand1] << std::endl;
+  }
+  
+  //NO SIB SUPPORT YET
+  void Add_rm32_r32(CPUContext& cc){
+    ModRM modrm = process_modrm(cc.m_Instruction.m_Operand1);
+
+    switch(modrm.m_State) {
+    case ModRMState::R:
+    {
+      cc.m_Registers[modrm.m_Rm] += cc.m_Registers[modrm.m_Reg];
+      std::cout << "Adding " << x86::Register2Str((x86::Register)modrm.m_Reg) << " to " << x86::Register2Str((x86::Register)modrm.m_Rm) << std::endl;
+      break;
+    }
+    case ModRMState::LR:
+    {
+      uint32_t dstPrevValue = cc.m_Bus->AccessX<uint32_t>(cc.m_Registers[modrm.m_Rm]);
+      uint32_t currRegValue = cc.m_Registers[modrm.m_Reg];
+      uint32_t result = dstPrevValue + currRegValue;
+      cc.m_Bus->WriteX<uint32_t>(cc.m_Registers[modrm.m_Rm], result);
+      std::cout << "Memory address " << std::hex << cc.m_Registers[modrm.m_Rm] << " modified to: " << result << std::endl;
+      break;
+    }
+    case ModRMState::LR_DISP8:
+    {
+      
+    }
+    default:
+    {
+      throw std::runtime_error("Invalid ModRM State encountered during Add_rm32_r32");
+    }
+    }
+  }
+}
+ 
+constexpr std::array<ExecutorCase, 255> GenerateExecutorTable(){
+  std::array<ExecutorCase, 255> table{};
+  table[Opcode::NOP] = executor_cases::Nop;
+  table[Opcode::HLT] = executor_cases::Hlt;
+  table[Opcode::MOV_R_IMM32] = executor_cases::Mov_r32_imm32;
+  table[Opcode::ADD_RM32_R32] = executor_cases::Add_rm32_r32;
+  return table;
+}
+
+static constexpr std::array<ExecutorCase, 255> s_ExecutorTable = GenerateExecutorTable();
+
+const std::array<ExecutorCase, 255>& GetExecutorTable() {
+  return s_ExecutorTable;
+}