From fd67be0d891d03ce5f49c0aa9d1be5d45a7ee458 Mon Sep 17 00:00:00 2001
From: Konstantin Nazarov <mail@knazarov.com>
Date: Mon, 9 Dec 2024 00:44:53 +0000
Subject: [PATCH] Move registers and pc counter to the VM class

---
 src/vm.cpp | 20 +++++++++-----------
 src/vm.hpp |  6 ++++++
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/vm.cpp b/src/vm.cpp
index b04a73b..3f62218 100644
--- a/src/vm.cpp
+++ b/src/vm.cpp
@@ -7,7 +7,6 @@
 #include <vector>
 #include <fstream>
 
-const int NUM_REGISTERS = 32; // Standard RISC-V has 32 registers
 
 inline int32_t sign_extend(int32_t value, int bits) {
   int32_t mask = 1 << (bits - 1);
@@ -53,22 +52,21 @@ std::vector<uint8_t> VM::read_memory(size_t start, size_t size) {
                               memory_.begin() + start + size);
 }
 
+uint32_t VM::read_register(size_t regnum) {
+  if (regnum >= NUM_REGISTERS) {
+    throw std::runtime_error("Register out of range");
+  }
+
+  return registers[regnum];
+}
+
 void VM::eval() {
   size_t memory_size = memory_.size();
   uint8_t *memory = &memory_[0];
 
-  uint32_t registers[NUM_REGISTERS] = {0};
-  uint32_t pc = 0;
-
-  auto fetch_instruction = [&memory, &pc]() -> uint32_t {
-    uint32_t instruction = 0;
-    std::memcpy(&instruction, memory + pc, sizeof(uint32_t)); // Load 4 bytes (little-endian)
-    return instruction;
-  };
-
   bool running = true;
   while (pc < memory_size && running) {
-    uint32_t instr = fetch_instruction();
+    uint32_t instr = *(uint32_t*)&memory[pc];
     if (instr == 0) break;
     //std::cout << "pc: " << std::hex << pc << std::dec << "\n";
     // std::cout << "instr: " << std::hex << instr << "\n";
diff --git a/src/vm.hpp b/src/vm.hpp
index 7bfbc2b..571e9b0 100644
--- a/src/vm.hpp
+++ b/src/vm.hpp
@@ -5,6 +5,8 @@
 #include <string>
 #include <vector>
 
+const int NUM_REGISTERS = 32; // Standard RISC-V has 32 registers
+
 std::vector<uint8_t>  load_program(const std::string&  filename, size_t memory_size);
 
 class VM {
@@ -14,7 +16,11 @@ public:
   void eval();
 
   std::vector<uint8_t> read_memory(size_t start, size_t size);
+  uint32_t read_register(size_t regnum);
 
 private:
   std::vector<uint8_t> memory_;
+
+  uint32_t registers[NUM_REGISTERS] = {0};
+  uint32_t pc = 0;
 };