diff --git a/include/IR/IR_basic.h b/include/IR/IR_basic.h
index caf3f46..5c52d78 100644
--- a/include/IR/IR_basic.h
+++ b/include/IR/IR_basic.h
@@ -84,6 +84,7 @@ class BRAction : public JMPActionItem {
                                         NaiveBackend::FuncLayout &layout,
                                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
                                         bool process_phi);
+  friend class CFGType BuildCFGForFunction(const std::shared_ptr<class FunctionDefItem> &func);
   std::string cond;
   std::string true_label_full;
   std::string false_label_full;
@@ -102,6 +103,7 @@ class UNConditionJMPAction : public JMPActionItem {
                                         NaiveBackend::FuncLayout &layout,
                                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
                                         bool process_phi);
+  friend class CFGType BuildCFGForFunction(const std::shared_ptr<class FunctionDefItem> &func);
   std::string label_full;
 
  public:
@@ -308,6 +310,7 @@ class BlockItem : public LLVMIRItemBase {
   friend void GenerateNaiveASM(std::ostream &os, std::shared_ptr<ModuleItem> prog);
   friend void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
                                        const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
+  friend class CFGType BuildCFGForFunction(const std::shared_ptr<class FunctionDefItem> &func);
   std::string label_full;
   std::vector<std::shared_ptr<ActionItem>> actions;
   std::shared_ptr<JMPActionItem> exit_action;
@@ -447,6 +450,7 @@ class SelectItem : public ActionItem {
 class FunctionDefItem : public LLVMIRItemBase {
   friend class IRBuilder;
   friend void GenerateNaiveASM(std::ostream &os, std::shared_ptr<ModuleItem> prog);
+  friend class CFGType BuildCFGForFunction(const std::shared_ptr<FunctionDefItem> &func);
   LLVMType return_type;
   std::string func_name_raw;
   std::vector<LLVMType> args;
@@ -566,6 +570,7 @@ class ModuleItem : public LLVMIRItemBase {
   friend class IRBuilder;
   friend std::shared_ptr<ModuleItem> BuildIR(std::shared_ptr<Program_ASTNode> src);
   friend void GenerateNaiveASM(std::ostream &os, std::shared_ptr<ModuleItem> prog);
+  friend std::shared_ptr<ModuleItem> Mem2Reg(std::shared_ptr<ModuleItem> src);
   std::vector<std::shared_ptr<ConstStrItem>> const_strs;
   std::vector<std::shared_ptr<FunctionDeclareItem>> function_declares;
   std::vector<std::shared_ptr<TypeDefItem>> type_defs;
diff --git a/include/opt/cfg.h b/include/opt/cfg.h
new file mode 100644
index 0000000..430025f
--- /dev/null
+++ b/include/opt/cfg.h
@@ -0,0 +1,31 @@
+#pragma once
+#include <deque>
+#include <list>
+#include <memory>
+#include <unordered_map>
+#include <vector>
+#include "IR/IR_basic.h"
+using CFGNodeCollection = std::list<class CFGNodeType *>;
+class CFGNodeType {
+ public:
+  std::vector<CFGNodeType *> successors, predecessors;
+  BlockItem *corresponding_block;
+  CFGNodeCollection dom;
+  CFGNodeType *idom;
+  std::vector<CFGNodeType *> successors_in_dom_tree;
+  CFGNodeCollection dom_frontier;
+};
+
+class CFGType {
+ public:
+  std::vector<std::shared_ptr<CFGNodeType>> nodes;
+  CFGNodeType *entry;
+  std::unordered_map<BlockItem *, CFGNodeType *> block_to_node;
+  std::unordered_map<std::string, BlockItem *> label_to_block;
+};
+
+CFGNodeCollection GetCFGNodeCollectionsIntersection(const CFGNodeCollection &a, const CFGNodeCollection &b);
+CFGNodeCollection GetCFGNodeCollectionsUnion(const CFGNodeCollection &a, const CFGNodeCollection &b);
+CFGNodeCollection GetCFGNodeCollectionsDifference(const CFGNodeCollection &a, const CFGNodeCollection &b);
+
+CFGType BuildCFGForFunction(const std::shared_ptr<FunctionDefItem> &func);
\ No newline at end of file
diff --git a/include/opt/mem2reg.h b/include/opt/mem2reg.h
new file mode 100644
index 0000000..d620907
--- /dev/null
+++ b/include/opt/mem2reg.h
@@ -0,0 +1,4 @@
+#pragma once
+#include "IR/IR_basic.h"
+
+std::shared_ptr<ModuleItem> Mem2Reg(std::shared_ptr<ModuleItem> src);
\ No newline at end of file
diff --git a/include/opt/opt.h b/include/opt/opt.h
new file mode 100644
index 0000000..4f57210
--- /dev/null
+++ b/include/opt/opt.h
@@ -0,0 +1,2 @@
+#include "mem2reg.h"
+#include "cfg.h"
\ No newline at end of file
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index e90b03b..4fc1ffa 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -2,8 +2,9 @@ add_subdirectory(ast)
 add_subdirectory(semantic)
 add_subdirectory(IR)
 add_subdirectory(naivebackend)
+add_subdirectory(opt)
 add_executable(zmxcc main.cpp)
-target_link_libraries(zmxcc semantic argparse IR naivebackend)
+target_link_libraries(zmxcc semantic argparse IR naivebackend opt)
 set_target_properties(zmxcc PROPERTIES
   RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}"
 )
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index 79e47c1..91c5d3a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -4,6 +4,7 @@
 #include "IR/IR.h"
 #include "naivebackend/naivebackend.h"
 #include "semantic/semantic.h"
+#include "opt/opt.h"
 
 int main(int argc, char **argv) {
   argparse::ArgumentParser program("zmxcc");
@@ -12,10 +13,9 @@ int main(int argc, char **argv) {
 
   program.add_argument("-o", "--output").help("output file path").nargs(1).required();
 
-  program.add_argument("--naive-IR")
-    .help("output unoptimized LLVM IR code")
-    .default_value(false)
-    .implicit_value(true);
+  program.add_argument("--naive-IR").help("output unoptimized LLVM IR code").default_value(false).implicit_value(true);
+
+  program.add_argument("--optimize-all").help("enable all optimizations").default_value(false).implicit_value(true);
 
   try {
     program.parse_args(argc, argv);
@@ -28,6 +28,7 @@ int main(int argc, char **argv) {
   auto input_file = program.get<std::string>("input");
   auto output_file = program.get<std::string>("output");
   bool output_naive_ir = program.get<bool>("--naive-IR");
+  bool optimize_all = program.get<bool>("--optimize-all");
 
   std::ifstream fin(input_file);
   std::ofstream fout(output_file);
@@ -41,9 +42,12 @@ int main(int argc, char **argv) {
       IR->RecursivePrint(fout);
       return 0;
     }
-
-    IR->RecursivePrint(std::cerr);
-    GenerateNaiveASM(fout, IR);
+    if (!optimize_all) {
+      GenerateNaiveASM(fout, IR);
+    } else {
+      auto IR_with_out_allocas = Mem2Reg(IR);
+      IR_with_out_allocas->RecursivePrint(fout);
+    }
   } catch (const SemanticError &err) {
     std::cout << err.what() << std::endl;
     return err.GetErrorCode();
diff --git a/src/opt/CMakeLists.txt b/src/opt/CMakeLists.txt
new file mode 100644
index 0000000..846e500
--- /dev/null
+++ b/src/opt/CMakeLists.txt
@@ -0,0 +1,5 @@
+include_directories(${CMAKE_SOURCE_DIR}/include/opt)
+
+file(GLOB NAIVE_BACKEND_SOURCES "*.cpp")
+add_library(opt STATIC ${NAIVE_BACKEND_SOURCES})
+target_link_libraries(opt PUBLIC ast)
\ No newline at end of file
diff --git a/src/opt/cfg.cpp b/src/opt/cfg.cpp
new file mode 100644
index 0000000..0450705
--- /dev/null
+++ b/src/opt/cfg.cpp
@@ -0,0 +1,109 @@
+#include "cfg.h"
+#include <string>
+CFGNodeCollection GetCFGNodeCollectionsIntersection(const CFGNodeCollection &a, const CFGNodeCollection &b) {
+  // assume that thety are both sorted
+  CFGNodeCollection res;
+  auto ita = a.begin();
+  auto itb = b.begin();
+  while (ita != a.end() && itb != b.end()) {
+    if (*ita == *itb) {
+      res.push_back(*ita);
+      ita++;
+      itb++;
+    } else if (*ita < *itb) {
+      ita++;
+    } else {
+      itb++;
+    }
+  }
+  return res;
+}
+
+CFGNodeCollection GetCFGNodeCollectionsUnion(const CFGNodeCollection &a, const CFGNodeCollection &b) {
+  // assume that thety are both sorted
+  CFGNodeCollection res;
+  auto ita = a.begin();
+  auto itb = b.begin();
+  while (ita != a.end() && itb != b.end()) {
+    if (*ita == *itb) {
+      res.push_back(*ita);
+      ita++;
+      itb++;
+    } else if (*ita < *itb) {
+      res.push_back(*ita);
+      ita++;
+    } else {
+      res.push_back(*itb);
+      itb++;
+    }
+  }
+  while (ita != a.end()) {
+    res.push_back(*ita);
+    ita++;
+  }
+  while (itb != b.end()) {
+    res.push_back(*itb);
+    itb++;
+  }
+  return res;
+}
+
+CFGNodeCollection GetCFGNodeCollectionsDifference(const CFGNodeCollection &a, const CFGNodeCollection &b) {
+  // assume that thety are both sorted
+  CFGNodeCollection res;
+  auto ita = a.begin();
+  auto itb = b.begin();
+  while (ita != a.end() && itb != b.end()) {
+    if (*ita == *itb) {
+      ita++;
+      itb++;
+    } else if (*ita < *itb) {
+      res.push_back(*ita);
+      ita++;
+    } else {
+      itb++;
+    }
+  }
+  while (ita != a.end()) {
+    res.push_back(*ita);
+    ita++;
+  }
+  return res;
+}
+
+CFGType BuildCFGForFunction(const std::shared_ptr<FunctionDefItem> &func) {
+  CFGType res;
+  if (!func->init_block) {
+    throw std::runtime_error("Function does not have an init block");
+  }
+  res.label_to_block[func->init_block->label_full] = func->init_block.get();
+  res.nodes.push_back(std::make_shared<CFGNodeType>());
+  res.entry = res.nodes.back().get();
+  res.entry->corresponding_block = func->init_block.get();
+  res.block_to_node[func->init_block.get()] = res.entry;
+  for (auto block_ptr : func->basic_blocks) {
+    res.label_to_block[block_ptr->label_full] = block_ptr.get();
+    res.nodes.push_back(std::make_shared<CFGNodeType>());
+    res.nodes.back()->corresponding_block = block_ptr.get();
+    res.block_to_node[block_ptr.get()] = res.nodes.back().get();
+  }
+  // now add information for successors and predecessors
+  for (auto node : res.nodes) {
+    auto block = node->corresponding_block;
+    if (block->exit_action) {
+      if (auto br = std::dynamic_pointer_cast<BRAction>(block->exit_action)) {
+        node->successors.push_back(res.block_to_node[res.label_to_block[br->true_label_full]]);
+        node->successors.push_back(res.block_to_node[res.label_to_block[br->false_label_full]]);
+      } else if (auto uncond = std::dynamic_pointer_cast<UNConditionJMPAction>(block->exit_action)) {
+        node->successors.push_back(res.block_to_node[res.label_to_block[uncond->label_full]]);
+      } else if (auto ret = std::dynamic_pointer_cast<RETAction>(block->exit_action)) {
+        // do nothing
+      } else {
+        throw std::runtime_error("Unknown exit action");
+      }
+    } else {
+      throw std::runtime_error("Block does not have an exit action");
+    }
+  }
+  return res;
+}
\ No newline at end of file
diff --git a/src/opt/mem2reg.cpp b/src/opt/mem2reg.cpp
new file mode 100644
index 0000000..fbc8ca5
--- /dev/null
+++ b/src/opt/mem2reg.cpp
@@ -0,0 +1,13 @@
+#include "mem2reg.h"
+#include "cfg.h"
+
+void ConductMem2RegForFunction(const std::shared_ptr<FunctionDefItem> &func, const CFGType &cfg) {}
+std::shared_ptr<ModuleItem> Mem2Reg(std::shared_ptr<ModuleItem> src) {
+  auto res = std::make_shared<ModuleItem>(*src);
+  for (auto &func : res->function_defs) {
+    func = std::make_shared<FunctionDefItem>(*func);
+    auto cfg = BuildCFGForFunction(func);
+    ConductMem2RegForFunction(func, cfg);
+  }
+  return res;
+}
\ No newline at end of file