diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0020c88354760069d8fb71afc8f2de7289487fc7..3aefb71f83453342fb498d86f61b2dbca704826e 100755
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -49,5 +49,6 @@ include_directories(${PROJECT_SOURCE_DIR})
 include_directories(${PROJECT_BINARY_DIR})
 include_directories(include/lightir)
 include_directories(include/optimization)
+include_directories(include/codegen)
 add_subdirectory(src)
 add_subdirectory(tests)
diff --git a/include/codegen.hpp b/include/codegen/codegen.hpp
similarity index 95%
rename from include/codegen.hpp
rename to include/codegen/codegen.hpp
index a78f5d47496564b40d3844104004ace997f1cf80..3b3b66ce65dd5784290ec33818ac4cf1555744ff 100644
--- a/include/codegen.hpp
+++ b/include/codegen/codegen.hpp
@@ -2,13 +2,17 @@
 #define CODEGEN_HPP
 
 #include "BasicBlock.h"
+#include "Constant.h"
 #include "Function.h"
 #include "IRprinter.h"
 #include "Instruction.h"
 #include "Module.h"
 #include "Value.h"
+#include "liverange.hpp"
 #include "logging.hpp"
 
+#define __RO_PART__
+
 #include <map>
 #include <ostream>
 #include <vector>
@@ -23,7 +27,7 @@ using std::vector;
 
 class CodeGen {
   public:
-    CodeGen(Module *module) : m(module) {}
+    CodeGen(Module *m_) : m(m_), LRA(m_, phi_map) {}
 
     string print() {
         string result;
@@ -143,12 +147,16 @@ class CodeGen {
     std::map<Function *, std::map<int, int>> func_arg_off; // to $sp
     std::map<Function *, int> func_arg_N; // total space for args
     std::map<BasicBlock *, std::vector<std::pair<Value *, Value *>>> phi_map;
+    std::map<Constant *, std::string> ROdata;
     unsigned int stackN; // function local vars and so on
 
     Function *cur_func;
 
     Module *m;
     vector<string> output;
+
+    // register allocation
+    LiveRangeAnalyzer LRA;
 };
 
 #endif
diff --git a/include/codegen/liverange.hpp b/include/codegen/liverange.hpp
new file mode 100644
index 0000000000000000000000000000000000000000..f16010dc840e59acbcd49c43c3781e5e7bcb1d18
--- /dev/null
+++ b/include/codegen/liverange.hpp
@@ -0,0 +1,76 @@
+#ifndef LIVERANGE_HPP
+#define LIVERANGE_HPP
+
+#include "BasicBlock.h"
+#include "Function.h"
+#include "Instruction.h"
+#include "Module.h"
+#include "Value.h"
+
+#include <algorithm>
+#include <iostream>
+#include <iterator>
+#include <map>
+#include <set>
+#include <string>
+
+using std::map;
+using std::pair;
+using std::set;
+using std::string;
+using std::vector;
+
+#define __LRA_PRINT__
+
+class LiveRangeAnalyzer {
+    friend class CodeGen;
+    using LiveSet = set<Value *>;
+    using PhiMap = map<BasicBlock *, vector<pair<Value *, Value *>>>;
+
+  public:
+    struct Interval {
+        Interval(int a, int b) : i(a), j(b) {}
+        Interval() = delete;
+        int i, j;
+    };
+    LiveRangeAnalyzer(Module *m_, PhiMap &phi_map_)
+        : m(m_), phi_map(phi_map_) {}
+    LiveRangeAnalyzer() = delete;
+
+    void run();
+    void clear();
+    void print(Function *func, bool printSet = true);
+    string print_liveSet(LiveSet &ls) {
+        string s = "[ ";
+        for (auto k : ls)
+            s += k->get_name() + " ";
+        s += "]";
+        return s;
+    }
+
+  private:
+    Module *m;
+    // Function *func;
+    map<Value *, Interval> liverange;
+    map<int, LiveSet> IN, OUT;
+    map<Value *, int> instr_id;
+    map<pair<Value *, Value *>, int> cpstmt_id;
+    const PhiMap &phi_map;
+
+    void make_id(Function *);
+    void run(Function *);
+    LiveSet joinFor(BasicBlock *bb);
+    void union_ip(LiveSet &dest, LiveSet &src) {
+        LiveSet res;
+        set_union(dest.begin(),
+                  dest.end(),
+                  src.begin(),
+                  src.end(),
+                  std::inserter(res, res.begin()));
+        dest = res;
+    }
+    // Require: out-set is already set
+    // Return: the in-set(will not set IN-map)
+    LiveSet transferFunction(Instruction *);
+};
+#endif
diff --git a/src/codegen/CMakeLists.txt b/src/codegen/CMakeLists.txt
index 2698e820d078912d1219f418416bfcb93ee67dc6..302c048c9dfee88dc5d8678788fc46b925591409 100644
--- a/src/codegen/CMakeLists.txt
+++ b/src/codegen/CMakeLists.txt
@@ -1,5 +1,6 @@
 add_library(codegen STATIC
     codegen.cpp
+    liverange.cpp
 )
 
 target_link_libraries(common)