diff --git a/src/codegen/codegen.cpp b/src/codegen/codegen.cpp
index 8e522752e5c66b631e2ffe7d0e66eb4a57b03b78..ca2e1063f3b4ca2e093d0925070c4dfcadd71d31 100644
--- a/src/codegen/codegen.cpp
+++ b/src/codegen/codegen.cpp
@@ -13,11 +13,16 @@
 #include "Instruction.h"
 #include "Type.h"
 #include "Value.h"
+#include "ast.hpp"
 
+#include <algorithm>
 #include <cstdint>
 #include <cstring>
+#include <sstream>
 #include <string>
+#include <sys/types.h>
 #include <utility>
+#include <vector>
 
 // $r0          $zero       constant 0
 // $r1          $ra         return address
@@ -95,6 +100,7 @@ CodeGen::run() {
     // funtions
     for (auto &func : m->get_functions()) {
         if (not func.is_declaration()) {
+            LRA.run(&func);
             cur_func = &func;
             output.push_back("");
             output.push_back(".globl " + func.get_name());
@@ -113,6 +119,24 @@ CodeGen::run() {
             stackMemDealloc();
         }
     }
+    // read only data
+    output.push_back(".section .rodata");
+    for (auto [constant, name] : ROdata) {
+        auto int_ = dynamic_cast<ConstantInt *>(constant);
+        auto float_ = dynamic_cast<ConstantFP *>(constant);
+        string value;
+        assert((int_ || float_) && "wrong type");
+        if (int_) {
+            value = to_string(int_->get_value());
+        } else {
+            std::stringstream ss;
+            float v = (float_->get_value());
+            ss << std::hex << *(uint32_t *)&v;
+            value = "0x" + ss.str();
+        }
+        output.push_back(name + ": ");
+        output.push_back(".word " + value);
+    }
 }
 
 void
@@ -145,8 +169,23 @@ void
 CodeGen::value2reg(Value *v, int id) {
     bool is_float = v->get_type()->is_float_type();
     auto reg_name = (is_float ? "$fa" : "$a") + to_string(id);
+    string tmp_ireg = "$t0";
     if (dynamic_cast<Constant *>(v)) {
         auto constant = static_cast<Constant *>(v);
+#ifdef __RO_PART__
+        if (ROdata.find(constant) == ROdata.end())
+            ROdata[constant] = ".LC" + to_string(ROdata.size());
+        string instr_ir, addr = ROdata[constant];
+        if (dynamic_cast<ConstantInt *>(constant))
+            instr_ir = "ld.w";
+        else if (dynamic_cast<ConstantFP *>(constant))
+            instr_ir = "fld.s";
+        else
+            assert(false && "wait for completion");
+        output.push_back("la.local " + tmp_ireg + ", " + addr);
+        output.push_back(instr_ir + " " + reg_name + ", " + tmp_ireg + ", 0");
+#else
+
         if (dynamic_cast<ConstantInt *>(constant)) {
             int k = static_cast<ConstantInt *>(constant)->get_value();
             if ((k & 0xfff) != k) {
@@ -159,7 +198,6 @@ CodeGen::value2reg(Value *v, int id) {
         } else if (dynamic_cast<ConstantFP *>(constant)) {
             // move the binary code to int-reg, then use movgr2fr to move the
             // value to float-reg
-            string tmp_ireg = "$t0";
             float k = static_cast<ConstantFP *>(constant)->get_value();
             int hex_int = *(uint32_t *)&k;
             if ((hex_int & 0xfff) != hex_int)
@@ -173,6 +211,7 @@ CodeGen::value2reg(Value *v, int id) {
 
         } else
             assert(false && "wait for completion");
+#endif
     } else if (dynamic_cast<GlobalVariable *>(v)) {
         output.push_back("la.local " + reg_name + ", " + v->get_name());
     } else if (dynamic_cast<AllocaInst *>(v)) {
@@ -218,7 +257,6 @@ void
 CodeGen::stackMemDealloc() {
     output.push_back("# epilog");
     // 7: return value should be determined already!
-    // output.push_back("addi.w $a0, $zero, 0");
     output.push_back(cur_func->get_name() + "_end:");
     output.push_back("ld.d $ra, $fp, -8");
     output.push_back("addi.d $sp, $sp, " + to_string(stackN));
@@ -391,6 +429,8 @@ CodeGen::IR2assem(BinaryInst *instr) {
     value2reg(instr->get_operand(1), 1);
 
     string instr_ir = instr->get_instr_op_name();
+    if (instr_ir == "sdiv")
+        instr_ir = "div";
     string suff = suffix(instr->get_type());
     output.push_back(instr_ir + suff +
                      (is_float ? " $fa0, $fa0, $fa1" : " $a0, $a0, $a1"));
diff --git a/src/codegen/liverange.cpp b/src/codegen/liverange.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..797b5a1c1727276cf8c97c3d545fb711218225ad
--- /dev/null
+++ b/src/codegen/liverange.cpp
@@ -0,0 +1,218 @@
+#include "liverange.hpp"
+
+#include "Function.h"
+#include "Instruction.h"
+
+#include <algorithm>
+#include <iterator>
+
+void
+LiveRangeAnalyzer::clear() {
+    IN.clear();
+    OUT.clear();
+    liverange.clear();
+    instr_id.clear();
+}
+
+LiveRangeAnalyzer::LiveSet
+LiveRangeAnalyzer::joinFor(BasicBlock *bb) {
+    LiveSet out;
+    for (auto succ : bb->get_succ_basic_blocks()) {
+        auto &irs = succ->get_instructions();
+        auto it = irs.begin();
+        while (it != irs.end() and it->is_phi())
+            ++it;
+        assert(it != irs.end() && "need to find first_ir from copy-stmt");
+        union_ip(out, IN[instr_id.at(&(*it))]);
+        // std::cout << "# " + it->print() << std::endl;
+    }
+    // std::cout << "\tget out: " << print_liveSet(out) << std::endl;
+    return out;
+}
+
+void
+LiveRangeAnalyzer::make_id(Function *func) {
+    // instruction numbering
+    // this is also the structure of the IR logically:
+    // ignore phi, add copy-statement
+    int ir_cnt = 0;
+    for (auto &bb : func->get_basic_blocks()) {
+        for (auto &instr : bb.get_instructions()) {
+            if (instr.is_phi())
+                continue;
+            if (instr.is_br() or instr.is_ret()) {
+                // insert copy-stmt in front of the jump ir
+                auto it = phi_map.find(&bb);
+                if (it != phi_map.end()) {
+                    for (auto pr : it->second) {
+                        cpstmt_id[pr] = ++ir_cnt;
+                    }
+                }
+            }
+            instr_id[&instr] = ++ir_cnt;
+        }
+    }
+}
+
+void
+LiveRangeAnalyzer::run(Function *func) {
+    clear();
+    make_id(func);
+#ifdef __LRA_PRINT__
+    print(func, false);
+#endif
+    bool cont = true;
+    while (cont) {
+        cont = false;
+        // reverse traverse BasicBlocks
+        for (auto rit_bb = func->get_basic_blocks().rbegin();
+             rit_bb != func->get_basic_blocks().rend();
+             ++rit_bb) {
+            auto bb = &(*rit_bb);
+
+            LiveSet bef_in, out;
+            bool last_ir = true;
+
+            // reverse traverse instructions
+            for (auto rit_ir = rit_bb->get_instructions().rbegin();
+                 rit_ir != rit_bb->get_instructions().rend();
+                 ++rit_ir) {
+                auto instr = &(*rit_ir);
+                if (instr->is_phi()) {
+                    assert(not last_ir && "If phi is the last ir, then data "
+                                          "flow fails due to ignorance of phi");
+                    continue;
+                }
+                //
+                // get out-set for this instruction
+                if (last_ir) {
+                    last_ir = false;
+                    out = joinFor(bb);
+                } else {
+                    out = bef_in;
+                }
+                OUT[instr_id.at(instr)] = out;
+                //
+                // get in-set
+                bef_in = transferFunction(instr);
+                cont |= bef_in != IN[instr_id.at(instr)];
+                IN[instr_id.at(instr)] = bef_in;
+
+                if (instr->is_ret() or instr->is_br()) {
+                    // deal with copy-stmt
+                    auto it = phi_map.find(bb);
+                    if (it != phi_map.end()) {
+                        for (auto rit = it->second.rbegin();
+                             rit != it->second.rend();
+                             ++rit) {
+                            auto [lv, rv] = *rit;
+                            if (last_ir) {
+                                last_ir = false;
+                                out = joinFor(bb);
+                            } else
+                                out = bef_in;
+
+                            OUT[cpstmt_id.at(*rit)] = out;
+                            // transfer manually
+                            out.erase(lv);
+                            if (dynamic_cast<Instruction *>(rv))
+                                out.insert(rv);
+                            cont |= out != IN[cpstmt_id.at(*rit)];
+                            bef_in = IN[cpstmt_id.at(*rit)] = out;
+                        }
+                    }
+                }
+            }
+        }
+    }
+#ifdef __LRA_PRINT__
+    print(func);
+#endif
+}
+
+LiveRangeAnalyzer::LiveSet
+LiveRangeAnalyzer::transferFunction(Instruction *instr) {
+    LiveSet in, out = OUT[instr_id.at(instr)];
+    LiveSet use;
+
+    // calculate use for this instruction
+    for (auto op : instr->get_operands()) {
+        // op type:
+        // - global
+        // - function
+        // - Constant
+        // - instruction
+        // - argument
+        // - BasicBlock
+        auto ins = dynamic_cast<Instruction *>(op);
+        if (ins) {
+            assert(not ins->is_void() && "instr as op should not be void");
+            use.insert(op);
+        }
+    }
+    // in = use + (out - def)
+    auto iter = out.find(instr);
+    if (iter != out.end())
+        out.erase(iter);
+    std::set_union(out.begin(),
+                   out.end(),
+                   use.begin(),
+                   use.end(),
+                   std::inserter(in, in.begin()));
+
+    return in;
+}
+
+void
+LiveRangeAnalyzer::print(Function *func, bool printSet) { // for debug
+    for (auto &bb : func->get_basic_blocks()) {
+        for (auto &instr : bb.get_instructions()) {
+            if (instr.is_phi()) // ignore phi
+                continue;
+            // insert copy-stmt
+            if ((instr.is_br() or instr.is_ret()) and
+                phi_map.find(&bb) != phi_map.end()) {
+                for (auto pr : phi_map.find(&bb)->second) {
+                    auto [lv, rv] = pr;
+                    auto idx = cpstmt_id.at(pr);
+                    std::cout
+                        << cpstmt_id[pr] << ". " << lv->get_name() << " = "
+                        << (rv->get_name() == "" ? rv->print() : rv->get_name())
+                        << std::endl;
+                    if (not printSet)
+                        continue;
+                    auto &in = IN.at(idx);
+                    auto &out = OUT.at(idx);
+                    std::cout << "\tin-set: " + print_liveSet(in) << "\n";
+                    std::cout << "\tout-set: " + print_liveSet(out) << "\n";
+                }
+            }
+            // normal ir
+            std::cout << instr_id[&instr] << ". " << instr.print() << " # "
+                      << &instr << std::endl;
+            if (not printSet)
+                continue;
+            auto idx = instr_id.at(&instr);
+            auto &in = IN.at(idx);
+            auto &out = OUT.at(idx);
+            std::cout << "\tin-set: " + print_liveSet(in) << "\n";
+            std::cout << "\tout-set: " + print_liveSet(out) << "\n";
+        }
+        /* if (phi_map.find(&bb) != phi_map.end()) {
+         *     for (auto pr : phi_map.find(&bb)->second) {
+         *         auto [lv, rv] = pr;
+         *         auto idx = cpstmt_id.at(pr);
+         *         std::cout << cpstmt_id[pr] << ". " << lv->get_name() << " = "
+         *                   << (rv->get_name() == "" ? rv->print()
+         *                                            : rv->get_name())
+         *                   << std::endl;
+         *         if (not printSet)
+         *             continue;
+         *         auto &in = IN.at(idx);
+         *         auto &out = OUT.at(idx);
+         *         std::cout << "\tin-set: " + print_liveSet(in) << "\n";
+         *         std::cout << "\tout-set: " + print_liveSet(out) << "\n";
+         *     }
+         * } */
+    }
+}