diff --git a/src/opt/optbackend.cpp b/src/opt/optbackend.cpp
index 3919cfc..a7e1be9 100644
--- a/src/opt/optbackend.cpp
+++ b/src/opt/optbackend.cpp
@@ -1,3 +1,5 @@
+#include <cstdint>
+#include <sstream>
 #include "IR/IR_basic.h"
 #include "opt/gen.h"
 namespace OptBackend {
@@ -99,6 +101,7 @@ void GenerateOptASM(std::ostream &os, std::shared_ptr<ModuleItem> prog) {
     // }
   }
 
+  size_t tmp_label_counter = 0;
   for (auto func_def : prog->function_defs) {
     std::cerr << "generating asm for function " << func_def->func_name_raw << std::endl;
     RemoveJumpOnlyBlock(func_def.get());
@@ -106,42 +109,114 @@ void GenerateOptASM(std::ostream &os, std::shared_ptr<ModuleItem> prog) {
     riscv->funcs.push_back(func_asm);
     func_asm->full_label = func_def->func_name_raw;
     FuncLayout &layout = func_layouts[func_def->func_name_raw];
+    std::vector<std::string> code_line_tmp;
     if (layout.total_frame_size < 2048) {
-      func_asm->code_lines.push_back("addi sp, sp, -" + std::to_string(layout.total_frame_size));
-      func_asm->code_lines.push_back("sw ra, " + std::to_string(layout.total_frame_size - 4) + "(sp)");
-      func_asm->code_lines.push_back("sw s0, " + std::to_string(layout.total_frame_size - 8) + "(sp)");
-      func_asm->code_lines.push_back("addi s0, sp, " + std::to_string(layout.total_frame_size));
-      func_asm->code_lines.push_back("sw s0, " + std::to_string(layout.total_frame_size - 12) + "(sp)");
+      code_line_tmp.push_back("addi sp, sp, -" + std::to_string(layout.total_frame_size));
+      code_line_tmp.push_back("sw ra, " + std::to_string(layout.total_frame_size - 4) + "(sp)");
+      code_line_tmp.push_back("sw s0, " + std::to_string(layout.total_frame_size - 8) + "(sp)");
+      code_line_tmp.push_back("addi s0, sp, " + std::to_string(layout.total_frame_size));
+      code_line_tmp.push_back("sw s0, " + std::to_string(layout.total_frame_size - 12) + "(sp)");
     } else {
-      func_asm->code_lines.push_back("li x31, " + std::to_string(layout.total_frame_size));
-      func_asm->code_lines.push_back("sub sp, sp, x31");
-      func_asm->code_lines.push_back("add x31, x31, sp");
-      func_asm->code_lines.push_back("sw ra, -4(x31)");
-      func_asm->code_lines.push_back("sw s0, -8(x31)");
-      func_asm->code_lines.push_back("sw x31, -12(x31)");
-      func_asm->code_lines.push_back("mv s0, x31");
+      code_line_tmp.push_back("li x31, " + std::to_string(layout.total_frame_size));
+      code_line_tmp.push_back("sub sp, sp, x31");
+      code_line_tmp.push_back("add x31, x31, sp");
+      code_line_tmp.push_back("sw ra, -4(x31)");
+      code_line_tmp.push_back("sw s0, -8(x31)");
+      code_line_tmp.push_back("sw x31, -12(x31)");
+      code_line_tmp.push_back("mv s0, x31");
     }
     if (func_def->init_block) {
-      func_asm->code_lines.push_back(".entrylabel." + func_def->init_block->label_full + ":");
+      code_line_tmp.push_back(".entrylabel." + func_def->init_block->label_full + ":");
       for (auto act : func_def->init_block->actions) {
-        OptBackend::GenerateASM(act, func_asm->code_lines, func_layouts[func_def->func_name_raw],
-                                prog->low_level_class_info);
+        OptBackend::GenerateASM(act, code_line_tmp, func_layouts[func_def->func_name_raw], prog->low_level_class_info);
       }
-      OptBackend::GenerateASM(func_def->init_block->exit_action, func_asm->code_lines,
-                              func_layouts[func_def->func_name_raw], prog->low_level_class_info);
+      OptBackend::GenerateASM(func_def->init_block->exit_action, code_line_tmp, func_layouts[func_def->func_name_raw],
+                              prog->low_level_class_info);
     }
     for (auto block : func_def->basic_blocks) {
-      if (func_asm->code_lines.size() > 0 && func_asm->code_lines.back() == "j .entrylabel." + block->label_full) {
-        func_asm->code_lines.pop_back();  // remove redundant jump
+      if (code_line_tmp.size() > 0 && code_line_tmp.back() == "j .entrylabel." + block->label_full) {
+        code_line_tmp.pop_back();  // remove redundant jump
       }
-      func_asm->code_lines.push_back(".entrylabel." + block->label_full + ":");
+      code_line_tmp.push_back(".entrylabel." + block->label_full + ":");
       for (auto act : block->actions) {
-        OptBackend::GenerateASM(act, func_asm->code_lines, func_layouts[func_def->func_name_raw],
-                                prog->low_level_class_info);
+        OptBackend::GenerateASM(act, code_line_tmp, func_layouts[func_def->func_name_raw], prog->low_level_class_info);
       }
-      OptBackend::GenerateASM(block->exit_action, func_asm->code_lines, func_layouts[func_def->func_name_raw],
+      OptBackend::GenerateASM(block->exit_action, code_line_tmp, func_layouts[func_def->func_name_raw],
                               prog->low_level_class_info);
     }
+    std::unordered_map<std::string, int64_t> label_to_line;
+    std::vector<std::string> code_line_tmp2;
+    bool branch_replaced = false;
+    std::unordered_set<std::string> is_branch;
+    is_branch.insert("beq");
+    is_branch.insert("bne");
+    is_branch.insert("blt");
+    is_branch.insert("bge");
+    is_branch.insert("bnez");
+    is_branch.insert("beqz");
+    do {
+      branch_replaced = false;
+      code_line_tmp2.clear();
+      label_to_line.clear();
+      for (size_t i = 0; i < code_line_tmp.size(); i++) {
+        if (code_line_tmp[i].substr(0, 12) == ".entrylabel.") {
+          label_to_line[code_line_tmp[i].substr(0, code_line_tmp[i].size() - 1)] = i;
+        }
+      }
+      for (size_t i = 0; i < code_line_tmp.size(); i++) {
+        std::stringstream ss(code_line_tmp[i]);
+        std::string tmp;
+        std::string label;
+        std::vector<std::string> tokens;
+        while (ss >> tmp) {
+          label = tmp;
+          tokens.push_back(tmp);
+        }
+        if (is_branch.find(tokens[0]) != is_branch.end()) {
+          if (label_to_line.find(label) == label_to_line.end()) {
+            goto write;
+            throw std::runtime_error("label " + label + " not found");
+          }
+          int64_t delta = label_to_line[label] - static_cast<int64_t>(i);
+          if (delta < -2000 || delta > 2000) {
+            std::string tmp_label_name = ".entrylabel.tmp_label." + std::to_string(tmp_label_counter++);
+            ss.clear();
+            if (tokens[0] == "beq") {
+              tokens[0] = "bne";
+            } else if (tokens[0] == "bne") {
+              tokens[0] = "beq";
+            } else if (tokens[0] == "blt") {
+              tokens[0] = "bge";
+            } else if (tokens[0] == "bge") {
+              tokens[0] = "blt";
+            } else if (tokens[0] == "bnez") {
+              tokens[0] = "beqz";
+            } else if (tokens[0] == "beqz") {
+              tokens[0] = "bnez";
+            } else {
+              throw std::runtime_error("unknown branch type");
+            }
+            for (size_t j = 0; j < tokens.size() - 1; j++) {
+              ss << tokens[j] << " ";
+            }
+            ss << tmp_label_name;
+            code_line_tmp2.push_back(ss.str());
+            code_line_tmp2.push_back("j " + label);
+            code_line_tmp2.push_back(tmp_label_name + ":");
+            branch_replaced = true;
+          } else {
+            code_line_tmp2.push_back(code_line_tmp[i]);
+          }
+        } else {
+          code_line_tmp2.push_back(code_line_tmp[i]);
+        }
+      }
+      code_line_tmp = code_line_tmp2;
+    } while (branch_replaced);
+    write:
+    for (const auto &code : code_line_tmp) {
+      func_asm->code_lines.push_back(code);
+    }
   }
 
   riscv->RecursivePrint(os);