diff --git a/include/IR/IR_basic.h b/include/IR/IR_basic.h
index 6de3ffd..caf3f46 100644
--- a/include/IR/IR_basic.h
+++ b/include/IR/IR_basic.h
@@ -72,7 +72,8 @@ class JMPActionItem : public ActionItem {
   std::shared_ptr<class PhiItem> corresponding_phi;
 };
 namespace NaiveBackend {
-void ScanForVar(class FuncLayout &layout, std::shared_ptr<ActionItem> action,  const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
+void ScanForVar(class FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
 void GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines, FuncLayout &layout,
                  const std::unordered_map<std::string, IRClassInfo> &low_level_class_info, bool process_phi);
 }  // namespace NaiveBackend
@@ -135,7 +136,8 @@ class RETAction : public JMPActionItem {
 
 class BinaryOperationAction : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
   friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
                                         NaiveBackend::FuncLayout &layout,
                                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
@@ -164,7 +166,8 @@ class BinaryOperationAction : public ActionItem {
 };
 class AllocaAction : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
   std::string name_full;
   LLVMType type;
   size_t num;
@@ -188,7 +191,8 @@ class AllocaAction : public ActionItem {
 };
 class LoadAction : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
   friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
                                         NaiveBackend::FuncLayout &layout,
                                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
@@ -213,7 +217,8 @@ class LoadAction : public ActionItem {
 };
 class StoreAction : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
   friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
                                         NaiveBackend::FuncLayout &layout,
                                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
@@ -238,7 +243,12 @@ class StoreAction : public ActionItem {
 };
 class GetElementPtrAction : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
+  friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
+                                        NaiveBackend::FuncLayout &layout,
+                                        const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
+                                        bool process_phi);
   std::string result_full;
   LLVMType ty;
   std::string ptr_full;
@@ -266,7 +276,8 @@ class GetElementPtrAction : public ActionItem {
 };
 class ICMPAction : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
   friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
                                         NaiveBackend::FuncLayout &layout,
                                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
@@ -295,7 +306,8 @@ class BlockItem : public LLVMIRItemBase {
   friend class IRBuilder;
   friend class FunctionDefItem;
   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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
   std::string label_full;
   std::vector<std::shared_ptr<ActionItem>> actions;
   std::shared_ptr<JMPActionItem> exit_action;
@@ -312,7 +324,8 @@ class BlockItem : public LLVMIRItemBase {
 };
 class CallItem : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
   friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
                                         NaiveBackend::FuncLayout &layout,
                                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
@@ -365,7 +378,12 @@ class CallItem : public ActionItem {
 
 class PhiItem : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
+  friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
+                                        NaiveBackend::FuncLayout &layout,
+                                        const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
+                                        bool process_phi);
   std::string result_full;
   LLVMType ty;
   std::vector<std::pair<std::string, std::string>> values;  // (val_i_full, label_i_full)
@@ -392,7 +410,12 @@ class PhiItem : public ActionItem {
 };
 class SelectItem : public ActionItem {
   friend class IRBuilder;
-  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 void NaiveBackend::ScanForVar(class NaiveBackend::FuncLayout &layout, std::shared_ptr<ActionItem> action,
+                                       const std::unordered_map<std::string, IRClassInfo> &low_level_class_info);
+  friend void NaiveBackend::GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines,
+                                        NaiveBackend::FuncLayout &layout,
+                                        const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
+                                        bool process_phi);
   std::string result_full;
   std::string cond_full;
   std::string true_val_full;
diff --git a/include/naivebackend/build_layout.hpp b/include/naivebackend/build_layout.hpp
index cd32276..2982fdc 100644
--- a/include/naivebackend/build_layout.hpp
+++ b/include/naivebackend/build_layout.hpp
@@ -39,8 +39,7 @@ inline void ScanForVar(FuncLayout &layout, std::shared_ptr<ActionItem> action,
       size_t element_idx = std::stoi(get_element_act->indices[1]);
       auto class_ty = std::get<LLVMIRCLASSTYPE>(get_element_act->ty);
       const IRClassInfo &class_info = low_level_class_info.at(class_ty.class_name_full);
-      size_t sz = class_info.member_var_size[element_idx];
-      layout.AllocateItem(get_element_act->result_full, sz);
+      layout.AllocateItem(get_element_act->result_full, 4);
     } else {
       throw std::runtime_error("GetElementPtrAction with more than 2 indices is not supported");
     }
diff --git a/include/naivebackend/codegen.hpp b/include/naivebackend/codegen.hpp
index 0f7277a..0ee32fd 100644
--- a/include/naivebackend/codegen.hpp
+++ b/include/naivebackend/codegen.hpp
@@ -1,7 +1,10 @@
 #pragma once
+#include <bit>
 #include <stdexcept>
 #include "naivebackend.h"
+#include "tools.h"
 namespace NaiveBackend {
+extern std::string cur_block_label_for_phi;
 inline void GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string> &code_lines, FuncLayout &layout,
                         const std::unordered_map<std::string, IRClassInfo> &low_level_class_info,
                         bool process_phi = false) {
@@ -73,7 +76,29 @@ inline void GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string
       throw std::runtime_error("Unknown bytes");
     }
   } else if (auto get_element_act = std::dynamic_pointer_cast<GetElementPtrAction>(act)) {
-    // TODO: implement this
+    if (get_element_act->indices.size() == 1) {
+      // array access
+      IRVar2RISCVReg(get_element_act->ptr_full, 4, "t0", layout, code_lines);
+      IRVar2RISCVReg(get_element_act->indices[0], 4, "t1", layout, code_lines);
+      size_t element_sz = CalcSize(get_element_act->ty);
+      code_lines.push_back("slli t1, t1, " + std::to_string(std::countr_zero(element_sz)));
+      code_lines.push_back("add t2, t0, t1");
+      GenerateWriteAccess(get_element_act->result_full, element_sz, "t2", layout, code_lines);
+    } else if (get_element_act->indices.size() == 2) {
+      // struct access
+      if (get_element_act->indices[0] != "0") {
+        throw std::runtime_error("struct access with non-zero offset is not supported");
+      }
+      size_t element_idx = std::stoull(get_element_act->indices[1]);
+      auto class_ty = std::get<LLVMIRCLASSTYPE>(get_element_act->ty);
+      const IRClassInfo &class_info = low_level_class_info.at(class_ty.class_name_full);
+      size_t offset = class_info.member_var_pos_after_align[element_idx];
+      IRVar2RISCVReg(get_element_act->ptr_full, 4, "t0", layout, code_lines);
+      code_lines.push_back("addi t2, t0, " + std::to_string(offset));
+      GenerateWriteAccess(get_element_act->result_full, 4, "t2", layout, code_lines);
+    } else {
+      throw std::runtime_error("Unknown getelementptr indices size");
+    }
   } else if (auto icmp_act = std::dynamic_pointer_cast<ICMPAction>(act)) {
     size_t sz = CalcSize(icmp_act->type);
     IRVar2RISCVReg(icmp_act->operand1_full, sz, "t0", layout, code_lines);
@@ -124,11 +149,33 @@ inline void GenerateASM(std::shared_ptr<ActionItem> act, std::vector<std::string
     if (!process_phi) {
       return;  // for efficiency, phi actions are implemented as store action in the previous block
     }
-    // TODO: implement this
-    // throw std::runtime_error("not implemented");
+    std::string self_label = NaiveBackend::cur_block_label_for_phi;
+    for (const auto &[val, label] : phi_act->values) {
+      if (label == self_label) {
+        size_t sz = CalcSize(phi_act->ty);
+        IRVar2RISCVReg(val, sz, "t0", layout, code_lines);
+        GenerateWriteAccess(phi_act->result_full, sz, "t0", layout, code_lines);
+        return;
+      }
+    }
+    throw std::runtime_error("cannot found label for phi action");
   } else if (auto select_act = std::dynamic_pointer_cast<SelectItem>(act)) {
-    // TODO: implement this
-    // throw std::runtime_error("not implemented");
+    LLVMType ty_int32 = LLVMIRIntType(32);
+    LLVMType ty_ptr = LLVMIRPTRType();
+    if (select_act->ty != ty_int32 && select_act->ty != ty_ptr) {
+      throw std::runtime_error("select action only support int32 or ptr");
+    }
+    IRVar2RISCVReg(select_act->cond_full, 1, "t0", layout, code_lines);
+    IRVar2RISCVReg(select_act->true_val_full, 4, "t1", layout, code_lines);
+    IRVar2RISCVReg(select_act->false_val_full, 4, "t2", layout, code_lines);
+    // use binary operation to implement select for efficiency
+    code_lines.push_back("slli t0, t0, 31");
+    code_lines.push_back("srai t0, t0, 31");
+    code_lines.push_back("and t1, t0, t1");
+    code_lines.push_back("not t0, t0");
+    code_lines.push_back("and t2, t0, t2");
+    code_lines.push_back("or t0, t1, t2");
+    GenerateWriteAccess(select_act->result_full, 4, "t0", layout, code_lines);
   } else {
     throw std::runtime_error("Unknown action type");
   }
diff --git a/include/naivebackend/naivebackend.h b/include/naivebackend/naivebackend.h
index 619e5f7..95c2bae 100644
--- a/include/naivebackend/naivebackend.h
+++ b/include/naivebackend/naivebackend.h
@@ -165,7 +165,7 @@ inline void GenerateReadAccess(std::string val, size_t bytes, std::string output
       throw std::runtime_error("Unknown bytes");
     }
   } else if (val.size() > 6 && val.substr(0, 6) == "@.str.") {
-    code_lines.push_back("la " + output_reg.substr(1, output_reg.size() - 1) + ", " + val);
+    code_lines.push_back("la " + output_reg + ", " + val.substr(1, val.size() - 1));
   } else {
     throw std::runtime_error("Unknown variable type with name=" + val);
   }
diff --git a/include/tools.h b/include/tools.h
index df51a49..ee7b96c 100644
--- a/include/tools.h
+++ b/include/tools.h
@@ -108,11 +108,17 @@ class LLVMIRIntType {
   size_t bits;
   LLVMIRIntType() = default;
   LLVMIRIntType(size_t bits) : bits(bits) {}
+  bool operator==(const LLVMIRIntType &r) const { return bits == r.bits; }
+};
+struct LLVMIRPTRType {
+  bool operator==(const LLVMIRPTRType &r) const { return true; }
+};
+struct LLVMVOIDType {
+  bool operator==(const LLVMVOIDType &r) const { return true; }
 };
-struct LLVMIRPTRType {};
-struct LLVMVOIDType {};
 struct LLVMIRCLASSTYPE {
   std::string class_name_full;
+  bool operator==(const LLVMIRCLASSTYPE &r) const { return class_name_full == r.class_name_full; }
 };
 using LLVMType = std::variant<LLVMIRIntType, LLVMIRPTRType, LLVMVOIDType, LLVMIRCLASSTYPE>;
 class IRClassInfo {
diff --git a/src/naivebackend/naivebackend.cpp b/src/naivebackend/naivebackend.cpp
index b73d08b..6baeeec 100644
--- a/src/naivebackend/naivebackend.cpp
+++ b/src/naivebackend/naivebackend.cpp
@@ -3,6 +3,9 @@
 #include "IR/IR_basic.h"
 #include "build_layout.hpp"
 #include "codegen.hpp"
+namespace NaiveBackend {
+std::string cur_block_label_for_phi;
+}
 using namespace NaiveBackend;
 void GenerateNaiveASM(std::ostream &os, std::shared_ptr<ModuleItem> prog) {
   auto riscv = std::make_shared<RISCVProgItem>();
@@ -60,6 +63,7 @@ void GenerateNaiveASM(std::ostream &os, std::shared_ptr<ModuleItem> prog) {
                                   prog->low_level_class_info);
       }
       if (func_def->init_block->exit_action->corresponding_phi) {
+        NaiveBackend::cur_block_label_for_phi = func_def->init_block->label_full;
         NaiveBackend::GenerateASM(func_def->init_block->exit_action->corresponding_phi, func_asm->code_lines,
                                   func_layouts[func_def->func_name_raw], prog->low_level_class_info, true);
       }
@@ -73,6 +77,7 @@ void GenerateNaiveASM(std::ostream &os, std::shared_ptr<ModuleItem> prog) {
                                   prog->low_level_class_info);
       }
       if (block->exit_action->corresponding_phi) {
+        NaiveBackend::cur_block_label_for_phi = block->label_full;
         NaiveBackend::GenerateASM(block->exit_action->corresponding_phi, func_asm->code_lines,
                                   func_layouts[func_def->func_name_raw], prog->low_level_class_info, true);
       }