diff --git a/docs/riscv-spec-20191213.pdf b/docs/riscv-spec-20191213.pdf
new file mode 100644
index 0000000..533c1cb
Binary files /dev/null and b/docs/riscv-spec-20191213.pdf differ
diff --git a/include/common.h b/include/common.h
index 17b43ff..bb12664 100644
--- a/include/common.h
+++ b/include/common.h
@@ -5,6 +5,14 @@
 #include <optional>
 #include <sstream>
 #include <string>
+#include <memory>
+#include <vector>
+#include <list>
+#include <unordered_set>
+#include <unordered_map>
+
+#define uptr(type) std::unique_ptr<type>
+#define sptr(type) std::shared_ptr<type>
 
 #define panic(message)                                                                                                 \
   do {                                                                                                                 \
diff --git a/include/mc_inst.h b/include/mc_inst.h
new file mode 100644
index 0000000..6a29d11
--- /dev/null
+++ b/include/mc_inst.h
@@ -0,0 +1,69 @@
+#pragma once
+#include "common.h"
+
+namespace codegen{
+
+// a?, t?, ra are caller-saved
+// s? are callee-saved
+// x0,gp,tp are preserved in user-space
+enum class RV64Reg {
+  x0 = 0,       // zero
+  x1,       // ra, caller
+  x2,       // sp, callee
+  x3,       // gp
+  x4,       // tp
+  x5,       // t0, caller
+  x6,x7,    // t1-2, caller
+  x8,       // s0/fp, callee
+  x9,       // s1, callee
+  x10,x11,  // a0-1,caller
+  x12,x13,x14,x15,x16,x17, // a2-7,caller
+  x18,x19,x20,x21,x22,x23,x24,x25,x26,x27, // s2-11,callee
+  x28,x29,x30,x31,  // t3-6,caller
+};
+
+inline std::string Reg2Name(RV64Reg reg) {
+  std::string regname = "x" + std::to_string((int)reg);
+  return regname;
+}
+
+class MOperand {
+public:
+  enum class type {
+    Virt,
+    Imm,
+    Reg,
+  } op_type;
+  int value;
+
+};
+
+class MInst {
+public:
+  enum class MInstTag {
+    Add, Sub, Rsb, Mul, Div, Mod, Lt, Le, Ge, Gt, Eq, Ne, And, Or,
+    LongMul, FMA, Mv, Branch, Jump, Return,  Load, Store,Compare, Call, Global,
+  } tag;
+
+  MInst(MInstTag tag) : tag(tag) {}
+};
+
+class MBasicBlock {
+
+};
+
+class MFunction {
+  std::list<uptr(MBasicBlock)> bbs;
+  
+};
+
+class MGlobalVar {
+
+};
+
+class MCModule {
+  std::list<uptr(MFunction)> functions;
+  std::list<uptr(MGlobalVar)> globals;
+};
+
+}
\ No newline at end of file
diff --git a/src/pass_mem2reg.cpp b/src/pass_mem2reg.cpp
index 3522de8..c3c6457 100644
--- a/src/pass_mem2reg.cpp
+++ b/src/pass_mem2reg.cpp
@@ -11,36 +11,6 @@
 
 namespace antlrSysY {
 
-static bool is_alloca_promotable(InstAllocaPtr_t inst) {
-  for (const auto use : inst->use_list) {
-    auto user = use.user;
-    if (dynamic_cast<InstLoad *>(user)) {
-      const auto li = dynamic_cast<InstLoad *>(user);
-      if (li->type != inst->type) {
-        return false;
-      }
-    }
-    else if (dynamic_cast<InstStore *>(user)) {
-      const auto si = dynamic_cast<InstStore *>(user);
-      if (si->operand_list[1] == inst || si->type != inst->type) {
-        return false;
-      }
-    }
-    else if (dynamic_cast<InstGEP *>(user)) {
-      const auto gep = dynamic_cast<InstGEP *>(user);
-      for (int i = 1; i < gep->operand_list.size(); ++i) {
-        if (!Value::is<ConstantInt>(gep->operand_list[i]) || !Value::as<ConstantInt>(gep->operand_list[i])->value) {
-          return false;
-        }
-      }
-    }
-    else {
-      return false;
-    }
-  }
-  return true;
-}
-
 struct AllocaInfo {
   std::vector<BasicBlockPtr_t> def_blocks = {};
   std::vector<BasicBlockPtr_t> use_blocks = {};
@@ -241,6 +211,14 @@ static void _mem_2_reg(FunctionPtr_t func) {
     std::unordered_set<BasicBlockPtr_t> def_blocks(alloca_info.def_blocks.begin(), alloca_info.def_blocks.end());
     std::unordered_set<BasicBlockPtr_t> livein_blocks;
     live_in_blocks(ai, alloca_info, def_blocks, livein_blocks);
+    if (VLOG_IS_ON(6)) {
+      std::cout << "Live-in blocks of " << ai->name << ": [";
+      for (auto livein : livein_blocks) {
+        std::cout << livein->name << ", ";
+      }
+      std::cout << "]\n";
+      std::cout.flush();
+    }
     // llvm use IDF to calculate phi blocks.
     // But that is too complicated
     // SSA book Algo 3.1
@@ -256,9 +234,10 @@ static void _mem_2_reg(FunctionPtr_t func) {
         auto frontier_index = bb_to_id.at(frontier);
         if (!visited[frontier_index]) {
           visited[frontier_index] = true;
+          // livein-block opt is workable in IDF, but not here
           // if (livein_blocks.count(frontier)) {
-            auto inst_phi = build_InstPhi(TypeHelper::TYPE_I32, frontier->predecessors, frontier, ai->name);
-            phi_to_allocaid.insert({inst_phi, i});
+          auto inst_phi = build_InstPhi(TypeHelper::TYPE_I32, frontier->predecessors, frontier, ai->name);
+          phi_to_allocaid.insert({inst_phi, i});
           // }
           if (!def_blocks.count(frontier)) {
             worklist.push(frontier);
diff --git a/src/visitor.cpp b/src/visitor.cpp
index 6c3e9cd..5bcaa2b 100644
--- a/src/visitor.cpp
+++ b/src/visitor.cpp
@@ -533,9 +533,9 @@ std::any Visitor::visitLAndExp(SysyParser::LAndExpContext *ctx) {
   for (int i = 0; i < eq_exp_list.size(); ++i) {
     auto next_block = build_BasicBlock("", _state.current_func, _state.current_bb->itr);
     auto eq_exp     = any_to_Value(visitEqExp(eq_exp_list[i]));
-    auto condition = eq_exp;
+    auto condition  = eq_exp;
     if (!TypeHelper::isIntegerTypeI1(eq_exp->type))
-      condition  = build_InstBinary(InstTag::Ne, eq_exp, CONST0, _state.current_bb);
+      condition = build_InstBinary(InstTag::Ne, eq_exp, CONST0, _state.current_bb);
     build_InstBranch(condition, next_block, ctx->false_block, _state.current_bb);
     _state.current_bb = next_block;
   }
diff --git a/src/visitor_llir_gen.cpp b/src/visitor_llir_gen.cpp
index b94f85c..5ff0c06 100644
--- a/src/visitor_llir_gen.cpp
+++ b/src/visitor_llir_gen.cpp
@@ -157,7 +157,7 @@ static void _gen_blocks(std::ostream &ostr, const std::list<BasicBlockPtr_t> &bl
     }
     for (auto _inst : block->inst_list) {
       ostr << "  ";
-      VLOG(5) << "Build inst" << _inst->ir_seqno << ": " << _inst->to_string();
+      VLOG(7) << "Build inst" << _inst->ir_seqno << ": " << _inst->to_string();
       switch (_inst->tag) {
         case InstTag::Br: {
           auto inst = Value::as<InstBranch>(_inst);
@@ -166,7 +166,7 @@ static void _gen_blocks(std::ostream &ostr, const std::list<BasicBlockPtr_t> &bl
           if (inst->operand_list.size() == 1) {
             assert(Value::is<BasicBlock>(inst->operand_list[0]));
             auto bb_dest = Value::as<BasicBlock>(inst->operand_list[0]);
-            VLOG(6) << "br to " << bb_dest->name;
+            VLOG(7) << "br to " << bb_dest->name;
             assert(bb_dest->ir_seqno >= 0);
             ostr << "label %" << bb_dest->ir_seqno;
           }
@@ -481,7 +481,7 @@ static void _gen_blocks(std::ostream &ostr, const std::list<BasicBlockPtr_t> &bl
 void Visitor::llir_gen(std::ostream &ostr) {
 #pragma region GenLibFuncDecl
   for (auto &lib_func_name : libfunc_list) {
-    VLOG(6) << "Gen LibFunc " << lib_func_name;
+    VLOG(7) << "Gen LibFunc " << lib_func_name;
     auto lib_func      = _func_tab.get_name(lib_func_name).value();
     auto lib_func_type = std::dynamic_pointer_cast<FunctionType>(lib_func->type);
     ostr << "declare"