diff --git a/include/picrin.h b/include/picrin.h
index 7f9015e4..be785106 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -11,6 +11,12 @@ struct pic_env {
   struct pic_env *parent;
 };
 
+struct pic_proc {
+  union {
+    struct pic_irep *irep;
+  } u;
+};
+
 typedef struct {
   pic_value *sp;
   pic_value *stbase, *stend;
@@ -36,6 +42,8 @@ pic_value pic_intern_cstr(pic_state *, const char *);
 pic_value pic_parse(pic_state *, const char *);
 
 pic_value pic_eval(pic_state *, pic_value, struct pic_env *);
+pic_value pic_run(pic_state *, struct pic_proc *, pic_value);
+struct pic_proc *pic_codegen(pic_state *, pic_value, struct pic_env*);
 
 void pic_debug(pic_state *, pic_value);
 
diff --git a/src/vm.c b/src/vm.c
index 2617e686..51dabcc9 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -3,7 +3,9 @@
 #include "picrin.h"
 
 enum pic_instruction {
+  OP_PUSHNIL,
   OP_PUSHI,
+  OP_CONS,
   OP_ADD,
   OP_STOP
 };
@@ -15,10 +17,9 @@ struct pic_code {
   } u;
 };
 
-struct pic_proc {
-  union {
-    struct pic_code *code;
-  } u;
+struct pic_irep {
+  struct pic_code *code;
+  size_t clen, ccapa;
 };
 
 pic_value
@@ -27,15 +28,26 @@ pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
   struct pic_code *pc;
   pic_value *sp;
 
-  pc = proc->u.code;
+  pc = proc->u.irep->code;
   sp = pic->sp;
 
   while (1) {
     switch (pc->insn) {
+    case OP_PUSHNIL: {
+      *++sp = pic_nil_value();
+      break;
+    }
     case OP_PUSHI: {
       *++sp = pic_int_value(pc->u.i);
       break;
     }
+    case OP_CONS: {
+      pic_value a, b;
+      a = *sp--;
+      b = *sp--;
+      *++sp = pic_cons(pic, a, b);
+      break;
+    }
     case OP_ADD: {
       pic_value a, b;
       a = *sp--;
@@ -53,6 +65,79 @@ pic_run(pic_state *pic, struct pic_proc *proc, pic_value args)
   return *sp;
 }
 
+void
+pic_gen(pic_state *pic, struct pic_irep *irep, pic_value obj, struct pic_env *env)
+{
+  pic_value sCONS, sADD;
+
+  sCONS = pic_intern_cstr(pic, "cons");
+  sADD = pic_intern_cstr(pic, "add");
+
+  switch (pic_type(obj)) {
+  case PIC_TT_SYMBOL: {
+    /* not implemented */
+    break;
+  }
+  case PIC_TT_PAIR: {
+    pic_value proc;
+
+    proc = pic_car(pic, obj);
+    if (pic_eq_p(pic, proc, sCONS)) {
+      /* generate args in reverse order*/
+      pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))), env);
+      pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, obj)), env);
+      irep->code[irep->clen].insn = OP_CONS;
+      irep->clen++;
+      break;
+    }
+    else if (pic_eq_p(pic, proc, sADD)) {
+      /* generate args in reverse order*/
+      pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, pic_cdr(pic, obj))), env);
+      pic_gen(pic, irep, pic_car(pic, pic_cdr(pic, obj)), env);
+      irep->code[irep->clen].insn = OP_ADD;
+      irep->clen++;
+      break;
+    }
+    else {
+      /* not implemented */
+      break;
+    }
+  }
+  case PIC_TT_INT: {
+    irep->code[irep->clen].insn = OP_PUSHI;
+    irep->code[irep->clen].u.i = pic_int(obj);
+    irep->clen++;
+    break;
+  }
+  case PIC_TT_NIL: {
+    irep->code[irep->clen].insn = OP_PUSHNIL;
+    irep->clen++;
+    break;
+  }
+  }
+}
+
+struct pic_proc *
+pic_codegen(pic_state *pic, pic_value obj, struct pic_env *env)
+{
+  struct pic_proc *proc;
+  struct pic_irep *irep;
+  struct pic_code *code;
+
+  proc = pic_alloc(pic, sizeof(struct pic_proc));
+
+  proc->u.irep = irep = (struct pic_irep *)malloc(sizeof(struct pic_irep));
+  irep->code = code = (struct pic_code *)malloc(sizeof(struct pic_code) * 1024);
+  irep->clen = 0;
+  irep->ccapa = 1024;
+
+  pic_gen(pic, irep, obj, env);
+  irep->code[irep->clen].insn = OP_STOP;
+  irep->clen++;
+
+  return proc;
+}
+
 int
 main()
 {