diff --git a/examples/matrix.cpp b/examples/matrix.cpp
index 0c42165bc..09bbcb593 100644
--- a/examples/matrix.cpp
+++ b/examples/matrix.cpp
@@ -15,11 +15,14 @@ const char src[] =
 "\
 void test(fp32 *A, fp32 *B, fp32 *C, int32 i){\
   int32 j = 1;\
-  int32 test[16, 16] = 0;\
-  int32 test2[16, 16];\
-  int32 test3[16, 16];\
   int32 k;\
-  test = test2 + test3;\
+  i = i + j;\
+  for(k = 0; k < 10; k = k+1){\
+    int32 u = 1;\
+    u = u + i;\
+    if(k == 0)\
+     u = u + 2;\
+  }\
 }\
 ";
 
diff --git a/include/ir/builder.h b/include/ir/builder.h
index 4e1fd922c..3e0ba4293 100644
--- a/include/ir/builder.h
+++ b/include/ir/builder.h
@@ -1,6 +1,7 @@
 #ifndef TDL_INCLUDE_IR_BUILDER_H
 #define TDL_INCLUDE_IR_BUILDER_H
 
+#include <iostream>
 #include <vector>
 #include <string>
 #include "instructions.h"
@@ -37,9 +38,12 @@ public:
   // Insert
   template<typename InstTy>
   InstTy* insert(InstTy *inst, const std::string &name = ""){
-    if(block_)
-      block_->get_inst_list().insert(insert_point_, inst);
+    assert(block_);
+    block_->get_inst_list().insert(insert_point_, inst);
+    inst->set_parent(block_);
     inst->set_name(name);
+    insert_point_ = block_->end();
+    return inst;
   }
   // terminator instructions
   value* create_br(basic_block *dest);
diff --git a/include/ir/function.h b/include/ir/function.h
index 456faf5f3..52b1579d7 100644
--- a/include/ir/function.h
+++ b/include/ir/function.h
@@ -39,8 +39,6 @@ public:
   arg_iterator arg_end() { return args_.end(); }
   const_arg_iterator arg_begin() const { return args_.begin(); }
   const_arg_iterator arg_end() const { return args_.end(); }
-  // Accessors
-  function_type* get_function_ty() const;
   // Factory methods
   static function *create(function_type *ty, linkage_types_t linkage,
                           const std::string &name, module *mod);
@@ -49,6 +47,7 @@ private:
   module *parent_;
   args_t args_;
   bool init_;
+  function_type *fn_ty_;
 };
 
 }
diff --git a/include/ir/instructions.h b/include/ir/instructions.h
index 1d7ecffcd..53d437082 100644
--- a/include/ir/instructions.h
+++ b/include/ir/instructions.h
@@ -23,8 +23,9 @@ protected:
 public:
 
   // parent
-  const basic_block *get_parent() const { return parent_;}
-  basic_block *get_parent()             { return parent_; }
+  void set_parent(basic_block *block)   { parent_ = block; }
+  const basic_block *get_parent() const { return parent_;  }
+  basic_block *get_parent()             { return parent_;  }
 
 private:
   basic_block *parent_;
@@ -148,7 +149,7 @@ public:
   typedef llvm::CastInst::CastOps op_t;
 
 private:
-  bool is_valid(op_t op, value *arg, type *ty);
+  static bool is_valid(op_t op, value *arg, type *ty);
 
 public:
   // Factory methods
diff --git a/include/ir/type.h b/include/ir/type.h
index ebbbe5952..c089df4c2 100644
--- a/include/ir/type.h
+++ b/include/ir/type.h
@@ -2,6 +2,7 @@
 #define TDL_INCLUDE_IR_TYPE_H
 
 #include <vector>
+#include <iostream>
 
 namespace tdl{
 namespace ir{
@@ -34,7 +35,7 @@ public:
 
 public:
   //constructors
-  type(context &ctx, id_t id) : ctx_(ctx), id_(id) {}
+  type(context &ctx, id_t id) : ctx_(ctx), id_(id) { }
 
   //destructor
   virtual ~type(){}
diff --git a/include/ir/value.h b/include/ir/value.h
index bab034603..c8b162071 100644
--- a/include/ir/value.h
+++ b/include/ir/value.h
@@ -24,6 +24,7 @@ public:
   void add_use(use *arg);
   // name
   void set_name(const std::string &name);
+  const std::string &get_name() const { return name_; }
   type* get_type() const { return ty_; }
 
 private:
diff --git a/lib/codegen.cpp b/lib/codegen.cpp
index d6f41bba3..12732b1b4 100644
--- a/lib/codegen.cpp
+++ b/lib/codegen.cpp
@@ -310,7 +310,7 @@ inline void implicit_broadcast(ir::module *mod, ir::builder &builder, ir::value
 ir::value *binary_operator::llvm_op(ir::module *mod, ir::builder &builder, ir::value *lhs, ir::value *rhs, const std::string &name) const
 {
   bool is_float = false, is_ptr = false, is_int = false, is_signed = false;
-//  implicit_cast(builder, lhs, rhs, is_float, is_ptr, is_int, is_signed);
+  implicit_cast(builder, lhs, rhs, is_float, is_ptr, is_int, is_signed);
 //  implicit_broadcast(mod, builder, lhs, rhs);
   if(op_==MUL && is_float)
     return builder.create_fmul(lhs, rhs, name);
diff --git a/lib/ir/basic_block.cpp b/lib/ir/basic_block.cpp
index 359c55d0c..29361b3b7 100644
--- a/lib/ir/basic_block.cpp
+++ b/lib/ir/basic_block.cpp
@@ -9,18 +9,22 @@ class phi_node;
 
 basic_block::basic_block(context &ctx, const std::string &name, function *parent):
   value(type::get_label_ty(ctx), name), ctx_(ctx), parent_(parent){
-
 }
 
 basic_block* basic_block::create(context &ctx, const std::string &name, function *parent){
   return new basic_block(ctx, name, parent);
 }
 
+void basic_block::add_predecessor(basic_block *pred) {
+  preds_.push_back(pred);
+}
+
 basic_block::iterator basic_block::get_first_non_phi(){
   auto it = begin();
   for(; it != end(); it++)
-  if(!dynamic_cast<phi_node*>(*it))
+  if(!dynamic_cast<phi_node*>(*it)){
     return it;
+  }
   return it;
 }
 
diff --git a/lib/ir/builder.cpp b/lib/ir/builder.cpp
index b26c1946e..a2c7ef809 100644
--- a/lib/ir/builder.cpp
+++ b/lib/ir/builder.cpp
@@ -35,16 +35,25 @@ value *builder::get_int32(unsigned val) {
   return constant_int::get(type::get_int32_ty(ctx_), val);
 }
 
+type *builder::get_float_ty()
+{ return type::get_float_ty(ctx_); }
+
+type *builder::get_double_ty()
+{ return type::get_double_ty(ctx_); }
+
 
 //===----------------------------------------------------------------------===//
 //                               terminator instructions
 //===----------------------------------------------------------------------===//
 
 value* builder::create_br(basic_block *dest){
+  dest->add_predecessor(block_);
   return insert(branch_inst::create(dest));
 }
 
 value* builder::create_cond_br(value *cond, basic_block *if_dest, basic_block *else_dest){
+  if_dest->add_predecessor(block_);
+  else_dest->add_predecessor(block_);
   return insert(branch_inst::create(cond, if_dest, else_dest));
 }
 
diff --git a/lib/ir/function.cpp b/lib/ir/function.cpp
index b7cc14df5..2def17325 100644
--- a/lib/ir/function.cpp
+++ b/lib/ir/function.cpp
@@ -18,16 +18,16 @@ argument *argument::create(type *ty, const std::string &name,
 /* function */
 function::function(function_type *ty, linkage_types_t linkage,
                    const std::string &name, module *parent)
-    : global_object(ty, 0, linkage, name), parent_(parent) {
+    : global_object(ty, 0, linkage, name), parent_(parent), fn_ty_(ty) {
+  unsigned num_params = fn_ty_->get_num_params();
+  // skip if no parameter
+  if(num_params == 0)
+    return;
   // create arguments
-  function_type *fn_ty = get_function_ty();
-  unsigned num_params = fn_ty->get_num_params();
-  if(num_params > 0) {
-    args_.resize(num_params);
-    for(unsigned i = 0; i < num_params; i++){
-      type *param_ty = fn_ty->get_param_ty(i);
-      args_.push_back(argument::create(param_ty, "", this, i));
-    }
+  args_.resize(num_params);
+  for(unsigned i = 0; i < num_params; i++){
+    type *param_ty = fn_ty_->get_param_ty(i);
+    args_[i] = argument::create(param_ty, "", this, i);
   }
 }
 
@@ -38,10 +38,6 @@ function *function::create(function_type *ty, linkage_types_t linkage,
 }
 
 
-function_type* function::get_function_ty() const
-{ return static_cast<function_type*>(get_type()); }
-
-
 }
 }
 
diff --git a/lib/ir/instructions.cpp b/lib/ir/instructions.cpp
index d330e015d..92a42fb00 100644
--- a/lib/ir/instructions.cpp
+++ b/lib/ir/instructions.cpp
@@ -26,7 +26,7 @@ instruction::instruction(type *ty, unsigned num_ops, const std::string &name, in
 //===----------------------------------------------------------------------===//
 
 phi_node::phi_node(type *ty, unsigned num_reserved, std::string const &name, instruction *next)
-  : instruction(ty, num_reserved, name, next){ }
+  : instruction(ty, num_reserved, name, next), blocks_(num_reserved){ }
 
 // Set incoming value
 void phi_node::set_incoming_value(unsigned i, value *v){
@@ -152,6 +152,11 @@ unary_inst::unary_inst(type *ty, value *v, const std::string &name, instruction
 //                               cast_inst classes
 //===----------------------------------------------------------------------===//
 
+// TODO
+bool cast_inst::is_valid(op_t op, value *arg, type *ty) {
+  return true;
+}
+
 cast_inst *cast_inst::create(op_t op, value *arg, type *ty, const std::string &name, instruction *next){
   assert(is_valid(op, arg, ty) && "Invalid cast!");
   // Construct and return the appropriate CastInst subclass
diff --git a/lib/ir/module.cpp b/lib/ir/module.cpp
index c1979881b..d5ad53e26 100644
--- a/lib/ir/module.cpp
+++ b/lib/ir/module.cpp
@@ -1,5 +1,6 @@
 #include "ir/basic_block.h"
 #include "ir/module.h"
+#include "ir/type.h"
 
 namespace tdl{
 namespace ir{
@@ -28,10 +29,10 @@ void module::set_value(const std::string& name, ir::value *value){
 
 ir::phi_node* module::make_phi(ir::type *ty, unsigned num_values, ir::basic_block *block){
   basic_block::iterator insert = block->get_first_non_phi();
-  if(insert == block->end())
+  if(*insert)
     builder_.set_insert_point(insert);
   ir::phi_node *res = builder_.create_phi(ty, num_values);
-  if(insert == block->end())
+  if(*insert)
     builder_.set_insert_point(block);
   return res;
 }