diff --git a/README.md b/README.md
index 4e0c9f97..67eda464 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ Generate high-firrtl from chirrtl (using [firrtl](https://github.com/chipsallian
 
     $./firrtl/utils/bin/firrtl -i SimTop.fir -X high -o SimTop.hi.fir
 
-Compile high-firttl to C++
+Compile high-firrtl to C++
 
     $ make compile MODE=0
 
diff --git a/src/.patternDetect.cpp.swp b/src/.patternDetect.cpp.swp
new file mode 100644
index 00000000..7a2ca767
Binary files /dev/null and b/src/.patternDetect.cpp.swp differ
diff --git a/src/exprOpt.cpp b/src/exprOpt.cpp
index 5a795d30..23a367aa 100644
--- a/src/exprOpt.cpp
+++ b/src/exprOpt.cpp
@@ -90,7 +90,8 @@ void ExpTree::treeOpt() {
       }
       continue;
     }
-    /* width = 1 xor 0*/
+    
+    /* width = 1 or 0*/
     for (size_t i = 0; i < top->child.size(); i ++) {
       if (top->child[i]) s.push(std::make_tuple(top->child[i], top, i));
     }
@@ -119,4 +120,4 @@ void graph::exprOpt() {
   }
 
   reconnectAll();
-}
+}
\ No newline at end of file
diff --git a/src/patternDetect.cpp b/src/patternDetect.cpp
index 8adf5e9e..f0efdffa 100644
--- a/src/patternDetect.cpp
+++ b/src/patternDetect.cpp
@@ -1,6 +1,7 @@
 #include <cstdio>
 #include <string>
 #include "common.h"
+#include <stack>
 /* detect and optimize some specific patterns */
 /* behind constantAnalysis */
 Node* getLeafNode(bool isArray, ENode* enode);
@@ -22,7 +23,55 @@ static ENode* isDshlOne(ENode* enode) {
 static bool isBitsOne(ENode* enode) {
   return (enode->opType == OP_BITS && enode->values[0] == enode->values[1]);
 }
-bool checkPatern1(Node* node) {
+// [(1 << expr) &  1] -> (expr == 0)
+// if (pattern == (A & 1)) return A
+// else return nullptr
+static ENode* isBitAndOne(ENode* enode) {
+  if (enode->opType != OP_AND || enode->getChild(1)->opType != OP_INT) {
+    return nullptr;
+  }
+  auto value = firStrBase(enode->getChild(1)->strVal);
+  if (value.second != "1") {
+    return nullptr;
+  }
+  if (!enode->getChild(0)) {
+    return nullptr;
+  }
+  return enode->getChild(0);
+}
+
+/* pattern 4:
+  node expr_lo = cat(expr_A, expr_B) 
+  node expr_hi = cat(expr_C, expr_D) 
+  node _expr_T = cat(expr_hi, expr_lo) 
+  node expr = orr(_expr_T) 
+  optimize:
+  expr = ( orr(expr_A) | orr(expr_B) | orr(expr_C) | orr(expr_D) )
+*/
+bool checkNestedCat(ENode* enode, std::vector<ENode*>& leafNodes, bool hasCat) {
+  if (enode->opType == OP_EMPTY && enode->nodePtr) {
+    Node* refNode = enode->nodePtr;
+    if (refNode->assignTree.size() == 1) {
+      return checkNestedCat(refNode->assignTree[0]->getRoot(), leafNodes, hasCat);
+    }
+    return false;
+  }
+  if (enode->opType == OP_CAT) {
+    if (!enode->getChild(0) || !enode->getChild(1)) {
+      return false;
+    }
+    hasCat = true;
+    return checkNestedCat(enode->getChild(0), leafNodes, hasCat) && checkNestedCat(enode->getChild(1), leafNodes, hasCat);
+  }
+  if (enode->opType == OP_BITS && hasCat) {
+    leafNodes.push_back(enode);
+    return true;
+  }
+  return false;
+}
+
+// (1 << expr) 
+bool checkPattern1(Node* node) {
   if (node->isArray() || node->type != NODE_OTHERS || node->assignTree.size() != 1) return false;
   ENode* root = node->assignTree[0]->getRoot();
   ENode* shiftENode = isDshlOne(root);
@@ -47,15 +96,181 @@ bool checkPatern1(Node* node) {
   if (ret) node->status = DEAD_NODE;
   return ret;
 }
+// ((1<<expr) & 1) 
+bool checkPattern2(Node* node) {
+  if (node->isArray() || node->type != NODE_OTHERS || node->assignTree.size() != 1) {
+    return false;
+  }
+  ENode* root = node->assignTree[0]->getRoot();
+  ENode* bitAndNode = isBitAndOne(root);
+
+
+  // if (pattern == (A & 1)) bitAndNode is A
+  if (!bitAndNode) {
+    return false;
+  }
+  
+  ENode* shiftNode = nullptr;
+  if (bitAndNode->opType == OP_DSHL && bitAndNode->getChild(0)->opType == OP_INT && firStrBase(bitAndNode->getChild(0)->strVal).second == "1") {
+    shiftNode = bitAndNode->getChild(1);
+  } else {
+    shiftNode = nullptr;
+  }
+
+  if (!shiftNode) {
+    return false;
+  }
+  return true;
+}
+
+// A & 1
+bool checkPattern3(Node *node) {
+  if (node->isArray() || node->type != NODE_OTHERS || node->assignTree.size() != 1) {
+    return false;
+  }
+  ENode* root = node->assignTree[0]->getRoot();
+  if (root->opType != OP_AND) {
+    return false;
+  }
+  if (root->getChild(1)->opType != OP_INT) {
+    return false;
+  }
+  auto value = firStrBase(root->getChild(1)->strVal);
+  if (value.second != "1") {
+    return false;
+  }
+  return true;
+}
+
+/* orr (expr), expr = cat(expr_A, expr_B)
+ * orr(cat(expr_A, expr_B))
+ * maybe recursive
+ */
+bool checkPattern4(Node* node) {
+  if (node->isArray() || node->type != NODE_OTHERS || node->assignTree.size() != 1) {
+    return false;
+  }
+  ENode* root = node->assignTree[0]->getRoot();
+  if (root->opType != OP_ORR) {
+    return false;
+  }
+  std::vector<ENode*> leafNodes;
+  if (!root->getChild(0)) {
+    return false; // never happen
+  }
+  bool res = checkNestedCat(root->getChild(0), leafNodes, false);
+  if (res && leafNodes.size() > 1) {
+    ENode* newRoot = new ENode(OP_OR);
+    newRoot->width = root->width;
+    newRoot->sign = root->sign;
+    for (ENode* leaf : leafNodes) {
+      ENode* orr = new ENode(OP_ORR);
+      orr->width = 1;
+      orr->addChild(leaf->dup());
+      newRoot->addChild(orr);
+    }
+    printf("p4 tree before optimize:\n");
+    root->display();
+    ExpTree* newTree = new ExpTree(newRoot, new ENode(node));
+    node->assignTree.clear();
+    node->assignTree.push_back(newTree);
+    printf("p4 tree after optimize:\n");
+    newTree->display();
+  }
+  return res;
+}
+
+void testCheckPattern4() {
+  Node *node = new Node();
+  node->type = NODE_OTHERS;
+  node->assignTree.push_back(new ExpTree(new ENode(OP_ORR)));
+  ENode *orr = node->assignTree[0]->getRoot();
+  orr->addChild(new ENode(OP_CAT));
+  ENode* cat = orr->getChild(0);
+  ENode* bits1 = new ENode(OP_BITS);
+  bits1->width = 2;
+  bits1->addVal(0);
+  bits1->addVal(1);
+  cat->addChild(bits1);
+  ENode* bits2 = new ENode(OP_BITS);
+  bits2->width = 2;
+  bits2->addVal(0);
+  bits2->addVal(1);
+  cat->addChild(bits2);
+  Assert(checkPattern4(node), "testCheckPattern4 case 1 failed");
+
+  // Test case for pattern: node B = cat(C, D); node A = orr(B);
+  Node *nodeB = new Node();
+  nodeB->type = NODE_OTHERS;
+  nodeB->assignTree.push_back(new ExpTree(new ENode(OP_CAT)));
+  ENode *catB = nodeB->assignTree[0]->getRoot();
+  
+  // Add children C and D to cat node
+  ENode* enodeC = new ENode(OP_BITS);
+  enodeC->width = 2;
+  enodeC->addVal(0);
+  enodeC->addVal(1);
+  catB->addChild(enodeC);
+  
+  ENode* enodeD = new ENode(OP_BITS); 
+  enodeD->width = 2;
+  enodeD->addVal(0);
+  enodeD->addVal(1);
+  catB->addChild(enodeD);
+
+  // Create node A with orr operation
+  Node *nodeA = new Node();
+  nodeA->type = NODE_OTHERS;
+  nodeA->assignTree.push_back(new ExpTree(new ENode(OP_ORR)));
+  ENode *orrA = nodeA->assignTree[0]->getRoot();
+  
+  // Link orr to node B
+  ENode *refB = new ENode(OP_EMPTY);
+  refB->nodePtr = nodeB;
+  orrA->addChild(refB);
+
+  Assert(checkPattern4(nodeA), "testCheckPattern4 case 2 failed");
+}
 
 void graph::patternDetect() {
   int num1 = 0;
+  int num2 = 0;
+  int num3 = 0;
+  int num4 = 0;
+
+  //testCheckPattern4();
+
+  // check pattern4
+  for (SuperNode* super : sortedSuper) {
+    for (Node* member : super->member) {
+      num4 += checkPattern4(member);
+    }
+  }
+
+  // check pattern3
+  for (SuperNode* super : sortedSuper) {
+    for (Node* member : super->member) {
+      num3 += checkPattern3(member);
+    }
+  }
+
+  // check pattern2
+  for (SuperNode* super : sortedSuper) {
+    for (Node* member : super->member) {
+      num2 += checkPattern2(member);
+    }
+  }
+
+
+  // check pattern1, and optimize
   for (SuperNode* super : sortedSuper) {
     for (Node* member : super->member) {
-      num1 += checkPatern1(member);
+      num1 += checkPattern1(member);
     }
   }
   removeNodesNoConnect(DEAD_NODE);
   reconnectAll();
-  printf("[patternDetect] find %d pattern1\n", num1);
-}
\ No newline at end of file
+  printf("[patternDetect] find %d pattern1, %d pattern2((1<<expr) & 1), %d pattern3(A & 1) %d pattern4(orr(cat(expr)))\n", num1, num2, num3, num4);
+}
+
+