diff --git a/src/SysYIROptPre.cpp b/src/SysYIROptPre.cpp
index 3123801..edd9333 100644
--- a/src/SysYIROptPre.cpp
+++ b/src/SysYIROptPre.cpp
@@ -17,14 +17,6 @@
 
 namespace sysy {
 
-void SysYOptPre::SysYOptimizateAll() -> void {
-  SysYDelAfterBr();
-  SysYBlockMerge();
-  SysYDelNoPreBLock();
-  SysYDelEmptyBlock();
-  SysYAddReturn();
-}
-
 /**
  * use删除operand,以免扰乱后续分析
  * instr: 要删除的指令
@@ -61,20 +53,20 @@ void SysYOptPre::SysYDelInstAfterBr() {
         Branchiter = instructions.erase(Branchiter);
       
       if (Branch) {  // 更新前驱后继关系
-        auto thelastinst = basicBlock->getInstructions().end();
-        --thelastinst;
+        auto thelastinstinst = basicBlock->getInstructions().end();
+        --thelastinstinst;
         auto &Successors = basicBlock->getSuccessors();
         for (auto iterSucc = Successors.begin(); iterSucc != Successors.end();) {
           (*iterSucc)->removePredecessor(basicBlock.get());
           basicBlock->removeSuccessor(*iterSucc);
         }
-        if (thelastinst->get()->isUnconditional()) {
-          BasicBlock* branchBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
+        if (thelastinstinst->get()->isUnconditional()) {
+          BasicBlock* branchBlock = dynamic_cast<BasicBlock *>(thelastinstinst->get()->getOperand(0));
           basicBlock->addSuccessor(branchBlock);
           branchBlock->addPredecessor(basicBlock.get());
-        } else if (thelastinst->get()->isConditional()) {
-          BasicBlock* thenBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
-          BasicBlock* elseBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2));
+        } else if (thelastinstinst->get()->isConditional()) {
+          BasicBlock* thenBlock = dynamic_cast<BasicBlock *>(thelastinstinst->get()->getOperand(1));
+          BasicBlock* elseBlock = dynamic_cast<BasicBlock *>(thelastinstinst->get()->getOperand(2));
           basicBlock->addSuccessor(thenBlock);
           basicBlock->addSuccessor(elseBlock);
           thenBlock->addPredecessor(basicBlock.get());
@@ -90,7 +82,7 @@ void SysYOptPre::SysYBlockMerge() {
   auto &functions = pModule->getFunctions(); //std::map<std::string, std::unique_ptr<Function>>
   for (auto &function : functions) {
     // auto basicBlocks = function.second->getBasicBlocks();
-    Function* func = function.second.get();
+    auto &func = function.second;
     for (auto blockiter = func->getBasicBlocks().begin();
          blockiter != func->getBasicBlocks().end();) {
       if (blockiter->get()->getNumSuccessors() == 1) {
@@ -104,16 +96,16 @@ void SysYOptPre::SysYBlockMerge() {
           auto nextarguments = nextBlock->getArguments();
           // 删除br指令
           if (block->getNumInstructions() != 0) {
-            auto thelastinst = block->end();
-            (--thelastinst);
-            if (thelastinst->get()->isUnconditional()) {
-              usedelete(thelastinst->get());
-              block->getInstructions().erase(thelastinst);
-            } else if (thelastinst->get()->isConditional()) {
+            auto thelastinstinst = block->end();
+            (--thelastinstinst);
+            if (thelastinstinst->get()->isUnconditional()) {
+              usedelete(thelastinstinst->get());
+              block->getInstructions().erase(thelastinstinst);
+            } else if (thelastinstinst->get()->isConditional()) {
               // 如果是条件分支，判断条件是否相同，主要优化相同布尔表达式
-              if (thelastinst->get()->getOperand(1)->getName() == thelastinst->get()->getOperand(1)->getName()) {
-                usedelete(thelastinst->get());
-                block->getInstructions().erase(thelastinst);
+              if (thelastinstinst->get()->getOperand(1)->getName() == thelastinstinst->get()->getOperand(1)->getName()) {
+                usedelete(thelastinstinst->get());
+                block->getInstructions().erase(thelastinstinst);
               }
             }
           }
@@ -125,11 +117,12 @@ void SysYOptPre::SysYBlockMerge() {
             institer = nextBlock->getInstructions().erase(institer);   
           }
           // 合并参数
+          // TODO：是否需要去重?
           for (auto &argm : nextarguments) {
             argm->setParent(block);
             block->insertArgument(argm);
           }
-          // // // 改变block 和 next 之间的关系
+          // 更新前驱后继关系，类似树节点操作
           block->removeSuccessor(nextBlock);
           nextBlock->removePredecessor(block);
           std::list<BasicBlock *> succshoulddel;
@@ -142,16 +135,8 @@ void SysYOptPre::SysYBlockMerge() {
             nextBlock->removeSuccessor(del);
           }
 
-          // // // 添加block 和 next 的后继 之间的关系
-          // block->addSuccessor(nextBlock->getSuccessors()[0]);
-          // nextBlock->getSuccessors()[0]->addPredecessor(blockiter->get());
-          // // // 删除next 和 next后继的关系
-          // nextBlock->getSuccessors()[0]->removePredecessor(nextBlock);
-          // nextBlock->removeSuccessor(nextBlock->getSuccessors()[0]);
-          // std::cout << nextBlock->getName() << std::endl;
+          func->removeBasicBlock(nextBlock);
 
-          function.second->removeBasicBlock(nextBlock);
-          // ++blockiter;
         } else {
           blockiter++;
         }
@@ -162,12 +147,344 @@ void SysYOptPre::SysYBlockMerge() {
   }
 }
 
-
+// 删除无前驱块，兼容SSA后的处理
 void SysYOptPre::SysYDelNoPreBLock() {
+  
+  auto &functions = pModule->getFunctions(); // std::map<std::string, std::unique_ptr<sysy::Function>>
+  for (auto &function : functions) {
+    auto &func = function.second;
+
+    for (auto &block : func->getBasicBlocks()) {
+      block->setreachableFalse();
+    }
+    // 对函数基本块做一个拓扑排序，排查不可达基本块
+    auto entryBlock = func->getEntryBlock();
+    entryBlock->setreachableTrue();
+    std::queue<BasicBlock *> blockqueue;
+    blockqueue.push(entryBlock);
+    while (!blockqueue.empty()) {
+      auto block = blockqueue.front();
+      blockqueue.pop();
+      for (auto &succ : block->getSuccessors()) {
+        if (!succ->getreachable()) {
+          succ->setreachableTrue();
+          blockqueue.push(succ);
+        }
+      }
+    }
+
+    // 删除不可达基本块指令
+    for (auto blockIter = func->getBasicBlocks().begin(); blockIter != func->getBasicBlocks().end();blockIter++) {
+      
+      if (!blockIter->get()->getreachable()) 
+        for (auto &iterInst : blockIter->get()->getInstructions()) 
+          usedelete(iterInst.get());
+    
+    }
+
+    
+    for (auto blockIter = func->getBasicBlocks().begin(); blockIter != func->getBasicBlocks().end();blockIter++) {
+      if (!blockIter->get()->getreachable()) {
+        //// 处理phi指令
+        // 删除不可达基本块的phi指令的操作数
+        for (auto succblock : blockIter->get()->getSuccessors()) {
+          int indexphi = 1;
+          for (auto pred : succblock->getPredecessors()) {
+            if (pred == blockIter->get()) {
+              break;
+            }
+            indexphi++;
+          }
+          for (auto &phiinst : succblock->getInstructions()) {
+            if (phiinst->getKind() != Instruction::kPhi) {
+              break;
+            }
+            phiinst->removeOperand(indexphi);
+          }
+        }
+        // 删除不可达基本块
+        func->removeBasicBlock(blockIter->get());
+      }
+    }
+  }
 }
 
+void SysyOptimization::SysyDelEmptyBlock() {
+  auto &functions = pModule->getFunctions();
+  for (auto &function : functions) {
+    // 收集不可达基本块
+    // 这里的不可达基本块是指没有实际指令的基本块
+    // 当一个基本块没有实际指令例如只有phi指令和一个uncondbr指令时，也会被视作不可达
+    auto basicBlocks = function.second->getBasicBlocks();
+    std::map<sysy::BasicBlock *, BasicBlock *> EmptyBlocks;
+    // 空块儿和后继的基本块的映射
+    for (auto &basicBlock : basicBlocks) {
+      if (basicBlock->getNumInstructions() == 0) {
+        if (basicBlock->getNumSuccessors() == 1) {
+          EmptyBlocks[basicBlock.get()] = basicBlock->getSuccessors().front();
+        }
+      }
+      else{
+        // 如果只有phi指令和一个uncondbr。(phi)*(uncondbr)?
+          // 判断除了最后一个指令之外是不是只有phi指令
+        bool onlyPhi = true;
+        for (auto &inst : basicBlock->getInstructions()) {
+          if (!inst->isPhi() && !inst->isUnconditional()) {
+            onlyPhi = false;
+            break;
+          }
+        }
+        if(onlyPhi)
+          EmptyBlocks[basicBlock.get()] = basicBlock->getSuccessors().front();
+      }
+      
+      
+    }
+    // 更新基本块信息，增加必要指令
+    for (auto &basicBlock : basicBlocks) {
+      // 把空块转换成只有跳转指令的不可达块
+      if (distance(basicBlock->begin(), basicBlock->end()) == 0) {
+        if (basicBlock->getNumSuccessors() == 0) {
+          continue;
+        }
+        if (basicBlock->getNumSuccessors() > 1) {
+          assert("");
+        }
+        pBuilder->setPosition(basicBlock.get(), basicBlock->end());
+        pBuilder->createUncondBrInst(basicBlock->getSuccessors()[0], {});
+        continue;
+      }
 
+      auto thelastinst = basicBlock->getInstructions().end();
+      --thelastinst;
+
+      // 根据br指令传递的后继块信息，跳过空块链
+      if (thelastinst->get()->getKind()->isUnconditional()) {
+        BasicBlock* OldBrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
+        BasicBlock *thelastBlockOld = nullptr;
+        // 如果空块链表为多个块
+        while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))) !=
+               EmptyBlocks.end()) {
+          thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
+          thelastinst->get()->replaceOperand(0, EmptyBlocks[thelastBlockOld]);
+        }
+
+        basicBlock->removeSuccessor(OldBrBlock);
+        OldBrBlock->removePredecessor(basicBlock.get());
+        basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0)));
+        dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->addPredecessor(basicBlock.get());
+
+        if (thelastBlockOld != nullptr) {
+          int indexphi = 0;
+          for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getPredecessors()) {
+            if (pred == thelastBlockOld) {
+              break;
+            }
+            indexphi++;
+          }
+
+          // 更新phi指令的操作数
+          // 移除thelastBlockOld对应的phi操作数
+          for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->getInstructions()) {
+            if (InstInNew->isPhi()) {
+              dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
+            } else {
+              break;
+            }
+          }
+        }
+
+      } else if (thelastinst->get()->getKind() == Instruction::kCondBr) {
+        auto OldThenBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
+        auto OldElseBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2));
+
+        BasicBlock *thelastBlockOld = nullptr;
+        while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))) !=
+               EmptyBlocks.end()) {
+          thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
+          thelastinst->get()->replaceOperand(
+              1, EmptyBlocks[dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))]);
+        }
+        basicBlock->removeSuccessor(OldThenBlock);
+        OldThenBlock->removePredecessor(basicBlock.get());
+        // 处理 then 和 else 分支合并的情况
+        if (dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1)) ==
+            dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))) {
+          auto thebrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
+          usedelete(thelastinst->get());
+          thelastinst = basicBlock->getInstructions().erase(thelastinst);
+          pBuilder->setPosition(basicBlock.get(), basicBlock->end());
+          pBuilder->createUncondBrInst(thebrBlock, {});
+          continue;
+        }
+        basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1)));
+        dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->addPredecessor(basicBlock.get());
+        // auto indexInNew = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getPredecessors().
+
+        if (thelastBlockOld != nullptr) {
+          int index = 0;
+          for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->getPredecessors()) {
+            if (pred == thelastBlockOld) {
+              break;
+            }
+            index++;
+          }
+
+          for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->getInstructions()) {
+            if (InstInNew->isPhi()) {
+              dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
+            } else {
+              break;
+            }
+          }
+        }
+
+        thelastBlockOld = nullptr;
+        while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))) !=
+               EmptyBlocks.end()) {
+          thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2));
+          thelastinst->get()->replaceOperand(
+              2, EmptyBlocks[dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))]);
+        }
+        basicBlock->removeSuccessor(OldElseBlock);
+        OldElseBlock->removePredecessor(basicBlock.get());
+        // 处理 then 和 else 分支合并的情况
+        if (dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1)) ==
+            dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))) {
+          auto thebrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1));
+          usedelete(thelastinst->get());
+          thelastinst = basicBlock->getInstructions().erase(thelastinst);
+          pBuilder->setPosition(basicBlock.get(), basicBlock->end());
+          pBuilder->createUncondBrInst(thebrBlock, {});
+          continue;
+        }
+        basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2)));
+        dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))->addPredecessor(basicBlock.get());
+
+        if (thelastBlockOld != nullptr) {
+          int index = 0;
+          for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))->getPredecessors()) {
+            if (pred == thelastBlockOld) {
+              break;
+            }
+            index++;
+          }
+          for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))->getInstructions()) {
+            if (InstInNew->isPhi()) {
+              dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
+            } else {
+              break;
+            }
+          }
+        }
+      } else {
+        if (basicBlock->getNumSuccessors() == 1) {
+          pBuilder->setPosition(basicBlock.get(), basicBlock->end());
+          pBuilder->createUncondBrInst(basicBlock->getSuccessors()[0], {});
+          auto thelastinst = basicBlock->getInstructions().end();
+          (--thelastinst);
+          auto OldBrBlock = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
+          sysy::BasicBlock *thelastBlockOld = nullptr;
+          while (EmptyBlocks.find(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))) !=
+                 EmptyBlocks.end()) {
+            thelastBlockOld = dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0));
+
+            thelastinst->get()->replaceOperand(
+                0, EmptyBlocks[dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))]);
+          }
+          
+          basicBlock->removeSuccessor(OldBrBlock);
+          OldBrBlock->removePredecessor(basicBlock.get());
+          basicBlock->addSuccessor(dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0)));
+          dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->addPredecessor(basicBlock.get());
+          if (thelastBlockOld != nullptr) {
+            int index = 0;
+            for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getPredecessors()) {
+              if (pred == thelastBlockOld) {
+                break;
+              }
+              index++;
+            }
+
+            for (auto &InstInNew : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getInstructions()) {
+              if (InstInNew->isPhi()) {
+                dynamic_cast<PhiInst *>(InstInNew.get())->removeOperand(indexphi + 1);
+              } else {
+                break;
+              }
+            }
+          }
+        }
+      }
+    }
+
+    for (auto iter = function.second->getBasicBlocks().begin(); iter != function.second->getBasicBlocks().end();) {
+      
+      if (EmptyBlocks.find(iter->get()) != EmptyBlocks.end()) {
+        // EntryBlock跳过
+        if (iter->get() == function.second->getEntryBlock()) {
+          ++iter;
+          continue;
+        }
+
+        for (auto &iterInst : iter->get()->getInstructions()) 
+          usedelete(iterInst.get());
+        // 删除不可达基本块的phi指令的操作数
+        for (auto &succ : iter->get()->getSuccessors()) {
+          int index = 0;
+          for (auto &pred : succ->getPredecessors()) {
+            if (pred == iter->get()) {
+              break;
+            }
+            index++;
+          }
+
+          for (auto &instinsucc : succ->getInstructions()) {
+            if (instinsucc->isPhi()) {
+              dynamic_cast<PhiInst *>(instinsucc.get())->removeOperand(index);
+            } else {
+              break;
+            }
+          }
+        }
+
+        function.second->removeBasicBlock((iter++)->get());
+      } else {
+        ++iter;
+      }
+    }
+  }
+}
+
+// 如果函数没有返回指令，则添加一个默认返回指令(主要解决void函数没有返回指令的问题)
 void SysYOptPre::SysYAddReturn() {
+  auto &functions = pModule->getFunctions();
+  for (auto &function : functions) {
+    auto &func = function.second;
+    auto &basicBlocks = func->getBasicBlocks();
+    for (auto &block : basicBlocks) {
+      if (block->getNumSuccessors() == 0) {
+        // 如果基本块没有后继块，则添加一个返回指令
+        if (block->getNumInstructions() == 0) {
+          pBuilder->setPosition(block.get(), block->end());
+          pBuilder->createReturnInst({});
+        }
+        auto thelastinst = block->getInstructions().end();
+        --thelastinst;
+        if (thelastinst->get()->getKind() != Instruction::kReturn) {
+          pBuilder->setPosition(block.get(), block->end());
+          // TODO: 如果int float函数缺少返回值是否需要报错
+          if (func->getReturnType()->isInt()) {
+            pBuilder->createReturnInst(ConstantValue::get(0));
+          } else if (func->getReturnType()->isFloat()) {
+            pBuilder->createReturnInst(ConstantValue::get(0.0F));
+          } else {
+            pBuilder->createReturnInst({});
+          }
+        }
+      }
+    }
+  }
 }
 
 }  // namespace sysy
diff --git a/src/include/SysYIROptPre.h b/src/include/SysYIROptPre.h
index 71a723d..db27b82 100644
--- a/src/include/SysYIROptPre.h
+++ b/src/include/SysYIROptPre.h
@@ -7,6 +7,9 @@ namespace sysy {
 
 // 优化前对SysY IR的预处理，也可以视作部分CFG优化
 // 主要包括删除无用指令、合并基本块、删除空块等
+// 这些操作可以在SysY IR生成时就完成，但为了简化IR生成过程，
+// 这里将其放在SysY IR生成后进行预处理
+// 同时兼容phi节点的处理，可以再mem2reg后再次调用优化
 class SysYOptPre {
  private:
   Module *pModule;
@@ -15,6 +18,13 @@ class SysYOptPre {
  public:
   SysYOptPre(Module *pMoudle, IRBuilder *pBuilder) : pModule(pMoudle), pBuilder(pBuilder) {}
 
+  void SysYOptimizateAfterIR(){
+    SysYDelAfterBr();
+    SysYBlockMerge();
+    SysYDelNoPreBLock();
+    SysYDelEmptyBlock();
+    SysYAddReturn();
+  }
   void SysYDelInstAfterBr(); // 删除br后面的指令
   void SysYDelEmptyBlock(); // 空块删除
   void SysYDelNoPreBLock(); // 删除无前驱块