修复若干bug

TODO.md

@@ -3,20 +3,27 @@
 ### 1. **前端必须模块**
 - **词法/语法分析**（已完成）：
   - `SysYLexer`/`SysYParser`：ANTLR生成的解析器
-- **IR生成核心**：
+- **IR生成核心**：(已完成)
   - `SysYIRGenerator`：将AST转换为中间表示（IR）
   - `IRBuilder`：构建指令和基本块的工具类（你们正在实现的部分）
+- **IR打印器**：(基本完成)
+  - `SysYIRPrinter`: 打印llvm ir格式的指令，优化遍后查看优化效果，la指令,subarray数组翻译范式需要改进
 
 ### 2. **中端必要优化（最小集合）**
+- **CFG优化**：(待测试)
+  - `SysYIROptPre`：CFG优化顺便解决IR生成的缺陷（void自动添加ret指令，合并嵌套if/while语句生成的多个exit（后续可以实现回填机制））
+
 常量传播
 | 优化阶段          | 关键作用                          | 是否必须 |
 |-------------------|----------------------------------|----------|
-| `Mem2Reg`         | 消除冗余内存访问，转换为SSA形式   | ✅ 核心   |
+| `Mem2Reg`         | 消除冗余内存访问，转换为SSA形式   | ✅ 核心   |（必须）
-| `DCE` (死代码消除) | 移除无用指令                      | ✅ 必要   |
+| `DCE` (死代码消除) | 移除无用指令                      | ✅ 必要   |（必须）
-| `DFE` (死函数消除) | 移除未使用的函数                  | ✅ 必要   |
+| `DFE` (死函数消除) | 移除未使用的函数                  | ✅ 必要   |（必须）
-| `FuncAnalysis`    | 函数调用关系分析                  | ✅ 基础   |
 | `Global2Local`    | 全局变量降级为局部变量            | ✅ 重要   |
 
+还需要做 Reg2Mem
+
+
 ### 3. **后端核心流程（必须实现）**
 ```mermaid
 graph LR

src/CMakeLists.txt

@@ -17,6 +17,7 @@ add_executable(sysyc
   SysYIRGenerator.cpp
   # Backend.cpp
   SysYIRPrinter.cpp
+  SysYIROptPre.cpp
   RISCv32Backend.cpp
 )
 target_include_directories(sysyc PRIVATE ${CMAKE_CURRENT_BINARY_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/include)

src/SysYIROptPre.cpp

@@ -0,0 +1,489 @@
+/**
+ * @file: Sysyoptimization.cpp
+ * @brief  CFG优化
+ * @Author : Ixeux email:you@domain.com
+ * @Version : 1.0
+ * @Creat Date : 2024-08-10
+ *
+ */
+#include "SysYIROptPre.h"
+#include <cassert>
+#include <list>
+#include <map>
+#include <memory>
+#include <string>
+#include "IR.h"
+#include "IRBuilder.h"
+
+namespace sysy {
+
+/**
+ * use删除operand,以免扰乱后续分析
+ * instr: 要删除的指令
+ */
+void SysYOptPre::usedelete(Instruction *instr) {
+  for (auto &use : instr->getOperands()) {
+    Value* val = use->getValue();
+    // std::cout << delete << val->getName() << std::endl;
+    val->removeUse(use);
+  }
+}
+
+
+// 删除br后的无用指令
+void SysYOptPre::SysYDelInstAfterBr() {
+  auto &functions = pModule->getFunctions();
+  for (auto &function : functions) {
+    auto basicBlocks = function.second->getBasicBlocks();
+    for (auto &basicBlock : basicBlocks) {
+      bool Branch = false;
+      auto &instructions = basicBlock->getInstructions();
+      auto Branchiter = instructions.end();
+      for (auto iter = instructions.begin(); iter != instructions.end(); ++iter) {
+        if (Branch) 
+          usedelete(iter->get());
+        else if ((*iter)->isTerminator()){
+          Branch = true;
+          Branchiter = iter;
+        }
+      }
+      if (Branchiter != instructions.end()) ++Branchiter;
+      while (Branchiter != instructions.end()) 
+        Branchiter = instructions.erase(Branchiter);
+      
+      if (Branch) {  // 更新前驱后继关系
+        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 (thelastinstinst->get()->isUnconditional()) {
+          BasicBlock* branchBlock = dynamic_cast<BasicBlock *>(thelastinstinst->get()->getOperand(0));
+          basicBlock->addSuccessor(branchBlock);
+          branchBlock->addPredecessor(basicBlock.get());
+        } 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());
+          elseBlock->addPredecessor(basicBlock.get());
+        }
+      }
+    }
+  }
+}
+
+
+void SysYOptPre::SysYBlockMerge() {
+  auto &functions = pModule->getFunctions(); //std::map<std::string, std::unique_ptr<Function>>
+  for (auto &function : functions) {
+    // auto basicBlocks = function.second->getBasicBlocks();
+    auto &func = function.second;
+    for (auto blockiter = func->getBasicBlocks().begin();
+         blockiter != func->getBasicBlocks().end();) {
+      if (blockiter->get()->getNumSuccessors() == 1) {
+        // 如果当前块只有一个后继块
+        // 且后继块只有一个前驱块
+        // 则将当前块和后继块合并
+        if (((blockiter->get())->getSuccessors()[0])->getNumPredecessors() == 1) {
+          // std::cout << "merge block: " << blockiter->get()->getName() << std::endl;
+          BasicBlock* block = blockiter->get();
+          BasicBlock* nextBlock = blockiter->get()->getSuccessors()[0];
+          auto nextarguments = nextBlock->getArguments();
+          // 删除br指令
+          if (block->getNumInstructions() != 0) {
+            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 (thelastinstinst->get()->getOperand(1)->getName() == thelastinstinst->get()->getOperand(1)->getName()) {
+                usedelete(thelastinstinst->get());
+                block->getInstructions().erase(thelastinstinst);
+              }
+            }
+          }
+          // 将后继块的指令移动到当前块
+          // 并将后继块的父指针改为当前块
+          for (auto institer = nextBlock->begin(); institer != nextBlock->end();) {
+            institer->get()->setParent(block);
+            block->getInstructions().emplace_back(institer->release());
+            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);
+          }
+          // 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;
+          for (auto &succ : nextBlock->getSuccessors()) {
+            block->addSuccessor(succ);
+            succ->replacePredecessor(nextBlock, block);
+            succshoulddel.push_back(succ);
+          }
+          for (auto del : succshoulddel) {
+            nextBlock->removeSuccessor(del);
+          }
+
+          func->removeBasicBlock(nextBlock);
+
+        } else {
+          blockiter++;
+        }
+      } else {
+        blockiter++;
+      }
+    }
+  }
+}
+
+// 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();) {
+      if (!blockIter->get()->getreachable()) {
+        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，注意迭代器不可达问题
+        func->removeBasicBlock((blockIter++)->get());
+      } else {
+        blockIter++;
+      }
+    }
+  }
+}
+
+void SysYOptPre::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()->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(0))->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 indexphi = 0;
+          for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(1))->getPredecessors()) {
+            if (pred == thelastBlockOld) {
+              break;
+            }
+            indexphi++;
+          }
+
+          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 indexphi = 0;
+          for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(2))->getPredecessors()) {
+            if (pred == thelastBlockOld) {
+              break;
+            }
+            indexphi++;
+          }
+          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 indexphi = 0;
+            for (auto &pred : dynamic_cast<BasicBlock *>(thelastinst->get()->getOperand(0))->getPredecessors()) {
+              if (pred == thelastBlockOld) {
+                break;
+              }
+              indexphi++;
+            }
+
+            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

src/include/IR.h

@@ -372,9 +372,9 @@ class BasicBlock;
   unsigned getNumPredecessors() const { return predecessors.size(); }  ///< 获取前驱数量
   unsigned getNumSuccessors() const { return successors.size(); }      ///< 获取后继数量
   Function* getParent() const { return parent; }                      ///< 获取父函数
-  void setParent(Function *func) { parent = func; }                            ///< 设置父函数
+  void setParent(Function *func) { parent = func; }                   ///< 设置父函数
   inst_list& getInstructions() { return instructions; }               ///< 获取指令列表
-  arg_list& getArguments() { return arguments; }  ///< 获取分配空间后的形式参数列表
+  arg_list& getArguments() { return arguments; }                      ///< 获取分配空间后的形式参数列表
   const block_list& getPredecessors() const { return predecessors; }  ///< 获取前驱列表
   block_list& getSuccessors() { return successors; }                  ///< 获取后继列表
   block_set& getDominants() { return dominants; }

src/include/IRBuilder.h

@@ -315,7 +315,7 @@ class IRBuilder {
 
     auto fatherArrayValue = dynamic_cast<Value *>(fatherArray);
     auto childArray = new AllocaInst(fatherArrayValue->getType(), subDims, block, childArrayName);
-    auto inst = new GetSubArrayInst(fatherArray, childArray, indices, block, name);
+    auto inst = new GetSubArrayInst(fatherArray, childArray, indices, block, childArrayName);
     assert(inst);
     block->getInstructions().emplace(position, inst);
     return inst;

src/include/SysYIROptPre.h

@@ -0,0 +1,37 @@
+#pragma once
+
+#include "IR.h"
+#include "IRBuilder.h"
+
+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;
+  IRBuilder *pBuilder;
+
+ public:
+  SysYOptPre(Module *pMoudle, IRBuilder *pBuilder) : pModule(pMoudle), pBuilder(pBuilder) {}
+
+  void SysYOptimizateAfterIR(){
+    SysYDelInstAfterBr();
+    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
+  void SysYBlockMerge();    // 合并基本块(主要针对嵌套if while的exit块，
+                            // 也可以修改IR生成实现回填机制
+  void SysYAddReturn();     // 添加return指令(主要针对Void函数)
+  void usedelete(Instruction *instr); // use删除
+};
+
+}  // namespace sysy

src/sysyc.cpp

@@ -9,6 +9,7 @@ using namespace antlr4;
 // #include "Backend.h"
 #include "SysYIRGenerator.h"
 #include "SysYIRPrinter.h"
+#include "SysYIROptPre.h"
 // #include "LLVMIRGenerator.h"
 using namespace sysy;
 
@@ -79,6 +80,10 @@ int main(int argc, char **argv) {
     auto moduleIR = generator.get(); 
     SysYPrinter printer(moduleIR);
     printer.printIR();
+    auto builder = generator.getBuilder();
+    SysYOptPre optPre(moduleIR, builder);
+    optPre.SysYOptimizateAfterIR();
+    printer.printIR();
     return EXIT_SUCCESS;
   }
   return EXIT_SUCCESS;