增加Reg2Mem,但是会生成死存储指令，需要死代码删除支持识别死存储指令

src/Reg2Mem.cpp

@@ -0,0 +1,129 @@
+#include "Reg2Mem.h"
+#include <cstddef>
+#include <iostream>
+#include <list>
+#include <memory>
+
+namespace sysy {
+
+/**
+ * 删除phi节点
+ * 删除phi节点后可能会生成冗余存储代码
+ */
+void Reg2Mem::DeletePhiInst(){
+  auto &functions = pModule->getFunctions();
+  for (auto &function : functions) {
+    auto basicBlocks = function.second->getBasicBlocks();
+    for (auto &basicBlock : basicBlocks) {
+
+      for (auto iter = basicBlock->begin(); iter != basicBlock->end();) {
+        auto &instruction = *iter;
+        if (instruction->isPhi()) {
+          auto predBlocks = basicBlock->getPredecessors();
+          // 寻找源和目的
+          // 目的就是phi指令的第一个操作数
+          // 源就是phi指令的后续操作数
+          auto destination = instruction->getOperand(0);
+          int predBlockindex = 0;
+          for (auto &predBlock : predBlocks) {
+            ++predBlockindex;
+            // 判断前驱块儿只有一个后继还是多个后继
+            // 如果有多个
+            auto source = instruction->getOperand(predBlockindex);
+            if (source == destination) {
+              continue;
+            }
+            // std::cout << predBlock->getNumSuccessors() << std::endl;
+            if (predBlock->getNumSuccessors() > 1) {
+              // 创建一个basicblock
+              auto newbasicBlock = function.second->addBasicBlock();
+              std::stringstream ss;
+              ss << " phidel.L" << pBuilder->getLabelIndex();
+              newbasicBlock->setName(ss.str());
+              ss.str("");
+              // // 修改前驱后继关系
+              basicBlock->replacePredecessor(predBlock, newbasicBlock);
+              // predBlock = newbasicBlock;
+              newbasicBlock->addPredecessor(predBlock);
+              newbasicBlock->addSuccessor(basicBlock.get());
+              predBlock->removeSuccessor(basicBlock.get());
+              predBlock->addSuccessor(newbasicBlock);
+              // std::cout << "the block name is " << basicBlock->getName() << std::endl;
+              // for (auto pb : basicBlock->getPredecessors()) {
+              //   // newbasicBlock->addPredecessor(pb);
+              //   std::cout << pb->getName() << std::endl;
+              // }
+              // sysy::BasicBlock::conectBlocks(newbasicBlock, static_cast<BasicBlock *>(basicBlock.get()));
+              // 若后为跳转指令，应该修改跳转指令所到达的位置
+              auto thelastinst = predBlock->end();
+              (--thelastinst);
+
+              if (thelastinst->get()->isConditional() || thelastinst->get()->isUnconditional()) {  // 如果是跳转指令
+                auto opnum = thelastinst->get()->getNumOperands();
+                for (size_t i = 0; i < opnum; i++) {
+                  if (thelastinst->get()->getOperand(i) == basicBlock.get()) {
+                    thelastinst->get()->replaceOperand(i, newbasicBlock);
+                  }
+                }
+              }
+              // 在新块中插入store指令
+              pBuilder->setPosition(newbasicBlock, newbasicBlock->end());
+              // pBuilder->createStoreInst(source, destination);
+              if (source->isInt() || source->isFloat()) {
+                pBuilder->createStoreInst(source, destination);
+              } else {
+                auto loadInst = pBuilder->createLoadInst(source);
+                pBuilder->createStoreInst(loadInst, destination);
+              }
+              // pBuilder->createMoveInst(Instruction::kMove, destination->getType(), destination, source,
+              // newbasicBlock);
+              pBuilder->setPosition(newbasicBlock, newbasicBlock->end());
+              pBuilder->createUncondBrInst(basicBlock.get(), {});
+            } else {
+              // 如果前驱块只有一个后继
+              auto thelastinst = predBlock->end();
+              (--thelastinst);
+              // std::cout << predBlock->getName() << std::endl;
+              // std::cout << thelastinst->get() << std::endl;
+              // std::cout << "First point  11 " << std::endl;
+              if (thelastinst->get()->isConditional() || thelastinst->get()->isUnconditional()) {
+                // 在跳转语句前insert st指令
+                pBuilder->setPosition(predBlock, thelastinst);
+              } else {
+                pBuilder->setPosition(predBlock, predBlock->end());
+              }
+
+              if (source->isInt() || source->isFloat()) {
+                pBuilder->createStoreInst(source, destination);
+              } else {
+                auto loadInst = pBuilder->createLoadInst(source);
+                pBuilder->createStoreInst(loadInst, destination);
+              }
+            }
+          }
+          // 删除phi指令
+          auto &instructions = basicBlock->getInstructions();
+          usedelete(iter->get());
+          iter = instructions.erase(iter);
+          if (basicBlock->getNumInstructions() == 0) {
+            if (basicBlock->getNumSuccessors() == 1) {
+              pBuilder->setPosition(basicBlock.get(), basicBlock->end());
+              pBuilder->createUncondBrInst(basicBlock->getSuccessors()[0], {});
+            }
+          }
+        } else {
+          break;
+        }
+      }
+    }
+  }
+}
+
+void Reg2Mem::usedelete(Instruction *instr) {
+  for (auto &use : instr->getOperands()) {
+    auto val = use->getValue();
+    val->removeUse(use);
+  }
+}
+
+}  // namespace sysy