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/include/Reg2Mem.h

@@ -0,0 +1,23 @@
+#pragma once
+
+#include "IR.h"
+#include "IRBuilder.h"
+
+namespace sysy {
+/**
+ * Reg2Mem(后端未做phi指令翻译)
+ */
+class Reg2Mem {
+private:
+  Module *pModule;
+  IRBuilder *pBuilder;
+
+public:
+  Reg2Mem(Module *pMoudle, IRBuilder *pBuilder) : pModule(pMoudle), pBuilder(pBuilder) {}
+
+  void DeletePhiInst();
+  // 删除UD关系, 因为删除了phi指令会修改ud关系
+  void usedelete(Instruction *instr);
+};
+
+} // namespace sysy