[midend-reg2mem]增加reg2mem遍，应用未定义值，增加inst迭代器查找方法，通过编译且脚本运行通过率不变

src/include/IR.h

@@ -525,6 +525,10 @@ public:
   iterator begin() { return instructions.begin(); }
   iterator end() { return instructions.end(); }
   iterator terminator() { return std::prev(end()); }
+  iterator findInstIterator(Instruction *inst) {
+    return std::find_if(instructions.begin(), instructions.end(),
+                        [inst](const std::unique_ptr<Instruction> &i) { return i.get() == inst; });
+  }  ///< 查找指定指令的迭代器
   bool hasSuccessor(BasicBlock *block) const {
     return std::find(successors.begin(), successors.end(), block) != successors.end();
   }  ///< 判断是否有后继块