[backend]重构了后端

src/CMakeLists.txt

@@ -28,6 +28,9 @@ add_executable(sysyc
   Mem2Reg.cpp
   Reg2Mem.cpp
   RISCv64Backend.cpp
+  RISCv64ISel.cpp
+  RISCv64RegAlloc.cpp
+  RISCv64AsmPrinter.cpp
 )
 
 # 设置 include 路径，包含 ANTLR 运行时库和项目头文件