[midend]部分DCE遍实现（传播活跃代码），修改优化遍运行逻辑，TODO：完善优化遍的getAnalysisUsage，删除无用代码

src/CMakeLists.txt

@@ -25,7 +25,7 @@ add_executable(sysyc
   Pass.cpp
   Dom.cpp
   Liveness.cpp
-  # DeadCodeElimination.cpp
+  DCE.cpp
   AddressCalculationExpansion.cpp
   # Mem2Reg.cpp
   # Reg2Mem.cpp