[死代码删除]:保证扩展性、模块化构建死代码删除，包括消除无用store,alloca,load,globalval,mem2reg引入的无用alloca以及reg2mem导致的store-load-store冗余存储

src/sysyc.cpp

@@ -11,6 +11,7 @@ using namespace antlr4;
 #include "SysYIRPrinter.h"
 #include "SysYIROptPre.h"
 #include "SysYIRAnalyser.h"
+#include "DeadCodeElimination.h"
 #include "Mem2Reg.h"
 #include "Reg2Mem.h"
 // #include "LLVMIRGenerator.h"
@@ -86,12 +87,24 @@ int main(int argc, char **argv) {
     auto builder = generator.getBuilder();
     SysYOptPre optPre(moduleIR, builder);
     optPre.SysYOptimizateAfterIR();
-    Mem2Reg mem2reg(moduleIR, builder);
+    ControlFlowAnalysis cfa(moduleIR);
+    cfa.init();
+    ActiveVarAnalysis ava;
+    ava.init(moduleIR);
+    printer.printIR();
+
+    
+    DeadCodeElimination dce(moduleIR, &cfa, &ava);
+    dce.runDCEPipeline();
+    
+    Mem2Reg mem2reg(moduleIR, builder, &cfa, &ava);
     mem2reg.mem2regPipeline();
     printer.printIR();
     Reg2Mem reg2mem(moduleIR, builder);
     reg2mem.DeletePhiInst();
     printer.printIR();
+    dce.runDCEPipeline();
+    printer.printIR();
     return EXIT_SUCCESS;
   }
   return EXIT_SUCCESS;