Merge pull request #461 from BrianGodd/lab6

[LAB6] 111550083

Author: YingMuo

lab6/llvm-pass.so.cc

@@ -15,7 +15,24 @@ PreservedAnalyses LLVMPass::run(Module &M, ModuleAnalysisManager &MAM) {
   ConstantInt *debug_arg = ConstantInt::get(Int32Ty, 48763);
 
   for (auto &F : M) {
-    errs() << "func: " << F.getName() << "\n";
+    //errs() << "func: " << F.getName() << "\n";
+    if(F.getName() == "main")
+    {
+      //1. get into debug mode with id = 48763
+      IRBuilder<> Builder(&*F.getEntryBlock().getFirstInsertionPt());
+      Builder.CreateCall(debug_func, {debug_arg});
+      
+      //2. let argv[1] to custom string
+      Argument *argvArg = F.getArg(1);
+      Value *index = ConstantInt::get(Int32Ty, 1);
+      Value *argv_ptr = Builder.CreateInBoundsGEP(Builder.getInt8PtrTy(), argvArg, index); //指標指向的型別 (i8*)
+      Value *custom = Builder.CreateGlobalStringPtr("hayaku... motohayaku!");
+      Builder.CreateStore(custom, argv_ptr); //將argv[1]位址指向custom並儲存
+
+      //3. change argc to 48763
+      Argument *argcArg = F.getArg(0);
+      argcArg->replaceAllUsesWith(debug_arg);
+    }
 
   }
   return PreservedAnalyses::none();