Merge pull request #436 from mamie1031/lab6

[LAB6] 313581017

Author: YingMuo

lab6/llvm-pass.so.cc

@@ -14,11 +14,39 @@ PreservedAnalyses LLVMPass::run(Module &M, ModuleAnalysisManager &MAM) {
   FunctionCallee debug_func = M.getOrInsertFunction("debug", Int32Ty);
   ConstantInt *debug_arg = ConstantInt::get(Int32Ty, 48763);
 
+  bool Modified = false;
+
   for (auto &F : M) {
     errs() << "func: " << F.getName() << "\n";
 
+    if (F.getName() != "main") continue;
+    BasicBlock &EntryBB = F.getEntryBlock();
+    IRBuilder<> Builder(&*EntryBB.getFirstInsertionPt());
+    // 1：Insert debug(48763)
+    Builder.CreateCall(debug_func, {debug_arg});
+
+    // 2：Set argv[1] to "hayaku... motohayaku!"
+    Constant *StrConst = ConstantDataArray::getString(Ctx, "hayaku... motohayaku!");
+    GlobalVariable *StrVar = new GlobalVariable(
+        M, StrConst->getType(), true, GlobalValue::PrivateLinkage, StrConst, ".str");
+    Constant *StrPtr = ConstantExpr::getPointerCast(StrVar, Type::getInt8PtrTy(Ctx));
+
+    // Get argv[1]
+    Value *Argv = F.getArg(1);
+    // Calculate the address of argv[1]（argv + 1）
+    Value *Argv1Ptr = Builder.CreateGEP(Type::getInt8PtrTy(Ctx), Argv,
+                                       ConstantInt::get(Type::getInt64Ty(Ctx), 1));
+    // Set argv[1] to new string
+    Builder.CreateStore(StrPtr, Argv1Ptr);
+
+    // 3：Set argc to 48763
+    Value *Argc = F.getArg(0);
+    Value *ArgcPtr = Builder.CreateAlloca(Int32Ty, nullptr, "argc.ptr");
+    Builder.CreateStore(debug_arg, ArgcPtr);
+    Argc->replaceAllUsesWith(Builder.CreateLoad(Int32Ty, ArgcPtr));
+    Modified = true;
   }
-  return PreservedAnalyses::none();
+  return Modified ? PreservedAnalyses::none() : PreservedAnalyses::all();
 }
 
 extern "C" ::llvm::PassPluginLibraryInfo LLVM_ATTRIBUTE_WEAK