Ex2. Dynamic BasicBlock Count

count-bb.cpp

bool CountBasicBlocks::initialize(Module &M) { 
    Function *Main = M.getFunction("main");
    assert(Main && "Error: count-bb requires a main function");

    Type *I64Ty = Type::getInt64Ty(M.getContext());

    // Create and insert a new GlobalVariable to track the number 
    // of basic blocks that are executed during the program's run
    //   int64 bbCounter = 0;
    new GlobalVariable(
              M                           // Module
            , I64Ty                       // Type
            , false                       // isConstant
            , GlobalValue::CommonLinkage  // Linkage
            , ConstantInt::get(I64Ty, 0)  // Initializer 
            , "bbCounter");               // Name

    // Create a declaration for the setupAtExit function
    Type *VoidTy = Type::getVoidTy(M.getContext());
    FunctionType *FTy = FunctionType::get(VoidTy, VoidTy);
    Constant *setupAtExitFunc = M.getOrInsertFunction("setupAtExit", FTy);

    // Insert a call to setupAtExit() at the start of main
    BasicBlock *BB = &Main->front();
    Instruction *I = &BB->front();
    CallInst::Create(setupAtExitFunc, "", I);

    return true; // modified IR
}