llvm dev - Mar 2014 - [LLVMdev] How can i insert an add instruction in IR file llvm?

i want to insert add instruction in IR llvm format, instruction like x = x + 1 ,
where x is global variable , 
i try to use: 
GlobalVariable* x = new
GlobalVariable(mod,Type::getInt32Ty(Context),false,GlobalValue::CommonLinkage,0,"xCounter");
Value one =  ConstantInt::get(Type::getInt32Ty(Context),1);
newInst = BinaryOperator::Create(Instruction::Add, , one ,"counter",
insertPos);
but an error occur, 
it is not accept type GlobalVariable, 
How can i define a global variable and set its value , and final i print its
value on screen ?
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