LLVM IR: getting the value of an address

Question

I'm trying to write a LLVM pass to analyse the following IR:

  %d = alloca i32, align 4
  store i32 0, i32* %d, align 4
  %1 = load i32* %d, align 4
  %2 = add nsw i32 %1, 2
  store i32 %2, i32* %d, align 4

What I need to do is to figure out the final value of d.

For the store i32 0, i32* %d, align 4 I used ConstantInt casting for the operand 0 and found the assigned value for d (which is 0). But I'm struggling with how to find the value for the d in last store instruction:

store i32 %2, i32* %d, align 4

As I know, %2 is a pointer to the result of the instruction %2 = add nsw i32 %1, 2 and similar thing to the %1.

Do I need to backtrack for %2 to find the value of %2 or is there a simpler method for this?

EDIT:

Following is the code I used so far:

void analyse(BasicBlock* BB)
{
    for (auto &I: *BB) 
    {
        if (isa<StoreInst>(I)) 
        {
            Value *v = I.getOperand(0);
            Instruction *i = dyn_cast<Instruction>(I.getOperand(1));

            if (isa<ConstantInt>(v)) 
            {
                llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(v);
                int value = CI->getZExtValue();
                std::string ope = i->getName().str().c_str();
                std::cout << "ope " << value << " \n";
            }
        }
    }
}

Answer 1

Way to solve this is to back track. In this case:

store i32 %2, i32* %d, align 4
%2 = add nsw i32 %1, 2
%1 = load i32* %d, align 4

so it's checking the operand is an instruction, and if so, check the type of the instruction (i.e: isa(v), isa(v) or isa(v) etc), and then find the value.