LLVM get constant integer back from Value*

Question

I create a llvm::Value* from a integer constant like this:

llvm::Value* constValue = llvm::ConstantInt::get( llvmContext , llvm::APInt( node->someInt() ))         


        

Answer 1

Eli's answer is great, but it's missing the final part, which is getting the integer back. The full picture should look like this:

if (ConstantInt* CI = dyn_cast(Val)) {
  if (CI->getBitWidth() <= 32) {
    constIntValue = CI->getSExtValue();
  }
}

Of course, you can also change it to <= 64 if constIntValue is a 64-bit integer, etc.

And as Eli wrote, if you are confident the value is indeed of type ConstInt, you can use cast instead of dyn_cast.