[llvm-dev] [LLVMdev] Interprocedural use-def chains

Dounia Khaldi via llvm-dev llvm-dev at lists.llvm.org
Tue Jul 26 15:05:00 PDT 2016

Thanks for your reply.

Yes, I was about to recurse over the use list of the argument in the called
function. I did not want to pursue that because with this solution, I am
going to implement the interprocedural part myself and was wondering if
that was not already done. I was not also 100% sure that this will work for
any type of arguments.

If, based on your response, this is my only solution then I will go for it.


On Tue, Jul 26, 2016 at 5:51 PM, Sanjoy Das <sanjoy at playingwithpointers.com>

> Hi Dounia,
> Dounia Khaldi via llvm-dev wrote:
> > I have been using the USE class to access the use-def chains of
> > different values. However, what I have noticed is that the set of users
> > of a particular value is limited for the appearance of that variable in
> > the current function.
> >
> > How can I get the interprocedural use of a particular value? For
> > example, if a variable /a/ is used as an argument in a function call
> > /foo/, the USE analysis would go to the definition of/foo/, and get me
> > the users of that argument in the called function as well. Currently,
> > what USE does is that it returns the call as a use and stops there.
> Why not just recurse to uses of the corresponding llvm::Argument
> instance?  Is there a reason why you're avoiding that?  This won't
> work for varargs, but that's a difficult problem anyway.
> Specifically, I'm saying:
>   if (user is CallInst or InvokeInst) {
>     unsigned ArgNo = // Get argument no. of Use &
>     if (auto *F = getCallTargetIfPossible()) {
>       pushToWorklist(F->getArgument(ArgNo)->users()); // Or recurse
>     }
>   }
> -- Sanjoy

Research Assistant Professor
Institute for Advanced Computational Science
Stony Brook University
Stony Brook, NY 11794-5250
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