How to get the arguments of a function call in LLVM?

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#1

Hello,

I am using the following to capture the values of the arguments in a call function:

for (auto &BB : F) {
for (auto &II : BB) {
if (CallInst *c = dyn_cast (&II)){
if ( Function *func = c->getCalledFunction()){
if ( func->getName() =="__kmpc_for_static_init_4" ||
func->getName() == “__kmpc_for_static_fini” )
{
errs() << func->getName();
errs() << “\n”;
for(auto arg = func->arg_begin(); arg != func->arg_end(); ++arg) {
errs() << arg << “\n”;
if(auto ci = dyn_cast(arg))
errs() << ci->getValue() << “\n”;
}
}
}
}
}
}

I am looking for two specific calls for OMP in the *.ll file. For the following:

call void @__kmpc_for_static_init_4(%struct.ident_t* @0, i32 %17, i32 34, i32* %8, i32* %5, i32* %6, i32* %7, i32 1, i32 1)

I am able to see it and get the following:
__kmpc_for_static_init_4
%struct.ident_t* %0
i32 %1
i32 %2
i32* %3
i32* %4
i32* %5
i32* %6
i32 %7
i32 %8

The three arguments ( third ( schedule) and the last two; loop increment and chunk size are constant). The innermost loop should get them but it seems the test command fails on these three arguments. Also, the argument variable are different from the actual variable from the *.ll file.

Any comments.

Thanks,

#2

I think you need to get the arguments from the CallInst, not func. func is getting the arguments from the function defintion. If you want the arguments from the call site you want them from CallInst.

#3

Hi Abid,

  CallInst has a member getArgOperand(No) which returns the values passed
  at the call site. The code below iterates over function arguments
  instead.

  Cheers,
    Johannes