[LLVMdev] How to get the name and argument of a function

[Nick Lewycky]

songlh at cs.wisc.edu wrote:
> Hi everyone:
>
>     The code I am analyzing is :
>
>     int main()
>     {
>         int i = 0;
>         printf("hello world!");
>         printf( "%d" , i );
>     }
>
>
>
>     I want to get each place where printf is called, and the argument used
> during that call.
>
>     so I write llvm pass code like:
>
>     void Myfunction( Function&  F){
>         for( Function::iterator b = F.begin() , be = F.end() ;
>          b != be; ++b){
>             for(BasicBlock::iterator i = b.begin() , ie = b.end();
>              i != ie; i ++){
>                 if( isa<CallInst>(&(*i)) || isa<InvokeInst>(&(*i))){
>                     //how could I get the function name and argument
>                     //used here
>                 }
>             }
>
>         }
>     }
>
>
>     How could I get the function name and the arguments when I know an
> Instruction is a function call?

There's a worked example at 
http://wiki.llvm.org/HowTo:_Find_all_call_sites_of_a_function .

With the CallInst/InvokeInst you can query getArgOperand() to get the 
arguments or getCallee() which return a Function -- or it might not. If 
the call is an indirect call (ie., function pointer) then you don't know 
what it's calling. Ignoring indirect calls, you can call getName() on a 
function to get its name.

Personally, I rely heavily on the doxygen to find my way around the API: 
http://llvm.org/doxygen/hierarchy.html . Look up "CallInst" for example. 
The getName() method isn't on Function, but all the way on the base 
class Value.

Nick

>
>     thanks a lot!
>
>     Best wishes!
>
>                                                   Linhai Song
>
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