llvm dev - May 2009 - [LLVMdev] Get the call graph SCCs from a function pass

On 5/10/09, Török Edwin <edwintorok at gmail.com>
wrote:
> On 2009-05-10 20:11, Nick Johnson wrote:
>  > Hello,
>  >
>  > I'm writing a Function Pass.  This function pass needs access to
the
>  > CallGraph and CallGraph SCCs.  Is there any way I can get CallGraph
>  > information without changing my pass to a CallGraphSCCPass ?
>
>
> Does getAnalysis<CallGraph>() work?
>
AFAIK, it's not a pass.
>  But I'm not sure if using a FunctionPass to access Callgraph data is a
>  good idea, transformations can
>  change it (for example dead code elimination can remove edges).
>
I'm just using it to interpret profiling information correctly; in
that respect, it doesn't matter if transformations change the IR, so
long as the CallGraph data reflects the IR against which profiling was
done.

Nick

On 2009-05-10 21:18, Nick Johnson wrote:
> On 5/10/09, Török Edwin <edwintorok at gmail.com> wrote:
>   
>> On 2009-05-10 20:11, Nick Johnson wrote:
>>  > Hello,
>>  >
>>  > I'm writing a Function Pass.  This function pass needs access
to the
>>  > CallGraph and CallGraph SCCs.  Is there any way I can get
CallGraph
>>  > information without changing my pass to a CallGraphSCCPass ?
>>
>>
>> Does getAnalysis<CallGraph>() work?
>>
>>     
> AFAIK, it's not a pass.
>
>   
It is, see lib/Analysis/IPA/CallGraph.cpp:

static RegisterAnalysisGroup<CallGraph> X("Call Graph");
static RegisterPass<BasicCallGraph>
Y("basiccg", "Basic CallGraph Construction", false, true);
static RegisterAnalysisGroup<CallGraph, true> Z(Y);

I know that using getAnalysis<CallGraph> works in a ModulePass, but
never tried it in a FunctionPass.
>>  But I'm not sure if using a FunctionPass to access Callgraph data
is a
>>  good idea, transformations can
>>  change it (for example dead code elimination can remove edges).
>>
>>     
> I'm just using it to interpret profiling information correctly; in
> that respect, it doesn't matter if transformations change the IR, so
> long as the CallGraph data reflects the IR against which profiling was
> done.
>   
Ok.

Best regards,
--Edwin

>>> Does getAnalysis<CallGraph>() work?
Thanks Edwin, that works!

What about the CallGraphSCC ?  It looks like one can declare a
CallGraphSCCPass, but I don't see any other way to get the SCCs of the
call graph.


-- 
Nick Johnson