[LLVMdev] Callgraph inaccuracy

[Christian Convey]

Hi Will,

Are you actively maintaining the version of DSA found in poolalloc?  In a
response to a question I posted earlier today, Reid Kleckner wondered if
poolalloc (and by extension, DSA?) is unmaintained.

- Christian

On Thu, May 28, 2015 at 4:59 PM, Will Dietz <willdtz at gmail.com> wrote:

> I'm working on this issue, thank you for reporting it.
>
> The short answer is that the callgraph reported by TD is the same as
> discovered/computed during BU
> (and BU can't determine the indirect call can only target C2).
>
> I've added this example, and a few other related tests, to the DSA's
> test suite[1] to document
> this behavior while I'm working out what the best solution is.
>
> I'll try to post back here when it's resolved one way or the other,
> but feel free to bug me if you don't hear back in a few days :).
>
> ~Will
>
> [1]
> https://github.com/llvm-mirror/poolalloc/commit/32b43cd23e3d18f7080f9c966d9b4b3b3fb6962d
>
> On Sun, May 24, 2015 at 4:31 AM, Maxim Olifer <olifer.maxim at gmail.com>
> wrote:
> > Hello,
> >
> > I am trying to extract a callgraph using DSA, but the analysis looks
> quite
> > pessimistic. I use TDD analysis and here is my test code:
> >
> > #include <stdlib.h>
> >
> > typedef void (*tX)(int a, int b);
> > typedef void (*tY)(int a);
> >
> > typedef struct {
> >       tX p ;
> >       int n;
> > } msg;
> >
> > static void A1(int a) { }
> > static void B2(int a, int b) { }
> > static void C2(int a, int b) { }
> >
> >
> > tY q;
> >
> > static void decode(tX decoder_f){
> >     decoder_f(1,2);
> > }
> >
> > int main(void) {
> >     msg *a = malloc(sizeof(msg));
> >     q = &A1;
> >     a->p = &B2;
> >     decode(&C2);
> >
> >     return 0;
> > }
> >
> > The result that I get is:
> >
> > main: [malloc decode ]
> > A1: []
> > B2: []
> > C2: []
> > decode: [A1 B2 C2 ]
> >
> > Why does "decode" function have two extra callees (A1 and B2)? Is it
> > possible to filter them out?
> >
> > Kind Regards,
> > Maxim
> >
> >
> > _______________________________________________
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> >
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