llvm dev - Apr 2015 - [LLVMdev] function pointer alias analysis

Hi

I see when LLVM builds the CallGraph SCCs. a function calling through
a function pointer is conservatively assumed to call internal and
external functions. Therefore, it has an edges pointing to the
externalnode2, ie. the externalnode representing outgoing calls from
this module.

does LLVM have any function pointer analysis capabilities in the mainline ?

Thanks,
-Trent

I'm not aware of such analyses in the mainline. Did you try DSAA in the
poolalloc project? Also, how precise do you need the analysis to be?

On Sat, Apr 18, 2015 at 5:20 PM Xin Tong <trent.tong at gmail.com> wrote:
> Hi
>
> I see when LLVM builds the CallGraph SCCs. a function calling through
> a function pointer is conservatively assumed to call internal and
> external functions. Therefore, it has an edges pointing to the
> externalnode2, ie. the externalnode representing outgoing calls from
> this module.
>
> does LLVM have any function pointer analysis capabilities in the mainline ?
>
> Thanks,
> -Trent
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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On 4/19/15 12:09 PM, Jingyue Wu wrote:
> I'm not aware of such analyses in the mainline. Did you try DSAA in 
> the poolalloc project? Also, how precise do you need the analysis to be?
If you use DSA, I recommend using the analysis in CallTargets.cpp and 
using the pass that uses TD instead of EQTD.

As an FYI, I recently discovered that DSA (but not poolalloc) mainline 
compiles with LLVM mainline (thanks Will Dietz!).  On 
https://github.com/jtcriswell/llvm-dsa, I have the LLVM tree and the 
poolalloc tree set up to compile LLVM and DSA.  If you look at the 
source code for CallTargetMarker in 
https://github.com/jtcriswell/llvm-dsa/blob/master/projects/poolalloc/lib/DSA/CallTargets.cpp,
you'll see what you need to do to get the targets of an indirect 
function call.

If you have any questions, please let me know.

Regards,

John Criswell
> On Sat, Apr 18, 2015 at 5:20 PM Xin Tong <trent.tong at gmail.com 
> <mailto:trent.tong at gmail.com>> wrote:
>
>     Hi
>
>     I see when LLVM builds the CallGraph SCCs. a function calling through
>     a function pointer is conservatively assumed to call internal and
>     external functions. Therefore, it has an edges pointing to the
>     externalnode2, ie. the externalnode representing outgoing calls from
>     this module.
>
>     does LLVM have any function pointer analysis capabilities in the
>     mainline ?
>
>     Thanks,
>     -Trent
>     _______________________________________________
>     LLVM Developers mailing list
>     LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu>
>     http://llvm.cs.uiuc.edu
>     http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

-- 
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell

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