Re: Pointer analysis in GCC-4.3.0 - Getting spurious pointsTo pair.

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On Mon, Jun 15, 2009 at 12:33 PM, Seema Ravandale<ravandaless@xxxxxxxxx> wrote:
> Hi.
>
> Gimple code of the program I have tried to get the pointsTo
> information is as follow:
>
>  A = 0;
>  B = &A;
>  C = &B;
>  D = &C;
>  D.1255 = *D;
>  D = (int * * *) D.1255;
>
> The expected pointsTo pairs  are,
> B = { A } , A = { },  C = { B }, D.1255 = { B }, D = { B  C }
>
> But with GCC-4.3.0, and command line options  -fdump-ipa-all
> -funit-at-a-time  -fipa-pta, we are getting spurious pointsTo pairs
> as,
> D.1255 = { B A } , D = { B C A }
>
> Is the current analysis Flow-insensitive? Even if It is, the sperious
> information, D -> A should not occur.
> Please, Can someone clarify on this?

IPA-PTA is completely bogus (and its results are unused).  Further
GCC 4.3 has a very large number of known oddities with computing
points-to information, GCC 4.4 is a lot better here but only GCC 4.5
has fixes for all (known) bugs.

Richard.

> - Seema
>


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