* Pointer analysis in GCC-4.3.0 - Getting spurious pointsTo pair.
[not found] <ee5d809b0905270045u4775e419q3da30a3e3b8157e8@mail.gmail.com>
@ 2009-06-15 10:33 ` Seema Ravandale
2009-06-15 11:19 ` Richard Guenther
0 siblings, 1 reply; 2+ messages in thread
From: Seema Ravandale @ 2009-06-15 10:33 UTC (permalink / raw)
To: gcc, gcc-help
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?
- Seema
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Pointer analysis in GCC-4.3.0 - Getting spurious pointsTo pair.
2009-06-15 10:33 ` Pointer analysis in GCC-4.3.0 - Getting spurious pointsTo pair Seema Ravandale
@ 2009-06-15 11:19 ` Richard Guenther
0 siblings, 0 replies; 2+ messages in thread
From: Richard Guenther @ 2009-06-15 11:19 UTC (permalink / raw)
To: Seema Ravandale; +Cc: gcc, gcc-help
On Mon, Jun 15, 2009 at 12:33 PM, Seema Ravandale<ravandaless@gmail.com> 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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[not found] <ee5d809b0905270045u4775e419q3da30a3e3b8157e8@mail.gmail.com>
2009-06-15 10:33 ` Pointer analysis in GCC-4.3.0 - Getting spurious pointsTo pair Seema Ravandale
2009-06-15 11:19 ` Richard Guenther
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