Date: Mon, 25 Jun 2007 19:25:59 +0400 From: Andrey Chernov <ache@nagual.pp.ru> To: Ed Schouten <ed@fxq.nl> Cc: kan@freebsd.org, current@freebsd.org Subject: Re: Silent gcc 4.2.0 loop optimization bug with -O2 Message-ID: <20070625152559.GA54055@nagual.pp.ru> In-Reply-To: <20070625151508.GO27942@hoeg.nl> References: <20070625130913.GA50273@nagual.pp.ru> <20070625133951.GA51324@nagual.pp.ru> <8e5ef5f70706250659v48f64410wb5399985a571087e@mail.gmail.com> <20070625145627.GA53685@nagual.pp.ru> <20070625151508.GO27942@hoeg.nl>
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On Mon, Jun 25, 2007 at 05:15:08PM +0200, Ed Schouten wrote:
> I did some more stripping and it turns out this is the problem
>=20
> | int
> | main(int argc, char *argv[])
> | {
> | int i;
> | int numbers[4] =3D { 0xdead, 0xbeef, 0x1337, 0x4242 };
> |=20
> | for (i =3D 1; i <=3D 12; i++) {
> | if (i <=3D 4)
> | printf("%d: %x\n", i, numbers[i-1]);
> | else if (i >=3D 7 && i <=3D 9)
> | printf("MUST BE HERE!!! %d\n", i);
> | }
> | }
>=20
> When you increase the size of the array to 6 or higher, it does what you
> want. It clearly looks like a compiler bug; the size of the array
> shouldn't have an effect on the amount of iterations.=20
>=20
> You should really file a bug at GCC's to make sure this gets fixed in
> 4.2.1.
I am not familiar with gcc bugs reporting system at all. Could somebody=20
running 4.2.1 snapshot tells, is it already fixed, by chance? If no, could=
=20
sumebody fill bug report to them or provide detailed instructions how to=20
do that, please?
In any case, we must change default CFLAGS from
-O2 -fno-strict-aliasing -pipe
to
-O -pipe
for -current immediately.
--=20
http://ache.pp.ru/
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