From: Michael Matz <matz@suse.de>
To: Aldy Hernandez <aldyh@redhat.com>
Cc: Jeff Law <jeffreyalaw@gmail.com>, gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: Regression with recent change
Date: Tue, 14 Sep 2021 14:13:11 +0000 (UTC) [thread overview]
Message-ID: <alpine.LSU.2.20.2109141406570.12583@wotan.suse.de> (raw)
In-Reply-To: <CAGm3qMU9uEVj=NEZ=mFVnRXbp_eNqH8Qg7mWdmbpmaWabtLpsw@mail.gmail.com>
Hello,
On Mon, 13 Sep 2021, Aldy Hernandez via Gcc-patches wrote:
The testcase still tests what it's supposed to test with ...
> > typedef unsigned short uint16_t;
> >
> > uint16_t a, b;
> >
> > int *j_global;
> > uint16_t f(void)
> > {
> > int c, **p;
> > short d = 2, e = 4;
> >
... "c = a;" added here (i.e. it still hangs before the pr55107 change).
> > for (;; b++)
> > {
> > int *j = j_global, k = 0;
> >
> > for (; *j; j++)
> > {
> > for(; c; c++)
> > for(; k < 1; k++)
> > {
> > short *f = &d;
> >
> > if(b)
> > return *f;
> > }
> > }
> >
> > if(!c)
> > d *= e;
> >
> > a = d;
> > if ((a ? b = 0 : (**p ? : 1) != (d != 1 ? 1 : (b = 0))) != ((k ? a
> : 0)
> > < (a * (c = k))))
> > **p = 0;
> > }
> > }
> >
>
> Thanks for getting rid of the noise here.
>
> I've simplified the above to show what's going on in the warning on
> nds32-elf:
>
> int george, *global;
> int stuff(), readme();
>
> int
> f (void)
> {
> int store;
>
> for (;;)
> {
> int k = 0;
>
> while (global)
> {
> for (; store; ++store)
Yeah, that seems a correct warning, your 'store' (the 'c' in the original
testcase) is really used uninitialized (when 'global' aka '*j_global' is
non-zero). Sorry for not noticing earlier, I was only getting rid of
warnings, not carefully looking at the testcase itself. I think with
above initialization of 'c' it's conforming, and still a correct test for
the original bug.
> This looks like a latent bug. For that matter, the above snippet warns
> with -fdisable-tree-thread2, even on x86-64 (and before my patch).
Ciao,
Michael.
next prev parent reply other threads:[~2021-09-14 14:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <889cbb03-3a02-65e4-7790-c903293bacf7@gmail.com>
2021-09-13 13:29 ` Aldy Hernandez
2021-09-13 13:40 ` Jeff Law
2021-09-13 14:18 ` Michael Matz
2021-09-13 14:33 ` Jeff Law
2021-09-13 17:03 ` Aldy Hernandez
2021-09-14 14:13 ` Michael Matz [this message]
2021-09-14 14:53 ` Aldy Hernandez
2021-09-14 15:59 ` Jeff Law
2021-04-29 15:52 Jeff Law
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