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From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/104986] [12/13/14 Regression] bogus writing 1 byte into a region of size 0 with -fwrapv and -O2 -fpeel-loops since r12-4698-gf6d012338bf87f42
Date: Sat, 02 Sep 2023 20:02:51 +0000	[thread overview]
Message-ID: <bug-104986-4-g3Zd7n2s0m@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-104986-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104986

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |needs-bisection
      Known to work|                            |13.1.0

--- Comment #13 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Looks like SCEV can figure out the bounds more correctly in GCC 13+ which fixes
the warning and the missed optimization.

GCC 12.3.0:
```
Estimating # of iterations of loop 1
Matching expression match.pd:2119, generic-match.cc:693
Matching expression match.pd:2122, generic-match.cc:753
Matching expression match.pd:2129, generic-match.cc:776
Analyzing # of iterations of loop 1
  exit condition [prephitmp_30, + , -1] != 0
  bounds on difference of bases: -5 ... 1
Applying pattern match.pd:182, generic-match.cc:30997
Applying pattern match.pd:5698, generic-match.cc:11425
Matching expression match.pd:2119, generic-match.cc:693
Matching expression match.pd:2122, generic-match.cc:753
Matching expression match.pd:2129, generic-match.cc:776
Applying pattern match.pd:354, generic-match.cc:5780
  result:
    # of iterations (unsigned int) prephitmp_30, bounded by 4294967295
Statement (exit)if (nb_24 != 0)
 is executed at most (unsigned int) prephitmp_30 (bounded by 4294967295) + 1
times in loop 1.
```

While GCC 13+:
```
Estimating # of iterations of loop 1
Matching expression match.pd:2404, generic-match.cc:727
Matching expression match.pd:2407, generic-match.cc:787
Matching expression match.pd:2414, generic-match.cc:810
Analyzing # of iterations of loop 1
  exit condition [prephitmp_30, + , -1] != 0
  bounds on difference of bases: -5 ... 0
Applying pattern match.pd:182, generic-match.cc:33250
Applying pattern match.pd:6155, generic-match.cc:21253
Matching expression match.pd:2404, generic-match.cc:727
Matching expression match.pd:2407, generic-match.cc:787
Matching expression match.pd:2414, generic-match.cc:810
Applying pattern match.pd:365, generic-match.cc:21998
  result:
    # of iterations (unsigned int) prephitmp_30, bounded by 5
Statement (exit)if (nb_24 != 0)
 is executed at most (unsigned int) prephitmp_30 (bounded by 5) + 1 times in
loop 1.
```

      parent reply	other threads:[~2023-09-02 20:02 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-19 17:07 [Bug middle-end/104986] New: [12 Regression] bogus writing 1 byte into a region of size 0 with -fwrapv and -O2 -fpeel-loops andres at anarazel dot de
2022-03-21  8:53 ` [Bug middle-end/104986] " rguenth at gcc dot gnu.org
2022-03-21  9:31 ` [Bug middle-end/104986] [12 Regression] bogus writing 1 byte into a region of size 0 with -fwrapv and -O2 -fpeel-loops since r12-4698-gf6d012338bf87f42 marxin at gcc dot gnu.org
2022-03-23  9:45 ` aldyh at gcc dot gnu.org
2022-03-23 13:05 ` rguenth at gcc dot gnu.org
2022-03-23 14:45 ` aldyh at gcc dot gnu.org
2022-03-23 14:46 ` amacleod at redhat dot com
2022-03-23 14:49 ` aldyh at gcc dot gnu.org
2022-03-23 14:58 ` amacleod at redhat dot com
2022-03-23 15:05 ` rguenth at gcc dot gnu.org
2022-04-19  5:20 ` jakub at gcc dot gnu.org
2022-05-06  8:33 ` [Bug middle-end/104986] [12/13 " jakub at gcc dot gnu.org
2022-07-26 12:38 ` rguenth at gcc dot gnu.org
2023-05-08 12:24 ` [Bug middle-end/104986] [12/13/14 " rguenth at gcc dot gnu.org
2023-09-02 20:02 ` pinskia at gcc dot gnu.org [this message]

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