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From: "bernd.edlinger at hotmail dot de" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/58143] wrong code at -O3 on x86_64-linux-gnu
Date: Tue, 20 Aug 2013 00:21:00 -0000 [thread overview]
Message-ID: <bug-58143-4-8xMnH8F8Bj@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-58143-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58143
Bernd Edlinger <bernd.edlinger at hotmail dot de> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |bernd.edlinger at hotmail dot de
--- Comment #4 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
Created attachment 30674
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30674&action=edit
slightly simplified test case
attached is a slightly simplified test case.
The problem seems to start in the optimizer pass 097t.lim1
where the following expression is identified as loop-invariant of loop 3.
Moving statement
_23 = -2147483648 - c.1_22;
(cost 1) out of loop 3.
unfortunatley it is executed unconditionally now.
later the optimizer pass 110t.ivcanon uses the possible overflow
in this statement as an argument, why the loop must be executed exactly once.
Induction variable (int) 2147483647 + 1 * iteration does not wrap in statement
_23 = -2147483648 - prephitmp_8;
in loop 2.
Statement _23 = -2147483648 - prephitmp_8;
is executed at most 0 (bounded by 0) + 1 times in loop 2.
and shortly after that an apparently pointless loop-exit is removed.
Removed pointless exit: if (prephitmp_8 != 0)
however that is based on a worng assumption, and causes worng code.
next prev parent reply other threads:[~2013-08-20 0:21 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-13 0:05 [Bug middle-end/58143] New: " su at cs dot ucdavis.edu
2013-08-13 0:08 ` [Bug middle-end/58143] " pinskia at gcc dot gnu.org
2013-08-13 0:24 ` su at cs dot ucdavis.edu
2013-08-14 21:11 ` mikpe at it dot uu.se
2013-08-20 0:21 ` bernd.edlinger at hotmail dot de [this message]
2013-08-20 0:59 ` bernd.edlinger at hotmail dot de
2013-08-20 22:25 ` bernd.edlinger at hotmail dot de
2013-08-21 8:53 ` bernd.edlinger at hotmail dot de
2013-08-21 17:41 ` [Bug tree-optimization/58143] [4.8/4.9 regression] wrong code at -O3 ebotcazou at gcc dot gnu.org
2013-08-21 18:02 ` jakub at gcc dot gnu.org
2013-08-21 21:50 ` bernd.edlinger at hotmail dot de
2013-08-23 9:15 ` bernd.edlinger at hotmail dot de
2013-08-23 9:16 ` jakub at gcc dot gnu.org
2013-08-23 12:08 ` bernd.edlinger at hotmail dot de
2013-08-23 12:59 ` jakub at gcc dot gnu.org
2013-08-25 22:08 ` bernd.edlinger at hotmail dot de
2013-08-28 21:30 ` bernd.edlinger at hotmail dot de
2013-10-15 8:15 ` rguenth at gcc dot gnu.org
2013-10-15 8:17 ` rguenth at gcc dot gnu.org
2013-10-15 8:39 ` bernd.edlinger at hotmail dot de
2013-10-15 9:05 ` rguenth at gcc dot gnu.org
2013-10-15 9:41 ` rguenth at gcc dot gnu.org
2013-10-15 11:03 ` rguenth at gcc dot gnu.org
2013-10-15 11:45 ` bernd.edlinger at hotmail dot de
2013-10-15 11:54 ` rguenth at gcc dot gnu.org
2013-10-15 11:54 ` rguenther at suse dot de
2013-10-15 13:21 ` bernd.edlinger at hotmail dot de
2013-10-15 13:27 ` rguenther at suse dot de
2013-10-15 13:36 ` mikpelinux at gmail dot com
2013-10-15 13:38 ` bernd.edlinger at hotmail dot de
2013-10-15 13:40 ` rguenther at suse dot de
2013-10-16 9:51 ` jakub at gcc dot gnu.org
2013-10-17 9:59 ` rguenth at gcc dot gnu.org
2013-10-17 10:08 ` [Bug tree-optimization/58143] [4.8 " rguenth at gcc dot gnu.org
2013-11-18 15:14 ` rguenth at gcc dot gnu.org
2013-11-18 15:15 ` rguenth at gcc dot gnu.org
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