From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-345591-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 4665 invoked by alias); 1 Feb 2011 11:28:12 -0000
Received: (qmail 4655 invoked by uid 22791); 1 Feb 2011 11:28:11 -0000
X-SWARE-Spam-Status: No, hits=-2.8 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00,TW_KD
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 01 Feb 2011 11:28:07 +0000
From: "rakdver at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/45122] [4.6 Regression] -funsafe-loop-optimizations causes FAIL: gcc.c-torture/execute/pr27285.c execution
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Keywords: diagnostic
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rakdver at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: aoliva at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.6.0
X-Bugzilla-Changed-Fields:
Message-ID: <bug-45122-4-tbiZZAIHXG@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-45122-4@http.gcc.gnu.org/bugzilla/>
References: <bug-45122-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Date: Tue, 01 Feb 2011 11:28:00 -0000
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2011-02/txt/msg00057.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45122

--- Comment #16 from Zdenek Dvorak <rakdver at gcc dot gnu.org> 2011-02-01 11:27:13 UTC ---
(In reply to comment #15)
> Ah, the reason why pr19210-* fail is that those loops have non-const/pure call
> in it.  So, while single_exit (loop) == exit, loop_only_exit_p (loop, exit)
> still returns false.
> So, the question is if we really need to give up on -funsafe-loop-optimizations
> whenever loop_only_exit_p (loop, exit), or if a single_exit (loop) == exit
> test would be sufficient for that.

I believe single_exit (loop) test would sufficiently match the expectations of
-funsafe-loop-optimizations.  This would misscompile code like

while (b)
  {
    foo(b);
    b -= 8;
  }

in the case that b is not divisible by 8, on the assumption that there are no
nontrivial infinite loops; which seems reasonable.