From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-307116-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 31388 invoked by alias); 30 Jan 2010 16:07:08 -0000
Received: (qmail 31324 invoked by uid 48); 30 Jan 2010 16:06:57 -0000
Date: Sat, 30 Jan 2010 16:07:00 -0000
Message-ID: <20100130160657.31323.qmail@sourceware.org>
X-Bugzilla-Reason: CC
References: <bug-42720-17567@http.gcc.gnu.org/bugzilla/>
Subject: [Bug tree-optimization/42720] Problematic condition simplification logic at unswitch-loops pass
In-Reply-To: <bug-42720-17567@http.gcc.gnu.org/bugzilla/>
Reply-To: gcc-bugzilla@gcc.gnu.org
To: gcc-bugs@gcc.gnu.org
From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
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: 2010-01/txt/msg03423.txt.bz2



------- Comment #9 from rguenth at gcc dot gnu dot org  2010-01-30 16:06 -------
(In reply to comment #6)
> The interesting thing is that the empty loop is not removed by
> the control-dependent DCE pass that follows the 2nd VRP.
> 
> This happens because
> 
> 
> <bb 3>:
>   if (obj_7(D) != 0B)
>     goto <bb 5>;
>   else
>     goto <bb 4>;
> 
> <bb 4>:
>   # i_36 = PHI <0(3)>
> 
> <bb 10>:
>   # i_25 = PHI <i_36(4), i_35(12)>
>   i_35 = i_25 + 1;
>   if (i_35 != num_6(D))
>     goto <bb 12>;
>   else
>     goto <bb 8>;
> 
> <bb 12>:
>   goto <bb 10>;
> 
> ...
> 
> <bb 7>:
> Invalid sum of incoming frequencies 6888, should be 7735
>   # s_2 = PHI <s_19(6), s_23(11)>
>   i_20 = i_18 + 1;
>   if (i_20 != num_6(D))
>     goto <bb 13>;
>   else
>     goto <bb 8>;
> 
> ...
> 
> <bb 8>:
>   # s_3 = PHI <s_2(7), 0(10)>
> 
> 
> the PHI node defining s_3 marks the controlling statement necessary
> which in turn marks the loop necessary.  Now the question is if this
> is an inherent limitation of CD-DCE or if the controlling stmt
> should be that in BB3 instead (the immediate common dominator of
> bb7 and bb10 is bb3).  Steven?  You implemented that CD-DCE stuff?

-> PR42906


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42720