From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-439612-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 12917 invoked by alias); 8 Jan 2014 11:08:50 -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
Received: (qmail 12876 invoked by uid 48); 8 Jan 2014 11:08:46 -0000
From: "vries at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/59715] [4.7/4.8/4.9 Regression] wrong code at -Os and above on x86_64-linux-gnu
Date: Wed, 08 Jan 2014 11:08:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 4.9.0
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: vries at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.7.4
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-59715-4-EwvX7EFyKy@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-59715-4@http.gcc.gnu.org/bugzilla/>
References: <bug-59715-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 7bit
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-SW-Source: 2014-01/txt/msg00754.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59715

--- Comment #5 from vries at gcc dot gnu.org ---
The test passes with -fno-tree-tail-merge. But I don't see anything wrong with
the transformation (merging of empty blocks) done by the pass. 

AFAICT, the problem is introduced by pass_dominator. test.c.126t.slsr looks ok,
but test.c.127t.dom2 look wrong. The test passes with -fno-tree-dominator-opts.

test.c.126t.slsr:
...
  <bb 2>:
  b.0_4 = b;
  if (b.0_4 == 0)
    goto <bb 4>;
  else
    goto <bb 3>;

  <bb 3>:
  goto <bb 7>;

  <bb 4>:
  a.1_5 = a;
  if (a.1_5 != 0)
    goto <bb 5>;
  else
    goto <bb 6>;

  <bb 5>:
  b = a.1_5;
  c_7 = 1 % a.1_5;
  if (c_7 != 0)
    goto <bb 6>;
  else
    goto <bb 3>;

  <bb 6>:
  b = 0;

  <bb 7>:
  b.0_9 = b;
  printf ("%d\n", b.0_9);
  return 0;
...
we're taking the path bb2 -> bb4 -> bb5 (b = 2) -> bb6 (b = 0) -> bb7

test.c.127t.dom2:
...
  <bb 2>:
  b.0_4 = b;
  if (b.0_4 == 0)
    goto <bb 4>;
  else
    goto <bb 3>;

  <bb 3>:
  goto <bb 6>;

  <bb 4>:
  a.1_5 = a;
  if (a.1_5 != 0)
    goto <bb 5>;
  else
    goto <bb 6>;

  <bb 5>:
  b = a.1_5;
  c_7 = 1 % a.1_5;
  if (c_7 != 0)
    goto <bb 6>;
  else
    goto <bb 3>;

  <bb 6>:
  b.0_9 = b;
  printf ("%d\n", b.0_9);
  return 0;
...
we're taking the path bb2 -> bb4 -> bb5 (b = 2) -> bb6