From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-454700-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 30749 invoked by alias); 23 Jun 2014 14:13:06 -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 30707 invoked by uid 48); 23 Jun 2014 14:13:01 -0000
From: "ysrumyan at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/61576] [4.10 Regression] wrong code at -O3 on x86_64-linux-gnu
Date: Mon, 23 Jun 2014 14:13:00 -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: 4.10.0
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: ysrumyan at gmail dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.10.0
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-61576-4-UwbRNWkySJ@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-61576-4@http.gcc.gnu.org/bugzilla/>
References: <bug-61576-4@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: 2014-06/txt/msg01782.txt.bz2

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61576

--- Comment #4 from Yuri Rumyantsev <ysrumyan at gmail dot com> ---
There is an issue with phi-node and reduction stmt - after r211302 new hammock
was inserted between reduction stmt and bb containing phi:

  <bb 6>:
  d.6_12 = d_lsm.14_17 + 1;
  if (c.8_13 != 0)
    goto <bb 7>;
  else
    goto <bb 8>;

  <bb 7>:

  <bb 8>:
  # iftmp.7_15 = PHI <1(7), _19(6)>

  <bb 9>:
  # d_lsm.14_16 = PHI <d_lsm.14_17(5), d.6_12(8)>

but algorithm for converting conditional scalar reduction assumes that basic
block containing reduction is one of predecessors of phi-block. I added check
on it and test is passed.

BTW I wonder why such code motion has been done - in fact, redundant
computations were introduced in loop, before this fix all computations related
to hammock were hoisted out off loop:

  <bb 4>:
  d_lsm.14_25 = d;
  c.8_13 = c;
  f.9_14 = f;
  _18 = f.9_14 != 0;
  _19 = (int) _18;
  iftmp.7_15 = c.8_13 != 0 ? 1 : _19;
  e_lsm.15_26 = e;

  <bb 5>:
  # d_lsm.14_17 = PHI <d_lsm.14_25(4), d_lsm.14_16(9)>
  # e_lsm.15_1 = PHI <e_lsm.15_26(4), e_lsm.15_24(9)>
  b.4_10 ={v} b;
  if (b.4_10 != 0)
    goto <bb 6>;
  else
    goto <bb 7>;

  <bb 6>:
  d.6_12 = d_lsm.14_17 + 1;

  <bb 7>:
  # d_lsm.14_16 = PHI <d_lsm.14_17(5), d.6_12(6)>
  # e_lsm.15_24 = PHI <e_lsm.15_1(5), iftmp.7_15(6)>

I will send for review patch after required testing completion.