From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-438221-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 31269 invoked by alias); 19 Dec 2013 18:30:08 -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 31179 invoked by uid 48); 19 Dec 2013 18:30:05 -0000
From: "xinliangli at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/59303] [4.9 Regression] uninit-pred-8_b.c and uninit-pred-9_b.c fail after better optimizations
Date: Thu, 19 Dec 2013 18:30:00 -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: diagnostic
X-Bugzilla-Severity: normal
X-Bugzilla-Who: xinliangli at gmail dot com
X-Bugzilla-Status: NEW
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 4.9.0
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-59303-4-mpizq0RaeZ@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-59303-4@http.gcc.gnu.org/bugzilla/>
References: <bug-59303-4@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: 2013-12/txt/msg01876.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59303

--- Comment #5 from davidxl <xinliangli at gmail dot com> ---
Fixing this requires more powerful predicate analysis with the help of value
equivalent classes.

>>From the dump:

      "Use in stmt blah (v_1);
      is guarded by :
      if (_23 != 0)"


_23 = pephitmp_22 | _8, so the use guard is

        prephitmp_22 != 0 || _8 != 0

prephitmp_22 = PHI <0(13), prephitmp_21(3), so the guard can be translated to

        prephitmp_21 != 0 || _8 != 0

prephitmp_21 = r_9(D) <= 19, so the predicate becomes

         r_9(D) <= 19 || _8 != 0


For the def:

[CHECK] Found def edge 1 in v_1 = PHI <v_14(D)(13), r_9(D)(3)>
Operand defs of phi v_1 = PHI <v_14(D)(13), r_9(D)(3)>
is guarded by :
       if (_8 != 0)
      (.OR.)
        (.NOT.) if (_8 != 0)
        (.AND.)
         if (_13 != 0)

the predicate is
       _8 != 0 || _13 != 0

where _13 = _10 | _12, 10_ = (r_9(D) <= 19), _12 = l_11(D) != 0

so the predicate is
       _8 != 0 || r_9(D) <= 19 || 1_11(D) != 0

which is the superset for the use.


Perhaps we need to do around of predicate normalization before comparison.

David