From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-388154-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 12925 invoked by alias); 6 Apr 2012 16:59:46 -0000
Received: (qmail 12907 invoked by uid 22791); 6 Apr 2012 16:59:43 -0000
X-SWARE-Spam-Status: No, hits=-3.5 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00
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; Fri, 06 Apr 2012 16:59:31 +0000
From: "pthaugen at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/52890] New: Revision 185336 causes 10% degradation on cpu2000 benchmark 252.eon
Date: Fri, 06 Apr 2012 16:59:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Keywords:
X-Bugzilla-Severity: normal
X-Bugzilla-Who: pthaugen at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields:
Message-ID: <bug-52890-4@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
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: 2012-04/txt/msg00436.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52890

             Bug #: 52890
           Summary: Revision 185336 causes 10% degradation on cpu2000
                    benchmark 252.eon
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pthaugen@gcc.gnu.org
                CC: bergner@gcc.gnu.org, mjambor@suse.cz
              Host: powerpc64-linux
            Target: powerpc64-linux
             Build: powerpc64-linux


Following testcase extracted from benchmark file mrXZRectangle.cc.

$ cat test.cc
// g++ -m64 -O2 -mcpu=power7 -S test.cc
class ggVector3 {
public:
    ggVector3() {e[0] = 1.0; e[1] = e[2] = 0.0; }
    ggVector3(double e0, double e1, double e2) {
                   e[0] = e0; e[1] = e1; e[2] = e2; }
    double e[3];
};

class ggONB3 {
public:
    ggONB3() {  }
    ggONB3(const ggVector3& a, const ggVector3& b, const ggVector3& c) {
         U = a; V = b; W = c; }
private:
    ggVector3 U,V,W;
};

class mrViewingHitRecord {
public:
    ggONB3 UVW;
};

void foo(mrViewingHitRecord& VHR)
{

      VHR.UVW = ggONB3(ggVector3 (1, 0, 0),
                       ggVector3 (0, 0, -1),
                       ggVector3 (0, 1, 0));
}

Revision 185335 produces tight sequence of 8-byte stores:

        stfd 0,8(3)
        stfd 0,16(3)
        stfd 0,24(3)
        stfd 0,32(3)
        ...

Revision 185336, with additional check for SLOW_UNALIGNED_ACCESS now causes
path through store_bit_field() which generates a much larger sequence of byte
stores.

        stb 8,0(3)
        stb 10,1(3)
        stb 9,2(3)
        stb 9,3(3)
        stb 9,4(3)
        stb 9,5(3)
        ...