From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-440652-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 24153 invoked by alias); 17 Jan 2014 01:18:30 -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 24124 invoked by uid 48); 17 Jan 2014 01:18:26 -0000
From: "mikeb01 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/58928] Different results from gcc when -mlzcnt is used
Date: Fri, 17 Jan 2014 01:18:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 4.8.2
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: mikeb01 at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags:
X-Bugzilla-Changed-Fields:
Message-ID: <bug-58928-4-tyUZdhjQsB@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-58928-4@http.gcc.gnu.org/bugzilla/>
References: <bug-58928-4@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/msg01794.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58928

--- Comment #2 from Michael Barker <mikeb01 at gmail dot com> ---
> Hope helps

What hardware platform are you testing on?  I'm running on Ivy Bridge:

Intel(R) Xeon(R) CPU E5620 @2.40GHz

Could you put the assembler that you see on the ticket:

With -mlzcnt:

0000000000400580 <lzcnt>:
  400580:    55                       push   %rbp
  400581:    48 89 e5                 mov    %rsp,%rbp
  400584:    48 89 7d e8              mov    %rdi,-0x18(%rbp)
  400588:    48 8b 45 e8              mov    -0x18(%rbp),%rax
  40058c:    48 89 45 f8              mov    %rax,-0x8(%rbp)
  400590:    f3 48 0f bd 45 f8        lzcnt  -0x8(%rbp),%rax
  400596:    48 98                    cltq   
  400598:    5d                       pop    %rbp
  400599:    c3                       retq   

Without -mlzcnt:

0000000000400580 <lzcnt>:
  400580:    55                       push   %rbp
  400581:    48 89 e5                 mov    %rsp,%rbp
  400584:    48 89 7d e8              mov    %rdi,-0x18(%rbp)
  400588:    48 8b 45 e8              mov    -0x18(%rbp),%rax
  40058c:    48 89 45 f8              mov    %rax,-0x8(%rbp)
  400590:    48 0f bd 45 f8           bsr    -0x8(%rbp),%rax
  400595:    48 83 f0 3f              xor    $0x3f,%rax
  400599:    48 98                    cltq   
  40059b:    5d                       pop    %rbp
  40059c:    c3                       retq