From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-495996-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 94252 invoked by alias); 31 Aug 2015 14:43:43 -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 94076 invoked by uid 48); 31 Aug 2015 14:43:39 -0000
From: "glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/67413] New: Complex NOP expanded to several operations
Date: Mon, 31 Aug 2015 14:43:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 6.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: glisse at gcc dot gnu.org
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution:
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: bug_id short_desc product version bug_status keywords bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-67413-4@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: 2015-08/txt/msg02138.txt.bz2

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67413

            Bug ID: 67413
           Summary: Complex NOP expanded to several operations
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: glisse at gcc dot gnu.org
  Target Milestone: ---

_Complex unsigned f(_Complex int i){return i;}

yields

        movl    %edi, %eax
        shrq    $32, %rdi
        salq    $32, %rdi
        orq     %rdi, %rax
        ret

I read somewhere that complex integers are a deprecated gcc extension, but gcc
only warns in pedantic mode, and it should not be too hard to improve the
generated code.

Note that tree optimizers currently also fail to optimize the corresponding
code:

long f(long x){
  long y = x >> 32;
  y <<= 32;
  int z = x;
  return z | y;
}

(using & CST instead of >> and << does not help)