From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
 id 2F174388A83F; Wed, 13 May 2020 08:58:43 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2F174388A83F
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
 s=default; t=1589360323;
 bh=qiVJ7AULXcgclGaHkK70oZnWxcffuGdYoAIgTdOOuLg=;
 h=From:To:Subject:Date:From;
 b=Skvr4Astf29YMGuARHL809GmzANGZZzgWpsk54au4S+7O6Ty5DqA9ZjoR16UQfdv+
 ZjfW8Qyj5OM/nxK1zyuTQmThBeIUOll11eMe+RlZOlManrvuLBCA2TfIcpnZPes5ao
 4W884gCWD9ki3mfHclN1F40YhRfDZ/RJ33KKZEQ4=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/95102] New: missed if-conversion
Date: Wed, 13 May 2020 08:58:43 +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: 11.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth 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
 bug_severity priority component assigned_to reporter target_milestone
Message-ID: <bug-95102-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
X-BeenThere: gcc-bugs@gcc.gnu.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Gcc-bugs mailing list <gcc-bugs.gcc.gnu.org>
List-Unsubscribe: <http://gcc.gnu.org/mailman/options/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=unsubscribe>
List-Archive: <https://gcc.gnu.org/pipermail/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-request@gcc.gnu.org?subject=help>
List-Subscribe: <http://gcc.gnu.org/mailman/listinfo/gcc-bugs>,
 <mailto:gcc-bugs-request@gcc.gnu.org?subject=subscribe>
X-List-Received-Date: Wed, 13 May 2020 08:58:43 -0000

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D95102

            Bug ID: 95102
           Summary: missed if-conversion
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
  Target Milestone: ---

If you rewrite gcc.target/i386/pr54855-9.c to a form GIMPLE looks like after
some PRE you end up with

typedef float vec __attribute__((vector_size(16)));

vec
foo (vec x, float a)
{
  if (!(x[0] < a))
    x[0] =3D a;
  return x;
}

which is no longer recognized as the same and emits

foo:
.LFB0:
        .cfi_startproc
        comiss  %xmm0, %xmm1
        ja      .L2
        movss   %xmm1, %xmm0
.L2:
        ret

instead of

foo:
.LFB1:=20=20
        .cfi_startproc
        minss   %xmm1, %xmm0
        ret

this is because RTL if-conversion does not recognize

    7: r86:SF=3Dvec_select(r84:V4SF,parallel)
    8: flags:CCFP=3Dcmp(r85:SF,r86:SF)
      REG_DEAD r86:SF
    9: pc=3D{(flags:CCFP>0)?L14:pc}
      REG_DEAD flags:CCFP
      REG_BR_PROB 536870916

   10: NOTE_INSN_BASIC_BLOCK 3
   12: r84:V4SF=3Dvec_merge(vec_duplicate(r85:SF),r84:V4SF,0x1)
      REG_DEAD r85:SF

   14: L14:
   15: NOTE_INSN_BASIC_BLOCK 4
   20: xmm0:V4SF=3Dr84:V4SF

the form it does recognize is

    8: r82:SF=3Dvec_select(r84:V4SF,parallel)
    9: flags:CCFP=3Dcmp(r85:SF,r82:SF)
   10: pc=3D{(flags:CCFP>0)?L28:pc}
      REG_DEAD flags:CCFP
      REG_BR_PROB 536870916

   28: L28:
   14: NOTE_INSN_BASIC_BLOCK 3
    5: r85:SF=3Dr82:SF
      REG_DEAD r82:SF

   15: L15:
   16: NOTE_INSN_BASIC_BLOCK 4
   18: r87:V4SF=3Dvec_merge(vec_duplicate(r85:SF),r84:V4SF,0x1)=