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 33F0A3858D3C; Sun,  5 Nov 2023 22:02:18 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 33F0A3858D3C
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1699221738;
	bh=l426dekOqbf2ABE3OCpCRvaFrWKQ2UWaUERFcSPUEfU=;
	h=From:To:Subject:Date:From;
	b=M6yL3cReNKI3Hl+iANnex4vaCdY1Z/3AeNZjapWaodNU3d7k7GIwvbXwBEAHoPSg5
	 P052lzYXzIMNS2X2V5utC7HRWQIUjQKfF9P2PKFT4OHBQw+Ipt1pEQHXyOXF4gHnXZ
	 ISPPJvN8SZCF5jlZP3rLvS3zTHgadG+61IwYDqyA=
From: "lis8215 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/112398] New: Suboptimal code generation for xor
 pattern on subword data
Date: Sun, 05 Nov 2023 22:02:17 +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-Version: 14.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: lis8215 at gmail dot com
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-112398-4@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
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112398

            Bug ID: 112398
           Summary: Suboptimal code generation for xor pattern on subword
                    data
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lis8215 at gmail dot com
  Target Milestone: ---

These minimal examples showcase the issue:

uint8_t neg8 (const uint8_t *src)
{
    return ~*src;
    // or return *src ^ 0xff;
}

uint16_t neg16 (const uint16_t *src)
{
    return ~*src;
    // or return *src ^ 0xffff;
}

GCC transforms xor here to not + zero_extend, which isn't the best choice.
I guess combiner have to try xor pattern instead of not + zero_extend as it
might be cheaper.=