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 B9BDB3857437; Fri, 17 Feb 2023 17:59:00 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org B9BDB3857437
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1676656740;
	bh=Feogtp0uELvzZfqsSP7JMufkkuD0V/2Vken74+WiMeE=;
	h=From:To:Subject:Date:From;
	b=aWVWJMOE/NzOPf61ZSvI5/Xc9CojaXexrNtb5JXgNXGfliU8cho0J4XXn3GwiuACi
	 i4Q7h+G72TFEoneFJzyKzzou6JEwGnnF+iSiAnmF6sXvoJBeuAxcLE65pmEE/74vca
	 5v1k6r1H3/zKBlQTrav45i2nWOb3hrrc0Iie4TZQ=
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108840] New: Aarch64 doesn't optimize away shift counter
 masking
Date: Fri, 17 Feb 2023 17:59:00 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub 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-108840-4@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=3D108840

            Bug ID: 108840
           Summary: Aarch64 doesn't optimize away shift counter masking
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

As mentioned in=20
https://gcc.gnu.org/pipermail/gcc-patches/2023-February/612214.html
aarch64 doesn't optimize away and instructions masking shift count if there=
 is
more than one shift with the same count.  Consider -O2 -fno-tree-vectorize:
int
foo (int x, int y)
{
  return x << (y & 31);
}

void
bar (int x[3], int y)
{
  x[0] <<=3D (y & 31);
  x[1] <<=3D (y & 31);
  x[2] <<=3D (y & 31);
}

void
baz (int x[3], int y)
{
  y &=3D 31;
  x[0] <<=3D y;
  x[1] <<=3D y;
  x[2] <<=3D y;
}

void corge (int, int, int);

void
qux (int x, int y, int z, int n)
{
  n &=3D 31;
  corge (x << n, y << n, z >> n);
}

foo is optimized correctly, combine matches the shift with masking, but in =
the
rest of cases due to costs the desirable combination is rejected.  Shift wi=
th
embedded masking of the count should have rtx_cost the same as normal shift
when it is actually under the hood the shift itself.=