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 542323858D39; Mon,  6 Mar 2023 10:38:41 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 542323858D39
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1678099121;
	bh=2TVGaaF4TsHVSjXwTb9gU8WSFOYYnNVR97w0vXRsZ/Y=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=EeHNTtCUzxTsvEn6reIwk626tjZY+JvP9x39yiGrgHrFx/gPCSrWkPhX6QJTjT7r5
	 pehcIrjVD1mGAX6+VKIOtyPcY1nPpbHyiRMNK50ojXZ3clMOWdmuz/azF5+beFq8k3
	 HHfSx34lSi4haALW/1LtLL+nNwoaIpV77UZ9uexc=
From: "rsandifo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/106594] [13 Regression] sign-extensions no
 longer merged into addressing mode
Date: Mon, 06 Mar 2023 10:38:38 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: rtl-optimization
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: missed-optimization, patch
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rsandifo at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P1
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 13.0
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: 
Message-ID: <bug-106594-4-mYjVIpmtJ3@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-106594-4@http.gcc.gnu.org/bugzilla/>
References: <bug-106594-4@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=3D106594

--- Comment #19 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.o=
rg> ---
I completely agree with comment 18.  See:
https://gcc.gnu.org/pipermail/gcc-patches/2022-September/601472.html
for some more on a similar theme.

make_compound_operation_int already has code to convert
(and (subreg X) (const_int N)) into (zero_extend X) when
nonzero_bits indicates that that's safe.  I think the AArch64
regression can be fixed by extending that to:

  (and (mult (subreg x) (const_int N2)) (const_int N))
  -> (mult (sign_extend X) (const_int N2))

for power-of-N2, with the nonzero_bits test adjusted for N2.
(mult is the canonical form here, since it's part of an address.)

Testing a patch for that.  Hopefully that should be less
risky than changing the expand/make_compound_operation
dance in stage 4.=