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 E4E0638708D1; Sat, 15 Jun 2024 13:51:55 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org E4E0638708D1
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1718459515;
	bh=jfA+NL9ZRERrx3ZiWwg7chdFFj4u6hvEAeFqz3LojZg=;
	h=From:To:Subject:Date:From;
	b=U4/tXE2wrK1RU2SkiVUqP5D2zSzAzCgkdc3ew42lWDIBu5kF5wl8bSYNWNDXvV+rT
	 TgzD/b3flHUi7RQf0tmPAKbOVqTh0z9h7+GSzhKXACYby44VKZaBWeDHGeTEmMgF17
	 Yw3zn1UFityfjlF0EDapgyWnkTt/MQaRB/kyfl3g=
From: "lis8215 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/115505] New: missing optimization: thumb1 use
 ldmia/stmia for load store DI/DF data when possible
Date: Sat, 15 Jun 2024 13:51:55 +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: 15.0
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
 attachments.created
Message-ID: <bug-115505-4@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=3D115505

            Bug ID: 115505
           Summary: missing optimization: thumb1 use ldmia/stmia for load
                    store DI/DF data when possible
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lis8215 at gmail dot com
  Target Milestone: ---

Created attachment 58438
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D58438&action=3Dedit
possible solution patch

At the moment GCC emits two ldr/str instructions for DI/DF modes load/store.
However there's a trick to use ldmia/stmia when address register in not
used anymore/dead or reused.

I don't know if it affects arm and/or thumb2 as well.
Patch for possible solution for thumb1 provided.

Comparing code size with the patch gives for v6-m/nofp:
       libgcc:  -52 bytes / -0.10%
Newlib's libc:  -68 bytes / -0.03%
         libm:  -96 bytes / -0.10%
    libstdc++: -140 bytes / -0.02%=