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 92C403858C35; Wed, 24 Jan 2024 16:42:58 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 92C403858C35
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1706114578;
	bh=ssjsjGQEfqnpHysOHPHoOlwcKr+qcyKYTqYxUH3Wtpw=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=c3TfKDc4wsbUGG6YNO/UG9+2YO3OOvUKK52+8GlHVCbi5UrCA3dGigTJejwzIi6ON
	 0pWU8+7+F/rEMTttwYkSukl5uF+pw6Cy1Tt84uSwPN0eaypgM0kM5/kRf4TYH0Rabx
	 qO0P6Jr84rTImeJw2VsW15gOmZzHyDe/N+7dXBP8=
From: "rearnsha at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/113542] [14 Regression] gcc.target/arm/bics_3.c
 regression after change for pr111267
Date: Wed, 24 Jan 2024 16:42:58 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 14.0
X-Bugzilla-Keywords: missed-optimization, testsuite-fail
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rearnsha at gcc dot gnu.org
X-Bugzilla-Status: NEW
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: keywords
Message-ID: <bug-113542-4-N1aQ949uOj@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-113542-4@http.gcc.gnu.org/bugzilla/>
References: <bug-113542-4@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=3D113542

Richard Earnshaw <rearnsha at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization

--- Comment #2 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
The costing code is expecting

(parallel [
        (set (reg:SI 124 [ _7 ])
            (ne:SI (reg:SI 122 [ _2 ])
                (const_int 0 [0])))
        (clobber (reg:CC 100 cc))
    ])


To result in the assembler output

SUBS r124, R122, #1
SBC  r124, R122, r124

so really should have a cost of 8 (two insns).  But for some reason the thu=
mb2
back-end is not generating that output in this case.  Overall, that means t=
hat
for bic_si_test

BIC r0, r0, r1
SUBS r1, r0, #1
SBC r0, r0, r1

is neither better nor worse than

BICS r0, r0, r1
IT ne
MOVNE r0, #1

and certainly better than

BICS r0, r0, r1
ITE ne
MOVNE r2, #1
MOVEQ r2, #0

at least when it comes to code size.

So the test is somewhat flaky, but there is a further problem with the comp=
iler
not generating the expected sequence for NE(reg, 0) in Thumb2.=