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 43328385414F; Tue, 11 Oct 2022 22:30:57 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 43328385414F
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1665527457;
	bh=6wWT4DvS5bEGrwnh9FfAHCUjn3E+CU/lFT+KihVTTeY=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=xeNL0/0hlH/g10ZfkA1byABfdTskXDzjme6tFC9X9fBHnEIt9ocW6W6ccqRnembXr
	 jZnZGSNilpKTb0+oW2K22HXYWW2sBQpJfnLBwu9gIszuktXIaHY7LsG8IH/QH/ru+b
	 AekF1SqOGGFK8+osexgl47KDcJEoRepNHrOpI/P8=
From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/107172] [13 Regression] wrong code with "-O1 -ftree-vrp"
 on x86_64-linux-gnu since r13-1268-g8c99e307b20c502e
Date: Tue, 11 Oct 2022 22:30:56 +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: 13.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: hjl.tools at gmail dot com
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-107172-4-kbjyGJh2E9@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-107172-4@http.gcc.gnu.org/bugzilla/>
References: <bug-107172-4@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=3D107172

--- Comment #17 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Segher Boessenkool from comment #14)
> (In reply to H.J. Lu from comment #13)
> > (In reply to Segher Boessenkool from comment #12)
> > >=20
> > > To determine the semantics of this piece of RTL you need to see the s=
etter(s)
> > > of reg 17 feeding this use.  In this case, the setter was
> > >   (set (reg:CCC 17)
> > >        (ne:CCC (reg:SI 82)
> > >                (const_int 0 [0])))
> > > which has no meaning for a use that uses "ltu".
> >=20
> > What should a valid setter look like?  It should set reg 17 in CCC mode=
 if
> > reg 82 in SI mode isn't 0.
>=20
> CCCmode can only represent the result of a comparison, like any other MOD=
E_CC
> thing.  The i386 CCCmode means only the carry bit can be used for this, so
> you
> beed to do an unsigned comparison against (const_int 1).  This will end up
> with
> the opposite polarity of what you said I guess, you need "geu" instead?

Since it checks if the input register is 0, compare against (const_int 1)
won't work here.=