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 261013858439; Mon, 24 Oct 2022 13:31:10 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 261013858439
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1666618270;
	bh=GlN2rEAlb5jYZ5TDnBfOrUACAjkuL7lOXMZf6MZWhlc=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=bZ5Ob//Zw4ks0ywVAEVtXLI4FzxIWaDnMepv/j28+oT0uzvnu3n0N9aBFPhnP/xJW
	 Dbxe1hcHKaP7fxRSkxOBO/iIP7LqIqz+36+4UH+bJynwIZHDdZYqyR3h8Mhdeys2Ok
	 I59eKAV2X+KMGLRbiLgdsFgDNjjsqWdIIx8yV00E=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/107176] [10/11/12/13 Regression] Wrong code
 at -Os on x86_64-pc-linux-gnu since r7-2012-g43aabfcfd4139e4c
Date: Mon, 24 Oct 2022 13:31:09 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: ASSIGNED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P2
X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org
X-Bugzilla-Target-Milestone: 10.5
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: see_also
Message-ID: <bug-107176-4-thH4mWGWkS@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-107176-4@http.gcc.gnu.org/bugzilla/>
References: <bug-107176-4@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=3D107176

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=3D42512

--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
PR42512 is also related and its "fix" is even worse...  it's worse in that
it hides wrong cases but also throws away correct ones.  But it also
shows that we still mishandle that testcase with or without the fix(es).

It seems that the intent of the SCC analysis in interpret_loop_phi is to
look at the linear operation (or the chain of linear operations) associated
in a way that it matches

 (T2)(init + ev)

from which then (T2) { init, +, ev } follows.

So when

 PHI' =3D (int)(signed char)PHI + 11

we directly match (int)(signed char){ init, +, 11 }

and for

 PHI' =3D (long)((unsigned)PHI + -90u) + 91

we'd have to associate the outer + 91 which we can't do (but effectively
do due to the present bug).=