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 891283858C98; Mon, 26 Feb 2024 18:50:57 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 891283858C98
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1708973457;
	bh=V7FYNG0u4fpqBWjlKXJjEaEsBBF7F+pgJUWJXgL4LnI=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=AB7sTxwIXmkxloMxwo/Hxmdcs+EqrHrqSfgXkWUJU7bpDFMbo4wRZmX1aewpjreCu
	 SxsGAKdOpeOZV468z7EB6klxGh5+4fi10/Tr8zWSQavm0jQHt+PL6DAzer2t4kXzUP
	 E/VqSGsGJB6gsRaWWNg/8zsVNBAYXvNaX6v8evQQ=
From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/114121] wrong code with _BitInt() arithmetics
 at -O2
Date: Mon, 26 Feb 2024 18:50:57 +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: 14.0
X-Bugzilla-Keywords: wrong-code
X-Bugzilla-Severity: normal
X-Bugzilla-Who: jakub 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: 
Message-ID: <bug-114121-4-v3GdPe4On3@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-114121-4@http.gcc.gnu.org/bugzilla/>
References: <bug-114121-4@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=3D114121

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Indeed.  And -O2 -fno-tree-vectorize works.

I've changed it to
unsigned a, b, c, d, e;
unsigned _BitInt(256) f;

__attribute__((noipa)) unsigned short
bswap16 (int t)
{
  return __builtin_bswap16 (t);
}

void
foo (unsigned z, unsigned _BitInt(512) y, unsigned *r)
{
  unsigned t =3D __builtin_sub_overflow_p (0, y << 509, f);
  z *=3D bswap16 (t);
  d =3D __builtin_sub_overflow_p (c, 3, (unsigned _BitInt(512)) 0);
  unsigned q =3D z + c + b;
  unsigned short n =3D q >> (8 + a);
  *r =3D b + e + n;
}

int
main ()
{
  unsigned x;
  foo (8, 2, &x);
  if (x !=3D 8)
    __builtin_abort ();
}
and bswap16 is called with 1 with -O2 -fno-tree-vectorize and 0 with -O2, so
the problem is either during the computation of y << 509 (but that is fairly
simple thing out of bitintlower, set highest limb to the lowest limb << 61 =
and
clear all others),
or during the sub overflow.=