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 22A073858CDB; Thu,  2 Mar 2023 23:24:26 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 22A073858CDB
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1677799466;
	bh=eOVcyAmK1bsdgYcrT+ECbeRR7qC17fe7rhtGkbm2nWk=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=dxoQFac1sE2hnPbJCT8uKjiqT/SL4r0t6mwLLAZ8MzbM1aKgf0+7UA9RMbj6eKKzi
	 Z0IUBdYFiomIGofPh5yccf2DiNzIx6yTaRBPmIA8aFlKhNYxIYKsvbBNPdghOSq4Ro
	 l8AN4UIS0j0FlDgwc10tSOXqDuJJbE4t5scS7Mqo=
From: "nok.raven at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/108992] Regression: Branch direction
 canonicalization leads to pointless tail duplication / CSE/sinking by
 inverting branch
Date: Thu, 02 Mar 2023 23:24:26 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: middle-end
X-Bugzilla-Version: 6.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: nok.raven at gmail dot com
X-Bugzilla-Status: RESOLVED
X-Bugzilla-Resolution: INVALID
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-108992-4-Yu0LJulRmV@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-108992-4@http.gcc.gnu.org/bugzilla/>
References: <bug-108992-4@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=3D108992

--- Comment #6 from Nikita Kniazev <nok.raven at gmail dot com> ---
> Did you see this in real code or you just noticed this while looking at c=
ode generation?

If you mean do I have any benchmark - unfortunately no. I noticed it for a
while by poking different code to compare Clang codegen to GCC.

> In the first case GCC predicts that the cond is going to be true 66% of t=
he time

The 66% thing is what I also noticed for a while.

> because there is comparison against 0 prediction going in the heurstics.

The duplication happens even if I make cond int and compare with any other
value

void use(int *);
void use2(int *);

void foo(int * p, int cond)
{
    if (cond =3D=3D 789) {
        use(p);
    }
    use2(p);
}=