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 08A863858C31; Sun, 28 May 2023 23:05:40 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 08A863858C31
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1685315141;
	bh=6i7koPg0Ufi3rNs8cKZ8VfPe/8DdvpxzI/khmqcQNhk=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=W1oQt8tLBXHC9ogd4YyOFUzV0difCz9ScP8Z5FDf4P9PzZT1io6ELM4Lm2qHWm/3h
	 zEqXr9LSUrt8c63SKeaisNWP1ZGXz65oZYSLea4CReHGYkMjkr2ixdnicH7Q+hIPW0
	 oVKS8Ty/KrUxuuX6K94vlTjOVhfs7SooB0NidROw=
From: "pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/85234] missed optimisation opportunity for (x
 >> CST)!=0 is not optimized to   (((unsigned)x) >=  (1<<CST)
Date: Sun, 28 May 2023 23:05:40 +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: 8.0.1
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: pinskia 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-85234-4-xZLt7jCBC0@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-85234-4@http.gcc.gnu.org/bugzilla/>
References: <bug-85234-4@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=3D85234

--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Here is the testcase for the constants besides 0:L
```
#define N 3
#define unsigned int
#define cmp =3D=3D
#define M 0xf0000000u
_Bool f(unsigned x, int t)
{
        return (x << N) cmp (M << N);
}
_Bool f1(unsigned x, int t)
{
        return ((x^M) & (-1u>>N)) cmp 0;
}

_Bool f2(unsigned x, int t)
{
        return (x & (-1u>>N)) cmp (M & (-1u>>N));
}

_Bool g(unsigned x, int t)
{
        return (x >> N) cmp M;
}
_Bool g2(unsigned x, int t)
{
        _Bool tttt =3D 0;
        if (tttt)
        return 0;
        return (x & (-1u<<N)) cmp (M << N);
}
#if M=3D=3D0
_Bool g1(unsigned x, int t)
{
        return (x >=3D (1u<<N)) cmp M;
}
#endif
```
The tttt is defined somehow but I can't figure it out right now.=20

Note for f, The bottom N bits need not to be set, that is basically what (M=
 <<
N) specifies.=