Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210505033945.1282851-1-ak@linux.intel.com> <YJI/OwoflyY2IXvf@hirez.programming.kicks-ass.net>
 <875yzxh8j8.fsf@oldenburg.str.redhat.com> <20210505143916.GS4032392@tassilo.jf.intel.com>
In-Reply-To: <20210505143916.GS4032392@tassilo.jf.intel.com>
From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Wed, 5 May 2021 09:41:09 -0700
Message-ID: <CAKwvOdneTkwm1xmte2SxwR=pcp3vi320kQuQHtVNVbnqLbcP3Q@mail.gmail.com>
Subject: Re: [PATCH] sched: Work around undefined behavior in sched class checking
To:     Andi Kleen <ak@linux.intel.com>
Cc:     Florian Weimer <fweimer@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>,
        linux-toolchains@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, May 5, 2021 at 7:39 AM Andi Kleen <ak@linux.intel.com> wrote:
>
> >  Would you please provide a
> > minimal test case?
>
> You can only reproduce it with a LTO build because it needs knowledge
> between different translation units for this specific case.
>
> But gcc will totally do the optimization even without LTO if it can
> prove the same inside a single TU.

It would be helpful to isolate a test case that doesn't rely on LTO,
if possible.
-- 
Thanks,
~Nick Desaulniers