From: Peter Zijlstra <peterz@infradead.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Matthias Kaehlcke <mka@chromium.org>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H . Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
Manoj Gupta <manojgupta@chromium.org>,
Tiancong Wang <tcwang@chromium.org>,
Stephen Hines <srhines@google.com>,
clang-built-linux@googlegroups.com,
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Subject: Re: [PATCH] lib: Add shared copy of __lshrti3 from libgcc
Date: Mon, 18 Mar 2019 10:14:28 +0100 [thread overview]
Message-ID: <20190318091428.GI6058@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKwvOdkfb_DT2p2vvxK2ye6JpGYB4qqCc8yECU_JEkrc+6HXDA@mail.gmail.com>
On Fri, Mar 15, 2019 at 03:06:37PM -0700, Nick Desaulniers wrote:
> On Fri, Mar 15, 2019 at 1:54 PM Matthias Kaehlcke <mka@chromium.org> wrote:
> >
> > The compiler may emit calls to __lshrti3 from the compiler runtime
> > library, which results in undefined references:
> >
> > arch/x86/kvm/x86.o: In function `mul_u64_u64_shr':
> > include/linux/math64.h:186: undefined reference to `__lshrti3'
>
> Looks like Clang will emit this at -Oz (but not -O2):
> https://godbolt.org/z/w1_2YC
*OMG*, what is that compiler smoking and why do we want that?
It doesn't even do that for "-Os".
So where "-Os" is "Optimize for Sadness" this "-Oz" thing is like a
downright depression. Please just take it out back. Don't enable crap
like this.
next prev parent reply other threads:[~2019-03-18 9:14 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-15 20:54 [PATCH] lib: Add shared copy of __lshrti3 from libgcc Matthias Kaehlcke
2019-03-15 22:06 ` Nick Desaulniers
2019-03-15 22:08 ` hpa
2019-03-15 23:34 ` Matthias Kaehlcke
2019-03-15 23:51 ` hpa
2019-03-15 22:12 ` hpa
2019-03-15 23:47 ` Matthias Kaehlcke
2019-03-15 23:53 ` hpa
2019-03-18 16:38 ` Matthias Kaehlcke
2019-03-15 23:29 ` Matthias Kaehlcke
2019-03-18 9:14 ` Peter Zijlstra [this message]
2019-03-18 14:43 ` David Laight
2019-03-18 14:54 ` Peter Zijlstra
2019-03-18 21:31 ` Matthias Kaehlcke
2019-03-18 21:50 ` hpa
2019-03-18 22:16 ` Matthias Kaehlcke
2019-03-18 23:44 ` hpa
2019-03-18 23:52 ` Matthias Kaehlcke
2019-03-18 23:54 ` hpa
2019-03-18 23:55 ` hpa
2019-03-19 17:10 ` Matthias Kaehlcke
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