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From: Nick Desaulniers <ndesaulniers@google.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Adrian Ratiu <adrian.ratiu@collabora.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Russell King <linux@armlinux.org.uk>,
	LKML <linux-kernel@vger.kernel.org>,
	Collabora Kernel ML <kernel@collabora.com>,
	Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH 2/2] arm: lib: xor-neon: disable clang vectorization
Date: Thu, 12 Nov 2020 13:55:36 -0800	[thread overview]
Message-ID: <CAKwvOdmCgWFgHof8fqep1hymeNc368Fn8rLDwzzCU58tV5wyXg@mail.gmail.com> (raw)
In-Reply-To: <20201112215033.GA438824@rani.riverdale.lan>

On Thu, Nov 12, 2020 at 1:50 PM Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> On Wed, Nov 11, 2020 at 04:15:59PM +0200, Adrian Ratiu wrote:
> > On Tue, 10 Nov 2020, Nick Desaulniers <ndesaulniers@google.com>
> > wrote:
> > >
> > > Yes, though additionally Arvind points out that this code is
> > > kind of curious if there was overlap; maybe the parameters
> > > should just be restrict-qualified.
> > >
> >
> > For now I think I'll just re-send the GCC changes and leave the
> > Clang optimization as is, until we better understand what's
> > happening and what's the best way to enable it.
> >
>
> Note that the __restrict__ keywords also help GCC -- it saves it from
> having to emit the non-vectorized version and switch between the two at
> runtime. If we can verify it's safe, it's a good thing to add all
> around.

100% agree.  Even a BUILD_BUG_ON or WARN_ON in callers to validate
such an invariant might be nice.
-- 
Thanks,
~Nick Desaulniers

WARNING: multiple messages have this Message-ID (diff)
From: Nick Desaulniers <ndesaulniers@google.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Adrian Ratiu <adrian.ratiu@collabora.com>,
	Russell King <linux@armlinux.org.uk>,
	LKML <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Collabora Kernel ML <kernel@collabora.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 2/2] arm: lib: xor-neon: disable clang vectorization
Date: Thu, 12 Nov 2020 13:55:36 -0800	[thread overview]
Message-ID: <CAKwvOdmCgWFgHof8fqep1hymeNc368Fn8rLDwzzCU58tV5wyXg@mail.gmail.com> (raw)
In-Reply-To: <20201112215033.GA438824@rani.riverdale.lan>

On Thu, Nov 12, 2020 at 1:50 PM Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> On Wed, Nov 11, 2020 at 04:15:59PM +0200, Adrian Ratiu wrote:
> > On Tue, 10 Nov 2020, Nick Desaulniers <ndesaulniers@google.com>
> > wrote:
> > >
> > > Yes, though additionally Arvind points out that this code is
> > > kind of curious if there was overlap; maybe the parameters
> > > should just be restrict-qualified.
> > >
> >
> > For now I think I'll just re-send the GCC changes and leave the
> > Clang optimization as is, until we better understand what's
> > happening and what's the best way to enable it.
> >
>
> Note that the __restrict__ keywords also help GCC -- it saves it from
> having to emit the non-vectorized version and switch between the two at
> runtime. If we can verify it's safe, it's a good thing to add all
> around.

100% agree.  Even a BUILD_BUG_ON or WARN_ON in callers to validate
such an invariant might be nice.
-- 
Thanks,
~Nick Desaulniers

_______________________________________________
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-11-12 21:55 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-06  5:14 [PATCH 0/2] arm: lib: xor-neon: Remove warn & disble neon vect Adrian Ratiu
2020-11-06  5:14 ` Adrian Ratiu
2020-11-06  5:14 ` [PATCH 1/2] arm: lib: xor-neon: remove unnecessary GCC < 4.6 warning Adrian Ratiu
2020-11-06  5:14   ` Adrian Ratiu
2020-11-06 14:46   ` Arnd Bergmann
2020-11-06 14:46     ` Arnd Bergmann
2020-11-06 18:03     ` Nathan Chancellor
2020-11-06 18:03       ` Nathan Chancellor
2020-11-06 21:46       ` Arnd Bergmann
2020-11-06 21:46         ` Arnd Bergmann
2020-11-06  5:14 ` [PATCH 2/2] arm: lib: xor-neon: disable clang vectorization Adrian Ratiu
2020-11-06  5:14   ` Adrian Ratiu
2020-11-06 10:14   ` Nathan Chancellor
2020-11-06 10:14     ` Nathan Chancellor
2020-11-06 11:50     ` Adrian Ratiu
2020-11-06 11:50       ` Adrian Ratiu
2020-11-06 18:01       ` Nathan Chancellor
2020-11-06 18:01         ` Nathan Chancellor
2020-11-06 19:52       ` Nick Desaulniers
2020-11-06 19:52         ` Nick Desaulniers
2020-11-07 18:07         ` Adrian Ratiu
2020-11-07 18:07           ` Adrian Ratiu
2020-11-09 19:53         ` Adrian Ratiu
2020-11-09 19:53           ` Adrian Ratiu
2020-11-10 21:41           ` Nick Desaulniers
2020-11-10 21:41             ` Nick Desaulniers
2020-11-10 22:15             ` Arvind Sankar
2020-11-10 22:15               ` Arvind Sankar
2020-11-10 22:36               ` Nick Desaulniers
2020-11-10 22:36                 ` Nick Desaulniers
2020-11-10 22:39                 ` Nick Desaulniers
2020-11-10 22:39                   ` Nick Desaulniers
2020-11-10 22:39                   ` Nick Desaulniers
2020-11-10 22:39                     ` Nick Desaulniers
2020-11-10 22:54                     ` Arvind Sankar
2020-11-10 22:54                       ` Arvind Sankar
2020-11-10 23:56             ` Adrian Ratiu
2020-11-10 23:56               ` Adrian Ratiu
2020-11-11  0:18               ` Nick Desaulniers
2020-11-11  0:18                 ` Nick Desaulniers
2020-11-11 14:15                 ` Adrian Ratiu
2020-11-11 14:15                   ` Adrian Ratiu
2020-11-12 21:50                   ` Arvind Sankar
2020-11-12 21:50                     ` Arvind Sankar
2020-11-12 21:55                     ` Nick Desaulniers [this message]
2020-11-12 21:55                       ` Nick Desaulniers
2020-11-07 10:22   ` Russell King - ARM Linux admin
2020-11-07 10:22     ` Russell King - ARM Linux admin
2020-11-07 18:12     ` Adrian Ratiu
2020-11-07 18:12       ` Adrian Ratiu
2020-11-08 17:40   ` Arvind Sankar
2020-11-08 17:40     ` Arvind Sankar
2020-11-08 18:09     ` Arvind Sankar
2020-11-08 18:09       ` Arvind Sankar
2020-11-08 20:14       ` Ard Biesheuvel
2020-11-08 20:14         ` Ard Biesheuvel

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