From: Nathan Chancellor <natechancellor@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Nicolas Pitre <nico@fluxnic.net>,
Nick Desaulniers <ndesaulniers@google.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Stefan Agner <stefan@agner.ch>,
Russell King <linux@armlinux.org.uk>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] ARM: xor-neon: Replace __GNUC__ checks with CONFIG_CC_IS_GCC
Date: Fri, 31 May 2019 11:32:27 -0700 [thread overview]
Message-ID: <20190531183227.GA34102@archlinux-epyc> (raw)
In-Reply-To: <CAK8P3a0a0hMsZDkqKsfsyCWpdvDni72tjAxCz2VeAaU56zqrXg@mail.gmail.com>
On Fri, May 31, 2019 at 10:05:22AM +0200, Arnd Bergmann wrote:
> If I remember correctly, we also had the same issue with older versions
> of clang, possibly even newer ones. Shouldn't we check for a minimum
> compiler version when building with clang to ensure that the code is
> really vectorized?
>
> Arnd
Even on tip of tree, it doesn't look like vectorization happens
properly. With -S -Rpass-missed='.*' added to the xor-neon.c command:
/home/nathan/cbl/linux-next/include/asm-generic/xor.h:15:2: remark: the cost-model indicates that interleaving is not beneficial [-Rpass-missed=loop-vectorize]
/home/nathan/cbl/linux-next/include/asm-generic/xor.h:11:1: remark: List vectorization was possible but not beneficial with cost 0 >= 0 [-Rpass-missed=slp-vectorizer]
xor_8regs_2(unsigned long bytes, unsigned long *p1, unsigned long *p2)
^
So right now, it doesn't look like there is a minimum version for clang
and I don't think adding a warning for clang is productive (what is a
user supposed to do?)
Cheers,
Nathan
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Nathan Chancellor <natechancellor@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <linux@armlinux.org.uk>,
Nicolas Pitre <nico@fluxnic.net>, Stefan Agner <stefan@agner.ch>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
clang-built-linux <clang-built-linux@googlegroups.com>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH] ARM: xor-neon: Replace __GNUC__ checks with CONFIG_CC_IS_GCC
Date: Fri, 31 May 2019 11:32:27 -0700 [thread overview]
Message-ID: <20190531183227.GA34102@archlinux-epyc> (raw)
In-Reply-To: <CAK8P3a0a0hMsZDkqKsfsyCWpdvDni72tjAxCz2VeAaU56zqrXg@mail.gmail.com>
On Fri, May 31, 2019 at 10:05:22AM +0200, Arnd Bergmann wrote:
> If I remember correctly, we also had the same issue with older versions
> of clang, possibly even newer ones. Shouldn't we check for a minimum
> compiler version when building with clang to ensure that the code is
> really vectorized?
>
> Arnd
Even on tip of tree, it doesn't look like vectorization happens
properly. With -S -Rpass-missed='.*' added to the xor-neon.c command:
/home/nathan/cbl/linux-next/include/asm-generic/xor.h:15:2: remark: the cost-model indicates that interleaving is not beneficial [-Rpass-missed=loop-vectorize]
/home/nathan/cbl/linux-next/include/asm-generic/xor.h:11:1: remark: List vectorization was possible but not beneficial with cost 0 >= 0 [-Rpass-missed=slp-vectorizer]
xor_8regs_2(unsigned long bytes, unsigned long *p1, unsigned long *p2)
^
So right now, it doesn't look like there is a minimum version for clang
and I don't think adding a warning for clang is productive (what is a
user supposed to do?)
Cheers,
Nathan
next prev parent reply other threads:[~2019-05-31 18:32 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-28 23:57 [PATCH] ARM: xor-neon: Replace __GNUC__ checks with CONFIG_CC_IS_GCC Nathan Chancellor
2019-05-28 23:57 ` Nathan Chancellor
2019-05-30 23:00 ` Nick Desaulniers
2019-05-30 23:00 ` Nick Desaulniers
2019-05-31 8:05 ` Arnd Bergmann
2019-05-31 8:05 ` Arnd Bergmann
2019-05-31 18:32 ` Nathan Chancellor [this message]
2019-05-31 18:32 ` Nathan Chancellor
2019-05-31 19:21 ` Arnd Bergmann
2019-05-31 19:21 ` Arnd Bergmann
2019-05-31 20:06 ` Nick Desaulniers
2019-05-31 20:06 ` Nick Desaulniers
2019-05-31 20:26 ` Nathan Chancellor
2019-05-31 20:26 ` Nathan Chancellor
2019-05-31 21:03 ` Arnd Bergmann
2019-05-31 21:03 ` Arnd Bergmann
2019-06-01 0:28 ` Nathan Chancellor
2019-06-01 0:28 ` Nathan Chancellor
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