From: Nathan Chancellor <natechancellor@gmail.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>, Nicolas Pitre <nico@fluxnic.net>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
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 13:26:05 -0700 [thread overview]
Message-ID: <20190531202605.GA78113@archlinux-epyc> (raw)
In-Reply-To: <CAKwvOdkyk3qLMPquSZqXCFauTADJU5X9qJi_fhJqbUuCYBH-6Q@mail.gmail.com>
On Fri, May 31, 2019 at 01:06:13PM -0700, Nick Desaulniers wrote:
> On Fri, May 31, 2019 at 12:21 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > clang, I would suggest dropping your patch then, and instead adding
>
> I disagree. The minimum version of gcc required to build the kernel
> is 4.6, so the comment about older versions of gcc is irrelevant and
> should be removed.
>
> Nathan's -Rpass warnings are warning that vectorization was not
> calculated to be profitable **for 1 of the 4 functions** by LLVM.
> Surely we wouldn't disable NEON opts for XOR because 1 of 4 was not
> vectorized?
Well I kept it short but clang warns that all of the loops are not
profitable.
However, the config option for xor-neon.c is CONFIG_XOR_BLOCKS, which
also controls the arm64 implementation. We wouldn't want to disable it
for clang altogether if it works on arm64 fine.
If it turns out to be broken for both, I suppose I would be okay with
disabling CONFIG_XOR_BLOCKS for clang but it should be done in a
separate patch as this one should be applied regardless of clang working
or not (because this warning will appear again when clang is fixed).
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: Nick Desaulniers <ndesaulniers@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
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>
Subject: Re: [PATCH] ARM: xor-neon: Replace __GNUC__ checks with CONFIG_CC_IS_GCC
Date: Fri, 31 May 2019 13:26:05 -0700 [thread overview]
Message-ID: <20190531202605.GA78113@archlinux-epyc> (raw)
In-Reply-To: <CAKwvOdkyk3qLMPquSZqXCFauTADJU5X9qJi_fhJqbUuCYBH-6Q@mail.gmail.com>
On Fri, May 31, 2019 at 01:06:13PM -0700, Nick Desaulniers wrote:
> On Fri, May 31, 2019 at 12:21 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > clang, I would suggest dropping your patch then, and instead adding
>
> I disagree. The minimum version of gcc required to build the kernel
> is 4.6, so the comment about older versions of gcc is irrelevant and
> should be removed.
>
> Nathan's -Rpass warnings are warning that vectorization was not
> calculated to be profitable **for 1 of the 4 functions** by LLVM.
> Surely we wouldn't disable NEON opts for XOR because 1 of 4 was not
> vectorized?
Well I kept it short but clang warns that all of the loops are not
profitable.
However, the config option for xor-neon.c is CONFIG_XOR_BLOCKS, which
also controls the arm64 implementation. We wouldn't want to disable it
for clang altogether if it works on arm64 fine.
If it turns out to be broken for both, I suppose I would be okay with
disabling CONFIG_XOR_BLOCKS for clang but it should be done in a
separate patch as this one should be applied regardless of clang working
or not (because this warning will appear again when clang is fixed).
Cheers,
Nathan
next prev parent reply other threads:[~2019-05-31 20:26 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
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 [this message]
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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