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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next prev parent reply other threads:[~2019-05-31 20:26 UTC|newest]
Thread overview: 9+ 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
2019-05-30 23:00 ` Nick Desaulniers
2019-05-31 8:05 ` Arnd Bergmann
2019-05-31 18:32 ` Nathan Chancellor
2019-05-31 19:21 ` Arnd Bergmann
2019-05-31 20:06 ` Nick Desaulniers
2019-05-31 20:26 ` Nathan Chancellor [this message]
2019-05-31 21:03 ` Arnd Bergmann
2019-06-01 0:28 ` Nathan Chancellor
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