linux-kernel - Re: [PATCH 2/2] arm: lib: xor-neon: disable clang vectorization

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Message-ID: <20201107102203.GV1551@shell.armlinux.org.uk>
Date:   Sat, 7 Nov 2020 10:22:03 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Adrian Ratiu <adrian.ratiu@...labora.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH 2/2] arm: lib: xor-neon: disable clang vectorization

On Fri, Nov 06, 2020 at 07:14:36AM +0200, Adrian Ratiu wrote:
> diff --git a/arch/arm/lib/xor-neon.c b/arch/arm/lib/xor-neon.c
> index e1e76186ec23..84c91c48dfa2 100644
> --- a/arch/arm/lib/xor-neon.c
> +++ b/arch/arm/lib/xor-neon.c
> @@ -18,6 +18,10 @@ MODULE_LICENSE("GPL");
>   * Pull in the reference implementations while instructing GCC (through
>   * -ftree-vectorize) to attempt to exploit implicit parallelism and emit
>   * NEON instructions.
> +

Please tidy this up before submission; we normally continue the "*" for
blank lines in comment blocks. Thanks.

> + * On Clang the loop vectorizer is enabled by default, but due to a bug
> + * (https://bugs.llvm.org/show_bug.cgi?id=40976) vectorization is broke
> + * so xor-neon is disabled in favor of the default reg implementations.
>   */
>  #ifdef CONFIG_CC_IS_GCC
>  #pragma GCC optimize "tree-vectorize"
> -- 
> 2.29.0
> 
> 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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