linux-kernel - Re: [PATCH] lib/raid6: use vdupq_n

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Message-ID: <20190228174728.GE226495@arrakis.emea.arm.com>
Date:   Thu, 28 Feb 2019 17:47:28 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     ndesaulniers@...gle.com
Cc:     will.deacon@....com, ard.biesheuvel@...aro.org, arnd@...db.de,
        broonie@...nel.org, linux@...linux.org.uk,
        linux-arm-kernel@...ts.infradead.org,
        Nathan Chancellor <natechancellor@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/raid6: use vdupq_n_u8 to avoid endianness warnings

On Mon, Feb 25, 2019 at 08:03:42PM -0800, ndesaulniers@...gle.com wrote:
> Clang warns: vector initializers are not compatible with NEON intrinsics
> in big endian mode [-Wnonportable-vector-initialization]
> 
> While this is usually the case, it's not an issue for this case since
> we're initializing the uint8x16_t (16x uint8_t's) with the same value.
> 
> Instead, use vdupq_n_u8 which both compilers lower into a single movi
> instruction: https://godbolt.org/z/vBrgzt
> 
> This avoids the static storage for a constant value.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/214
> Suggested-by: Nathan Chancellor <natechancellor@...il.com>
> Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
>  lib/raid6/neon.uc            | 5 ++---
>  lib/raid6/recov_neon_inner.c | 7 ++-----
>  2 files changed, 4 insertions(+), 8 deletions(-)

Queued for 5.1. Thanks.

-- 
Catalin