Re: [PATCH 4/5] xor/arm64: Use shared NEON intrinsics implementation from 32-bit ARM

[Christoph Hellwig <hch@lst.de>]

On Fri, Mar 27, 2026 at 03:45:56PM +0100, Ard Biesheuvel wrote:
> On Fri, 27 Mar 2026, at 14:50, Christoph Hellwig wrote:
> > On Fri, Mar 27, 2026 at 12:30:52PM +0100, Ard Biesheuvel wrote:
> >> From: Ard Biesheuvel <ardb@kernel.org>
> >> 
> >> Tweak the arm64 code so that the pure NEON intrinsics implementation of
> >> XOR is shared between arm64 and ARM.
> >
> > Instead of hiding the implementation in a header, just split xor-neon.c
> > into two .c files, one of which could be built by arm32 as well.
> 
> That is what patch 3/5 does. This patch wires up that version into arm64, and drops the copy that has become redundant as a result.

Yeah, sorry - I misread the series a little.

> 
> > probably
> > in the arm/ instead of the arm64/ subdirectory, but we can also add a
> > new arm-common one if that's what the arm maintainers prefer.
> 
> Having the shared pure NEON version in arm/ is perfectly fine.

So here would be my preference:

 - keep all the arm/arm64 code in lib/raid/xor/arm
 - have the neon and EOR3 code in a single xor-neon.c file, with an
   ifdef CONFIG_ARM64 around the EOE3 routines

This avoid the including of .c files which is always a bit ugly.
But if there is a strong argument to prefer including of the .c file I
can live with that as well.

> 
> Building it as a separate compilation unit for arm64 should also be straight-forward, the only issue is that the 2-way NEON version needs to be shared with the EOR3 compilation unit.
> 
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