Re: [PATCH] lib/crypto: x86/nh: Optimize nh_sse2()

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Nov 04, 2026 at 08:24:27PM -0800, Eric Biggers wrote:
> Various microoptimizations for nh_sse2().  Nothing too exciting:
> 
> - Instead of adding the message words to the key words and then
>   permuting both, do the following: permute both when loading, add the
>   permuted words, and multiply together adjacent pairs.  This saves two
>   pshufd instructions per 16 bytes processed, and the ones that remain
>   are now better separated in the flow.
> 
> - Reassign register aliases to put the most frequently used variables in
>   %xmm0-%xmm7, which take fewer bytes to encode in many instructions.
> 
> - Replace the unnecessary T7 with T0.
> 
> - Replace the 'add $0x30, KEY' with base+displacement addressing, which
>   was already being used anyway in most cases.
> 
> nh_sse2() shrinks from 1038 bytes to 913 bytes, and a quick benchmark
> (with AVX2 support disabled) shows 3% faster Adiantum encryption.
> 
> Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> ---
>  lib/crypto/x86/nh-sse2.S | 60 +++++++++++++++++++++-------------------
>  1 file changed, 31 insertions(+), 29 deletions(-)

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-next

- Eric