linux-kernel - Re: [PATCH 1/2] crypto: x86/sha256-ni

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Date: Tue, 9 Apr 2024 18:52:02 +0200
From: "Stefan Kanthak" <stefan.kanthak@...go.de>
To: "Eric Biggers" <ebiggers@...nel.org>,
	<linux-crypto@...r.kernel.org>
Cc: <linux-kernel@...r.kernel.org>,
	<ardb@...nel.org>
Subject: Re: [PATCH 1/2] crypto: x86/sha256-ni - convert to use rounds macros

"Eric Biggers" <ebiggers@...nel.org> wrote:

> +.macro do_4rounds i, m0, m1, m2, m3
> +.if \i < 16
> +        movdqu  \i*4(DATA_PTR), MSG
> +        pshufb  SHUF_MASK, MSG
> +        movdqa  MSG, \m0
> +.else
> +        movdqa  \m0, MSG
> +.endif
> +        paddd   \i*4(SHA256CONSTANTS), MSG

To load the round constant independent from and parallel to the previous
instructions which use \m0 I recommend to change the first lines of the
do_4rounds macro as follows (this might save 1+ cycle per macro invocation,
and most obviously 2 lines):

macro do_4rounds i, m0, m1, m2, m3
if \i < 16
        movdqu  \i*4(DATA_PTR), \m0
        pshufb  SHUF_MASK, \m0
endif
        movdqa  \i*4(SHA256CONSTANTS), MSG
        paddd   \m0, MSG
..

regards
Stefan