linux-kernel - RE: [PATCH v2 6/6] crypto: lib/sha - Combine round constants and message schedule

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Date:   Tue, 20 Oct 2020 21:36:00 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Arvind Sankar' <nivedita@...m.mit.edu>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 6/6] crypto: lib/sha - Combine round constants and
 message schedule

From: Arvind Sankar
> Sent: 20 October 2020 21:40
> 
> Putting the round constants and the message schedule arrays together in
> one structure saves one register, which can be a significant benefit on
> register-constrained architectures. On x86-32 (tested on Broadwell
> Xeon), this gives a 10% performance benefit.

I'm actually stunned it makes that much difference.
The object code must be truly horrid (before and after).

There are probably other strange tweaks that give a similar
improvement.

	David

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