From: David Laight <David.Laight@ACULAB.COM>
To: "'Juergen Gross'" <jgross@suse.com>,
Ingo Molnar <mingo@kernel.org>,
"Eric Biggers" <ebiggers3@gmail.com>
Cc: "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
"David S . Miller" <davem@davemloft.net>,
"Josh Poimboeuf" <jpoimboe@redhat.com>,
Jussi Kivilinna <jussi.kivilinna@iki.fi>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"syzkaller-bugs@googlegroups.com"
<syzkaller-bugs@googlegroups.com>,
Eric Biggers <ebiggers@google.com>,
"Peter Zijlstra" <a.p.zijlstra@chello.nl>
Subject: RE: [PATCH] crypto: x86/twofish-3way - Fix %rbp usage
Date: Tue, 19 Dec 2017 14:37:07 +0000 [thread overview]
Message-ID: <a4fecc01e8a14142a9add860aa2ec67a@AcuMS.aculab.com> (raw)
In-Reply-To: <44b42058-c465-4d1e-7710-198754efabe4@suse.com>
From: Juergen Gross
> Sent: 19 December 2017 08:05
..
>
> Exchanging 2 registers can be done without memory access via:
>
> xor reg1, reg2
> xor reg2, reg1
> xor reg1, reg2
That'll generate horrid data dependencies.
ISTR that there are some optimisations for the stack,
so even 'push reg1', 'mov reg2,reg1', 'pop reg2' might
be faster than the above.
David
next prev parent reply other threads:[~2017-12-19 14:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-28 18:36 WARNING: kernel stack regs has bad 'bp' value (2) syzbot
2017-11-30 9:17 ` Eric Biggers
2017-12-27 18:29 ` Dmitry Vyukov
2017-12-28 7:30 ` Dmitry Vyukov
2017-12-19 0:40 ` [PATCH] crypto: x86/twofish-3way - Fix %rbp usage Eric Biggers
2017-12-19 7:54 ` Ingo Molnar
2017-12-19 8:04 ` Juergen Gross
2017-12-19 14:37 ` David Laight [this message]
2017-12-19 17:35 ` Ingo Molnar
2017-12-19 22:37 ` Josh Poimboeuf
2017-12-28 7:02 ` Herbert Xu
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