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Date: Thu, 25 Jun 2015 07:33:21 +0300
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: optimizing bcrypt cracking on x86
Regarding the 2x2 MMX2 code on i7-4770K:
On Wed, Jun 24, 2015 at 07:10:07AM +0300, Solar Designer wrote:
> On 64-bit builds, though, I only got this to run at cumulative speeds
> like 780*8 = 6240 c/s, which is worse than 6595 c/s previously seen with
> OpenMP (and even worse than the slightly better speeds that can be seen
> with separate independent processes).
I managed to improve this to 796*8 = 6368 c/s by removing some of the
large displacements on loads, and instead keeping them in base registers
(using the extra GPRs that we have in 64-bit mode for this). For the
288 bytes of P, an offset into the middle of this range may be put into
a register, and then 256 out of the 288 bytes may be accessed via 1-byte
displacements (or alternatively 248 out of 288, but then we can also
access the first S-box via the same base register with 0x78 in the
1-byte displacement). Also, remembering that R13 is special just like
RBP (no without-displacement encoding) can sometimes be helpful.
This is still not good enough, though.
Alexander
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