[lkml]   [2017]   [Dec]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] crypto: x86/twofish-3way - Fix %rbp usage

* Eric Biggers <> wrote:

> There may be a small overhead caused by replacing 'xchg REG, REG' with
> the needed sequence 'mov MEM, REG; mov REG, MEM; mov REG, REG' once per
> round. But, counterintuitively, when I tested "ctr-twofish-3way" on a
> Haswell processor, the new version was actually about 2% faster.
> (Perhaps 'xchg' is not as well optimized as plain moves.)

XCHG has implicit LOCK semantics on all x86 CPUs, so that's not a surprising
result I think.



 \ /
  Last update: 2017-12-19 08:55    [W:0.186 / U:0.840 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site