Subject: Re: Performance of various memcpy()'s
To: <>
From: David Laight <>
List: tech-userlevel
Date: 10/28/2002 10:43:17
> Mixing word size and byte size registers is generally not a good idea.
> Intel manual says that it slows down performance, and I confirmed that
> via memcpy tests.

I only recall reading that the high bytes were expensive and that
writing to the low byte would stall if the register did not
have valid contents.  In this case stalling in %ecx is unlikely
to be an issue.
Also the cost of a short 'rep movsb' is so great that anything
is probably better!


David Laight: