Re: CVS commit: src/sys/netipsec

[David Laight <david%l8s.co.uk@localhost>]

> Arguing that gcc does a nice job would likely be met with skepticism,
> especially in the absense of good, hard numbers for various data sizes
> on various CPUs.  FreeBSD has a fairly well optimized bcopy for
> different cpus.  There is also a long history of distrust of gcc's
> ability to inline memcpy in a non-lame way.  You can search the
> archvies for a number of instances where hand written memcpy or bcopy
> routines did much better than gcc.

Indeed, on a modern x86 you do not want (ever) to execute movs{b,w,l}
unless it is repeated AND the repeat count is considerable
(unless you are optimising for space).

ISTR that something like:
1:      mov     (%esi,%ecx,4),%eax
        mov     %eax,(%edi,%ecx,4)
        dec     %ecx
        jnc     1b
is faster than 'rep movsw' for %ecx < (about) 16.

        David

-- 
David Laight: david%l8s.co.uk@localhost