[RFC] arm: use built-in byte swap function

[Russell King - ARM Linux]

On Thu, Jan 31, 2013 at 02:59:47PM -0600, Kim Phillips wrote:
> On Thu, 31 Jan 2013 09:28:01 +0000
> Russell King - ARM Linux <linux at arm.linux.org.uk> wrote:
> 
> > On Wed, Jan 30, 2013 at 08:09:00PM -0600, Kim Phillips wrote:
> > > v2:
> > > - at91 and lpd270 builds fixed by limiting to ARMv6 and above
> > >   (i.e., ARM cores that have support for the 'rev' instruction).
> > >   Otherwise, the compiler emits calls to libgcc's __bswapsi2 on
> > >   these ARMv4/v5 builds (and arch ARM doesn't link with libgcc).
> > 
> > Which compiler version?  gcc 4.5.4 doesn't do this, except for the 16-bit
> > swap, so I doubt that any later compiler does.
> 
> I've tried both gcc 4.6.3 [1] and 4.6.4 [2].  If you can point me to
> a 4.5.x, I'll try that, too, but as it stands now, if one moves the
> code added to swab.h below outside of its armv6 protection,
> gcc adds calls to __bswapsi2.

Take a look at the message I sent on the 29th towards the beginning of
this thread for details of gcc 4.5.4 behaviour.