Re: Thumb mode on ARM

[Richard Earnshaw <richard.earnshaw%buzzard.freeserve.co.uk@localhost>]

On Wed, 2008-10-29 at 09:03 +0100, Ignatios Souvatzis wrote:
> On Wed, Oct 29, 2008 at 09:15:19AM +0200, Mikko Rapeli wrote:
> > Hello,
> > 
> > I wrote down the instructions to get thumb mode userspace working with
> > NetBSD current:
> > 
> > http://wiki.netbsd.se/How_to_use_thumb_mode_on_ARM
> > 
> > It basically boils down to upgrading binutils and then building machine
> > independent parts to thumb and machine dependent parts to ARM with a
> > script.
> > 
> > Comments and additions are welcome.
> 
> Can you plese add a list of NetBSD ports for which this is useful? Some
> CPUs don't have thumb mode.

Thumb support is a practical proposition for any cpu implementing
architecture v5 or later, for CPUs implementing v7, then Thumb2 means it
may well be the option of choice for most applications.

R.

PS. In theory any v4T or later chip can support Thumb mode, but shared
library interworking on that architecture is tricky and the gains are
less obvious given the overhead of ensuring ARM/Thumb interworking in
all procedure calls.