'bx lr' vs 'mov pc,lr'

[Russell King - ARM Linux]

On Mon, Sep 14, 2009 at 01:56:16AM +0300, Felipe Contreras wrote:
> On Mon, Sep 14, 2009 at 1:15 AM, Daniel Silverstone
> <dsilvers at simtec.co.uk> wrote:
> > On Mon, Sep 14, 2009 at 12:55:24AM +0300, Felipe Contreras wrote:
> >> I noticed that in 'arch/arm/lib/delay.S' we are using 'mov pc, lr'
> >> instead of 'bx lr'. Why? It looks like 'mov pc, lr' is used all over
> >> the place, but I can't find out what's the reason.
> >
> > I'd guess at the reason being that not all ARM processors whose ports use
> > arch/arm/lib/delay.S support the bx instruction, whereas the 'mov pc, lr'
> > instruction is universally supported.
> 
> Are there really processors that don't support 'bx'? Can you give some examples?

Any ARMv3 CPU and any ARMv4 which doesn't support Thumb.  Eg, StrongARM.