Re: SVC (SWI) for Thumb

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

On Wed, Aug 14, 2013 at 07:37:44AM -0700, Matt Thomas wrote:
> >>    movs    r0, #(syscall - 254)/8
> >>    lsls    r0, r0, #3
> > 
> > Shouldn't that be a shift by 8 ?
> 
> No.  The add can only take a 3 bit value (hence, the divide by 8)
> 
> >>    adds    r0, r0, #((syscall - 254) & 7)

Hmmm... I was looking at the 0x3xxx instruction, not the 0x1exx one.

        David

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