Re: [OpenBIOS] [RFC 3/3] ppc: RTAS WIP

[Alexander Graf]

On 15.10.2010, at 00:38, Alexander Graf wrote:
> Am 15.10.2010 um 00:17 schrieb Andreas Färber :

[snip]
> /* saving non-volatile registers */
> > stw r13,  8(r4)
>
> I would recommend multiplying here:
>
> stw r13, (3 * 4)(r4)
>
> That makes it more readable.
> > stw r14, 12(r4)
> > stw r15, 16(r4)
> > stw r16, 20(r4)
> > stw r17, 24(r4)
> > stw r18, 28(r4)
> > stw r19, 32(r4)
> > stw r20, 36(r4)
> > stw r21, 40(r4)
> > stw r22, 44(r4)
> > stw r23, 48(r4)
> > stw r24, 52(r4)
> > stw r25, 56(r4)
> > stw r26, 60(r4)
> > stw r27, 64(r4)
> > stw r28, 68(r4)
> > stw r29, 72(r4)
> > stw r30, 76(r4)
> > stw r31, 80(r4)

Actually thinking about this a bit more, r13-r31 are already defined non-volatile by the C ABI, so you can be sure that the C function you're calling doesn't clobber them. You don't need to manually save/restore them :).

Alex