Subject: Re: [RFC PATCH] powerpc: Fix dubious r0 usage

From: Alan Modra <[email-masked]>
Date: Fri, 17 Feb 2017 23:51:25 +1030

On Fri, Feb 17, 2017 at 11:08:53PM +1100, Michael Ellerman wrote:
> Bleeding edge binutils no longer accepts r0 in places where the CPU
> interprets the value as a literal 0.

Wow!  That was quite some cleanup.  I think I'd better turn the error
into a warning..

> --- a/arch/powerpc/purgatory/trampoline.S
> +++ b/arch/powerpc/purgatory/trampoline.S
> @@ -67,7 +67,7 @@ master:
>  	mr	%r16,%r3	/* save dt address in reg16 */
>  	li	%r4,20
>  	LWZX_BE	%r6,%r3,%r4	/* fetch __be32 version number at byte 20 */
> -	cmpwi	%r0,%r6,2	/* v2 or later? */
> +	cmpwi	0,%r6,2		/* v2 or later? */
>  	blt	1f
>  	li	%r4,28
>  	STWX_BE	%r17,%r3,%r4	/* Store my cpu as __be32 at byte 28 */

With this one, it would probably be better to omit the zero (BF
field).

-- 
Alan Modra
Australia Development Lab, IBM