Re: [PATCH] powerpc/32: fix csum_partial_copy_generic()

Segher Boessenkool
2016-08-01T14:32:50Z

On Mon, Aug 01, 2016 at 03:45:59PM +0200, Christophe Leroy wrote:
> >>--- a/arch/powerpc/lib/checksum_32.S
> >>+++ b/arch/powerpc/lib/checksum_32.S
> >>@@ -127,7 +127,8 @@ _GLOBAL(csum_partial_copy_generic)
> >> stw r7,12(r1)
> >> stw r8,8(r1)
> >>
> >>- andi. r0,r4,1 /* is destination address even ? */
> >>+ rlwinm r0,r4,3,0x8 /* is destination address even ? */
> >>+ rlwnm r6,r6,r0,0,31 /* swap bytes for odd destination */
> >> cmplwi cr7,r0,0
> >> addic r12,r6,0
> >> addi r6,r4,-4
> >
> >That does not "swap bytes"; it shifts the word up by 8 bits, instead.
> >That may or may not do what is intended.
>
> Indeed it does what is intended, similar to what is done at the end of
> the function:
>
> ...
> beqlr+ cr7
> rlwinm r3,r3,8,0,31 /* swap bytes for odd destination */
> blr
>
> Should I fix the (both) comment(s) ?

It's quite confusing comment, so yes please. The code is hard enough to
understand as is!

Segher