[PATCH v2 2/2] powerpc32: optimise csum_partial() loop
scottwood at freescale.com
Thu Aug 6 12:31:41 AEST 2015
On Wed, 2015-08-05 at 19:30 -0500, Segher Boessenkool wrote:
> On Wed, Aug 05, 2015 at 03:29:35PM +0200, Christophe Leroy wrote:
> > On the 8xx, load latency is 2 cycles and taking branches also takes
> > 2 cycles. So let's unroll the loop.
> This is not true for most other 32-bit PowerPC; this patch makes
> performance worse on e.g. 6xx/7xx/7xxx. Let's not!
Chips with a load latency greater than 2 cycles should also benefit from the
unrolling. Have you benchmarked this somewhere and seen it reduce
performance? Do you know of any 32-bit PPC chips with a load latency less
than 2 cycles?
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