[patch, powerpc] increase array alignment for Altivec

[Sandra Loosemore]

On 05/20/2013 03:20 PM, David Edelsohn wrote:
> This seems like a reasonable change and *should* improve performance,
> but what is the actual effect on performance, especially recent POWER
> processors?  We have had some recent cases where increased alignment
> hurt performance because of secondary effects on spilling.

I've poked around a bit.  We seem to have no suitable Altivec hardware 
for bare-metal benchmarking (we do simulator testing for -te600 
instead), but we have a Freescale 8641D board available for GNU/Linux. 
It's about 5 years old so I don't know if it qualifies as a sufficiently 
recent processor?  (Like I said before, we can't justify spending a lot 
of time trying to get this patch on mainline, and I especially don't 
want to waste time setting up benchmarking that would not be useful anyway.)

-Sandra