As the ringbuffer may exist inside stolen memory, our access to it may
be via the GTT iomap. This implies we may only have WC access for which
the conventional memset() substitution of rep stos performs very badly,
so switch to the rep mov[dq] variants when available.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180319123528.28249-1-chris@chris-wilson.co.uk