[Intel-gfx] [PATCH] drm/i915/execlists: Shortcircuit queue_prio() for no internal levels

[Chris Wilson]

If there are no internal levels and the user priority-shift is zero, we
can help the compiler eliminate some dead code:

Function                                     old     new   delta
start_timeslice                              169     154     -15
__execlists_submission_tasklet              4696    4659     -37

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_lrc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 87e6c5bdd2dc..2020e35d59b6 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -446,6 +446,9 @@ static int queue_prio(const struct intel_engine_execlists *execlists)
 	 * we have to flip the index value to become priority.
 	 */
 	p = to_priolist(rb);
+	if (!I915_USER_PRIORITY_SHIFT)
+		return p->priority;
+
 	return ((p->priority + 1) << I915_USER_PRIORITY_SHIFT) - ffs(p->used);
 }
 
-- 
2.20.1