iris/gen9: Optimize slice and subslice load balancing behavior.

See "i965/gen9: Optimize slice and subslice load balancing behavior."
for the rationale.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/gallium/drivers/iris/iris_blorp.c

@@ -307,6 +307,12 @@ iris_blorp_exec(struct blorp_batch *blorp_batch,
 
    iris_require_command_space(batch, 1400);
 
+   const unsigned scale = params->fast_clear_op ? UINT_MAX : 1;
+   if (ice->state.current_hash_scale != scale) {
+      genX(emit_hashing_mode)(ice, batch, params->x1 - params->x0,
+                              params->y1 - params->y0, scale);
+   }
+
    blorp_exec(blorp_batch, params);
 
    /* We've smashed all state compared to what the normal 3D pipeline