[PATCH] drm/vmwgfx: Don't memcmp equivalent pointers

From: Ian Forbes <ian.forbes@broadcom.com>
To: dri-devel@lists.freedesktop.org
Cc: bcm-kernel-feedback-list@broadcom.com, zack.rusin@broadcom.com,
	martin.krastev@broadcom.com, maaz.mombasawala@broadcom.com,
	Ian Forbes <ian.forbes@broadcom.com>
Subject: [PATCH] drm/vmwgfx: Don't memcmp equivalent pointers
Date: Thu, 28 Mar 2024 14:07:16 -0500	[thread overview]
Message-ID: <20240328190716.27367-1-ian.forbes@broadcom.com> (raw)

These pointers are frequently the same and memcmp does not compare the pointers
before comparing their contents so this was wasting cycles comparing 16 KiB of
memory which will always be equal.

Fixes: bb6780aa5a1d9 ("drm/vmwgfx: Diff cursors when using cmds")
Signed-off-by: Ian Forbes <ian.forbes@broadcom.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index cd4925346ed4..fbcce84e2f4c 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -216,7 +216,7 @@ static bool vmw_du_cursor_plane_has_changed(struct vmw_plane_state *old_vps,
 	new_image = vmw_du_cursor_plane_acquire_image(new_vps);
 
 	changed = false;
-	if (old_image && new_image)
+	if (old_image && new_image && (old_image != new_image))
 		changed = memcmp(old_image, new_image, size) != 0;
 
 	return changed;
-- 
2.34.1

