sna: Add a loud DBG message when enabled

Having a reminder/alert when the debug tracing is enabled I find useful.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/sna/sna_driver.c

@@ -1418,6 +1418,10 @@ static void describe_sna(ScrnInfoPtr scrn)
 	xf86DrvMsg(scrn->scrnIndex, X_INFO,
 		   "SNA compiled: %s\n", BUILDER_DESCRIPTION);
 #endif
+#if HAS_DEBUG_FULL
+	ErrorF(scrn->scrnIndex, X_INFO,
+	       "SNA compiled with full debug logging; expect to run slowly\n");
+#endif
 #if !NDEBUG
 	xf86DrvMsg(scrn->scrnIndex, X_INFO,
 		   "SNA compiled with assertions enabled\n");