MDEV-18255: Server crashes in Bitmap<64u>::intersect

Calling st_select_lex::update_used_tables in JOIN::optimize_unflattened_subqueries
only when we are sure that the join have not been cleaned up.
This can happen for a case when we have a non-merged semi-join and an impossible
where which would lead to the cleanup of the join which has the non-merged semi-join

mysql-test/r/subselect_mat.result

@@ -2822,3 +2822,19 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 SELECT * FROM t2 WHERE f IN ( SELECT LEFT('foo',0) FROM t1 ORDER BY 1 );
 f
 DROP TABLE t1, t2;
+#
+# MDEV-18255: Server crashes in Bitmap<64u>::intersect
+#
+create table t1 (v1 varchar(1)) engine=myisam ;
+create table t2 (v1 varchar(1)) engine=myisam ;
+explain
+select 1 from t1 where exists
+(select 1 from t1 where t1.v1 in (select t2.v1 from t2 having t2.v1 < 'j')) ;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
+3	MATERIALIZED	NULL	NULL	NULL	NULL	NULL	NULL	NULL	no matching row in const table
+select 1 from t1 where exists
+(select 1 from t1 where t1.v1 in (select t2.v1 from t2 having t2.v1 < 'j')) ;
+1
+drop table t1,t2;

mysql-test/t/subselect_mat.test

@@ -267,3 +267,16 @@ explain
 SELECT * FROM t2 WHERE f IN ( SELECT LEFT('foo',0) FROM t1 ORDER BY 1 );
 SELECT * FROM t2 WHERE f IN ( SELECT LEFT('foo',0) FROM t1 ORDER BY 1 );
 DROP TABLE t1, t2;
+
+--echo #
+--echo # MDEV-18255: Server crashes in Bitmap<64u>::intersect
+--echo #
+create table t1 (v1 varchar(1)) engine=myisam ;
+create table t2 (v1 varchar(1)) engine=myisam ;
+
+explain
+select 1 from t1 where exists
+	(select 1 from t1 where t1.v1 in (select t2.v1 from t2 having t2.v1 < 'j')) ;
+select 1 from t1 where exists
+	(select 1 from t1 where t1.v1 in (select t2.v1 from t2 having t2.v1 < 'j')) ;
+drop table t1,t2;

sql/sql_lex.cc

@@ -3551,7 +3551,8 @@ bool st_select_lex::optimize_unflattened_subqueries(bool const_only)
           inner_join->select_options|= SELECT_DESCRIBE;
         }
         res= inner_join->optimize();
-        sl->update_used_tables();
+        if (!inner_join->cleaned)
+          sl->update_used_tables();
         sl->update_correlated_cache();
         is_correlated_unit|= sl->is_correlated;
         inner_join->select_options= save_options;