bit-functions-and-operators: Update reference manual links

functions-and-operators/bit-functions-and-operators.md

@@ -6,7 +6,7 @@ aliases: ['/docs/dev/functions-and-operators/bit-functions-and-operators/','/doc
 
 # Bit Functions and Operators
 
-TiDB supports all of the [bit functions and operators](https://dev.mysql.com/doc/refman/5.7/en/bit-functions.html) available in MySQL 5.7.
+TiDB supports all of the [bit functions and operators](https://dev.mysql.com/doc/refman/8.0/en/bit-functions.html) available in MySQL 8.0.
 
 **Bit functions and operators:**
 
@@ -19,3 +19,12 @@ TiDB supports all of the [bit functions and operators](https://dev.mysql.com/doc
 | [^](https://dev.mysql.com/doc/refman/8.0/en/bit-functions.html#operator_bitwise-xor) | Bitwise XOR |
 | [<<](https://dev.mysql.com/doc/refman/8.0/en/bit-functions.html#operator_left-shift) | Left shift |
 | [>>](https://dev.mysql.com/doc/refman/8.0/en/bit-functions.html#operator_right-shift) | Right shift |
+
+# MySQL Compatibility
+
+There are some differences between MySQL 8.0 and earlier versions of MySQL handle bit operations. TiDB aims to follow the MySQL 8.0 behaviour.
+
+## Known issues
+
+- [bitwise operations with binary args behavior changes between MySQL 5.7 and 8.0](https://github.com/pingcap/tidb/issues/30637)
+- [function bit\_count result is Inconsistent with MySQL](https://github.com/pingcap/tidb/issues/44621)