Enabling this option can give an about 10x performance increase on JIT operations. It can be desireable for e.g. high performance Apache mod_rewrite or HA-Proxy reqrep operations.
However, JIT should _only_ be enabled on architectures that are supported. Enabling JIT on unsupported platforms will result in a compilation failure. A list of supported architectures can be found here: https://pcre.org/original/doc/html/pcrejit.html#SEC3 .