Guilherme Ottoni HHVM's Profile-guided Region JIT Posted February 17, 2017 Our initial version of the HHVM JIT didn’t use profile-guided optimizations, and we suspected that we were leaving performance on the table because of that. After adding HHIR and beefing up the JIT backend in 2013, a couple of us embarked on the journey of building a profiling mechanism and leveraging it to improve the JIT’