Headshot of Guilherme Ottoni
Headshot of Guilherme Ottoni


Guilherme Ottoni

Software Engineer

Since joining Facebook in 2011, I’ve been focusing on compilation techniques to improve the performance of dynamic languages, particularly PHP and Hack.  I initially contributed to the HipHop compiler, which is a static compiler from PHP to C++.  After that, I moved on to building the HipHop Virtual Machine (HHVM), which is based on Just-In-Time (JIT) compilation. For many years now, I’ve been leading the design, implementation and optimization of the HHVM JIT compiler, and also HHVM’s overall performance effort. Because of its high performance, HHVM has been deployed to run not only Facebook, but also many other sites across the web, including Wikipedia, Baidu, Slack and Box.

In addition to my work on the HipHop compiler and HHVM, at Facebook I’ve also built and contributed to the HFSort and BOLT open-source binary-optimization tools, which use profiling to improve the code locality and performance of large-scale binaries deployed across Facebook and elsewhere.

I received my BS from FURG, MS from UNICAMP (both in Brazil) and PhD from Princeton University.


Compilers, code optimization, virtual machines, performance analysis and optimization, computer architecture and algorithms

Latest Publications