A hierarchical intermediate representation (IR) with five main levels is used in this compiler to serve as the common interface among all the frontend and backend components.
The "classic" Open64 branch is the Open Research Compiler (ORC), which produces code only for the Itanium (IA-64), and was funded by Intel.
[3] Open64 is also used in a number of research projects, such as the Unified Parallel C (UPC) and speculative multithreading work at various universities.
[5] AMD has extended and productized Open64 with optimizations designed for x86 multi-core processor advancements and multi-threaded code development.
[7] The University of Houston's OpenUH project, which is based on Open64, released a new version of its compiler suite in November 2015.