Oracle JRockit

SSA form

SSA (Single Static Assignment) form is a transform domain for intermediate code where each variable can be written to only once. This makes several optimizations and data flow analyses easier. The transform is possible since SSA form defines a join operator, Φ, that takes an arbitrary number of sources and one destination. The operator defines the destination to be "any of the source variables". Since Φ cannot be expressed as native code on any hardware architecture, SSA form has to be transformed back to normal form before code emission.