The Parrot system is divided into four main parts, each with its own specific task. Figure 8-1 shows the parts, and the way source code and control flows through Parrot. Each of the four parts of Parrot are covered briefly here, and the features and parts of the interpreter are covered in more detail in later sections.
Figure 8-1. Parrot’s flow
The flow starts with source code, which is passed into the parser module. The parser processes that source into a form that the compiler module can handle. The compiler module takes the processed source and emits bytecode, which Parrot can directly execute. That bytecode is passed into the optimizer module, which processes the bytecode and produces bytecode that should be faster than what the compiler emitted. Finally, the bytecode is handed off to the interpreter module, which interprets the bytecode. Since compilation and execution are so tightly woven in Perl, the control may well end up back at the parser to parse more code.
Parrot’s compiler module also has the capability to freeze bytecode to disk and read that frozen bytecode back again, bypassing the parser and compilation phases entirely. The bytecode can be directly executed, or handed to the optimizer to work on before execution. This may happen if you’ve loaded in a precompiled library and want Parrot to optimize the combination of your code and the library code. ...