Perl 6 and Parrot Essentials, Second Edition

Chapter 10. Parrot Intermediate Representation

The Parrot intermediate representation (PIR) is an overlay on top of Parrot assembly language, designed to make the developer’s life easier. It has many high-level features that ease the pain of working with PASM code, but it still isn’t a high-level language.

Internally, Parrot works a little differently with PASM and PIR source code, so each has different restrictions. The default is to run in a mixed mode that allows PASM code to combine with the higher-level syntax unique to PIR.

A file with a .pasm extension is treated as pure PASM code, as is any file run with the -a command-line option. This mode is mainly used for running pure PASM tests. Parrot treats any extension other than .pasm as a PIR file. For historical reasons, files containing PIR code generally have a .imc extension, but this is gradually shifting to a .pir extension.

The documentation in imcc/docs/ or docs/ and the test suite in imcc/t are good starting points for digging deeper into the PIR syntax and functionality.

Statements

The syntax of statements in PIR is much more flexible than PASM. All PASM opcodes are valid PIR code, so the basic syntax is the same. The statement delimiter is a newline \n, so each statement has to be on its own line. Any statement can start with a label. Comments are marked by a hash sign (#) and PIR allows POD blocks.

But unlike PASM, PIR has some higher-level constructs, including symbol operators:

I1 = 5                       # set I1, 5

named variables: ...