The Parrot intermediate representation (PIR), previously called Intermediate code (IMC), is one of the two
assembly language
In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence b ...
s for the
Parrot virtual machine
Parrot was a register-based process virtual machine designed to run dynamic languages efficiently. It is possible to compile Parrot assembly language and Parrot intermediate representation (PIR, an intermediate language) to Parrot bytecode a ...
. The other is
Parrot assembly language or PASM. Compared to PASM, PIR exists at a slightly higher
abstraction layer
In computing, an abstraction layer or abstraction level is a way of hiding the working details of a subsystem. Examples of software models that use layers of abstraction include the OSI model for network protocols, OpenGL, and other graphics libr ...
, and provides temporary registers and named registers, simplifying code generation.
While Parrot is still evolving, it is currently being used in many different capacities, and has undergone several releases.
Overview
PIR provides a set of abstractions that allow the programmer to ignore certain redundancies in the Parrot
bytecode
Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (norma ...
and quickly write code that adheres to the complexities of Parrot, such as the calling conventions.
Abstractions
PIR provides both type abstraction and
polymorphism to some degree. For example, the "
+" operator can be used with
int,
num or both:
.local int a
.local num b
a = 1
b = 1.1
.local num c
c = a + b
Calling conventions
The calling conventions in Parrot are complex, but all of that complexity can be hidden by using PIR directives:
.sub foo
.param int a
.param int b
.local int tmp
tmp = a + b
.return (tmp)
.end
Each of the directives prefixed with a "
." expands to the required Parrot bytecode, but does not directly represent any fundamental Parrot operation.
Example
The
hello world program in PIR is
.sub hello :main
print "Hello world!\n"
.end
If the program is saved as ''hello.pir'', it can be
compiled
In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs tha ...
and
executed with this command:
parrot hello.pir
External links
Writing PIRPIR examples
Assembly languages
Perl