Parrot Reference: Chapter 11 - Perl 6 and Parrot Essentials

by Allison Randal, Dan Sugalski, Leopold Tötsch

This chapter contains a condensed list of PASM opcodes, PIR directives and instructions, and Parrot command-line options, sorted alphabetically for easy reference. Any PASM opcode is valid in PIR code, so if you're looking up PIR syntax, you should check Section 11.1, Section 11.2, and Section 11.3.

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PASM Opcodes

For complete details on each opcode and the latest changes, read the documentation in docs/ops/, or look at all the .ops files in the ops/ directory.

We've followed a few conventions. DEST is always the register where the result of the operation is stored. Sometimes the original value of DEST is one of the source values. VAL indicates that the actual value might be a literal integer, float, or string, or a register containing an integer, float, string, or PMC. See the .ops files for the combinations allowed with a particular operation.

PIR Directives

This is a summary of PIR directives. Directives are preprocessed by the Parrot interpreter. Since PIR and PASM run on the same interpreter, many of the directives listed here are also valid in PASM code.

PIR Instructions

This section is a quick reference to PIR instructions. For more details and the latest changes, see imcc/docs/syntax.pod or dive into the source code in imcc/imcc.l and imcc/imcc.y.

Parrot Command-Line Options

Since Parrot is both an assembler and a bytecode interpreter, it has options to control both behaviors. Some options may have changed by the time you read this, especially options related to debugging and optimization. The document imcc/docs/running.pod should have the latest details. Or just run parrot —help.

General Usage

parrot [options] file [arguments]

The file is either an .imc (.pir) or .pasm source file or a Parrot bytecode file. Parrot creates an Array object to hold the command-line arguments and stores it in P5 on program start.

Assembler Options

-a, --pasm

Assume PASM input on stdin. When Parrot runs a source file with a .pasm extension, it parses the file as pure PASM code. This switch turns on PASM parsing (instead of the default PIR parsing) when a source file is read from stdin.


Assume PBC file on stdin. When Parrot runs a bytecode file with a .pbc extension, it immediately executes the file. This option tells Parrot to immediately execute a bytecode file piped in on stdin.

-d,--debug [hexbits]

Turn on debugging output. The -d switch takes an optional argument, which is a hex value of debug bits. (The individual bits are shown in Table 11-3.) When hexbits isn't specified, the default debugging level is 0001. If hexbits is separated from the -d switch by whitespace, it has to start with a number.

Table 11-3. Debug bits


Debug bit





















To produce a huge output on stderr, turn on all the debugging bits:

$ parrot -d 0ffff  . . .

Show debug option bits.


Print a short summary of options to stdout and exit.

-o outputfile

Act like an assembler. With this switch, Parrot won't run code unless it's combined with the -r switch. If the name of outputfile ends with a .pbc extension, Parrot writes a Parrot bytecode file. If outputfile ends with a .pasm extension, Parrot writes a PASM source file, even if the input file was also PASM. This can be handy to check various optimizations when you run Parrot with the -Op switch.

If the extension is .o or equivalent, Parrot generates an object file from the JITed program code, which can be used to create a standalone executable program. This isn't available on all platforms yet; see PLATFORMS for which platforms support this.


Immediately execute bytecode. This is the default unless -o is present. The combination of -r -o output.pbc writes a bytecode file and executes the generated PBC.


One -v switch (imcc -v) shows which files are worked on and prints a summary of register usage and optimization statistics. Two -v switches (imcc -v -v) also prints a line for each individual processing step.


Turn on yydebug for yacc/bison.


Show output of macro expansions and quit.


Print the program version to stdout and exit.


Turn on optimizations. The flags currently implemented are shown in Table 11-4.

Table 11-4. Optimizations




No optimization (default).


Optimizations without life info (e.g., branches and constants).


Optimizations with life info.


Optimize function call sequence.


Rearrange PASM registers with the most-used first.

Bytecode Interpreter Options

The interpreter options are mainly for selecting which run-time core to use for interpreting bytecode. The current default is the computed goto core if it's available. Otherwise, the fast core is used.


Activate bounds checking. This also runs with the slow core as a side effect.


Run with the fast core.


Run the computed goto core (CGoto).


Run with the JIT core if available.


Activate profiling. This prints a summary of opcode usage and execution times after the program stops. It also runs within the slow core.


Run with the CGoto-Prederefed core.


Run with the Prederefed core.


Run with the Switched core.


Trace execution. This also turns on the slow core.


Turn on warnings.


Turn off DOD/GC. This is for debugging only.


Wait for a keypress before running.


Clean up allocated memory when the final interpreter is destroyed. Parrot destroys created interpreters (e.g., threads) on exit but doesn't normally free all memory for the last terminating interpreter, since the operating system will do this anyway. This can create false positives when Parrot is run with a memory leak detector. To prevent this, use this option.


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