Perl 6 and Parrot Essentials, Second Edition

Loading Bytecode

In addition to running Parrot bytecode on the command line, you can also load precompiled bytecode directly into your PASM source file. The load_bytecode opcode takes a single argument: the name of the bytecode file to load. So, if you create a file named file.pasm containing a single subroutine:

# file.pasm
.pcc_sub _sub2:               # .pcc_sub stores a global sub
   print "in sub2\n"
   invoke P1

and compile it to bytecode using the -o command-line switch:

$ parrot -o file.pbc file.pasm

You can then load the compiled bytecode into main.pasm and directly call the subroutine defined in file.pasm:

# main.pasm
_main:
  load_bytecode "file.pbc"    # compiled file.pasm
  find_global P0, "_sub2"
  invokecc
  end

The load_bytecode opcode also works with source files, as long as Parrot has a compiler registered for that type of file:

# main2.pasm
_main:
  load_bytecode "file.pasm"  # PASM source code
  find_global P0, "_sub2"
  invokecc
  end

Subroutines marked with @LOAD run as soon as they’re loaded (before load_bytecode returns), rather than waiting to be called. A subroutine marked with @MAIN will always run first, no matter what name you give it or where you define it in the file.

# file3.pasm
.pcc_sub @LOAD _entry:        # mark the sub as to be run
  print "file3\n"
  invoke P1                   # return

# main3.pasm
_first:                       # first is never invoked
  print "never\n"
  invoke P1

.pcc_sub @MAIN _main:         # because _main is marked as the
  print "main\n"              # MAIN entry of program execution
  load_bytecode "file3.pasm"
  print "back\n"
  end

This example ...