/erts/emulator/utils/beam_makeops

#!/usr/bin/env perl
#
# %CopyrightBegin%
#
# Copyright Ericsson AB 1998-2011. All Rights Reserved.
#
# The contents of this file are subject to the Erlang Public License,
# Version 1.1, (the "License"); you may not use this file except in
# compliance with the License. You should have received a copy of the
# Erlang Public License along with this software. If not, it can be
# retrieved online at http://www.erlang.org/.
#
# Software distributed under the License is distributed on an "AS IS"
# basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
# the License for the specific language governing rights and limitations
# under the License.
#
# %CopyrightEnd%
#
use strict;
use vars qw($BEAM_FORMAT_NUMBER);

$BEAM_FORMAT_NUMBER = undef;

my $target = \&emulator_output;
my $outdir = ".";		# Directory for output files.
my $verbose = 0;
my $hot = 1;
my $num_file_opcodes = 0;
my $wordsize = 32;

# This is shift counts and mask for the packer.
my $WHOLE_WORD = '';
my @pack_instr;
my @pack_shift;
my @pack_mask;

$pack_instr[2] = ['6', 'i'];
$pack_instr[3] = ['0', '0', 'i'];
$pack_instr[4] = ['6', '6', '6', 'i']; # Only for 64 bit wordsize

$pack_shift[2] = ['0', 'BEAM_LOOSE_SHIFT'];
$pack_shift[3] = ['0', 'BEAM_TIGHT_SHIFT', '(2*BEAM_TIGHT_SHIFT)'];
$pack_shift[4] = ['0', 'BEAM_LOOSE_SHIFT', # Only for 64 bit wordsize
		  '(2*BEAM_LOOSE_SHIFT)',
		  '(3*BEAM_LOOSE_SHIFT)'];

$pack_mask[2]  = ['BEAM_LOOSE_MASK', $WHOLE_WORD];
$pack_mask[3]  = ['BEAM_TIGHT_MASK', 'BEAM_TIGHT_MASK', 'BEAM_TIGHT_MASK'];
$pack_mask[4]  = ['BEAM_LOOSE_MASK', # Only for 64 bit wordsize
		  'BEAM_LOOSE_MASK',
		  'BEAM_LOOSE_MASK',
		  $WHOLE_WORD];

# There are two types of instructions: generic and specific.
# The generic instructions are those generated by the Beam compiler.
# Corresponding to each generic instruction, there is generally a
# whole family of related specific instructions. Specific instructions
# are those executed by the VM interpreter during run-time.

# Maximum number of operands for a generic instruction.
# In beam_load.c the MAX_OPARGS refers to the maximum
# number of operands for generic instructions.
my $max_gen_operands = 8;

# Maximum number of operands for a specific instruction.
# Must be even. The beam_load.c file must be updated, too.
my $max_spec_operands = 6;

# The maximum number of primitive genop_types.

my $max_genop_types = 16;

my %gen_opnum;
my %num_specific;
my %gen_to_spec;
my %specific_op;

my %gen_arity;
my @gen_arity;

my @gen_opname;
my @op_to_name;

my @obsolete;

my %macro;
my %macro_flags;

my %hot_code;
my %cold_code;

my @unnumbered_generic;
my %unnumbered;

my %is_transformed;

#
# Code transformations.
#
my $te_max_vars = 0;		# Max number of variables ever needed.
my %gen_transform;
my %min_window;
my %match_engine_ops;		# All opcodes for the match engine.
my %gen_transform_offset;
my @transformations;
my @call_table;
my %call_table;
my @pred_table;
my %pred_table;

# Operand types for generic instructions.

my $compiler_types = "uiaxyfhz";
my $loader_types = "nprvlqo";
my $genop_types = $compiler_types . $loader_types;

#
# Defines the argument types and their loaded size assuming no packing.
#
my %arg_size = ('r' => 0,	# x(0) - x register zero
		'x' => 1,	# x(N), N > 0 - x register
		'y' => 1,	# y(N) - y register
		'i' => 1,	# tagged integer
		'a' => 1,	# tagged atom
		'n' => 0,	# NIL (implicit)
		'c' => 1,	# tagged constant (integer, atom, nil)
		's' => 1,	# tagged source; any of the above
		'd' => 1,	# tagged destination register (r, x, y)
		'f' => 1,	# failure label
		'j' => 1,	# either 'f' or 'p'
		'e' => 1,	# pointer to export entry
		'L' => 0,	# label
		'I' => 1,	# untagged integer
		't' => 1,	# untagged integer -- can be packed
		'b' => 1,	# pointer to bif
		'A' => 1,	# arity value
		'P' => 1,	# byte offset into tuple or stack
		'Q' => 1,	# like 'P', but packable
		'h' => 1,	# character
		'l' => 1,	# float reg
		'q' => 1,	# literal term
	     );

#
# Generate bits.
#
my %type_bit;
my @tag_type;

sub define_type_bit {
    my($tag,$val) = @_;
    defined $type_bit{$tag} and
	sanity("the tag '$tag' has already been defined with the value ",
	       $type_bit{$tag});
    $type_bit{$tag} = $val;
}

{
    my($bit) = 1;
    my(%bit);

    foreach (split('', $genop_types)) {
	push(@tag_type, $_);
	define_type_bit($_, $bit);
	$bit{$_} = $bit;
	$bit *= 2;
    }

    # Composed types.
    define_type_bit('d', $type_bit{'x'} | $type_bit{'y'} | $type_bit{'r'});
    define_type_bit('c', $type_bit{'i'} | $type_bit{'a'} |
		    $type_bit{'n'} | $type_bit{'q'});
    define_type_bit('s', $type_bit{'d'} | $type_bit{'i'} |
		    $type_bit{'a'} | $type_bit{'n'});
    define_type_bit('j', $type_bit{'f'} | $type_bit{'p'});

    # Aliases (for matching purposes).
    define_type_bit('I', $type_bit{'u'});
    define_type_bit('t', $type_bit{'u'});
    define_type_bit('A', $type_bit{'u'});
    define_type_bit('L', $type_bit{'u'});
    define_type_bit('b', $type_bit{'u'});
    define_type_bit('N', $type_bit{'u'});
    define_type_bit('U', $type_bit{'u'});
    define_type_bit('e', $type_bit{'u'});
    define_type_bit('P', $type_bit{'u'});
    define_type_bit('Q', $type_bit{'u'});
}

#
# Pre-define the 'fail' instruction. It is used internally
# by the 'try_me_else_fail' instruction.
#
$match_engine_ops{'TOP_fail'} = 1;

#
# Sanity checks.
#

{
    if (@tag_type > $max_genop_types) {
	sanity("\$max_genop_types is $max_genop_types, ",
	       "but there are ", scalar(@tag_type),
	       " primitive tags defined\n");
    }

    foreach my $tag (@tag_type) {
	sanity("tag '$tag': primitive tags must be named with lowercase letters")
	    unless $tag =~ /^[a-z]$/;
    }
}

#
# Parse command line options.
#

while (@ARGV && $ARGV[0] =~ /^-(.*)/) {
    $_ = $1;
    shift;
    ($target = \&emulator_output), next if /^emulator/;
    ($target = \&compiler_output), next if /^compiler/;
    ($outdir = shift), next if /^outdir/;
    ($wordsize = shift), next if /^wordsize/;
    ($verbose = 1), next if /^v/;
    die "$0: Bad option: -$_\n";
}

#
# Parse the input files.
#

while (<>) {
    my($op_num);
    chomp;
    if (s/\\$//) {
	$_ .= <>;
	redo unless eof(ARGV);
    }
    next if /^\s*$/;
    next if /^\#/;
    
    #
    # Handle assignments.
    #
    if (/^([\w_][\w\d_]+)=(.*)/) {
	no strict 'refs';
	my($name) = $1;
	$$name = $2;
	next;
    }

    #
    # Handle %hot/%cold.
    # 
    if (/^\%hot/) {
	$hot = 1;
	next;
    } elsif (/^\%cold/) {
	$hot = 0;
	next;
    }
    
    #
    # Handle macro definitions.
    #
    if (/^\%macro:(.*)/) {
	my($op, $macro, @flags) = split(' ', $1);
	defined($macro) and $macro =~ /^-/ and
	    &error("A macro must not start with a hyphen");
	foreach (@flags) {
	    /^-/ or &error("Flags for macros should start with a hyphen");
	}
	error("Macro for '$op' is already defined")
	    if defined $macro{$op};
	$macro{$op} = $macro;
	$macro_flags{$op} = join('', @flags);
	next;
    }

    #
    # Handle transformations.
    #
    if (/=>/) {
	&parse_transformation($_);
	next;
    }

    #
    # Parse off the number of the operation.
    #
    $op_num = undef;
    if (s/^(\d+):\s*//) {
	$op_num = $1;
	$op_num != 0 or &error("Opcode 0 invalid");
	&error("Opcode $op_num already defined")
	    if defined $gen_opname[$op_num];
    }

    #
    # Parse: Name/Arity  (generic instruction)
    #
    if (m@^(-)?(\w+)/(\d)\s*$@) {
	my($obsolete) = $1;
	my($name) = $2;
	my($arity) = $3;
	$name =~ /^[a-z]/ or &error("Opname must start with a lowercase letter");
	defined $gen_arity{$name} and $gen_arity{$name} != $arity and
	    &error("Opname $name already defined with arity $gen_arity{$name}");
	defined $unnumbered{$name,$arity} and
	    &error("Opname $name already defined with arity $gen_arity{$name}");
	
	if (defined $op_num) {	# Numbered generic operation
	    $gen_opname[$op_num] = $name;
	    $gen_arity[$op_num] = $arity;
	    $gen_opnum{$name,$arity} = $op_num;
	    $gen_arity{$name} = $arity;
	    $gen_to_spec{"$name/$arity"} = undef;
	    $num_specific{"$name/$arity"} = 0;
	    $min_window{"$name/$arity"} = 255;
	    $obsolete[$op_num] = $obsolete eq '-';
	} else {		# Unnumbered generic operation.
	    push(@unnumbered_generic, [$name, $arity]);
	    $unnumbered{$name,$arity} = 1;
	}
	next;
    }

    #
    # Parse specific instructions (only present in emulator/loader):
    #    Name Arg1 Arg2...
    #
    my($name, @args) = split;
    &error("too many operands")
	if @args > $max_spec_operands;
    &syntax_check($name, @args);
    my $arity = @args;
    if ($obsolete[$gen_opnum{$name,$arity}]) {
	error("specific instructions may not be specified for obsolete instructions");
    }
    push(@{$specific_op{"$name/$arity"}}, [$name, $hot, @args]);
    if (defined $op_num) {
	&error("specific instructions must not be numbered");
    } elsif (!defined($gen_arity{$name}) && !defined($unnumbered{$name,$arity})) {
	#
	# Create an unumbered generic instruction too.
	#
	push(@unnumbered_generic, [$name, $arity]);
	$unnumbered{$name,$arity} = 1;
    }
} continue {
    close(ARGV) if eof(ARGV);
}

$num_file_opcodes = @gen_opname;

#
# Number all generic operations without numbers.
#
{
    my $ref;

    foreach $ref (@unnumbered_generic) {
	my($name, $arity) = @$ref;
	my $op_num = @gen_opname;
	push(@gen_opname, $name);
	push(@gen_arity, $arity);
	$gen_opnum{$name,$arity} = $op_num;
	$gen_arity{$name} = $arity;
	$gen_to_spec{"$name/$arity"} = undef;
	$num_specific{"$name/$arity"} = 0;
	$min_window{"$name/$arity"} = 255;
    }
}

#
# Produce output for the chosen target.
#

&$target;

#
# Produce output needed by the emulator/loader.
#

sub emulator_output {
    my $i;
    my $name;
    my $key;			# Loop variable.

    #
    # Information about opcodes (beam_opcodes.c).
    #
    $name = "$outdir/beam_opcodes.c";
    open(STDOUT, ">$name") || die "Failed to open $name for writing: $!\n";
    &comment('C');
    print "#ifdef HAVE_CONFIG_H\n";
    print "#  include \"config.h\"\n";
    print "#endif\n\n";
    print '#include "sys.h"', "\n";
    print '#include "erl_vm.h"', "\n";
    print '#include "export.h"', "\n";
    print '#include "erl_process.h"', "\n";
    print '#include "bif.h"', "\n";
    print '#include "erl_atom_table.h"', "\n";
    print '#include "beam_load.h"', "\n";
    print "\n";

    print "char tag_to_letter[] = {\n  ";
    for ($i = 0; $i < length($genop_types); $i++) {
	print "'$tag_type[$i]', ";
    }
    for (; $i < @tag_type; $i++) {
	print "'_', ";
    }
    print "\n};\n";
    print "\n";

    #
    # Generate code for specific ops.
    #
    my($spec_opnum) = 0;
    print "OpEntry opc[] = {\n";
    foreach $key (sort keys %specific_op) {
	$gen_to_spec{$key} = $spec_opnum;
	$num_specific{$key} = @{$specific_op{$key}};

	#
	# Pick up all instructions and manufacture sort keys; we must have
	# the most specific instructions appearing first (e.g. an 'x' operand
	# should be matched before 's' or 'd').
	#
	my(%items) = ();
	foreach (@{$specific_op{$key}}) {
	    my($name, $hot, @args) = @{$_};
	    my($sign) = join('', @args);

	    # The primitive types should sort before other types.

	    my($sort_key) = $sign;
	    eval "\$sort_key =~ tr/$genop_types/./";
	    $sort_key .= ":$sign";
	    $items{$sort_key} = [$name, $hot, $sign, @args];
	}

	#
	# Now call the generator for the sorted result.
	#
	foreach (sort keys %items) {
	    my($name, $hot, $sign, @args) = @{$items{$_}};
	    my $arity = @args;
	    my($instr) = "${name}_$sign";
	    $instr =~ s/_$//;

	    #
	    # Call a generator to calculate size and generate macros
	    # for the emulator.
	    #
	    my($size, $code, $pack) = &basic_generator($name, $hot, @args);

	    #
	    # Save the generated $code for later.
	    #
	    if (defined $code) {
		if ($hot) {
		    push(@{$hot_code{$code}}, $instr);
		} else {
		    push(@{$cold_code{$code}}, $instr);
		}
	    }

	    #
	    # Calculate the bit mask which should be used to match this
	    # instruction.
	    #

	    my(@bits) = (0) x ($max_spec_operands/2);
	    my($i);
	    for ($i = 0; $i < $max_spec_operands && defined $args[$i]; $i++) {
		my $t = $args[$i];
		if (defined $type_bit{$t}) {
		    my $shift = $max_genop_types * ($i % 2);
		    $bits[int($i/2)] |= $type_bit{$t} << $shift;
		}
	    }

	    printf "/* %3d */  ", $spec_opnum;
	    my $print_name = $sign ne '' ? "${name}_$sign" : $name;
	    my $init = "{";
	    my $sep = "";
	    foreach (@bits) {
		$init .= sprintf("%s0x%X", $sep, $_);
		$sep = ",";
	    }
	    $init .= "}";
	    &init_item($print_name, $init, $size, $pack, $sign, 0);
	    $op_to_name[$spec_opnum] = $instr;
	    $spec_opnum++;
	}
    }
    print "};\n\n";
    print "int num_instructions = $spec_opnum;\n\n";

    #
    # Generate transformations.
    #

    &tr_gen(@transformations);

    #
    # Print the generic instruction table.
    #

    print "GenOpEntry gen_opc[] = {\n";
    for ($i = 0; $i < @gen_opname; $i++) {
	if ($i == $num_file_opcodes) {
	    print "\n/*\n * Internal generic instructions.\n */\n\n";
	}
	my($name) = $gen_opname[$i];
	my($arity) = $gen_arity[$i];
	printf "/* %3d */  ", $i;
	if (!defined $name) {
	    &init_item("", 0, 0, 0, -1);
	} else {
	    my($key) = "$name/$arity";
	    my($tr) = defined $gen_transform_offset{$key} ?
		$gen_transform_offset{$key} : -1;
	    my($spec_op) = $gen_to_spec{$key};
	    my($num_specific) = $num_specific{$key};
	    defined $spec_op or
		$obsolete[$gen_opnum{$name,$arity}] or
		$is_transformed{$name,$arity} or
		error("instruction $key has no specific instruction");
	    $spec_op = -1 unless defined $spec_op;
	    &init_item($name, $arity, $spec_op, $num_specific, $tr, $min_window{$key});
	}
    }
    print "};\n";

    #
    # Information about opcodes (beam_opcodes.h).
    #
    $name = "$outdir/beam_opcodes.h";
    open(STDOUT, ">$name") || die "Failed to open $name for writing: $!\n";
    &comment('C');
    print "#ifndef __OPCODES_H__\n";
    print "#define __OPCODES_H__\n\n";

    print "#define BEAM_FORMAT_NUMBER $BEAM_FORMAT_NUMBER\n";
    print "#define MAX_GENERIC_OPCODE ", $num_file_opcodes-1, "\n";
    print "#define NUM_GENERIC_OPS ", scalar(@gen_opname), "\n";
    print "#define NUM_SPECIFIC_OPS ", scalar(@op_to_name), "\n";
    print "\n";
    print "#ifdef ARCH_64\n";
    print "#  define BEAM_WIDE_MASK 0xFFFFUL\n";
    print "#  define BEAM_LOOSE_MASK 0x1FFFUL\n";
    print "#if HALFWORD_HEAP\n";
    print "#  define BEAM_TIGHT_MASK 0x1FFCUL\n";
    print "#else\n";
    print "#  define BEAM_TIGHT_MASK 0x1FF8UL\n";
    print "#endif\n";
    print "#  define BEAM_WIDE_SHIFT 32\n";
    print "#  define BEAM_LOOSE_SHIFT 16\n";
    print "#  define BEAM_TIGHT_SHIFT 16\n";
    print "#else\n";
    print "#  define BEAM_LOOSE_MASK 0xFFF\n";
    print "#  define BEAM_TIGHT_MASK 0xFFC\n";
    print "#  define BEAM_LOOSE_SHIFT 16\n";
    print "#  define BEAM_TIGHT_SHIFT 10\n";
    print "#endif\n";
    print "\n";

    #
    # Definitions of tags.
    #

    my $letter;
    my $tag_num = 0;

    &comment('C', "The following operand types for generic instructions",
	     "occur in beam files.");
    foreach $letter (split('', $compiler_types)) {
	print "#define TAG_$letter $tag_num\n";
	$tag_num++;
    }
    print "\n";
    &comment('C', "The following operand types are only used in the loader.");
    foreach $letter (split('', $loader_types)) {
	print "#define TAG_$letter $tag_num\n";
	$tag_num++;
    }
    print "\n#define BEAM_NUM_TAGS $tag_num\n\n";

    $i = 0;
    foreach (sort keys %match_engine_ops) {
	print "#define $_ $i\n";
	$i++;
    }
    print "#define NUM_TOPS $i\n";
    print "\n";

    print "#define TE_MAX_VARS $te_max_vars\n";
    print "\n";

    print "extern char tag_to_letter[];\n";
    print "extern Uint op_transform[];\n";
    print "\n";

    for ($i = 0; $i < @op_to_name; $i++) {
	print "#define op_$op_to_name[$i] $i\n";
    }
    print "\n";

    print "#define NUMBER_OF_OPCODES ",scalar(@op_to_name),"\n";
    for ($i = 0; $i < @op_to_name; $i++) {
	print "#define op_count_$op_to_name[$i] ",$i+scalar(@op_to_name),"\n";
    }
    print "\n";

    print "#define DEFINE_OPCODES";
    foreach (@op_to_name) {
	print " \\\n&&lb_$_,";
    }
    print "\n\n";

    print "#define DEFINE_COUNTING_OPCODES";
    foreach (@op_to_name) {
	print " \\\n&&lb_count_$_,";
    }
    print "\n\n";

    print "#define DEFINE_COUNTING_LABELS";
    for ($i = 0; $i < @op_to_name; $i++) {
	my($name) = $op_to_name[$i];
	print " \\\nCountCase($name): opc[$i].count++; goto lb_$name;";
    }
    print "\n\n";

    for ($i = 0; $i < @gen_opname; $i++) {
	print "#define genop_$gen_opname[$i]_$gen_arity[$i] $i\n"
	    if defined $gen_opname[$i];
    }


    print "#endif\n";


    #
    # Extension of transform engine.
    #

    $name = "$outdir/beam_tr_funcs.h";
    open(STDOUT, ">$name") || die "Failed to open $name for writing: $!\n";
    &comment('C');
    &tr_gen_call(@call_table);

    $name = "$outdir/beam_pred_funcs.h";
    open(STDOUT, ">$name") || die "Failed to open $name for writing: $!\n";
    &comment('C');
    &tr_gen_call(@pred_table);

    #
    # Implementation of operations for emulator.
    #
    $name = "$outdir/beam_hot.h";
    open(STDOUT, ">$name") || die "Failed to open $name for writing: $!\n";
    &comment('C');
    &print_code(\%hot_code);

    $name = "$outdir/beam_cold.h";
    open(STDOUT, ">$name") || die "Failed to open $name for writing: $!\n";
    &comment('C');
    &print_code(\%cold_code);

}

sub init_item {
    my($sep) = "";

    print "{";
    foreach (@_) {
	if (!defined $_) {
	    print "${sep}NULL";
	} elsif (/^\{/) {
	    print "$sep$_";
	} elsif (/^-?\d/) {
	    print "$sep$_";
	} else {
	    print "$sep\"$_\"";
	}
	$sep = ", ";
    }
    print "},\n";
}

sub q {
    my($str) = @_;
    "\"$str\"";
}

sub print_code {
    my($ref) = @_;
    my(%sorted);
    my($key, $label);		# Loop variables.

    foreach $key (keys %$ref) {
	my($sort_key);
	my($code) = '';
	foreach $label (@{$ref->{$key}}) {
	    $code .= "OpCase($label):\n";
	    $sort_key = $label;
	}
	foreach (split("\n", $key)) {
	    $code .= "    $_\n";
	}
	$code .= "\n";
	$sorted{$sort_key} = $code;
    }

    foreach (sort keys %sorted) {
	print $sorted{$_};
    }
}

#
# Produce output needed by the compiler back-end (assembler).
#

sub compiler_output {
    my($module) = 'beam_opcodes';
    my($name) = "${module}.erl";
    my($i);

    open(STDOUT, ">$outdir/$name") || die "Failed to open $name for writing: $!\n";
    print "-module($module).\n";
    &comment('erlang');

    print "-export([format_number/0]).\n";
    print "-export([opcode/2,opname/1]).\n";
    print "\n";
    print "-spec format_number() -> $BEAM_FORMAT_NUMBER.\n";
    print "format_number() -> $BEAM_FORMAT_NUMBER.\n\n";

    print "-spec opcode(atom(), 0..", $max_gen_operands, ") -> 1..", $num_file_opcodes-1, ".\n";
    for ($i = 0; $i < @gen_opname; $i++) {
	next unless defined $gen_opname[$i];
	print "%%" if $obsolete[$i];
	print "opcode(", &quote($gen_opname[$i]), ", $gen_arity[$i]) -> $i;\n";
    }
    print "opcode(Name, Arity) -> erlang:error(badarg, [Name,Arity]).\n\n";

    print "-spec opname(1..", $num_file_opcodes-1, ") -> {atom(),0..", $max_gen_operands, "}.\n";
    for ($i = 0; $i < @gen_opname; $i++) {
	next unless defined $gen_opname[$i];
	print "opname($i) -> {",
	&quote($gen_opname[$i]), ",$gen_arity[$i]};\n";
    }
    print "opname(Number) -> erlang:error(badarg, [Number]).\n";

    #
    # Generate .hrl file.
    #
    my($name) = "$outdir/${module}.hrl";
    open(STDOUT, ">$name") || die "Failed to open $name for writing: $!\n";
    &comment('erlang');

    for ($i = 0; $i < @tag_type && $i < 8; $i++) {
	print "-define(tag_$tag_type[$i], $i).\n";
    }
    print "\n";

}

#
# Check an operation for validity.
#
sub syntax_check {
    my($name, @args) = @_;
    my($i);

    &error("Bad opcode name '$name'")
	unless $name =~ /^[a-z][\w\d_]*$/;
    for ($i = 0; $i < @args; $i++) {
	&error("Argument " . ($i+1) . ": invalid type '$args[$i]'")
	    unless defined $arg_size{$args[$i]};
    }
}

sub error {
    my(@message) = @_;
    my($where) = $. ? "$ARGV($.): " : "";
    die $where, @message, "\n";
}

sub sanity {
    die "internal error: ", @_, "\n";
}

sub comment {
    my($lang, @comments) = @_;
    my($prefix);

    if ($lang eq 'C') {
	print "/*\n";
	$prefix = " * ";
    } elsif ($lang eq 'erlang') {
	$prefix = '%% ';
    } else {
	$prefix = '# ';
    }
    my(@prog) = split('/', $0);
    my($prog) = $prog[$#prog];

    if (@comments) {
	my $line;
	foreach $line (@comments) {
	    print "$prefix$line\n";
	}
    } else {
	print "$prefix Warning: Do not edit this file.\n";
	print "$prefix Auto-generated by '$prog'.\n";
    }
    if ($lang eq 'C') {
	print " */\n";
    }
    print "\n";
}

#
# Basic implementation of instruction in emulator loop
# (assuming no packing).
#

sub basic_generator {
    my($name, $hot, @args) = @_;
    my($size) = 0;
    my($macro) = '';
    my($flags) = '';
    my(@f);
    my(@f_types);
    my($fail_type);
    my($prefix) = '';
    my($tmp_arg_num) = 1;
    my($pack_spec) = '';
    my($var_decls) = '';
    my($gen_dest_arg) = 'StoreSimpleDest';
    my($i);

    # The following argument types should be included as macro arguments.
    my(%incl_arg) = ('c' => 1,
		     'i' => 1,
		     'a' => 1,
		     'A' => 1,
		     'N' => 1,
		     'U' => 1,
		     'I' => 1,
		     't' => 1,
		     'P' => 1,
		     'Q' => 1,
		     );

    # Pick up the macro to use and its flags (if any).

    $macro = $macro{$name} if defined $macro{$name};
    $flags = $macro_flags{$name} if defined $macro_flags{$name};

    #
    # Add any arguments to be included as macro arguments (for instance,
    # 'p' is usually not an argument, except for calls).
    #

    while ($flags =~ /-arg_(\w)/g) {
	$incl_arg{$1} = 1;
    };

    #
    # Pack arguments if requested.
    #

    if ($flags =~ /-pack/ && $hot) {
        ($prefix, $pack_spec, @args) = &do_pack(@args);
    }

    #
    # Calculate the size of the instruction and generate each argument for
    # the macro.
    #

    foreach (@args) {
	my($this_size) = $arg_size{$_};
      SWITCH:
	{
	    /^pack:(\d):(.*)/ and do { push(@f, $2);
				       push(@f_types, 'packed');
				       $this_size = $1;
				       last SWITCH;
				   };
	    /r/    and do { push(@f, "r(0)"); push(@f_types, $_); last SWITCH };
	    /[xy]/ and do { push(@f, "$_" . "b(Arg($size))");
			     push(@f_types, $_);
			     last SWITCH;
			};
	    /n/    and do { push(@f, "NIL"); push(@f_types, $_); last SWITCH };
	    /s/    and do { my($tmp) = "targ$tmp_arg_num";
			    $var_decls .= "Eterm $tmp; ";
			    $tmp_arg_num++;
			    push(@f, $tmp);
			    push(@f_types, $_);
			    $prefix .= "GetR($size, $tmp);\n";
			    last SWITCH; };
	    /d/    and do { $var_decls .= "Eterm dst; ";
			    push(@f, "dst");
			    push(@f_types, $_);
			    $prefix .= "dst = Arg($size);\n";
			    $gen_dest_arg = 'StoreResult';
			    last SWITCH;
			};
	    defined($incl_arg{$_})
		and do { push(@f, "Arg($size)");
			 push(@f_types, $_);
			 last SWITCH;
		     };

	    /[fp]/ and do { $fail_type = $_; last SWITCH };

	    /[eLIFEbASjPowlq]/ and do { last SWITCH; };

	    die "$name: The generator can't handle $_, at";
	}
	$size += $this_size;
    }

    #
    # If requested, pass a pointer to the destination register.
    # The destination must be the last operand.
    #
    if ($flags =~ /-gen_dest/) {
	push(@f, $gen_dest_arg);
    }

    #
    # Add a fail action macro if requested.
    #

    $flags =~ /-fail_action/ and do {
	if (!defined $fail_type) {
	    my($i);
	    for ($i = 0; $i < @f_types; $i++) {
		local($_) = $f_types[$i];
		/[rxycians]/ and do { push(@f, "Badmatch($f[$i])"); next };
	    }
	} elsif ($fail_type eq 'f') {
	    push(@f, "ClauseFail()");
	} else {
	    my($i);
	    for ($i = 0; $i < @f_types; $i++) {
		local($_) = $f_types[$i];
		/[rxycians]/ and do { push(@f, "Badmatch($f[$i])"); next };
	    }
	}
    };

    #
    # Add a size argument if requested.
    #

    $flags =~ /-size/ and do {
	push(@f, $size);
    };

    # Generate the macro if requested.
    my($code);
    if (defined $macro{$name}) {
	my($macro_code) = "$prefix$macro(" . join(', ', @f) . ");";
	$var_decls .= "BeamInstr tmp_packed1;"
	    if $macro_code =~ /tmp_packed1/;
	$var_decls .= "BeamInstr tmp_packed2;"
	    if $macro_code =~ /tmp_packed2/;
	if ($flags =~ /-nonext/) {
	    $code = join("\n",
			 "{ $var_decls",
			 $macro_code,
			 "}");
	} elsif ($flags =~ /-goto:(\S*)/) {
	    my $goto = $1;
	    $code = join("\n",
			 "{ $var_decls",
			 $macro_code,
			 "I += $size + 1;",
			 "goto $goto;",
			 "}");
	} else {
	    $code = join("\n",
			 "{ $var_decls",
			 "BeamInstr* next;",
			 "PreFetch($size, next);",
			 "$macro_code",
			 "NextPF($size, next);",
			 "}", "");
	}
    }

    # Return the size and code for the macro (if any).
    $size++;
    ($size, $code, $pack_spec);
}

sub do_pack {
    my(@args) = @_;
    my($packable_args) = 0;
    my @is_packable;		# Packability (boolean) for each argument.
    my $wide_packing = 0;

    #
    # Count the number of packable arguments.  If we encounter any 's' or 'd'
    # arguments, packing is not possible.
    #
    my $packable_types = "xytQ";
    foreach my $arg (@args) {
	if ($arg =~ /^[$packable_types]/) {
	    $packable_args++;
	    push @is_packable, 1;
	} elsif ($arg =~ /^I/ and $wordsize == 64 and $packable_args < 2) {
	    $wide_packing = 1;
	    push @is_packable, 1;
	    if (++$packable_args == 2) {
		# We can only pack two arguments. Turn off packing
		# for the rest of the arguments.
		$packable_types = "\xFF";
	    }
	} elsif ($arg =~ /^[sd]/) {
	    return ('', '', @args);
	} else {
	    push @is_packable, 0;
	}
    }

    #
    # Get out of here if too few or too many arguments.
    #
    return ('', '', @args) if $packable_args < 2;
    &error("too many packable arguments") if $packable_args > 4;

    my($size) = 0;
    my($pack_prefix) = '';
    my($down) = '';		# Pack commands (towards instruction
				# beginning).
    my($up) = '';		# Pack commands (storing back while
				# moving forward).
    my $args_per_word;
    if ($packable_args < 4 or $wordsize == 64) {
	$args_per_word = $packable_args;
    } else {
	# 4 packable argument, 32 bit wordsize. Need 2 words.
	$args_per_word = 2;
    }

    my @shift;
    my @mask;
    my @instr;

    if ($wide_packing) {
	@shift = ('0', 'BEAM_WIDE_SHIFT');
	@mask = ('BEAM_WIDE_MASK', $WHOLE_WORD);
	@instr = ('w', 'i');
    } else {
	@shift = @{$pack_shift[$args_per_word]};
	@mask = @{$pack_mask[$args_per_word]};
	@instr = @{$pack_instr[$args_per_word]};
    }

    #
    # Now generate the packing instructions.  One complication is that
    # the packing engine works from right-to-left, but we must generate
    # the instructions from left-to-right because we must calculate
    # instruction sizes from left-to-right.
    #
    # XXX Packing 3 't's in one word won't work.  Sorry.

    my $did_some_packing = 0;	# Nothing packed yet.
    my($ap) = 0;		# Argument number within word.
    my($tmpnum) = 1;		# Number of temporary variable.
    my($expr) = '';
    for (my $i = 0; $i < @args; $i++) {
	my($reg) = $args[$i];
	my($this_size) = $arg_size{$reg};
	if ($is_packable[$i]) {
	    $this_size = 0;
	    $did_some_packing = 1;

	    if ($ap == 0) {
		$pack_prefix .= "tmp_packed$tmpnum = Arg($size);\n";
		$up .= "p";
		$down = "P$down";
		$this_size = 1;
	    }

	    $down = "$instr[$ap]$down";
	    my($unpack) = &make_unpack($tmpnum, $shift[$ap], $mask[$ap]);
	    $args[$i] = "pack:$this_size:$reg" . "b($unpack)";

	    if (++$ap == $args_per_word) {
		$ap = 0;
		$tmpnum++;
	    }
	} elsif ($arg_size{$reg} && $did_some_packing) {
	    #
	    # This is an argument that can't be packed.  Normally, we must
	    # save it on the pack engine's stack, unless:
	    #
	    # 1. The argument has zero size (e.g. r(0)).  Such arguments
	    #    will not be loaded.  They disappear.
	    # 2. If the argument is on the left of the first packed argument,
	    #    the packing engine will never access it (because the engine
	    #    operates from right-to-left).
	    #

	    $down = "g${down}";
	    $up = "${up}p";
	}
	$size += $this_size;
    }

    my $pack_spec = $down . $up;
    return ($pack_prefix, $pack_spec, @args);
}

sub make_unpack {
    my($tmpnum, $shift, $mask) = @_;

    my($e) = "tmp_packed$tmpnum";
    $e = "($e>>$shift)" if $shift;
    $e .= "&$mask" unless $mask eq $WHOLE_WORD;
    $e;
}

sub quote {
    local($_) = @_;
    return "'$_'" if $_ eq 'try';
    return "'$_'" if $_ eq 'catch';
    return "'$_'" if $_ eq 'receive';
    return "'$_'" if $_ =~ /^[A-Z]/;
    $_;
}

#
# Parse instruction transformations when they first appear.
#
sub parse_transformation {
    local($_) = @_;
    my($orig) = $_;

    my($from, $to) = split(/\s*=>\s*/);
    my(@op);

    # The source instructions.

    my(@from) = split(/\s*\|\s*/, $from);
    foreach (@from) {
	if (/^(\w+)\((.*?)\)/) {
	    my($name, $arglist) = ($1, $2);
	    $_ = (&compile_transform_function($name, split(/\s*,\s*/, $arglist)));
	} else {
	    (@op) = split;
	    $_ = &compile_transform(1, @op);
	}
    }

    #
    # Check for a function which should be called to provide the new
    # instructions if the left-hand side matched.  Otherwise there is
    # an explicit list of instructions.
    #

    my @to;
    if ($to =~ /^(\w+)\((.*?)\)/) {
	my($name, $arglist) = ($1, $2);
	@to = (&compile_transform_function($name, split(/\s*,\s*/, $arglist)));
    } else {
	@to = split(/\s*\|\s*/, $to);
	foreach (@to) {
	    (@op) = split;
	    $_ = &compile_transform(0, @op);
	}
    }
    push(@transformations, [$., $orig, [@from], [reverse @to]]);
}

sub compile_transform_function {
    my($name, @args) = @_;

    [".$name", 0, @args];
}

sub compile_transform {
    my($src, $name, @ops) = @_;
    my $arity = 0;
    
    foreach (@ops) {
	my(@list) = &tr_parse_op($src, $_);
	$arity++ unless $list[1] eq '*';
	$_ = [ @list ];
    }

    if ($obsolete[$gen_opnum{$name,$arity}]) {
	error("obsolete function must not be used in transformations");
    }

    if ($src) {
	$is_transformed{$name,$arity} = 1;
    }
    
    [$name,$arity,@ops];
}

sub tr_parse_op {
    my($src, $op) = @_;
    my($var) = '';
    my($type) = '';
    my($type_val) = 0;
    my($cond) = '';
    my($cond_val) = '';

    local($_) = $op;

    # Get the variable name if any.

    if (/^([A-Z]\w*)(.*)/) {
	$var = $1;
	$_ = $2;
	&error("garbage after variable")
	    unless /^=(.*)/ or /^(\s*)$/;
	$_ = $1;
    }

    # Get the type if any.

    if (/^([a-z*]+)(.*)/) {
	$type = $1;
	$_ = $2;
	foreach (split('', $type)) {
	    &error("bad type in $op")
		unless defined $type_bit{$_} or $type eq '*';
	}
    }

    # Get an optional condition. (In source.)

    if (/^==(.*)/) {
	$cond = 'is_eq';
	$cond_val = $1;
	$_ = '';
    } elsif (/^\$is_bif(.*)/) {
	$cond = 'is_bif';
	$cond_val = -1;
	$_ = $1;
    } elsif (/^\$is_not_bif(.*)/) {
	$cond = 'is_not_bif';
	$cond_val = -1;
	$_ = $1;
    } elsif (m@^\$bif:(\w+):(\w+)/(\d)(.*)@) {
	$cond = 'is_bif';
	if ($1 eq 'erlang') {
	    $cond_val = "BIF_$2_$3";
	} else {
	    $cond_val = "BIF_$1_$2_$3";
	}
	$_ = $4;
    } elsif (m@^\$func:(\w+):(\w+)/([_\d])(.*)@) {
	my $arity = $3 eq '_' ? 1024 : $3;
	$cond = 'is_func';
	$cond_val = "$1:$2:$arity";
	$_ = $4;
    }

    # Get an optional value. (In destination.)
    if (/^=(.*)/) {
	$type_val = $1;
	$_ = '';
    }

    # Nothing more is allowed after the command.

    &error("garbage '$_' after operand: $op")
	unless /^\s*$/;

    # Test that destination has no conditions.

    unless ($src) {
	error("condition not allowed in destination: $op")
	    if $cond;
	error("variable name and type cannot be combined in destination: $op")
	    if $var && $type;
    }

    # Test that source has no values.
    if ($src) {
	error("value not allowed in source: $op")
	    if $type_val;
    }
    ($var,$type,$type_val,$cond,$cond_val);
}

#
# Generate code for all transformations.
#

sub tr_gen {
    my(@g) = @_;

    my($ref, $key, $instr);	# Loop variables.

    foreach $ref (@g) {
	my($line, $orig_transform, $from_ref, $to_ref) = @$ref;
	my $used_ref = used_vars($from_ref, $to_ref);
	my $so_far = tr_gen_from($line, $used_ref, @$from_ref);
	tr_gen_to($line, $orig_transform, $so_far, @$to_ref);
    }

    #
    # Print the generated transformation engine.
    #
    my($offset) = 0;
    print "Uint op_transform[] = {\n";
    foreach $key (sort keys %gen_transform) {
	$gen_transform_offset{$key} = $offset;
	my @instr = @{$gen_transform{$key}};

	#
	# If the last instruction is 'fail', remove it and
	# convert the previous 'try_me_else' to 'try_me_else_fail'.
	#
	if (is_instr($instr[$#instr], 'fail')) {
	    pop(@instr);
	    my $i = $#instr;
	    $i-- while !is_instr($instr[$i], 'try_me_else');
	    $instr[$i] = make_op('', 'try_me_else_fail');
	}

	foreach $instr (@instr) {
	    my($size, $instr_ref, $comment) = @$instr;
	    my($op, @args) = @$instr_ref;
	    print "    ";
	    if (!defined $op) {
		$comment =~ s/\n(.)/\n    $1/g;
		print "\n", $comment;
	    } else {
		$op = "TOP_$op";
		$match_engine_ops{$op} = 1;
		if ($comment ne '') {
		    printf "%-24s /* %s */\n", (join(", ", ($op, @args)) . ","),
		    $comment;
		} else {
		    print join(", ", ($op, @args)), ",\n";
		}
		$offset += $size;
	    }
	}
	print "\n";
    }
    print "/*\n";
    print " * Total number of words: $offset\n";
    print " */\n";
    print "};\n\n";
}

sub used_vars {
    my($from_ref,$to_ref) = @_;
    my %used;
    my %seen;

    foreach my $ref (@$from_ref) {
	my($name,$arity,@ops) = @$ref;
	if ($name =~ /^[.]/) {
	    foreach my $var (@ops) {
		$used{$var} = 1;
	    }
	} else {
	    # Any variable that is used at least twice on the
	    # left-hand side is used. (E.g. "move R R".)
	    foreach my $op (@ops) {
		my($var, $type, $type_val) = @$op;
		next if $var eq '';
		$used{$var} = 1 if $seen{$var};
		$seen{$var} = 1;
	    }
	}
    }

    foreach my $ref (@$to_ref) {
	my($name, $arity, @ops) = @$ref;
	if ($name =~ /^[.]/) {
	    foreach my $var (@ops) {
		$used{$var} = 1;
	    }
	} else {
	    foreach my $op (@ops) {
		my($var, $type, $type_val) = @$op;
		next if $var eq '';
		$used{$var} = 1;
	    }
	}
    }
    \%used;
}

sub tr_gen_from {
    my($line,$used_ref,@tr) = @_;
    my(%var) = ();
    my(%var_type);
    my($var_num) = 0;
    my(@code);
    my($min_window) = 0;
    my(@fix_rest_args);
    my(@fix_pred_funcs);
    my($op, $ref);		# Loop variables.
    my $where = "left side of transformation in line $line: ";
    my %var_used = %$used_ref;
    my $may_fail = 0;
    my $is_first = 1;

    foreach $ref (@tr) {
	my($name, $arity, @ops) = @$ref;
	my($key) = "$name/$arity";
	my($opnum);

	$may_fail = 1 unless $is_first;
	$is_first = 0;

	#
	# A name starting with a period is a C pred function to be called.
	#

	if ($name =~ /^\.(\w+)/) {
	    $name = $1;
	    $may_fail = 1;
	    my $var;
	    my(@args);

	    push(@fix_pred_funcs, scalar(@code));
	    push(@code, [$name, @ops]);
	    next;
	}

	#
	# Check that $name/$arity refers to a valid generic instruction.
	#

	&error($where, "invalid generic op $name/$arity")
	    unless defined $gen_opnum{$name,$arity};
	$opnum = $gen_opnum{$name,$arity};

	push(@code, make_op("$name/$arity", 'next_instr', $opnum));
	$min_window++;
	foreach $op (@ops) {
	    my($var, $type, $type_val, $cond, $val) = @$op;
	    my $ignored_var = "$var (ignored)";

	    if ($type ne '' && $type ne '*') {
		$may_fail = 1;

		#
		# The is_bif, is_not_bif, and is_func instructions have
		# their own built-in type test and don't need to
		# be guarded with a type test instruction.
		#
		$ignored_var = '';
		unless ($cond eq 'is_bif' or
			$cond eq 'is_not_bif' or
			$cond eq 'is_func') {
		    my($types) = '';
		    my($type_mask) = 0;
		    foreach (split('', $type)) {
			$types .= "$_ ";
			$type_mask |= $type_bit{$_};
		    }
		    if ($cond ne 'is_eq') {
			push(@code, &make_op($types, 'is_type', $type_mask));
		    } else {
			$cond = '';
			push(@code, &make_op("$types== $val", 'is_type_eq',
					     $type_mask, $val));
		    }
		}
	    }

	    if ($cond eq 'is_func') {
		my($m, $f, $a) = split(/:/, $val);
		$ignored_var = '';
		$may_fail = 1;
		push(@code, &make_op('', "$cond", "am_$m",
				     "am_$f", $a));
	    } elsif ($cond ne '') {
		$ignored_var = '';
		$may_fail = 1;
		push(@code, &make_op('', "$cond", $val));
	    }

	    if ($var ne '') {
		if (defined $var{$var}) {
		    $ignored_var = '';
		    $may_fail = 1;
		    push(@code, &make_op($var, 'is_same_var', $var{$var}));
		} elsif ($type eq '*') {
		    #
		    # Reserve a hole for a 'rest_args' instruction.
		    #
		    $ignored_var = '';
		    push(@fix_rest_args, scalar(@code));
		    push(@code, $var);
		} elsif ($var_used{$var}) {
		    $ignored_var = '';
		    $var_type{$var} = 'scalar';
		    $var{$var} = $var_num;
		    $var_num++;
		    push(@code, &make_op($var, 'set_var', $var{$var}));
		}
	    }
	    if (is_instr($code[$#code], 'set_var')) {
		my $ref = pop @code;
		my $comment = $ref->[2];
		my $var = $ref->[1][1];
		push(@code, make_op($comment, 'set_var_next_arg', $var));
	    } else {
		push(@code, &make_op($ignored_var, 'next_arg'));
	    }
	}

	# Remove redundant 'next_arg' instructions before the end
	# of the instruction.
	pop(@code) while is_instr($code[$#code], 'next_arg');
    }

    #
    # Insert the commit operation.
    #
    push(@code, make_op($may_fail ? '' : 'always reached', 'commit'));

    #
    # If there is an rest_args instruction, we must insert its correct
    # variable number (higher than any other).
    #
    my $index;
    &error("only one use of a '*' variable is allowed on the left hand side of a transformation")
	if @fix_rest_args > 1;
    foreach $index (@fix_rest_args) {
	my $var = $code[$index];
	$var{$var} = $var_num++;
	$var_type{$var} = 'array';
	splice(@code, $index, 1, &make_op($var, 'rest_args', $var{$var}));
    }

    foreach $index (@fix_pred_funcs) {
	my($name, @ops) = @{$code[$index]};
	my(@args);
	my $var;

	foreach $var (@ops) {
	    &error($where, "variable '$var' unbound")
		unless defined $var{$var};
	    if ($var_type{$var} eq 'scalar') {
		push(@args, "var[$var{$var}]");
	    } else {
		push(@args, "var+$var{$var}");
	    }
	}
	my $pi = tr_next_index(\@pred_table, \%pred_table, $name, @args);
	splice(@code, $index, 1, make_op("$name()", 'pred', $pi));
    }

    $te_max_vars = $var_num
	if $te_max_vars < $var_num;
    [$min_window, \%var, \%var_type, \@code];
}

sub tr_gen_to {
    my($line, $orig_transform, $so_far, @tr) = @_;
    my($min_window, $var_ref, $var_type_ref, $code_ref) = @$so_far;
    my(%var) = %$var_ref;
    my(%var_type) = %$var_type_ref;
    my(@code) = @$code_ref;
    my($op, $ref);		# Loop variables.
    my($where) = "right side of transformation in line $line: ";

    my $last_instr = $code[$#code];
    my $cannot_fail = is_instr($last_instr, 'commit') &&
	(get_comment($last_instr) =~ /^always/);

    foreach $ref (@tr) {
	my($name, $arity, @ops) = @$ref;

	#
	# A name starting with a period is a C function to be called.
	#

	if ($name =~ /^\.(\w+)/) {
	    $name = $1;
	    my $var;
	    my(@args);

	    foreach $var (@ops) {
		&error($where, "variable '$var' unbound")
		    unless defined $var{$var};
		if ($var_type{$var} eq 'scalar') {
		    push(@args, "var[$var{$var}]");
		} else {
		    push(@args, "var+$var{$var}");
		}
	    }
	    pop(@code);	# Get rid of 'commit' instruction
	    my $index = tr_next_index(\@call_table, \%call_table,
				      $name, @args);
	    push(@code, make_op("$name()", 'call_end', $index));
	    last;
	}

	#
	# Check that $name/$arity refers to a valid generic instruction.
	#

	my($key) = "$name/$arity";
	&error($where, "invalid generic op $name/$arity")
	    unless defined $gen_opnum{$name,$arity};
	my $opnum = $gen_opnum{$name,$arity};

	#
	# Create code to build the generic instruction.
	#

	push(@code, make_op("$name/$arity", 'new_instr', $opnum));
	foreach $op (@ops) {
	    my($var, $type, $type_val) = @$op;

	    if ($var ne '') {
		&error($where, "variable '$var' unbound")
		    unless defined $var{$var};
		push(@code, &make_op($var, 'store_var_next_arg', $var{$var}));
	    } elsif ($type ne '') {
		push(@code, &make_op('', 'store_type', "TAG_$type"));
		if ($type_val) {
		    push(@code, &make_op('', 'store_val', $type_val));
		}
		push(@code, make_op('', 'next_arg'));
	    }
	}
	pop(@code) if is_instr($code[$#code], 'next_arg');
    }

    push(@code, make_op('', 'end'))
	unless is_instr($code[$#code], 'call_end');

    #
    # Chain together all codes segments having the same first operation.
    #
    my($first_ref) = shift(@code);
    my($size, $first, $key) = @$first_ref;
    my($dummy, $op, $arity) = @$first;
    my($comment) = "\n/*\n * Line $line:\n *   $orig_transform\n */\n\n";
    $min_window{$key} = $min_window
	if $min_window{$key} > $min_window;

    my $prev_last;
    $prev_last = pop(@{$gen_transform{$key}})
	if defined @{$gen_transform{$key}}; # Fail

    if ($prev_last && !is_instr($prev_last, 'fail')) {
	error("Line $line: A previous transformation shadows '$orig_transform'");
    }
    unless ($cannot_fail) {
	unshift(@code, make_op('', 'try_me_else',
			       tr_code_len(@code)));
	push(@code, make_op(""), make_op("$key", 'fail'));
    }
    unshift(@code, make_op($comment));
    push(@{$gen_transform{$key}}, @code),
}

sub tr_code_len {
    my($sum) = 0;
    my($ref);

    foreach $ref (@_) {
	$sum += $$ref[0];
    }
    $sum;
}

sub make_op {
    my($comment, @op) = @_;
    [scalar(@op), [@op], $comment];
}

sub is_instr {
    my($ref,$op) = @_;
    return 0 unless ref($ref) eq 'ARRAY';
    $ref->[1][0] eq $op;
}

sub get_comment {
    my($ref,$op) = @_;
    return '' unless ref($ref) eq 'ARRAY';
    $ref->[2];
}

sub tr_next_index {
    my($lref,$href,$name,@args) = @_;
    my $code = "RVAL = $name(" . join(', ', 'st', @args) . "); break;\n";
    my $index;

    if (defined $$href{$code}) {
	$index = $$href{$code};
    } else {
	$index = scalar(@$lref);
	push(@$lref, $code);
	$$href{$code} = $index;
    }
    $index;
}

sub tr_gen_call {
    my(@call_table) = @_;
    my($i);

    for ($i = 0; $i < @call_table; $i++) {
	print "case $i: $call_table[$i]";
    }
}