lib/App/Scheme79asm.pm

   1 package App::Scheme79asm;
   2
   3 use 5.014000;
   4 use strict;
   5 use warnings;
   6
   7 use Data::Dumper qw/Dumper/;
   8 use Data::SExpression qw/consp scalarp/;
   9 use Scalar::Util qw/looks_like_number/;
  10
  11 our $VERSION = '0.002';
  12
  13 our %TYPES = (
  14         LIST => 0,
  15         SYMBOL => 1,
  16         NUMBER => 1,
  17         VAR => 2,
  18         VARIABLE => 2,
  19         CLOSURE => 3,
  20         PROC => 4,
  21         PROCEDURE => 4,
  22         IF => 5,
  23         COND => 5,
  24         CONDITIONAL => 5,
  25         CALL => 6,
  26         QUOTE => 7,
  27         QUOTED => 7,
  28
  29         MORE => 0,
  30         CAR => 1,
  31         CDR => 2,
  32         CONS => 3,
  33         ATOM => 4,
  34         PROGN => 5,
  35         MAKELIST => 6,
  36         FUNCALL => 7,
  37 );
  38
  39 *consp = *Data::SExpression::consp;
  40 *scalarp = *Data::SExpression::scalarp;
  41
  42 sub process {
  43         my ($self, $sexp, $location) = @_;
  44         die 'Toplevel is not a list: ', Dumper($sexp), "\n" unless ref $sexp eq 'ARRAY';
  45         my ($type, @addrs) = @$sexp;
  46         my $addr;
  47
  48         die 'Type of toplevel is not atom: '. Dumper($type), "\n" unless scalarp($type);
  49
  50         if (@addrs > 1) {
  51                 $addr = $self->{freeptr} + 1;
  52                 $self->{freeptr} += @addrs;
  53                 $self->process($addrs[$_], $addr + $_) for 0 .. $#addrs;
  54         } else {
  55                 $addr = $addrs[0];
  56         }
  57
  58         $addr = $self->process($addr) if ref $addr eq 'ARRAY';
  59         die 'Addr of toplevel is not atom: ', Dumper($addr), "\n" unless scalarp($addr);
  60
  61         my ($comment_type, $comment_addr) = ($type, $addr);
  62
  63         unless (looks_like_number $addr) { # is symbol
  64                 unless (exists $self->{symbols}{$addr}) {
  65                         $self->{symbols}{$addr} = $self->{nsymbols};
  66                         $self->{nsymbols}++;
  67                 }
  68                 $addr = $self->{symbols}{$addr}
  69         }
  70
  71         die 'Computed addr is not a number: ', Dumper($addr), "\n" unless looks_like_number $addr;
  72
  73         if (ref $type eq 'Data::SExpression::Symbol') {
  74                 die "No such type: $type\n" unless exists $TYPES{$type};
  75                 $type = $TYPES{$type};
  76         } elsif (!looks_like_number $type) {
  77                 die "Type is not a number or symbol: $type\n"
  78         }
  79
  80         die "Type too large: $type\n" unless $type < (1 << $self->{type_bits});
  81         die "Addr too large: $addr\n" unless $addr < (1 << $self->{addr_bits});
  82         my $result = ($type << $self->{addr_bits}) + $addr;
  83         unless ($location) {
  84                 $self->{freeptr}++;
  85                 $location = $self->{freeptr}
  86         }
  87         $self->{memory}[$location] = $result;
  88         $self->{comment}[$location] = "$comment_type $comment_addr";
  89         $location
  90 }
  91
  92 sub parse {
  93         my ($self, $string) = @_;
  94         my $ds = Data::SExpression->new({symbol_case => 'up', use_symbol_class => 1, fold_lists => 1});
  95
  96         my $sexp;
  97         while () {
  98                 last if $string =~ /^\s*$/;
  99                 ($sexp, $string) = $ds->read($string);
 100                 $self->process($sexp)
 101         }
 102 }
 103
 104 sub finish {
 105         my ($self) = @_;
 106         $self->{memory}[5] = $self->{memory}[$self->{freeptr}];
 107         $self->{comment}[5] = $self->{comment}[$self->{freeptr}];
 108         $self->{memory}[4] = $self->{freeptr};
 109         delete $self->{memory}[$self->{freeptr}]
 110 }
 111
 112 sub new {
 113         my ($class, %args) = @_;
 114         $args{type_bits} //= 3;
 115         $args{addr_bits} //= 8;
 116         $args{freeptr} //= 6;
 117         $args{memory} //= [0, 0, (1<<$args{addr_bits}), (1<<$args{addr_bits}), 0, 0, 0];
 118         $args{symbols}{NIL} = 0;
 119         $args{symbols}{T} = 1;
 120         $args{nsymbols} = 2;
 121         $args{comment} = ['(cdr part of NIL)', '(car part of NIL)', '(cdr part of T)', '(car part of T)', '(free storage pointer)', '', '(result of computation)'];
 122         bless \%args, $class
 123 }
 124
 125 sub print {
 126         my ($self, $fh) = @_;
 127         $fh //= \*STDOUT;
 128
 129         my $bits = $self->{type_bits} + $self->{addr_bits};
 130         my $index_length = length $#{$self->{memory}};
 131         my $index_format = '%' . $index_length . 'd';
 132         for my $index (0 .. $#{$self->{memory}}) {
 133                 my $val = $self->{memory}[$index];
 134                 my $comment = $self->{comment}[$index];
 135                 if ($index == 4) {
 136                         $val = "${bits}'d$val"
 137                 } else {
 138                         $val = $val ? sprintf "%d'b%0${bits}b", $bits, $val : '0';
 139                 }
 140                 my $spaces = ' ' x ($bits + 5 - (length $val));
 141                 $index = sprintf $index_format, $index;
 142                 say $fh "mem[$index] <= $val;$spaces // $comment"
 143         }
 144 }
 145
 146 sub parse_and_print {
 147         my ($self, $string, $fh) = @_;
 148         $self->parse($string);
 149         $self->finish;
 150         $self->print($fh);
 151 }
 152
 153 1;
 154 __END__
 155
 156 =encoding utf-8
 157
 158 =head1 NAME
 159
 160 App::Scheme79asm - assemble sexp to Verilog ROM for SIMPLE processor
 161
 162 =head1 SYNOPSIS
 163
 164   use App::Scheme79asm;
 165   my $asm = App::Scheme79asm->new(type_bits => 3, addr_bits => 5);
 166   $asm->parse_and_print('(number 70)');
 167
 168 =head1 DESCRIPTION
 169
 170 SIMPLE is a LISP processor defined in the 1979
 171 B<Design of LISP-Based Processors> paper by Steele and Sussman.
 172
 173 The SIMPLE processor expects input in a particular tagged-pointer
 174 format. This module takes a string containing a sequence of
 175 S-expressions. Each S-expression is a list of one of three types:
 176
 177 C<(tag value)>, for example C<(symbol nil)>, represents a value to be
 178 put in memory (for example a number, or a symbol, or a variable
 179 reference).
 180
 181 C<(tag list)>, where C<list> is of one of these three types,
 182 represents a tagged pointer. In this case, C<list> is (recursively)
 183 laid out in memory as per these rules, and a pointer to that location
 184 (and tagged C<tag>) is put somewhere in memory.
 185
 186 C<(tag list1 list2)>, where C<list1> and C<list2> are of one of these
 187 three types (not necessarily the same type). In this case, C<list1>
 188 and C<list2> are (recursively) laid out in memory such that C<list1>
 189 is at position X and C<list2> is at position X+1, and a pointer of
 190 type tag and value X is put somewhere in memory.
 191
 192 After this process the very last pointer placed in memory is moved to
 193 the special location 5 (which is where SIMPLE expects to find the
 194 expression to be evaluated).
 195
 196 In normal use a single S-expression will be supplied, representing an
 197 entire program.
 198
 199 The C<tag> is either a number, a type, or a primitive.
 200 The available types are:
 201
 202 =over
 203
 204 =item LIST
 205
 206 =item SYMBOL (syn. NUMBER)
 207
 208 =item VAR (syn. VARIABLE)
 209
 210 =item CLOSURE
 211
 212 =item PROC (syn. PROCEDURE)
 213
 214 =item IF (syn. COND, CONDITIONAL)
 215
 216 =item CALL
 217
 218 =item QUOTE (syn. QUOTED)
 219
 220 =back
 221
 222 The available primitives are:
 223
 224 =over
 225
 226 =item MORE
 227
 228 =item CAR
 229
 230 =item CDR
 231
 232 =item CONS
 233
 234 =item ATOM
 235
 236 =item PROGN
 237
 238 =item MAKELIST
 239
 240 =item FUNCALL
 241
 242 =back
 243
 244 The following methods are available:
 245
 246 =over
 247
 248 =item App::Scheme79asm->B<new>([key => value, key => value, ...])
 249
 250 Create a new assembler object. Takes a list of keys and values, here
 251 are the possible keys:
 252
 253 =over
 254
 255 =item type_bits
 256
 257 =item address_bits
 258
 259 A word is made of a type and an address, with the type occupying the
 260 most significant C<type_bits> (default 3) bits, and the address
 261 occupying the least significant C<address_bits> (default 8) bits.
 262 Therefore the word size is C<type_bits + address_bits> (default 13).
 263
 264 =item freeptr
 265
 266 A pointer to the last used byte in memory (default 6). The program
 267 will be laid out starting with location C<freeptr + 1>.
 268
 269 =item memory
 270
 271 The initial contents of the memory. Note that locations 4, 5, 6 will
 272 be overwritten, as will every location larger than the value of
 273 C<freeptr>.
 274
 275 =item comment
 276
 277 The initial comments for memory entries. C<< $comment->[$i] >> is the
 278 comment for C<< $memory->[$i] >>.
 279
 280 =item symbols
 281
 282 The initial symbol map, as a hashref from symbol name to the index of
 283 that symbol. Defaults to C<< {NIL => 0, T => 1} >>.
 284
 285 =item nsymbols
 286
 287 The number of distinct symbols in the initial symbols map (default 2).
 288
 289 =back
 290
 291 =item $asm->B<parse>(I<$string>)
 292
 293 Parse a sequence of S-expressions and lay it out in memory.
 294 Can be called multiple times to lay out multiple sequences of
 295 S-expressions one after another.
 296
 297 =item $asm->B<finish>
 298
 299 Move the last pointer to position 5, and put the free pointer at
 300 position 4. After all sequences of S-expressions have been given to
 301 B<parse>, this method should be called.
 302
 303 =item $asm->B<print>([I<$fh>])
 304
 305 Print a block of Verilog code assigning the memory contents to an
 306 array named C<mem> to the given filehandle (default STDOUT).
 307
 308 =item $asm->B<parse_and_print>(I<$string>[, I<$fh>])
 309
 310 Convenience method that calls B<parse>($string), B<finish>, and then
 311 B<print>($fh).
 312
 313 =back
 314
 315 =head1 SEE ALSO
 316
 317 L<http://repository.readscheme.org/ftp/papers/ai-lab-pubs/AIM-514.pdf>
 318
 319 =head1 AUTHOR
 320
 321 Marius Gavrilescu, E<lt>marius@ieval.roE<gt>
 322
 323 =head1 COPYRIGHT AND LICENSE
 324
 325 Copyright (C) 2018 by Marius Gavrilescu
 326
 327 This library is free software; you can redistribute it and/or modify
 328 it under the same terms as Perl itself, either Perl version 5.24.3 or,
 329 at your option, any later version of Perl 5 you may have available.
 330
 331
 332 =cut