I've restructured the opr code and the add code using the SimH logic
and I fixed up some bugs with the new command interpreter. I'm getting so close to cat.s working!
This commit is contained in:
Warren Toomey
+146
-88
@@ -27,6 +27,8 @@ use constant MAXPOSINT => 0377777; # Biggest signed integer
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use constant MAXADDR => 017777; # Largest memory address
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use constant LINKMASK => 01000000; # Mask for LINK register
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use constant EAESTEP => 077; # EAE step count mask
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use constant EAEIMASK => 0777700; # EAE instruction mask
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use constant SIGN => 0400000; # Sign bit
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### Main program ###
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@@ -40,7 +42,7 @@ while ( defined( $ARGV[0] ) && ( $ARGV[0] =~ m{^-} ) ) {
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# -b: set a breakpoint
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if ( $ARGV[0] eq "-b" ) {
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$singlestep = 1; shift(@ARGV);
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shift(@ARGV);
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$Breakpoint{ oct( shift(@ARGV) ) } = 1;
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}
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}
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@@ -166,8 +168,7 @@ sub simulate {
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oct("054") => \&sad,
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oct("060") => \&jmp,
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oct("064") => \&eae,
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oct("070") => \&iot,
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oct("074") => \&special,
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oct("074") => \&opr,
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);
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# Loop indefinitely
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@@ -183,7 +184,10 @@ sub simulate {
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my $indaddr = ($indirect) ? $Mem[$addr] & MAXADDR : $addr;
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# If this is a breakpoint, stop now and get a user command
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$singlestep = 1 if ( defined( $Breakpoint{$PC} ) );
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if ( defined( $Breakpoint{$PC} ) ) {
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$singlestep = 1;
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dprintf( "break at PC %06o\n", $PC );
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}
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get_user_command() if ($singlestep);
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dprintf( "PC %06o: ", $PC );
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@@ -194,7 +198,7 @@ sub simulate {
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if ( defined( $Oplist{$opcode} ) ) {
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$Oplist{$opcode}->( $instruction, $addr, $indaddr );
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} else {
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printf( STDERR "Unknown instruction 0%o at location 0%o\n",
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printf( STDERR "Unknown instruction 0%06o at location 0%06o\n",
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$instruction, $PC );
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exit(1);
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}
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@@ -243,14 +247,26 @@ sub tad {
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sub add {
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my ( $instruction, $addr, $indaddr ) = @_;
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dprintf( "add AC (value %06o) with addr %06o (%06o)\n",
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$PC, $AC, $indaddr, $Mem[$indaddr] );
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$LINK = 0;
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$AC = $AC + $Mem[$indaddr];
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if ( $AC & LINKMASK ) {
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$AC++; # End-around carry
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$LINK = LINKMASK;
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$AC, $indaddr, $Mem[$indaddr] );
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# $LINK = 0;
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# $AC = $AC + $Mem[$indaddr];
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# if ( $AC & LINKMASK ) {
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# $AC++; # End-around carry
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# $LINK = LINKMASK;
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# }
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# $AC = $AC & MAXINT;
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#
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# This logic shamelessly borrowed from SimH
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# https://github.com/simh/simh/blob/master/PDP18B/pdp18b_cpu.c
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my $sum= $AC + $Mem[$indaddr];
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if ($sum > MAXINT) { # end around carry
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$sum = ($sum + 1) & MAXINT;
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}
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$AC = $AC & MAXINT;
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if (((~$AC ^ $sum) & ($AC ^ $sum)) & SIGN) { # overflow?
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$LINK= LINKMASK; # set link
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}
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$AC= $sum;
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$PC++;
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}
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@@ -290,7 +306,7 @@ sub dzm {
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# Index and skip if zero
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sub isz {
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my ( $instruction, $addr, $indaddr ) = @_;
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dprintf( "isz %06o\n", $Mem[$indaddr] );
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dprintf( "isz %06o (value %06o)\n", $indaddr, $Mem[$indaddr] );
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$Mem[$indaddr]++;
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$Mem[$indaddr] &= MAXINT;
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$PC += ( $Mem[$indaddr] == 0 ) ? 2 : 1;
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@@ -313,79 +329,117 @@ sub jms {
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$PC = $indaddr;
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}
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# Special instructions
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sub special {
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my $instruction = shift;
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# OPR instructions
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sub opr {
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my ( $instruction, $addr, $indaddr ) = @_;
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# Deal with each one in turn
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# hlt
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# hlt: halt simulation
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if ( $instruction == 0740040 ) {
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printf( STDERR "PC %06o: program halted\n", $PC );
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dump_memory( 0, MAXADDR, 0 ) if ($debug);
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exit(1);
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}
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if ( $instruction == 0741100 ) { # spa: skip on positive AC
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dprintf( "spa AC %06o\n", $AC );
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# Because we are dealing with 18 bits, compare the range
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$PC += ( ( $AC >= 0 ) && ( $AC <= MAXPOSINT ) ) ? 2 : 1;
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return;
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}
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if ( $instruction == 0741200 ) { # sna: skip on non-zero AC
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dprintf( "sna AC %06o\n", $AC );
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$PC += ( $AC != 0 ) ? 2 : 1;
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return;
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}
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if ( $instruction == 0740200 ) { # sza: skip on zero AC
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dprintf( "sza AC %06o\n", $AC );
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$PC += ( $AC == 0 ) ? 2 : 1;
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return;
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}
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if ( $instruction == 0741400 ) { # szl: Skip when $LINK is zero
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dprintf( "szl LINK %0o\n", $LINK );
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$PC += ( $LINK == 0 ) ? 2 : 1;
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return;
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}
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if ( $instruction == 0740400 ) { # snl: Skip when $LINK not zero
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dprintf( "snl LINK %0o\n", $LINK );
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$PC += ( $LINK != 0 ) ? 2 : 1;
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return;
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}
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if ( $instruction == 0741000 ) { # ska: skip always
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dprintf("skp\n");
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$PC += 2;
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return;
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}
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# ral: rotate left or rcr: clear link then rotate left
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if ( ( $instruction == 0740010 ) || ( $instruction == 0744010 ) ) {
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$LINK = 0 if ( $instruction == 0744010 );
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$AC = $AC << 1 + ($LINK) ? 1 : 0;
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$LINK = $AC & LINKMASK;
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$AC = $AC & MAXINT;
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$PC++;
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return;
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}
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# rar: rotate right or rcr: clear link then rotate right
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if ( ( $instruction == 0740020 ) || ( $instruction == 0744020 ) ) {
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$LINK = 0 if ( $instruction == 0744020 );
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my $newlink = ( $AC & 1 ) ? LINKMASK : 0;
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$AC = ( $LINK | $AC ) >> 1;
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$LINK = $newlink;
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$PC++;
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return;
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}
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# law: load word into AC
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if ( ( $instruction >= 0760000 ) && ( $instruction <= MAXINT ) ) {
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my $indirect = ( $instruction >> 13 ) & 1;
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if ( $indirect) {
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dprintf( "law %06o into AC\n", $instruction );
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$AC = $instruction;
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$PC++;
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return;
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}
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printf( STDERR "PC %06o: unknown instruction %06o\n", $PC, $instruction );
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exit(1);
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# List of skip opcode names for the next section
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my @skipop= ( '', 'sma', 'sza', 'sza sma',
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'snl', 'snl sma', 'snl sza', 'snl sza sma',
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'skp', 'spa', 'sna', 'sna spa',
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'szl', 'szl spa', 'szl sna', 'szl sna spa');
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# This logic shamelessly borrowed from SimH
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# https://github.com/simh/simh/blob/master/PDP18B/pdp18b_cpu.c
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my $skip=0;
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my $i= ($instruction >> 6) & 017; # decode IR<8:11>
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dprintf("L.AC %d.%06o %s", ($LINK) ? 1 : 0, $AC, $skipop[$i]);
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$skip=1 if (($i == 1) && ($AC & SIGN) != 0); # sma
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$skip=1 if (($i == 2) && ($AC & MAXINT) == 0); # sza
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$skip=1 if (($i == 3) &&
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((($AC & MAXINT) == 0) || (($AC & SIGN) != 0))); # sza | sma
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$skip=1 if (($i == 4) && ($LINK)); # snl
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$skip=1 if (($i == 5) && ($LINK || ($AC >= SIGN))); # snl | sma
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$skip=1 if (($i == 6) && ($LINK || ($AC == 0))); # snl | sza
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$skip=1 if (($i == 7) &&
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($LINK || ($AC >= SIGN) || ($AC == 0))); # snl | sza | sma
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$skip=1 if ($i == 010); # skp
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$skip=1 if (($i == 011) && (($AC & SIGN) == 0)); # spa
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$skip=1 if (($i == 012) && (($AC & MAXINT) != 0)); # sna
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$skip=1 if (($i == 013) &&
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(($AC & MAXINT) != 0) && (($AC & SIGN) == 0)); # sna & spa
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$skip=1 if (($i == 014) && ($LINK == 0)); # szl
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$skip=1 if (($i == 015) && ($LINK == 0) && ($AC < SIGN)); # szl & spa
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$skip=1 if (($i == 016) && ($LINK == 0) && ($AC != 0)); # szl & sna
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$skip=1 if (($i == 017) &&
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($LINK == 0) && ($AC != 0) && ($AC != 0)); # szl & sna & spa
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# Clear operations
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if ($instruction & 010000) { # cla
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dprintf(" cla"); $AC=0;
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}
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if ($instruction & 004000) { # cli
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dprintf(" cli"); $LINK=0;
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}
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if ($instruction & 000002) { # cmi
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dprintf(" cmi"); $LINK= ($LINK) ? 0 : LINKMASK;
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}
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if ($instruction & 000001) { # cma
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dprintf(" cma"); $AC= ($AC ^ MAXINT) & MAXINT;
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}
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# Rotate instructions
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$i= $instruction & 02030;
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# Single rotate right
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if ($i == 020) {
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dprintf(" rar");
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my $newlink = ( $AC & 1 ) ? LINKMASK : 0;
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$AC = ( $LINK | $AC ) >> 1;
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$LINK = $newlink;
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}
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# Double rotate right
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if ($i == 02020) {
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dprintf(" rtr");
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my $msb= ($AC & 1) << 17;
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my $newlink = ( $AC & 2 ) ? LINKMASK : 0;
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$AC = (( $LINK | $AC ) >> 2) | $msb;
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$LINK = $newlink;
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}
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# Single rotate left
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if ($i == 010) {
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dprintf(" ral");
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my $newlink = ( $AC & SIGN ) ? LINKMASK : 0;
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my $lsb = $LINK ? 1 : 0;
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$AC= (($AC << 1) | $lsb) & MAXINT;
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$LINK = $newlink;
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}
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# Double rotate left
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if ($i == 02010) {
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dprintf(" rtl");
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my $newlink = ( $AC & 0200000 ) ? LINKMASK : 0;
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my $lsb = ( $AC & SIGN ) ? 1 : 0;
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my $twolsb = $LINK ? 2 : 0;
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$AC= (($AC << 2) | $twolsb | $lsb) & MAXINT;
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$LINK = $newlink;
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}
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# Impossible left and right rotates: 02030 or 00030. Do nothing!
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# Note: We didn't do the oas instruction above.
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$PC+= 1 + $skip;
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dprintf("\n");
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return;
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}
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# cal: used for system calls
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@@ -414,25 +468,25 @@ sub cal {
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sub eae {
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my ( $instruction, $addr, $indaddr ) = @_;
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my $step = $instruction & EAESTEP;
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$instruction &= EAEIMASK;
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if ( $instruction == 0660500 ) { # lrss: long right shift, signed
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# We ignore the MQ as it's not
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# used by any user-mode programs
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dprintf( "lrss %06o AC step %d\n", $AC, $step );
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# Save the AC's sign into LINK
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$LINK = ( $AC << 1 ) & LINKMASK;
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my $newlink = ( $AC << 1 ) & LINKMASK;
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# XXX: Do we need to preserve the AC sign?
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$AC = $AC >> $step;
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$AC = (($LINK |$AC) >> $step) & MAXINT;
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$LINK= $newlink;
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$PC++;
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return;
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}
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if ( $instruction == 0660711 ) { # alss: long left shift, signed
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if ( $instruction == 0660700 ) { # alss: long left shift, signed
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# We don't fill the lsb with LINK yet
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dprintf( "alss %06o AC step %d\n", $AC, $step );
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# Save the AC's sign into LINK
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$LINK = ( $AC << 1 ) & LINKMASK;
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# XXX: Do we need to preserve the AC sign?
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$AC = ( $AC << $step ) & MAXINT;
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$PC++;
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return;
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@@ -480,17 +534,21 @@ sub sys_open {
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# Get the start address of the string
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my $start = $Mem[ $PC + 1 ];
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# Convert this to a sensible ASCII filename
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my $filename = mem2arg($start);
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# Choose to open read-only or write-only
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my $readorwrite= ($Mem[ $PC + 2 ]) ? ">" : "<";
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dprintf( "open: base %06o, %s file %s\n", $start, $readorwrite, $filename );
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# Bump up the PC
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$PC += 3;
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# Convert this to a sensible ASCII filename
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my $filename = mem2arg($start);
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dprintf( "open: base %06o, file %s\n", $start, $filename );
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# Open the file
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if ( open( my $FH, "<", $filename ) ) {
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if ( open( my $FH, $readorwrite, $filename ) ) {
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# Find a place in the @FD array to store this filehandle. 99 is arbitrary
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# Find a place in the @FD array to store this filehandle.
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# 99 is arbitrary
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foreach my $fd ( 0 .. 99 ) {
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if ( !defined( $FD[$fd] ) ) {
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$FD[$fd] = $FH;
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@@ -573,7 +631,7 @@ sub sys_write {
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my $end = ( $start + $count - 1 ) & MAXADDR;
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die("sys_write: bad start/end addresses $start $end\n")
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if ( $end < $start );
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dprintf( "write: %d words from %o to fd %d\n", $count, $start, $fd );
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dprintf( "write: %d words from %06o to fd %d\n", $count, $start, $fd );
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# Bump up the PC
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$PC += 3;
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