[07] Initial work on VM Translator
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NOTES.md
4
NOTES.md
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@ -64,3 +64,7 @@ The hardest part about this was deciding what name to give to all the pins
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## Assembler
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## Assembler
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I think there are definitely some tricks with reducing lookup table sizes, but I wasn't really aiming for performance (I wrote it in ruby afterall). Also working on a rust implementation, just to learn rust.
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I think there are definitely some tricks with reducing lookup table sizes, but I wasn't really aiming for performance (I wrote it in ruby afterall). Also working on a rust implementation, just to learn rust.
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# VM (1)
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See `vm/README.md` for more details. Observations go here, implementation notes are there.
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@ -0,0 +1 @@
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| RAM[0] | RAM[256] |
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@ -0,0 +1,37 @@
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# VM Implementation
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We have 8 segments:
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- `argument`
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- `local`
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- `this/that`
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- `pointer`
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- `static` (shared)
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- `constant` (shared)
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- `temp` (shared)
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RAM Address | Usage
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============|=================
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0-15 | Virtual Registers
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16-255 | Static Variables (shared)
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256-2047 | Stack
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2048-16384 | Heap
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16384-24575 | Memory mapped I/O
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Register | Name | Usage
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==========|========|=========
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`RAM[0]` | `SP` | Stack Pointer
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`RAM[1]` | `LCL` | `local`
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`RAM[1]` | `ARG` | `argument`
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`RAM[3]` | `THIS` | `this`
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`RAM[4]` | `THAT` | `that`
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RAM[5-12] | `temp` Segment
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RAM[13-15]| General Purpose Registers
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The implementation is written in Modern PHP with static typing. Uses the following 3 classes
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- `CommandType` as a Enum for using command types as constants
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- `Parser`, mostly as defined in the specification
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- `CodeWriter`, mostly as defined in the specification
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- `VMTranslator` which combines the above
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@ -0,0 +1,139 @@
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<?php
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namespace captn3m0\NandToTetris;
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class CommandType {
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const CALL = 0;
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const PUSH = 1;
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const POP = 2;
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const LABEL= 3;
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const GOTO= 4;
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const IF= 5;
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const FUNC= 6;
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const RETURN= 7;
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const ARITHMETIC= 8;
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const ARITHMETIC_COMMANDS = ['add', 'sub', 'neg', 'eq', 'gt', 'lt', 'and', 'or', 'not'];
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public static function fromName(String $name) {
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if(in_array($name, self::ARITHMETIC_COMMANDS)) {
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return self::ARITHMETIC;
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} else {
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$map = ["call","push","pop","label","goto","if","func","return"];
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return array_search($name, $map);
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}
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}
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}
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class Parser {
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function __construct(String $inputFile ) {
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$this->file = fopen($inputFile, "r");
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}
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function arg1() {
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assert($this->command !== CommandType::RETURN);
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return $this->pieces[1];
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}
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function arg2() {
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assert(in_array($this->command, [CommandType::PUSH, CommandType::POP, CommandType::FUNC, CommandType::CALL]));
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return $this->pieces[2];
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}
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private function stripComment(String $line ) {
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$index = strpos($line, '//');
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if ($index == 0) {
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return '';
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}
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if ($index !== false) {
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return substr($line, 0, $index-1);
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} else {
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return $line;
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}
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}
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function commands() {
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while(!feof($this->file)) {
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$line = fgets($this->file);
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$line = $this->stripComment(trim($line));
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if (empty($line)) continue;
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$this->pieces = explode(" ", $line);
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$this->command = $pieces[0];
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yield $this->command;
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}
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fclose($this->file);
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}
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}
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class CodeWriter {
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function __construct($outputFile) {
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$this->file = fopen($outputFile, "w");
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}
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function writeArithmetic(String $command ) {
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throw new Exception("Not yet Implemented");
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}
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function writePushPop(Int $command, String $segment , Int $index) {
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throw new Exception("Not yet Implemented");
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}
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function close() {
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throw new Exception("Not yet Implemented");
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}
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}
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class VMTranslator {
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function __construct(String $fileOrDir ) {
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if (is_dir($fileOrDir)) {
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$this->files = glob("$fileOrDir/*.vm");
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} else {
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$this->files = [$fileOrDir];
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}
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foreach ($this->files as $file) {
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assert(is_readable($file));
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}
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$outputFile = $this->outputFile();
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$this->writer = new CodeWriter($outputFile);
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}
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function translate() {
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foreach ($this->files as $file) {
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$parser = new Parser($file);
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foreach ($parser->commands() as $command) {
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switch ($command) {
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case CommandType::ARITHMETIC:
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$this->writer->writeArithmetic($command);
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break;
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case CommandType::PUSH:
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case CommandType::POP:
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$segment = $parser->arg1();
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$index = $parser->arg2();
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$this->writer->writePushPop($command, $parser, $index);
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break;
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default:
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throw new Exception("Not Implemented", 1);
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break;
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}
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}
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}
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}
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private function outputFile() {
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return '/tmp/file.asm';
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}
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}
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if(isset($argv[1])) {
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$vmt = new VMTranslator($argv[1]);
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$vmt->translate();
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}
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