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diff --git a/docs/tutorial/OCamlLangImpl1.html b/docs/tutorial/OCamlLangImpl1.html deleted file mode 100644 index 73fe07bb84..0000000000 --- a/docs/tutorial/OCamlLangImpl1.html +++ /dev/null @@ -1,365 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" - "http://www.w3.org/TR/html4/strict.dtd"> - -<html> -<head> - <title>Kaleidoscope: Tutorial Introduction and the Lexer</title> - <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> - <meta name="author" content="Chris Lattner"> - <meta name="author" content="Erick Tryzelaar"> - <link rel="stylesheet" href="../_static/llvm.css" type="text/css"> -</head> - -<body> - -<h1>Kaleidoscope: Tutorial Introduction and the Lexer</h1> - -<ul> -<li><a href="index.html">Up to Tutorial Index</a></li> -<li>Chapter 1 - <ol> - <li><a href="#intro">Tutorial Introduction</a></li> - <li><a href="#language">The Basic Language</a></li> - <li><a href="#lexer">The Lexer</a></li> - </ol> -</li> -<li><a href="OCamlLangImpl2.html">Chapter 2</a>: Implementing a Parser and -AST</li> -</ul> - -<div class="doc_author"> - <p> - Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> - and <a href="mailto:idadesub@users.sourceforge.net">Erick Tryzelaar</a> - </p> -</div> - -<!-- *********************************************************************** --> -<h2><a name="intro">Tutorial Introduction</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>Welcome to the "Implementing a language with LLVM" tutorial. This tutorial -runs through the implementation of a simple language, showing how fun and -easy it can be. This tutorial will get you up and started as well as help to -build a framework you can extend to other languages. The code in this tutorial -can also be used as a playground to hack on other LLVM specific things. -</p> - -<p> -The goal of this tutorial is to progressively unveil our language, describing -how it is built up over time. This will let us cover a fairly broad range of -language design and LLVM-specific usage issues, showing and explaining the code -for it all along the way, without overwhelming you with tons of details up -front.</p> - -<p>It is useful to point out ahead of time that this tutorial is really about -teaching compiler techniques and LLVM specifically, <em>not</em> about teaching -modern and sane software engineering principles. In practice, this means that -we'll take a number of shortcuts to simplify the exposition. For example, the -code leaks memory, uses global variables all over the place, doesn't use nice -design patterns like <a -href="http://en.wikipedia.org/wiki/Visitor_pattern">visitors</a>, etc... but it -is very simple. If you dig in and use the code as a basis for future projects, -fixing these deficiencies shouldn't be hard.</p> - -<p>I've tried to put this tutorial together in a way that makes chapters easy to -skip over if you are already familiar with or are uninterested in the various -pieces. The structure of the tutorial is: -</p> - -<ul> -<li><b><a href="#language">Chapter #1</a>: Introduction to the Kaleidoscope -language, and the definition of its Lexer</b> - This shows where we are going -and the basic functionality that we want it to do. In order to make this -tutorial maximally understandable and hackable, we choose to implement -everything in Objective Caml instead of using lexer and parser generators. -LLVM obviously works just fine with such tools, feel free to use one if you -prefer.</li> -<li><b><a href="OCamlLangImpl2.html">Chapter #2</a>: Implementing a Parser and -AST</b> - With the lexer in place, we can talk about parsing techniques and -basic AST construction. This tutorial describes recursive descent parsing and -operator precedence parsing. Nothing in Chapters 1 or 2 is LLVM-specific, -the code doesn't even link in LLVM at this point. :)</li> -<li><b><a href="OCamlLangImpl3.html">Chapter #3</a>: Code generation to LLVM -IR</b> - With the AST ready, we can show off how easy generation of LLVM IR -really is.</li> -<li><b><a href="OCamlLangImpl4.html">Chapter #4</a>: Adding JIT and Optimizer -Support</b> - Because a lot of people are interested in using LLVM as a JIT, -we'll dive right into it and show you the 3 lines it takes to add JIT support. -LLVM is also useful in many other ways, but this is one simple and "sexy" way -to shows off its power. :)</li> -<li><b><a href="OCamlLangImpl5.html">Chapter #5</a>: Extending the Language: -Control Flow</b> - With the language up and running, we show how to extend it -with control flow operations (if/then/else and a 'for' loop). This gives us a -chance to talk about simple SSA construction and control flow.</li> -<li><b><a href="OCamlLangImpl6.html">Chapter #6</a>: Extending the Language: -User-defined Operators</b> - This is a silly but fun chapter that talks about -extending the language to let the user program define their own arbitrary -unary and binary operators (with assignable precedence!). This lets us build a -significant piece of the "language" as library routines.</li> -<li><b><a href="OCamlLangImpl7.html">Chapter #7</a>: Extending the Language: -Mutable Variables</b> - This chapter talks about adding user-defined local -variables along with an assignment operator. The interesting part about this -is how easy and trivial it is to construct SSA form in LLVM: no, LLVM does -<em>not</em> require your front-end to construct SSA form!</li> -<li><b><a href="OCamlLangImpl8.html">Chapter #8</a>: Conclusion and other -useful LLVM tidbits</b> - This chapter wraps up the series by talking about -potential ways to extend the language, but also includes a bunch of pointers to -info about "special topics" like adding garbage collection support, exceptions, -debugging, support for "spaghetti stacks", and a bunch of other tips and -tricks.</li> - -</ul> - -<p>By the end of the tutorial, we'll have written a bit less than 700 lines of -non-comment, non-blank, lines of code. With this small amount of code, we'll -have built up a very reasonable compiler for a non-trivial language including -a hand-written lexer, parser, AST, as well as code generation support with a JIT -compiler. While other systems may have interesting "hello world" tutorials, -I think the breadth of this tutorial is a great testament to the strengths of -LLVM and why you should consider it if you're interested in language or compiler -design.</p> - -<p>A note about this tutorial: we expect you to extend the language and play -with it on your own. Take the code and go crazy hacking away at it, compilers -don't need to be scary creatures - it can be a lot of fun to play with -languages!</p> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="language">The Basic Language</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>This tutorial will be illustrated with a toy language that we'll call -"<a href="http://en.wikipedia.org/wiki/Kaleidoscope">Kaleidoscope</a>" (derived -from "meaning beautiful, form, and view"). -Kaleidoscope is a procedural language that allows you to define functions, use -conditionals, math, etc. Over the course of the tutorial, we'll extend -Kaleidoscope to support the if/then/else construct, a for loop, user defined -operators, JIT compilation with a simple command line interface, etc.</p> - -<p>Because we want to keep things simple, the only datatype in Kaleidoscope is a -64-bit floating point type (aka 'float' in O'Caml parlance). As such, all -values are implicitly double precision and the language doesn't require type -declarations. This gives the language a very nice and simple syntax. For -example, the following simple example computes <a -href="http://en.wikipedia.org/wiki/Fibonacci_number">Fibonacci numbers:</a></p> - -<div class="doc_code"> -<pre> -# Compute the x'th fibonacci number. -def fib(x) - if x < 3 then - 1 - else - fib(x-1)+fib(x-2) - -# This expression will compute the 40th number. -fib(40) -</pre> -</div> - -<p>We also allow Kaleidoscope to call into standard library functions (the LLVM -JIT makes this completely trivial). This means that you can use the 'extern' -keyword to define a function before you use it (this is also useful for mutually -recursive functions). For example:</p> - -<div class="doc_code"> -<pre> -extern sin(arg); -extern cos(arg); -extern atan2(arg1 arg2); - -atan2(sin(.4), cos(42)) -</pre> -</div> - -<p>A more interesting example is included in Chapter 6 where we write a little -Kaleidoscope application that <a href="OCamlLangImpl6.html#example">displays -a Mandelbrot Set</a> at various levels of magnification.</p> - -<p>Lets dive into the implementation of this language!</p> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="lexer">The Lexer</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>When it comes to implementing a language, the first thing needed is -the ability to process a text file and recognize what it says. The traditional -way to do this is to use a "<a -href="http://en.wikipedia.org/wiki/Lexical_analysis">lexer</a>" (aka 'scanner') -to break the input up into "tokens". Each token returned by the lexer includes -a token code and potentially some metadata (e.g. the numeric value of a number). -First, we define the possibilities: -</p> - -<div class="doc_code"> -<pre> -(* The lexer returns these 'Kwd' if it is an unknown character, otherwise one of - * these others for known things. *) -type token = - (* commands *) - | Def | Extern - - (* primary *) - | Ident of string | Number of float - - (* unknown *) - | Kwd of char -</pre> -</div> - -<p>Each token returned by our lexer will be one of the token variant values. -An unknown character like '+' will be returned as <tt>Token.Kwd '+'</tt>. If -the curr token is an identifier, the value will be <tt>Token.Ident s</tt>. If -the current token is a numeric literal (like 1.0), the value will be -<tt>Token.Number 1.0</tt>. -</p> - -<p>The actual implementation of the lexer is a collection of functions driven -by a function named <tt>Lexer.lex</tt>. The <tt>Lexer.lex</tt> function is -called to return the next token from standard input. We will use -<a href="http://caml.inria.fr/pub/docs/manual-camlp4/index.html">Camlp4</a> -to simplify the tokenization of the standard input. Its definition starts -as:</p> - -<div class="doc_code"> -<pre> -(*===----------------------------------------------------------------------=== - * Lexer - *===----------------------------------------------------------------------===*) - -let rec lex = parser - (* Skip any whitespace. *) - | [< ' (' ' | '\n' | '\r' | '\t'); stream >] -> lex stream -</pre> -</div> - -<p> -<tt>Lexer.lex</tt> works by recursing over a <tt>char Stream.t</tt> to read -characters one at a time from the standard input. It eats them as it recognizes -them and stores them in in a <tt>Token.token</tt> variant. The first thing that -it has to do is ignore whitespace between tokens. This is accomplished with the -recursive call above.</p> - -<p>The next thing <tt>Lexer.lex</tt> needs to do is recognize identifiers and -specific keywords like "def". Kaleidoscope does this with a pattern match -and a helper function.<p> - -<div class="doc_code"> -<pre> - (* identifier: [a-zA-Z][a-zA-Z0-9] *) - | [< ' ('A' .. 'Z' | 'a' .. 'z' as c); stream >] -> - let buffer = Buffer.create 1 in - Buffer.add_char buffer c; - lex_ident buffer stream - -... - -and lex_ident buffer = parser - | [< ' ('A' .. 'Z' | 'a' .. 'z' | '0' .. '9' as c); stream >] -> - Buffer.add_char buffer c; - lex_ident buffer stream - | [< stream=lex >] -> - match Buffer.contents buffer with - | "def" -> [< 'Token.Def; stream >] - | "extern" -> [< 'Token.Extern; stream >] - | id -> [< 'Token.Ident id; stream >] -</pre> -</div> - -<p>Numeric values are similar:</p> - -<div class="doc_code"> -<pre> - (* number: [0-9.]+ *) - | [< ' ('0' .. '9' as c); stream >] -> - let buffer = Buffer.create 1 in - Buffer.add_char buffer c; - lex_number buffer stream - -... - -and lex_number buffer = parser - | [< ' ('0' .. '9' | '.' as c); stream >] -> - Buffer.add_char buffer c; - lex_number buffer stream - | [< stream=lex >] -> - [< 'Token.Number (float_of_string (Buffer.contents buffer)); stream >] -</pre> -</div> - -<p>This is all pretty straight-forward code for processing input. When reading -a numeric value from input, we use the ocaml <tt>float_of_string</tt> function -to convert it to a numeric value that we store in <tt>Token.Number</tt>. Note -that this isn't doing sufficient error checking: it will raise <tt>Failure</tt> -if the string "1.23.45.67". Feel free to extend it :). Next we handle -comments: -</p> - -<div class="doc_code"> -<pre> - (* Comment until end of line. *) - | [< ' ('#'); stream >] -> - lex_comment stream - -... - -and lex_comment = parser - | [< ' ('\n'); stream=lex >] -> stream - | [< 'c; e=lex_comment >] -> e - | [< >] -> [< >] -</pre> -</div> - -<p>We handle comments by skipping to the end of the line and then return the -next token. Finally, if the input doesn't match one of the above cases, it is -either an operator character like '+' or the end of the file. These are handled -with this code:</p> - -<div class="doc_code"> -<pre> - (* Otherwise, just return the character as its ascii value. *) - | [< 'c; stream >] -> - [< 'Token.Kwd c; lex stream >] - - (* end of stream. *) - | [< >] -> [< >] -</pre> -</div> - -<p>With this, we have the complete lexer for the basic Kaleidoscope language -(the <a href="OCamlLangImpl2.html#code">full code listing</a> for the Lexer is -available in the <a href="OCamlLangImpl2.html">next chapter</a> of the -tutorial). Next we'll <a href="OCamlLangImpl2.html">build a simple parser that -uses this to build an Abstract Syntax Tree</a>. When we have that, we'll -include a driver so that you can use the lexer and parser together. -</p> - -<a href="OCamlLangImpl2.html">Next: Implementing a Parser and AST</a> -</div> - -<!-- *********************************************************************** --> -<hr> -<address> - <a href="http://jigsaw.w3.org/css-validator/check/referer"><img - src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a> - <a href="http://validator.w3.org/check/referer"><img - src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a> - - <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> - <a href="mailto:idadesub@users.sourceforge.net">Erick Tryzelaar</a><br> - <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br> - Last modified: $Date$ -</address> -</body> -</html> |