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remove some unhelpful language from the tutorial
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============================================= | ||
My First Language Frontend: Table of Contents | ||
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Introduction to the "Kaleidoscope" Language Tutorial | ||
==================================================== | ||
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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. | ||
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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. | ||
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It is useful to point out ahead of time that this tutorial is really | ||
about teaching compiler techniques and LLVM specifically, *not* 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 uses global variables | ||
all over the place, doesn't use nice design patterns like | ||
`visitors <http://en.wikipedia.org/wiki/Visitor_pattern>`_, 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. | ||
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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: | ||
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- `Chapter #1 <#language>`_: Introduction to the Kaleidoscope | ||
language, and the definition of its Lexer - 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 C++ instead of using lexer and parser | ||
generators. LLVM works just fine with such tools, feel free | ||
to use one if you prefer. | ||
- `Chapter #2 <LangImpl02.html>`_: Implementing a Parser and AST - | ||
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. | ||
:) | ||
- `Chapter #3 <LangImpl03.html>`_: Code generation to LLVM IR - With | ||
the AST ready, we can show off how easy generation of LLVM IR really | ||
is. | ||
- `Chapter #4 <LangImpl04.html>`_: Adding JIT and Optimizer Support | ||
- 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 show off its power. :) | ||
- `Chapter #5 <LangImpl05.html>`_: Extending the Language: Control | ||
Flow - 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. | ||
- `Chapter #6 <LangImpl06.html>`_: Extending the Language: | ||
User-defined Operators - 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. | ||
- `Chapter #7 <LangImpl07.html>`_: Extending the Language: Mutable | ||
Variables - 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 *not* require your front-end to construct SSA | ||
form! | ||
- `Chapter #8 <LangImpl08.html>`_: Compiling to Object Files - This | ||
chapter explains how to take LLVM IR and compile it down to object | ||
files. | ||
- `Chapter #9 <LangImpl09.html>`_: Extending the Language: Debug | ||
Information - Having built a decent little programming language with | ||
control flow, functions and mutable variables, we consider what it | ||
takes to add debug information to standalone executables. This debug | ||
information will allow you to set breakpoints in Kaleidoscope | ||
functions, print out argument variables, and call functions - all | ||
from within the debugger! | ||
- `Chapter #10 <LangImpl10.html>`_: Conclusion and other useful LLVM | ||
tidbits - 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. | ||
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By the end of the tutorial, we'll have written a bit less than 1000 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. | ||
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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! | ||
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