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remove some unhelpful language from the tutorial
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@357863 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -174,15 +174,10 @@ Language-Specific Optimizations
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-------------------------------
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One thing about LLVM that turns off many people is that it does not
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solve all the world's problems in one system (sorry 'world hunger',
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someone else will have to solve you some other day). One specific
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solve all the world's problems in one system. One specific
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complaint is that people perceive LLVM as being incapable of performing
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high-level language-specific optimization: LLVM "loses too much
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information".
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Unfortunately, this is really not the place to give you a full and
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unified version of "Chris Lattner's theory of compiler design". Instead,
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I'll make a few observations:
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information". Here are a few observations about this:
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First, you're right that LLVM does lose information. For example, as of
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this writing, there is no way to distinguish in the LLVM IR whether an
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104
docs/tutorial/MyFirstLanguageFrontend/index.rst
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104
docs/tutorial/MyFirstLanguageFrontend/index.rst
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@ -0,0 +1,104 @@
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=============================================
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My First Language Frontend: Table of Contents
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=============================================
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Introduction to the "Kaleidoscope" Language Tutorial
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====================================================
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Welcome to the "Implementing a language with LLVM" tutorial. This
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tutorial runs through the implementation of a simple language, showing
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how fun and easy it can be. This tutorial will get you up and started as
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well as help to build a framework you can extend to other languages. The
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code in this tutorial can also be used as a playground to hack on other
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LLVM specific things.
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The goal of this tutorial is to progressively unveil our language,
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describing how it is built up over time. This will let us cover a fairly
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broad range of language design and LLVM-specific usage issues, showing
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and explaining the code for it all along the way, without overwhelming
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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
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about teaching compiler techniques and LLVM specifically, *not* about
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teaching modern and sane software engineering principles. In practice,
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this means that we'll take a number of shortcuts to simplify the
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exposition. For example, the code uses global variables
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all over the place, doesn't use nice design patterns like
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`visitors <http://en.wikipedia.org/wiki/Visitor_pattern>`_, etc... but
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it is very simple. If you dig in and use the code as a basis for future
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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
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easy to skip over if you are already familiar with or are uninterested
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in the various pieces. The structure of the tutorial is:
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- `Chapter #1 <#language>`_: Introduction to the Kaleidoscope
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language, and the definition of its Lexer - This shows where we are
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going and the basic functionality that we want it to do. In order to
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make this tutorial maximally understandable and hackable, we choose
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to implement everything in C++ instead of using lexer and parser
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generators. LLVM works just fine with such tools, feel free
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to use one if you prefer.
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- `Chapter #2 <LangImpl02.html>`_: Implementing a Parser and AST -
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With the lexer in place, we can talk about parsing techniques and
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basic AST construction. This tutorial describes recursive descent
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parsing and operator precedence parsing. Nothing in Chapters 1 or 2
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is LLVM-specific, the code doesn't even link in LLVM at this point.
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:)
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- `Chapter #3 <LangImpl03.html>`_: Code generation to LLVM IR - With
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the AST ready, we can show off how easy generation of LLVM IR really
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is.
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- `Chapter #4 <LangImpl04.html>`_: Adding JIT and Optimizer Support
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- Because a lot of people are interested in using LLVM as a JIT,
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we'll dive right into it and show you the 3 lines it takes to add JIT
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support. LLVM is also useful in many other ways, but this is one
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simple and "sexy" way to show off its power. :)
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- `Chapter #5 <LangImpl05.html>`_: Extending the Language: Control
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Flow - With the language up and running, we show how to extend it
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with control flow operations (if/then/else and a 'for' loop). This
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gives us a chance to talk about simple SSA construction and control
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flow.
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- `Chapter #6 <LangImpl06.html>`_: Extending the Language:
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User-defined Operators - This is a silly but fun chapter that talks
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about extending the language to let the user program define their own
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arbitrary unary and binary operators (with assignable precedence!).
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This lets us build a significant piece of the "language" as library
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routines.
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- `Chapter #7 <LangImpl07.html>`_: Extending the Language: Mutable
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Variables - This chapter talks about adding user-defined local
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variables along with an assignment operator. The interesting part
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about this is how easy and trivial it is to construct SSA form in
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LLVM: no, LLVM does *not* require your front-end to construct SSA
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form!
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- `Chapter #8 <LangImpl08.html>`_: Compiling to Object Files - This
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chapter explains how to take LLVM IR and compile it down to object
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files.
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- `Chapter #9 <LangImpl09.html>`_: Extending the Language: Debug
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Information - Having built a decent little programming language with
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control flow, functions and mutable variables, we consider what it
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takes to add debug information to standalone executables. This debug
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information will allow you to set breakpoints in Kaleidoscope
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functions, print out argument variables, and call functions - all
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from within the debugger!
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- `Chapter #10 <LangImpl10.html>`_: Conclusion and other useful LLVM
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tidbits - This chapter wraps up the series by talking about
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potential ways to extend the language, but also includes a bunch of
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pointers to info about "special topics" like adding garbage
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collection support, exceptions, debugging, support for "spaghetti
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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
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of non-comment, non-blank, lines of code. With this small amount of
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code, we'll have built up a very reasonable compiler for a non-trivial
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language including a hand-written lexer, parser, AST, as well as code
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generation support with a JIT compiler. While other systems may have
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interesting "hello world" tutorials, I think the breadth of this
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tutorial is a great testament to the strengths of LLVM and why you
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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
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play with it on your own. Take the code and go crazy hacking away at it,
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compilers don't need to be scary creatures - it can be a lot of fun to
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play with languages!
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