make a bunch of cleanups in wording and tone

llvm-svn: 357865

docs/tutorial/MyFirstLanguageFrontend/index.rst

@@ -1,104 +1,81 @@
 =============================================
-My First Language Frontend: Table of Contents
+My First Language Frontend with LLVM Tutorial
 =============================================
 
-Introduction to the "Kaleidoscope" Language Tutorial
-====================================================
+Welcome to the "My First Language Frontend with LLVM" tutorial. Here we
+run through the implementation of a simple language, showing
+how fun and easy it can be.  This tutorial will get you up and running
+fast and show a concrete example of something that uses LLVM to generate
+code.
 
-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.
+This tutorial introduces the simple "Kaleidoscope" language, building it
+iteratively over the course of several chapters, showing how it is built
+over time. This lets us cover a range of language design and LLVM-specific
+ideas, showing and explaining the code for it all along the way,
+and reduces the amount of overwhelming details up front.  We strongly
+encourage that you *work with this code* - make a copy and hack it up and
+experiment.
 
-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.
-
-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
+Warning: In order to focus on teaching compiler techniques and LLVM
+specifically,
+this tutorial does *not* show best practices in software engineering
+principles.  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.
+instead keeps things simple and focuses on the topics at hand.
 
-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:
+This tutorial is structured into chapters covering individual topics,
+allowing you to skip ahead or over things as you wish:
 
--  `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 #1 <LangImpl01.html>`_: Introduction to the Kaleidoscope
+   language, and the definition of its Lexer.  This shows where we are
+   going and the basic functionality that we want to build.  A lexer
+   is also the first part of building a parser for a language, and we
+   use a simple C++ lexer which is easy to understand.
 -  `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.
+   parsing and operator precedence parsing.
+-  `Chapter #3 <LangImpl03.html>`_: Code generation to LLVM IR - with
+   the AST ready, we show how easy it is to generate LLVM IR, and show
+   a simple way to incorporate LLVM into your project.
 -  `Chapter #4 <LangImpl04.html>`_: Adding JIT and Optimizer Support
-   - Because a lot of people are interested in using LLVM as a JIT,
+   - One great thing about LLVM is its support for JIT compilation, so
    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. :)
+   support. Later chapters show how to generate .o files.
 -  `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 - With the basic language up and running, we show how to extend
+   it with control flow operations ('if' statement and a 'for' loop). This
+   gives us a chance to talk about 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.
+   User-defined Operators - This chapter extends the language to let
+   users define 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!
+   variables along with an assignment operator. This shows how easy it is
+   to construct SSA form in LLVM: LLVM does *not* require your front-end
+   to construct SSA form in order to use it!
 -  `Chapter #8 <LangImpl08.html>`_: Compiling to Object Files - This
    chapter explains how to take LLVM IR and compile it down to object
-   files.
+   files, like a static compiler does.
 -  `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!
+   Information - A real language needs to support debuggers, so we add
+   debug information that allows setting breakpoints in Kaleidoscope
+   functions, print out argument variables, and call functions!
 -  `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
+   potential ways to extend the language, and includes some
+   pointers to info on "special topics" like adding garbage
    collection support, exceptions, debugging, support for "spaghetti
-   stacks", and a bunch of other tips and tricks.
+   stacks", and random tips and tricks.
 
 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
+code, we'll have built up a nice little 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.
-
-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!
-
-
+generation support with a JIT compiler.  The breadth of this
+tutorial is a great testament to the strengths of LLVM and shows why
+it is such a popular target for language designers.