diff options
| author | Sean Silva <silvas@purdue.edu> | 2012-12-05 00:26:32 +0000 |
|---|---|---|
| committer | Sean Silva <silvas@purdue.edu> | 2012-12-05 00:26:32 +0000 |
| commit | ee47edfd8e2dd048522ebd47305aeefbe9d8729c (patch) | |
| tree | 1149ccaddfcba655771ab114e383a2cae3b6b200 /docs/tutorial/OCamlLangImpl3.html | |
| parent | 4e5448053163e0d9c2107b240ccdb5a95c107b07 (diff) | |
docs: Sphinxify `docs/tutorial/`
Sorry for the massive commit, but I just wanted to knock this one down
and it is really straightforward.
There are still a couple trivial (i.e. not related to the content)
things left to fix:
- Use of raw HTML links where :doc:`...` and :ref:`...` could be used
instead. If you are a newbie and want to help fix this it would make
for some good bite-sized patches; more experienced developers should
be focusing on adding new content (to this tutorial or elsewhere, but
please _do not_ waste your time on formatting when there is such dire
need for documentation (see docs/SphinxQuickstartTemplate.rst to get
started writing)).
- Highlighting of the kaleidoscope code blocks (currently left as bare
`::`). I will be working on writing a custom Pygments highlighter for
this, mostly as training for maintaining the `llvm` code-block's lexer
in-tree. I want to do this because I am extremely unhappy with how it
just "gives up" on the slightest deviation from the expected syntax
and leaves the whole code-block un-highlighted.
More generally I am looking at writing some Sphinx extensions and
keeping them in-tree as well, to support common use cases that
currently have no good solution (like "monospace text inside a link").
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169343 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/tutorial/OCamlLangImpl3.html')
| -rw-r--r-- | docs/tutorial/OCamlLangImpl3.html | 1093 |
1 files changed, 0 insertions, 1093 deletions
diff --git a/docs/tutorial/OCamlLangImpl3.html b/docs/tutorial/OCamlLangImpl3.html deleted file mode 100644 index a49a0b5d9c..0000000000 --- a/docs/tutorial/OCamlLangImpl3.html +++ /dev/null @@ -1,1093 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" - "http://www.w3.org/TR/html4/strict.dtd"> - -<html> -<head> - <title>Kaleidoscope: Implementing code generation to LLVM IR</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: Code generation to LLVM IR</h1> - -<ul> -<li><a href="index.html">Up to Tutorial Index</a></li> -<li>Chapter 3 - <ol> - <li><a href="#intro">Chapter 3 Introduction</a></li> - <li><a href="#basics">Code Generation Setup</a></li> - <li><a href="#exprs">Expression Code Generation</a></li> - <li><a href="#funcs">Function Code Generation</a></li> - <li><a href="#driver">Driver Changes and Closing Thoughts</a></li> - <li><a href="#code">Full Code Listing</a></li> - </ol> -</li> -<li><a href="OCamlLangImpl4.html">Chapter 4</a>: Adding JIT and Optimizer -Support</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">Chapter 3 Introduction</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>Welcome to Chapter 3 of the "<a href="index.html">Implementing a language -with LLVM</a>" tutorial. This chapter shows you how to transform the <a -href="OCamlLangImpl2.html">Abstract Syntax Tree</a>, built in Chapter 2, into -LLVM IR. This will teach you a little bit about how LLVM does things, as well -as demonstrate how easy it is to use. It's much more work to build a lexer and -parser than it is to generate LLVM IR code. :) -</p> - -<p><b>Please note</b>: the code in this chapter and later require LLVM 2.3 or -LLVM SVN to work. LLVM 2.2 and before will not work with it.</p> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="basics">Code Generation Setup</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p> -In order to generate LLVM IR, we want some simple setup to get started. First -we define virtual code generation (codegen) methods in each AST class:</p> - -<div class="doc_code"> -<pre> -let rec codegen_expr = function - | Ast.Number n -> ... - | Ast.Variable name -> ... -</pre> -</div> - -<p>The <tt>Codegen.codegen_expr</tt> function says to emit IR for that AST node -along with all the things it depends on, and they all return an LLVM Value -object. "Value" is the class used to represent a "<a -href="http://en.wikipedia.org/wiki/Static_single_assignment_form">Static Single -Assignment (SSA)</a> register" or "SSA value" in LLVM. The most distinct aspect -of SSA values is that their value is computed as the related instruction -executes, and it does not get a new value until (and if) the instruction -re-executes. In other words, there is no way to "change" an SSA value. For -more information, please read up on <a -href="http://en.wikipedia.org/wiki/Static_single_assignment_form">Static Single -Assignment</a> - the concepts are really quite natural once you grok them.</p> - -<p>The -second thing we want is an "Error" exception like we used for the parser, which -will be used to report errors found during code generation (for example, use of -an undeclared parameter):</p> - -<div class="doc_code"> -<pre> -exception Error of string - -let context = global_context () -let the_module = create_module context "my cool jit" -let builder = builder context -let named_values:(string, llvalue) Hashtbl.t = Hashtbl.create 10 -let double_type = double_type context -</pre> -</div> - -<p>The static variables will be used during code generation. -<tt>Codgen.the_module</tt> is the LLVM construct that contains all of the -functions and global variables in a chunk of code. In many ways, it is the -top-level structure that the LLVM IR uses to contain code.</p> - -<p>The <tt>Codegen.builder</tt> object is a helper object that makes it easy to -generate LLVM instructions. Instances of the <a -href="http://llvm.org/doxygen/IRBuilder_8h-source.html"><tt>IRBuilder</tt></a> -class keep track of the current place to insert instructions and has methods to -create new instructions.</p> - -<p>The <tt>Codegen.named_values</tt> map keeps track of which values are defined -in the current scope and what their LLVM representation is. (In other words, it -is a symbol table for the code). In this form of Kaleidoscope, the only things -that can be referenced are function parameters. As such, function parameters -will be in this map when generating code for their function body.</p> - -<p> -With these basics in place, we can start talking about how to generate code for -each expression. Note that this assumes that the <tt>Codgen.builder</tt> has -been set up to generate code <em>into</em> something. For now, we'll assume -that this has already been done, and we'll just use it to emit code.</p> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="exprs">Expression Code Generation</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>Generating LLVM code for expression nodes is very straightforward: less -than 30 lines of commented code for all four of our expression nodes. First -we'll do numeric literals:</p> - -<div class="doc_code"> -<pre> - | Ast.Number n -> const_float double_type n -</pre> -</div> - -<p>In the LLVM IR, numeric constants are represented with the -<tt>ConstantFP</tt> class, which holds the numeric value in an <tt>APFloat</tt> -internally (<tt>APFloat</tt> has the capability of holding floating point -constants of <em>A</em>rbitrary <em>P</em>recision). This code basically just -creates and returns a <tt>ConstantFP</tt>. Note that in the LLVM IR -that constants are all uniqued together and shared. For this reason, the API -uses "the foo::get(..)" idiom instead of "new foo(..)" or "foo::Create(..)".</p> - -<div class="doc_code"> -<pre> - | Ast.Variable name -> - (try Hashtbl.find named_values name with - | Not_found -> raise (Error "unknown variable name")) -</pre> -</div> - -<p>References to variables are also quite simple using LLVM. In the simple -version of Kaleidoscope, we assume that the variable has already been emitted -somewhere and its value is available. In practice, the only values that can be -in the <tt>Codegen.named_values</tt> map are function arguments. This code -simply checks to see that the specified name is in the map (if not, an unknown -variable is being referenced) and returns the value for it. In future chapters, -we'll add support for <a href="LangImpl5.html#for">loop induction variables</a> -in the symbol table, and for <a href="LangImpl7.html#localvars">local -variables</a>.</p> - -<div class="doc_code"> -<pre> - | Ast.Binary (op, lhs, rhs) -> - let lhs_val = codegen_expr lhs in - let rhs_val = codegen_expr rhs in - begin - match op with - | '+' -> build_fadd lhs_val rhs_val "addtmp" builder - | '-' -> build_fsub lhs_val rhs_val "subtmp" builder - | '*' -> build_fmul lhs_val rhs_val "multmp" builder - | '<' -> - (* Convert bool 0/1 to double 0.0 or 1.0 *) - let i = build_fcmp Fcmp.Ult lhs_val rhs_val "cmptmp" builder in - build_uitofp i double_type "booltmp" builder - | _ -> raise (Error "invalid binary operator") - end -</pre> -</div> - -<p>Binary operators start to get more interesting. The basic idea here is that -we recursively emit code for the left-hand side of the expression, then the -right-hand side, then we compute the result of the binary expression. In this -code, we do a simple switch on the opcode to create the right LLVM instruction. -</p> - -<p>In the example above, the LLVM builder class is starting to show its value. -IRBuilder knows where to insert the newly created instruction, all you have to -do is specify what instruction to create (e.g. with <tt>Llvm.create_add</tt>), -which operands to use (<tt>lhs</tt> and <tt>rhs</tt> here) and optionally -provide a name for the generated instruction.</p> - -<p>One nice thing about LLVM is that the name is just a hint. For instance, if -the code above emits multiple "addtmp" variables, LLVM will automatically -provide each one with an increasing, unique numeric suffix. Local value names -for instructions are purely optional, but it makes it much easier to read the -IR dumps.</p> - -<p><a href="../LangRef.html#instref">LLVM instructions</a> are constrained by -strict rules: for example, the Left and Right operators of -an <a href="../LangRef.html#i_add">add instruction</a> must have the same -type, and the result type of the add must match the operand types. Because -all values in Kaleidoscope are doubles, this makes for very simple code for add, -sub and mul.</p> - -<p>On the other hand, LLVM specifies that the <a -href="../LangRef.html#i_fcmp">fcmp instruction</a> always returns an 'i1' value -(a one bit integer). The problem with this is that Kaleidoscope wants the value to be a 0.0 or 1.0 value. In order to get these semantics, we combine the fcmp instruction with -a <a href="../LangRef.html#i_uitofp">uitofp instruction</a>. This instruction -converts its input integer into a floating point value by treating the input -as an unsigned value. In contrast, if we used the <a -href="../LangRef.html#i_sitofp">sitofp instruction</a>, the Kaleidoscope '<' -operator would return 0.0 and -1.0, depending on the input value.</p> - -<div class="doc_code"> -<pre> - | Ast.Call (callee, args) -> - (* Look up the name in the module table. *) - let callee = - match lookup_function callee the_module with - | Some callee -> callee - | None -> raise (Error "unknown function referenced") - in - let params = params callee in - - (* If argument mismatch error. *) - if Array.length params == Array.length args then () else - raise (Error "incorrect # arguments passed"); - let args = Array.map codegen_expr args in - build_call callee args "calltmp" builder -</pre> -</div> - -<p>Code generation for function calls is quite straightforward with LLVM. The -code above initially does a function name lookup in the LLVM Module's symbol -table. Recall that the LLVM Module is the container that holds all of the -functions we are JIT'ing. By giving each function the same name as what the -user specifies, we can use the LLVM symbol table to resolve function names for -us.</p> - -<p>Once we have the function to call, we recursively codegen each argument that -is to be passed in, and create an LLVM <a href="../LangRef.html#i_call">call -instruction</a>. Note that LLVM uses the native C calling conventions by -default, allowing these calls to also call into standard library functions like -"sin" and "cos", with no additional effort.</p> - -<p>This wraps up our handling of the four basic expressions that we have so far -in Kaleidoscope. Feel free to go in and add some more. For example, by -browsing the <a href="../LangRef.html">LLVM language reference</a> you'll find -several other interesting instructions that are really easy to plug into our -basic framework.</p> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="funcs">Function Code Generation</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p>Code generation for prototypes and functions must handle a number of -details, which make their code less beautiful than expression code -generation, but allows us to illustrate some important points. First, lets -talk about code generation for prototypes: they are used both for function -bodies and external function declarations. The code starts with:</p> - -<div class="doc_code"> -<pre> -let codegen_proto = function - | Ast.Prototype (name, args) -> - (* Make the function type: double(double,double) etc. *) - let doubles = Array.make (Array.length args) double_type in - let ft = function_type double_type doubles in - let f = - match lookup_function name the_module with -</pre> -</div> - -<p>This code packs a lot of power into a few lines. Note first that this -function returns a "Function*" instead of a "Value*" (although at the moment -they both are modeled by <tt>llvalue</tt> in ocaml). Because a "prototype" -really talks about the external interface for a function (not the value computed -by an expression), it makes sense for it to return the LLVM Function it -corresponds to when codegen'd.</p> - -<p>The call to <tt>Llvm.function_type</tt> creates the <tt>Llvm.llvalue</tt> -that should be used for a given Prototype. Since all function arguments in -Kaleidoscope are of type double, the first line creates a vector of "N" LLVM -double types. It then uses the <tt>Llvm.function_type</tt> method to create a -function type that takes "N" doubles as arguments, returns one double as a -result, and that is not vararg (that uses the function -<tt>Llvm.var_arg_function_type</tt>). Note that Types in LLVM are uniqued just -like <tt>Constant</tt>s are, so you don't "new" a type, you "get" it.</p> - -<p>The final line above checks if the function has already been defined in -<tt>Codegen.the_module</tt>. If not, we will create it.</p> - -<div class="doc_code"> -<pre> - | None -> declare_function name ft the_module -</pre> -</div> - -<p>This indicates the type and name to use, as well as which module to insert -into. By default we assume a function has -<tt>Llvm.Linkage.ExternalLinkage</tt>. "<a href="LangRef.html#linkage">external -linkage</a>" means that the function may be defined outside the current module -and/or that it is callable by functions outside the module. The "<tt>name</tt>" -passed in is the name the user specified: this name is registered in -"<tt>Codegen.the_module</tt>"s symbol table, which is used by the function call -code above.</p> - -<p>In Kaleidoscope, I choose to allow redefinitions of functions in two cases: -first, we want to allow 'extern'ing a function more than once, as long as the -prototypes for the externs match (since all arguments have the same type, we -just have to check that the number of arguments match). Second, we want to -allow 'extern'ing a function and then defining a body for it. This is useful -when defining mutually recursive functions.</p> - -<div class="doc_code"> -<pre> - (* If 'f' conflicted, there was already something named 'name'. If it - * has a body, don't allow redefinition or reextern. *) - | Some f -> - (* If 'f' already has a body, reject this. *) - if Array.length (basic_blocks f) == 0 then () else - raise (Error "redefinition of function"); - - (* If 'f' took a different number of arguments, reject. *) - if Array.length (params f) == Array.length args then () else - raise (Error "redefinition of function with different # args"); - f - in -</pre> -</div> - -<p>In order to verify the logic above, we first check to see if the pre-existing -function is "empty". In this case, empty means that it has no basic blocks in -it, which means it has no body. If it has no body, it is a forward -declaration. Since we don't allow anything after a full definition of the -function, the code rejects this case. If the previous reference to a function -was an 'extern', we simply verify that the number of arguments for that -definition and this one match up. If not, we emit an error.</p> - -<div class="doc_code"> -<pre> - (* Set names for all arguments. *) - Array.iteri (fun i a -> - let n = args.(i) in - set_value_name n a; - Hashtbl.add named_values n a; - ) (params f); - f -</pre> -</div> - -<p>The last bit of code for prototypes loops over all of the arguments in the -function, setting the name of the LLVM Argument objects to match, and registering -the arguments in the <tt>Codegen.named_values</tt> map for future use by the -<tt>Ast.Variable</tt> variant. Once this is set up, it returns the Function -object to the caller. Note that we don't check for conflicting -argument names here (e.g. "extern foo(a b a)"). Doing so would be very -straight-forward with the mechanics we have already used above.</p> - -<div class="doc_code"> -<pre> -let codegen_func = function - | Ast.Function (proto, body) -> - Hashtbl.clear named_values; - let the_function = codegen_proto proto in -</pre> -</div> - -<p>Code generation for function definitions starts out simply enough: we just -codegen the prototype (Proto) and verify that it is ok. We then clear out the -<tt>Codegen.named_values</tt> map to make sure that there isn't anything in it -from the last function we compiled. Code generation of the prototype ensures -that there is an LLVM Function object that is ready to go for us.</p> - -<div class="doc_code"> -<pre> - (* Create a new basic block to start insertion into. *) - let bb = append_block context "entry" the_function in - position_at_end bb builder; - - try - let ret_val = codegen_expr body in -</pre> -</div> - -<p>Now we get to the point where the <tt>Codegen.builder</tt> is set up. The -first line creates a new -<a href="http://en.wikipedia.org/wiki/Basic_block">basic block</a> (named -"entry"), which is inserted into <tt>the_function</tt>. The second line then -tells the builder that new instructions should be inserted into the end of the -new basic block. Basic blocks in LLVM are an important part of functions that -define the <a -href="http://en.wikipedia.org/wiki/Control_flow_graph">Control Flow Graph</a>. -Since we don't have any control flow, our functions will only contain one -block at this point. We'll fix this in <a href="OCamlLangImpl5.html">Chapter -5</a> :).</p> - -<div class="doc_code"> -<pre> - let ret_val = codegen_expr body in - - (* Finish off the function. *) - let _ = build_ret ret_val builder in - - (* Validate the generated code, checking for consistency. *) - Llvm_analysis.assert_valid_function the_function; - - the_function -</pre> -</div> - -<p>Once the insertion point is set up, we call the <tt>Codegen.codegen_func</tt> -method for the root expression of the function. If no error happens, this emits -code to compute the expression into the entry block and returns the value that -was computed. Assuming no error, we then create an LLVM <a -href="../LangRef.html#i_ret">ret instruction</a>, which completes the function. -Once the function is built, we call -<tt>Llvm_analysis.assert_valid_function</tt>, which is provided by LLVM. This -function does a variety of consistency checks on the generated code, to -determine if our compiler is doing everything right. Using this is important: -it can catch a lot of bugs. Once the function is finished and validated, we -return it.</p> - -<div class="doc_code"> -<pre> - with e -> - delete_function the_function; - raise e -</pre> -</div> - -<p>The only piece left here is handling of the error case. For simplicity, we -handle this by merely deleting the function we produced with the -<tt>Llvm.delete_function</tt> method. This allows the user to redefine a -function that they incorrectly typed in before: if we didn't delete it, it -would live in the symbol table, with a body, preventing future redefinition.</p> - -<p>This code does have a bug, though. Since the <tt>Codegen.codegen_proto</tt> -can return a previously defined forward declaration, our code can actually delete -a forward declaration. There are a number of ways to fix this bug, see what you -can come up with! Here is a testcase:</p> - -<div class="doc_code"> -<pre> -extern foo(a b); # ok, defines foo. -def foo(a b) c; # error, 'c' is invalid. -def bar() foo(1, 2); # error, unknown function "foo" -</pre> -</div> - -</div> - -<!-- *********************************************************************** --> -<h2><a name="driver">Driver Changes and Closing Thoughts</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p> -For now, code generation to LLVM doesn't really get us much, except that we can -look at the pretty IR calls. The sample code inserts calls to Codegen into the -"<tt>Toplevel.main_loop</tt>", and then dumps out the LLVM IR. This gives a -nice way to look at the LLVM IR for simple functions. For example: -</p> - -<div class="doc_code"> -<pre> -ready> <b>4+5</b>; -Read top-level expression: -define double @""() { -entry: - %addtmp = fadd double 4.000000e+00, 5.000000e+00 - ret double %addtmp -} -</pre> -</div> - -<p>Note how the parser turns the top-level expression into anonymous functions -for us. This will be handy when we add <a href="OCamlLangImpl4.html#jit">JIT -support</a> in the next chapter. Also note that the code is very literally -transcribed, no optimizations are being performed. We will -<a href="OCamlLangImpl4.html#trivialconstfold">add optimizations</a> explicitly -in the next chapter.</p> - -<div class="doc_code"> -<pre> -ready> <b>def foo(a b) a*a + 2*a*b + b*b;</b> -Read function definition: -define double @foo(double %a, double %b) { -entry: - %multmp = fmul double %a, %a - %multmp1 = fmul double 2.000000e+00, %a - %multmp2 = fmul double %multmp1, %b - %addtmp = fadd double %multmp, %multmp2 - %multmp3 = fmul double %b, %b - %addtmp4 = fadd double %addtmp, %multmp3 - ret double %addtmp4 -} -</pre> -</div> - -<p>This shows some simple arithmetic. Notice the striking similarity to the -LLVM builder calls that we use to create the instructions.</p> - -<div class="doc_code"> -<pre> -ready> <b>def bar(a) foo(a, 4.0) + bar(31337);</b> -Read function definition: -define double @bar(double %a) { -entry: - %calltmp = call double @foo(double %a, double 4.000000e+00) - %calltmp1 = call double @bar(double 3.133700e+04) - %addtmp = fadd double %calltmp, %calltmp1 - ret double %addtmp -} -</pre> -</div> - -<p>This shows some function calls. Note that this function will take a long -time to execute if you call it. In the future we'll add conditional control -flow to actually make recursion useful :).</p> - -<div class="doc_code"> -<pre> -ready> <b>extern cos(x);</b> -Read extern: -declare double @cos(double) - -ready> <b>cos(1.234);</b> -Read top-level expression: -define double @""() { -entry: - %calltmp = call double @cos(double 1.234000e+00) - ret double %calltmp -} -</pre> -</div> - -<p>This shows an extern for the libm "cos" function, and a call to it.</p> - - -<div class="doc_code"> -<pre> -ready> <b>^D</b> -; ModuleID = 'my cool jit' - -define double @""() { -entry: - %addtmp = fadd double 4.000000e+00, 5.000000e+00 - ret double %addtmp -} - -define double @foo(double %a, double %b) { -entry: - %multmp = fmul double %a, %a - %multmp1 = fmul double 2.000000e+00, %a - %multmp2 = fmul double %multmp1, %b - %addtmp = fadd double %multmp, %multmp2 - %multmp3 = fmul double %b, %b - %addtmp4 = fadd double %addtmp, %multmp3 - ret double %addtmp4 -} - -define double @bar(double %a) { -entry: - %calltmp = call double @foo(double %a, double 4.000000e+00) - %calltmp1 = call double @bar(double 3.133700e+04) - %addtmp = fadd double %calltmp, %calltmp1 - ret double %addtmp -} - -declare double @cos(double) - -define double @""() { -entry: - %calltmp = call double @cos(double 1.234000e+00) - ret double %calltmp -} -</pre> -</div> - -<p>When you quit the current demo, it dumps out the IR for the entire module -generated. Here you can see the big picture with all the functions referencing -each other.</p> - -<p>This wraps up the third chapter of the Kaleidoscope tutorial. Up next, we'll -describe how to <a href="OCamlLangImpl4.html">add JIT codegen and optimizer -support</a> to this so we can actually start running code!</p> - -</div> - - -<!-- *********************************************************************** --> -<h2><a name="code">Full Code Listing</a></h2> -<!-- *********************************************************************** --> - -<div> - -<p> -Here is the complete code listing for our running example, enhanced with the -LLVM code generator. Because this uses the LLVM libraries, we need to link -them in. To do this, we use the <a -href="http://llvm.org/cmds/llvm-config.html">llvm-config</a> tool to inform -our makefile/command line about which options to use:</p> - -<div class="doc_code"> -<pre> -# Compile -ocamlbuild toy.byte -# Run -./toy.byte -</pre> -</div> - -<p>Here is the code:</p> - -<dl> -<dt>_tags:</dt> -<dd class="doc_code"> -<pre> -<{lexer,parser}.ml>: use_camlp4, pp(camlp4of) -<*.{byte,native}>: g++, use_llvm, use_llvm_analysis -</pre> -</dd> - -<dt>myocamlbuild.ml:</dt> -<dd class="doc_code"> -<pre> -open Ocamlbuild_plugin;; - -ocaml_lib ~extern:true "llvm";; -ocaml_lib ~extern:true "llvm_analysis";; - -flag ["link"; "ocaml"; "g++"] (S[A"-cc"; A"g++"]);; -</pre> -</dd> - -<dt>token.ml:</dt> -<dd class="doc_code"> -<pre> -(*===----------------------------------------------------------------------=== - * Lexer Tokens - *===----------------------------------------------------------------------===*) - -(* 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> -</dd> - -<dt>lexer.ml:</dt> -<dd class="doc_code"> -<pre> -(*===----------------------------------------------------------------------=== - * Lexer - *===----------------------------------------------------------------------===*) - -let rec lex = parser - (* Skip any whitespace. *) - | [< ' (' ' | '\n' | '\r' | '\t'); stream >] -> lex stream - - (* 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 - - (* number: [0-9.]+ *) - | [< ' ('0' .. '9' as c); stream >] -> - let buffer = Buffer.create 1 in - Buffer.add_char buffer c; - lex_number buffer stream - - (* Comment until end of line. *) - | [< ' ('#'); stream >] -> - lex_comment stream - - (* Otherwise, just return the character as its ascii value. *) - | [< 'c; stream >] -> - [< 'Token.Kwd c; lex stream >] - - (* end of 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 >] - -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 >] - -and lex_comment = parser - | [< ' ('\n'); stream=lex >] -> stream - | [< 'c; e=lex_comment >] -> e - | [< >] -> [< >] -</pre> -</dd> - -<dt>ast.ml:</dt> -<dd class="doc_code"> -<pre> -(*===----------------------------------------------------------------------=== - * Abstract Syntax Tree (aka Parse Tree) - *===----------------------------------------------------------------------===*) - -(* expr - Base type for all expression nodes. *) -type expr = - (* variant for numeric literals like "1.0". *) - | Number of float - - (* variant for referencing a variable, like "a". *) - | Variable of string - - (* variant for a binary operator. *) - | Binary of char * expr * expr - - (* variant for function calls. *) - | Call of string * expr array - -(* proto - This type represents the "prototype" for a function, which captures - * its name, and its argument names (thus implicitly the number of arguments the - * function takes). *) -type proto = Prototype of string * string array - -(* func - This type represents a function definition itself. *) -type func = Function of proto * expr -</pre> -</dd> - -<dt>parser.ml:</dt> -<dd class="doc_code"> -<pre> -(*===---------------------------------------------------------------------=== - * Parser - *===---------------------------------------------------------------------===*) - -(* binop_precedence - This holds the precedence for each binary operator that is - * defined *) -let binop_precedence:(char, int) Hashtbl.t = Hashtbl.create 10 - -(* precedence - Get the precedence of the pending binary operator token. *) -let precedence c = try Hashtbl.find binop_precedence c with Not_found -> -1 - -(* primary - * ::= identifier - * ::= numberexpr - * ::= parenexpr *) -let rec parse_primary = parser - (* numberexpr ::= number *) - | [< 'Token.Number n >] -> Ast.Number n - - (* parenexpr ::= '(' expression ')' *) - | [< 'Token.Kwd '('; e=parse_expr; 'Token.Kwd ')' ?? "expected ')'" >] -> e - - (* identifierexpr - * ::= identifier - * ::= identifier '(' argumentexpr ')' *) - | [< 'Token.Ident id; stream >] -> - let rec parse_args accumulator = parser - | [< e=parse_expr; stream >] -> - begin parser - | [< 'Token.Kwd ','; e=parse_args (e :: accumulator) >] -> e - | [< >] -> e :: accumulator - end stream - | [< >] -> accumulator - in - let rec parse_ident id = parser - (* Call. *) - | [< 'Token.Kwd '('; - args=parse_args []; - 'Token.Kwd ')' ?? "expected ')'">] -> - Ast.Call (id, Array.of_list (List.rev args)) - - (* Simple variable ref. *) - | [< >] -> Ast.Variable id - in - parse_ident id stream - - | [< >] -> raise (Stream.Error "unknown token when expecting an expression.") - -(* binoprhs - * ::= ('+' primary)* *) -and parse_bin_rhs expr_prec lhs stream = - match Stream.peek stream with - (* If this is a binop, find its precedence. *) - | Some (Token.Kwd c) when Hashtbl.mem binop_precedence c -> - let token_prec = precedence c in - - (* If this is a binop that binds at least as tightly as the current binop, - * consume it, otherwise we are done. *) - if token_prec < expr_prec then lhs else begin - (* Eat the binop. *) - Stream.junk stream; - - (* Parse the primary expression after the binary operator. *) - let rhs = parse_primary stream in - - (* Okay, we know this is a binop. *) - let rhs = - match Stream.peek stream with - | Some (Token.Kwd c2) -> - (* If BinOp binds less tightly with rhs than the operator after - * rhs, let the pending operator take rhs as its lhs. *) - let next_prec = precedence c2 in - if token_prec < next_prec - then parse_bin_rhs (token_prec + 1) rhs stream - else rhs - | _ -> rhs - in - - (* Merge lhs/rhs. *) - let lhs = Ast.Binary (c, lhs, rhs) in - parse_bin_rhs expr_prec lhs stream - end - | _ -> lhs - -(* expression - * ::= primary binoprhs *) -and parse_expr = parser - | [< lhs=parse_primary; stream >] -> parse_bin_rhs 0 lhs stream - -(* prototype - * ::= id '(' id* ')' *) -let parse_prototype = - let rec parse_args accumulator = parser - | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e - | [< >] -> accumulator - in - - parser - | [< 'Token.Ident id; - 'Token.Kwd '(' ?? "expected '(' in prototype"; - args=parse_args []; - 'Token.Kwd ')' ?? "expected ')' in prototype" >] -> - (* success. *) - Ast.Prototype (id, Array.of_list (List.rev args)) - - | [< >] -> - raise (Stream.Error "expected function name in prototype") - -(* definition ::= 'def' prototype expression *) -let parse_definition = parser - | [< 'Token.Def; p=parse_prototype; e=parse_expr >] -> - Ast.Function (p, e) - -(* toplevelexpr ::= expressio |