Chapter 5, 6, and 7 of the ocaml/kaleidoscope tutorial
and fix some tabs in chapter 3 and 4.
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+ "http://www.w3.org/TR/html4/strict.dtd">
+
+<html>
+<head>
+ <title>Kaleidoscope: Extending the Language: User-defined Operators</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="../llvm.css" type="text/css">
+</head>
+
+<body>
+
+<div class="doc_title">Kaleidoscope: Extending the Language: User-defined Operators</div>
+
+<ul>
+<li><a href="index.html">Up to Tutorial Index</a></li>
+<li>Chapter 6
+ <ol>
+ <li><a href="#intro">Chapter 6 Introduction</a></li>
+ <li><a href="#idea">User-defined Operators: the Idea</a></li>
+ <li><a href="#binary">User-defined Binary Operators</a></li>
+ <li><a href="#unary">User-defined Unary Operators</a></li>
+ <li><a href="#example">Kicking the Tires</a></li>
+ <li><a href="#code">Full Code Listing</a></li>
+ </ol>
+</li>
+<li><a href="OCamlLangImpl7.html">Chapter 7</a>: Extending the Language: Mutable
+Variables / SSA Construction</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>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="intro">Chapter 6 Introduction</a></div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>Welcome to Chapter 6 of the "<a href="index.html">Implementing a language
+with LLVM</a>" tutorial. At this point in our tutorial, we now have a fully
+functional language that is fairly minimal, but also useful. There
+is still one big problem with it, however. Our language doesn't have many
+useful operators (like division, logical negation, or even any comparisons
+besides less-than).</p>
+
+<p>This chapter of the tutorial takes a wild digression into adding user-defined
+operators to the simple and beautiful Kaleidoscope language. This digression now
+gives us a simple and ugly language in some ways, but also a powerful one at the
+same time. One of the great things about creating your own language is that you
+get to decide what is good or bad. In this tutorial we'll assume that it is
+okay to use this as a way to show some interesting parsing techniques.</p>
+
+<p>At the end of this tutorial, we'll run through an example Kaleidoscope
+application that <a href="#example">renders the Mandelbrot set</a>. This gives
+an example of what you can build with Kaleidoscope and its feature set.</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="idea">User-defined Operators: the Idea</a></div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>
+The "operator overloading" that we will add to Kaleidoscope is more general than
+languages like C++. In C++, you are only allowed to redefine existing
+operators: you can't programatically change the grammar, introduce new
+operators, change precedence levels, etc. In this chapter, we will add this
+capability to Kaleidoscope, which will let the user round out the set of
+operators that are supported.</p>
+
+<p>The point of going into user-defined operators in a tutorial like this is to
+show the power and flexibility of using a hand-written parser. Thus far, the parser
+we have been implementing uses recursive descent for most parts of the grammar and
+operator precedence parsing for the expressions. See <a
+href="OCamlLangImpl2.html">Chapter 2</a> for details. Without using operator
+precedence parsing, it would be very difficult to allow the programmer to
+introduce new operators into the grammar: the grammar is dynamically extensible
+as the JIT runs.</p>
+
+<p>The two specific features we'll add are programmable unary operators (right
+now, Kaleidoscope has no unary operators at all) as well as binary operators.
+An example of this is:</p>
+
+<div class="doc_code">
+<pre>
+# Logical unary not.
+def unary!(v)
+ if v then
+ 0
+ else
+ 1;
+
+# Define > with the same precedence as <.
+def binary> 10 (LHS RHS)
+ RHS < LHS;
+
+# Binary "logical or", (note that it does not "short circuit")
+def binary| 5 (LHS RHS)
+ if LHS then
+ 1
+ else if RHS then
+ 1
+ else
+ 0;
+
+# Define = with slightly lower precedence than relationals.
+def binary= 9 (LHS RHS)
+ !(LHS < RHS | LHS > RHS);
+</pre>
+</div>
+
+<p>Many languages aspire to being able to implement their standard runtime
+library in the language itself. In Kaleidoscope, we can implement significant
+parts of the language in the library!</p>
+
+<p>We will break down implementation of these features into two parts:
+implementing support for user-defined binary operators and adding unary
+operators.</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="binary">User-defined Binary Operators</a></div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>Adding support for user-defined binary operators is pretty simple with our
+current framework. We'll first add support for the unary/binary keywords:</p>
+
+<div class="doc_code">
+<pre>
+type token =
+ ...
+ <b>(* operators *)
+ | Binary | Unary</b>
+
+...
+
+and lex_ident buffer = parser
+ ...
+ | "for" -> [< 'Token.For; stream >]
+ | "in" -> [< 'Token.In; stream >]
+ <b>| "binary" -> [< 'Token.Binary; stream >]
+ | "unary" -> [< 'Token.Unary; stream >]</b>
+</pre>
+</div>
+
+<p>This just adds lexer support for the unary and binary keywords, like we
+did in <a href="OCamlLangImpl5.html#iflexer">previous chapters</a>. One nice
+thing about our current AST, is that we represent binary operators with full
+generalisation by using their ASCII code as the opcode. For our extended
+operators, we'll use this same representation, so we don't need any new AST or
+parser support.</p>
+
+<p>On the other hand, we have to be able to represent the definitions of these
+new operators, in the "def binary| 5" part of the function definition. In our
+grammar so far, the "name" for the function definition is parsed as the
+"prototype" production and into the <tt>Ast.Prototype</tt> AST node. To
+represent our new user-defined operators as prototypes, we have to extend
+the <tt>Ast.Prototype</tt> AST node like this:</p>
+
+<div class="doc_code">
+<pre>
+(* 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
+ <b>| BinOpPrototype of string * string array * int</b>
+</pre>
+</div>
+
+<p>Basically, in addition to knowing a name for the prototype, we now keep track
+of whether it was an operator, and if it was, what precedence level the operator
+is at. The precedence is only used for binary operators (as you'll see below,
+it just doesn't apply for unary operators). Now that we have a way to represent
+the prototype for a user-defined operator, we need to parse it:</p>
+
+<div class="doc_code">
+<pre>
+(* prototype
+ * ::= id '(' id* ')'
+ <b>* ::= binary LETTER number? (id, id)
+ * ::= unary LETTER number? (id) *)</b>
+let parse_prototype =
+ let rec parse_args accumulator = parser
+ | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e
+ | [< >] -> accumulator
+ in
+ let parse_operator = parser
+ | [< 'Token.Unary >] -> "unary", 1
+ | [< 'Token.Binary >] -> "binary", 2
+ in
+ let parse_binary_precedence = parser
+ | [< 'Token.Number n >] -> int_of_float n
+ | [< >] -> 30
+ 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))
+ <b>| [< (prefix, kind)=parse_operator;
+ 'Token.Kwd op ?? "expected an operator";
+ (* Read the precedence if present. *)
+ binary_precedence=parse_binary_precedence;
+ 'Token.Kwd '(' ?? "expected '(' in prototype";
+ args=parse_args [];
+ 'Token.Kwd ')' ?? "expected ')' in prototype" >] ->
+ let name = prefix ^ (String.make 1 op) in
+ let args = Array.of_list (List.rev args) in
+
+ (* Verify right number of arguments for operator. *)
+ if Array.length args != kind
+ then raise (Stream.Error "invalid number of operands for operator")
+ else
+ if kind == 1 then
+ Ast.Prototype (name, args)
+ else
+ Ast.BinOpPrototype (name, args, binary_precedence)</b>
+ | [< >] ->
+ raise (Stream.Error "expected function name in prototype")
+</pre>
+</div>
+
+<p>This is all fairly straightforward parsing code, and we have already seen
+a lot of similar code in the past. One interesting part about the code above is
+the couple lines that set up <tt>name</tt> for binary operators. This builds
+names like "binary@" for a newly defined "@" operator. This then takes
+advantage of the fact that symbol names in the LLVM symbol table are allowed to
+have any character in them, including embedded nul characters.</p>
+
+<p>The next interesting thing to add, is codegen support for these binary
+operators. Given our current structure, this is a simple addition of a default
+case for our existing binary operator node:</p>
+
+<div class="doc_code">
+<pre>
+let codegen_expr = function
+ ...
+ | Ast.Binary (op, lhs, rhs) ->
+ let lhs_val = codegen_expr lhs in
+ let rhs_val = codegen_expr rhs in
+ begin
+ match op with
+ | '+' -> build_add lhs_val rhs_val "addtmp" builder
+ | '-' -> build_sub lhs_val rhs_val "subtmp" builder
+ | '*' -> build_mul 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
+ <b>| _ ->
+ (* If it wasn't a builtin binary operator, it must be a user defined
+ * one. Emit a call to it. *)
+ let callee = "binary" ^ (String.make 1 op) in
+ let callee =
+ match lookup_function callee the_module with
+ | Some callee -> callee
+ | None -> raise (Error "binary operator not found!")
+ in
+ build_call callee [|lhs_val; rhs_val|] "binop" builder</b>
+ end
+</pre>
+</div>
+
+<p>As you can see above, the new code is actually really simple. It just does
+a lookup for the appropriate operator in the symbol table and generates a
+function call to it. Since user-defined operators are just built as normal
+functions (because the "prototype" boils down to a function with the right
+name) everything falls into place.</p>
+
+<p>The final piece of code we are missing, is a bit of top level magic:</p>
+
+<div class="doc_code">
+<pre>
+let codegen_func the_fpm = function
+ | Ast.Function (proto, body) ->
+ Hashtbl.clear named_values;
+ let the_function = codegen_proto proto in
+
+ <b>(* If this is an operator, install it. *)
+ begin match proto with
+ | Ast.BinOpPrototype (name, args, prec) ->
+ let op = name.[String.length name - 1] in
+ Hashtbl.add Parser.binop_precedence op prec;
+ | _ -> ()
+ end;</b>
+
+ (* Create a new basic block to start insertion into. *)
+ let bb = append_block "entry" the_function in
+ position_at_end bb builder;
+ ...
+</pre>
+</div>
+
+<p>Basically, before codegening a function, if it is a user-defined operator, we
+register it in the precedence table. This allows the binary operator parsing
+logic we already have in place to handle it. Since we are working on a
+fully-general operator precedence parser, this is all we need to do to "extend
+the grammar".</p>
+
+<p>Now we have useful user-defined binary operators. This builds a lot
+on the previous framework we built for other operators. Adding unary operators
+is a bit more challenging, because we don't have any framework for it yet - lets
+see what it takes.</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="unary">User-defined Unary Operators</a></div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>Since we don't currently support unary operators in the Kaleidoscope
+language, we'll need to add everything to support them. Above, we added simple
+support for the 'unary' keyword to the lexer. In addition to that, we need an
+AST node:</p>
+
+<div class="doc_code">
+<pre>
+type expr =
+ ...
+ (* variant for a unary operator. *)
+ | Unary of char * expr
+ ...
+</pre>
+</div>
+
+<p>This AST node is very simple and obvious by now. It directly mirrors the
+binary operator AST node, except that it only has one child. With this, we
+need to add the parsing logic. Parsing a unary operator is pretty simple: we'll
+add a new function to do it:</p>
+
+<div class="doc_code">
+<pre>
+(* unary
+ * ::= primary
+ * ::= '!' unary *)
+and parse_unary = parser
+ (* If this is a unary operator, read it. *)
+ | [< 'Token.Kwd op when op != '(' && op != ')'; operand=parse_expr >] ->
+ Ast.Unary (op, operand)
+
+ (* If the current token is not an operator, it must be a primary expr. *)
+ | [< stream >] -> parse_primary stream
+</pre>
+</div>
+
+<p>The grammar we add is pretty straightforward here. If we see a unary
+operator when parsing a primary operator, we eat the operator as a prefix and
+parse the remaining piece as another unary operator. This allows us to handle
+multiple unary operators (e.g. "!!x"). Note that unary operators can't have
+ambiguous parses like binary operators can, so there is no need for precedence
+information.</p>
+
+<p>The problem with this function, is that we need to call ParseUnary from
+somewhere. To do this, we change previous callers of ParsePrimary to call
+<tt>parse_unary</tt> instead:</p>
+
+<div class="doc_code">
+<pre>
+(* binoprhs
+ * ::= ('+' primary)* *)
+and parse_bin_rhs expr_prec lhs stream =
+ ...
+ <b>(* Parse the unary expression after the binary operator. *)
+ let rhs = parse_unary stream in</b>
+ ...
+
+...
+
+(* expression
+ * ::= primary binoprhs *)
+and parse_expr = parser
+ | [< lhs=<b>parse_unary</b>; stream >] -> parse_bin_rhs 0 lhs stream
+</pre>
+</div>
+
+<p>With these two simple changes, we are now able to parse unary operators and build the
+AST for them. Next up, we need to add parser support for prototypes, to parse
+the unary operator prototype. We extend the binary operator code above
+with:</p>
+
+<div class="doc_code">
+<pre>
+(* prototype
+ * ::= id '(' id* ')'
+ * ::= binary LETTER number? (id, id)
+ <b>* ::= unary LETTER number? (id)</b> *)
+let parse_prototype =
+ let rec parse_args accumulator = parser
+ | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e
+ | [< >] -> accumulator
+ in
+ <b>let parse_operator = parser
+ | [< 'Token.Unary >] -> "unary", 1
+ | [< 'Token.Binary >] -> "binary", 2
+ in</b>
+ let parse_binary_precedence = parser
+ | [< 'Token.Number n >] -> int_of_float n
+ | [< >] -> 30
+ 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))
+ <b>| [< (prefix, kind)=parse_operator;
+ 'Token.Kwd op ?? "expected an operator";
+ (* Read the precedence if present. *)
+ binary_precedence=parse_binary_precedence;
+ 'Token.Kwd '(' ?? "expected '(' in prototype";
+ args=parse_args [];
+ 'Token.Kwd ')' ?? "expected ')' in prototype" >] ->
+ let name = prefix ^ (String.make 1 op) in
+ let args = Array.of_list (List.rev args) in
+
+ (* Verify right number of arguments for operator. *)
+ if Array.length args != kind
+ then raise (Stream.Error "invalid number of operands for operator")
+ else
+ if kind == 1 then
+ Ast.Prototype (name, args)
+ else
+ Ast.BinOpPrototype (name, args, binary_precedence)</b>
+ | [< >] ->
+ raise (Stream.Error "expected function name in prototype")
+</pre>
+</div>
+
+<p>As with binary operators, we name unary operators with a name that includes
+the operator character. This assists us at code generation time. Speaking of,
+the final piece we need to add is codegen support for unary operators. It looks
+like this:</p>
+
+<div class="doc_code">
+<pre>
+let rec codegen_expr = function
+ ...
+ | Ast.Unary (op, operand) ->
+ let operand = codegen_expr operand in
+ let callee = "unary" ^ (String.make 1 op) in
+ let callee =
+ match lookup_function callee the_module with
+ | Some callee -> callee
+ | None -> raise (Error "unknown unary operator")
+ in
+ build_call callee [|operand|] "unop" builder
+</pre>
+</div>
+
+<p>This code is similar to, but simpler than, the code for binary operators. It
+is simpler primarily because it doesn't need to handle any predefined operators.
+</p>
+
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="example">Kicking the Tires</a></div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>It is somewhat hard to believe, but with a few simple extensions we've
+covered in the last chapters, we have grown a real-ish language. With this, we
+can do a lot of interesting things, including I/O, math, and a bunch of other
+things. For example, we can now add a nice sequencing operator (printd is
+defined to print out the specified value and a newline):</p>
+
+<div class="doc_code">
+<pre>
+ready> <b>extern printd(x);</b>
+Read extern: declare double @printd(double)
+ready> <b>def binary : 1 (x y) 0; # Low-precedence operator that ignores operands.</b>
+..
+ready> <b>printd(123) : printd(456) : printd(789);</b>
+123.000000
+456.000000
+789.000000
+Evaluated to 0.000000
+</pre>
+</div>
+
+<p>We can also define a bunch of other "primitive" operations, such as:</p>
+
+<div class="doc_code">
+<pre>
+# Logical unary not.
+def unary!(v)
+ if v then
+ 0
+ else
+ 1;
+
+# Unary negate.
+def unary-(v)
+ 0-v;
+
+# Define > with the same precedence as >.
+def binary> 10 (LHS RHS)
+ RHS < LHS;
+
+# Binary logical or, which does not short circuit.
+def binary| 5 (LHS RHS)
+ if LHS then
+ 1
+ else if RHS then
+ 1
+ else
+ 0;
+
+# Binary logical and, which does not short circuit.
+def binary& 6 (LHS RHS)
+ if !LHS then
+ 0
+ else
+ !!RHS;
+
+# Define = with slightly lower precedence than relationals.
+def binary = 9 (LHS RHS)
+ !(LHS < RHS | LHS > RHS);
+
+</pre>
+</div>
+
+
+<p>Given the previous if/then/else support, we can also define interesting
+functions for I/O. For example, the following prints out a character whose
+"density" reflects the value passed in: the lower the value, the denser the
+character:</p>
+
+<div class="doc_code">
+<pre>
+ready>
+<b>
+extern putchard(char)
+def printdensity(d)
+ if d > 8 then
+ putchard(32) # ' '
+ else if d > 4 then
+ putchard(46) # '.'
+ else if d > 2 then
+ putchard(43) # '+'
+ else
+ putchard(42); # '*'</b>
+...
+ready> <b>printdensity(1): printdensity(2): printdensity(3) :
+ printdensity(4): printdensity(5): printdensity(9): putchard(10);</b>
+*++..
+Evaluated to 0.000000
+</pre>
+</div>
+
+<p>Based on these simple primitive operations, we can start to define more
+interesting things. For example, here's a little function that solves for the
+number of iterations it takes a function in the complex plane to
+converge:</p>
+
+<div class="doc_code">
+<pre>
+# determine whether the specific location diverges.
+# Solve for z = z^2 + c in the complex plane.
+def mandleconverger(real imag iters creal cimag)
+ if iters > 255 | (real*real + imag*imag > 4) then
+ iters
+ else
+ mandleconverger(real*real - imag*imag + creal,
+ 2*real*imag + cimag,
+ iters+1, creal, cimag);
+
+# return the number of iterations required for the iteration to escape
+def mandleconverge(real imag)
+ mandleconverger(real, imag, 0, real, imag);
+</pre>
+</div>
+
+<p>This "z = z<sup>2</sup> + c" function is a beautiful little creature that is the basis
+for computation of the <a
+href="http://en.wikipedia.org/wiki/Mandelbrot_set">Mandelbrot Set</a>. Our
+<tt>mandelconverge</tt> function returns the number of iterations that it takes
+for a complex orbit to escape, saturating to 255. This is not a very useful
+function by itself, but if you plot its value over a two-dimensional plane,
+you can see the Mandelbrot set. Given that we are limited to using putchard
+here, our amazing graphical output is limited, but we can whip together
+something using the density plotter above:</p>
+
+<div class="doc_code">
+<pre>
+# compute and plot the mandlebrot set with the specified 2 dimensional range
+# info.
+def mandelhelp(xmin xmax xstep ymin ymax ystep)
+ for y = ymin, y < ymax, ystep in (
+ (for x = xmin, x < xmax, xstep in
+ printdensity(mandleconverge(x,y)))
+ : putchard(10)
+ )
+
+# mandel - This is a convenient helper function for ploting the mandelbrot set
+# from the specified position with the specified Magnification.
+def mandel(realstart imagstart realmag imagmag)
+ mandelhelp(realstart, realstart+realmag*78, realmag,
+ imagstart, imagstart+imagmag*40, imagmag);
+</pre>
+</div>
+
+<p>Given this, we can try plotting out the mandlebrot set! Lets try it out:</p>
+
+<div class="doc_code">
+<pre>
+ready> <b>mandel(-2.3, -1.3, 0.05, 0.07);</b>
+*******************************+++++++++++*************************************
+*************************+++++++++++++++++++++++*******************************
+**********************+++++++++++++++++++++++++++++****************************
+*******************+++++++++++++++++++++.. ...++++++++*************************
+*****************++++++++++++++++++++++.... ...+++++++++***********************
+***************+++++++++++++++++++++++..... ...+++++++++*********************
+**************+++++++++++++++++++++++.... ....+++++++++********************
+*************++++++++++++++++++++++...... .....++++++++*******************
+************+++++++++++++++++++++....... .......+++++++******************
+***********+++++++++++++++++++.... ... .+++++++*****************
+**********+++++++++++++++++....... .+++++++****************
+*********++++++++++++++........... ...+++++++***************
+********++++++++++++............ ...++++++++**************
+********++++++++++... .......... .++++++++**************
+*******+++++++++..... .+++++++++*************
+*******++++++++...... ..+++++++++*************
+*******++++++....... ..+++++++++*************
+*******+++++...... ..+++++++++*************
+*******.... .... ...+++++++++*************
+*******.... . ...+++++++++*************
+*******+++++...... ...+++++++++*************
+*******++++++....... ..+++++++++*************
+*******++++++++...... .+++++++++*************
+*******+++++++++..... ..+++++++++*************
+********++++++++++... .......... .++++++++**************
+********++++++++++++............ ...++++++++**************
+*********++++++++++++++.......... ...+++++++***************
+**********++++++++++++++++........ .+++++++****************
+**********++++++++++++++++++++.... ... ..+++++++****************
+***********++++++++++++++++++++++....... .......++++++++*****************
+************+++++++++++++++++++++++...... ......++++++++******************
+**************+++++++++++++++++++++++.... ....++++++++********************
+***************+++++++++++++++++++++++..... ...+++++++++*********************
+*****************++++++++++++++++++++++.... ...++++++++***********************
+*******************+++++++++++++++++++++......++++++++*************************
+*********************++++++++++++++++++++++.++++++++***************************
+*************************+++++++++++++++++++++++*******************************
+******************************+++++++++++++************************************
+*******************************************************************************
+*******************************************************************************
+*******************************************************************************
+Evaluated to 0.000000
+ready> <b>mandel(-2, -1, 0.02, 0.04);</b>
+**************************+++++++++++++++++++++++++++++++++++++++++++++++++++++
+***********************++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+*********************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
+*******************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++...
+*****************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++.....
+***************++++++++++++++++++++++++++++++++++++++++++++++++++++++++........
+**************++++++++++++++++++++++++++++++++++++++++++++++++++++++...........
+************+++++++++++++++++++++++++++++++++++++++++++++++++++++..............
+***********++++++++++++++++++++++++++++++++++++++++++++++++++........ .
+**********++++++++++++++++++++++++++++++++++++++++++++++.............
+********+++++++++++++++++++++++++++++++++++++++++++..................
+*******+++++++++++++++++++++++++++++++++++++++.......................
+******+++++++++++++++++++++++++++++++++++...........................
+*****++++++++++++++++++++++++++++++++............................
+*****++++++++++++++++++++++++++++...............................
+****++++++++++++++++++++++++++...... .........................
+***++++++++++++++++++++++++......... ...... ...........
+***++++++++++++++++++++++............
+**+++++++++++++++++++++..............
+**+++++++++++++++++++................
+*++++++++++++++++++.................
+*++++++++++++++++............ ...
+*++++++++++++++..............
+*+++....++++................
+*.......... ...........
+*
+*.......... ...........
+*+++....++++................
+*++++++++++++++..............
+*++++++++++++++++............ ...
+*++++++++++++++++++.................
+**+++++++++++++++++++................
+**+++++++++++++++++++++..............
+***++++++++++++++++++++++............
+***++++++++++++++++++++++++......... ...... ...........
+****++++++++++++++++++++++++++...... .........................
+*****++++++++++++++++++++++++++++...............................
+*****++++++++++++++++++++++++++++++++............................
+******+++++++++++++++++++++++++++++++++++...........................
+*******+++++++++++++++++++++++++++++++++++++++.......................
+********+++++++++++++++++++++++++++++++++++++++++++..................
+Evaluated to 0.000000
+ready> <b>mandel(-0.9, -1.4, 0.02, 0.03);</b>
+*******************************************************************************
+*******************************************************************************
+*******************************************************************************
+**********+++++++++++++++++++++************************************************
+*+++++++++++++++++++++++++++++++++++++++***************************************
++++++++++++++++++++++++++++++++++++++++++++++**********************************
+++++++++++++++++++++++++++++++++++++++++++++++++++*****************************
+++++++++++++++++++++++++++++++++++++++++++++++++++++++*************************
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++**********************
++++++++++++++++++++++++++++++++++.........++++++++++++++++++*******************
++++++++++++++++++++++++++++++++.... ......+++++++++++++++++++****************
++++++++++++++++++++++++++++++....... ........+++++++++++++++++++**************
+++++++++++++++++++++++++++++........ ........++++++++++++++++++++************
++++++++++++++++++++++++++++......... .. ...+++++++++++++++++++++**********
+++++++++++++++++++++++++++........... ....++++++++++++++++++++++********
+++++++++++++++++++++++++............. .......++++++++++++++++++++++******
++++++++++++++++++++++++............. ........+++++++++++++++++++++++****
+++++++++++++++++++++++........... ..........++++++++++++++++++++++***
+++++++++++++++++++++........... .........++++++++++++++++++++++*
+++++++++++++++++++............ ...........++++++++++++++++++++
+++++++++++++++++............... .............++++++++++++++++++
+++++++++++++++................. ...............++++++++++++++++
+++++++++++++.................. .................++++++++++++++
++++++++++.................. .................+++++++++++++
+++++++........ . ......... ..++++++++++++
+++............ ...... ....++++++++++
+.............. ...++++++++++
+.............. ....+++++++++
+.............. .....++++++++
+............. ......++++++++
+........... .......++++++++
+......... ........+++++++
+......... ........+++++++
+......... ....+++++++
+........ ...+++++++
+....... ...+++++++
+ ....+++++++
+ .....+++++++
+ ....+++++++
+ ....+++++++
+ ....+++++++
+Evaluated to 0.000000
+ready> <b>^D</b>
+</pre>
+</div>
+
+<p>At this point, you may be starting to realize that Kaleidoscope is a real
+and powerful language. It may not be self-similar :), but it can be used to
+plot things that are!</p>
+
+<p>With this, we conclude the "adding user-defined operators" chapter of the
+tutorial. We have successfully augmented our language, adding the ability to
+extend the language in the library, and we have shown how this can be used to
+build a simple but interesting end-user application in Kaleidoscope. At this
+point, Kaleidoscope can build a variety of applications that are functional and
+can call functions with side-effects, but it can't actually define and mutate a
+variable itself.</p>
+
+<p>Strikingly, variable mutation is an important feature of some
+languages, and it is not at all obvious how to <a href="OCamlLangImpl7.html">add
+support for mutable variables</a> without having to add an "SSA construction"
+phase to your front-end. In the next chapter, we will describe how you can
+add variable mutation without building SSA in your front-end.</p>
+
+</div>
+
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="code">Full Code Listing</a></div>
+<!-- *********************************************************************** -->
+
+<div class="doc_text">
+
+<p>
+Here is the complete code listing for our running example, enhanced with the
+if/then/else and for expressions.. To build this example, 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
+<*.{byte,native}>: use_llvm_executionengine, use_llvm_target
+<*.{byte,native}>: use_llvm_scalar_opts, use_bindings
+</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";;
+ocaml_lib ~extern:true "llvm_executionengine";;
+ocaml_lib ~extern:true "llvm_target";;
+ocaml_lib ~extern:true "llvm_scalar_opts";;
+
+flag ["link"; "ocaml"; "g++"] (S[A"-cc"; A"g++"]);;
+dep ["link"; "ocaml"; "use_bindings"] ["bindings.o"];;
+</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
+
+ (* control *)
+ | If | Then | Else
+ | For | In
+
+ (* operators *)
+ | Binary | Unary
+</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 >]
+ | "if" -> [< 'Token.If; stream >]
+ | "then" -> [< 'Token.Then; stream >]
+ | "else" -> [< 'Token.Else; stream >]
+ | "for" -> [< 'Token.For; stream >]
+ | "in" -> [< 'Token.In; stream >]
+ | "binary" -> [< 'Token.Binary; stream >]
+ | "unary" -> [< 'Token.Unary; 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 unary operator. *)
+ | Unary of char * expr
+
+ (* variant for a binary operator. *)
+ | Binary of char * expr * expr
+
+ (* variant for function calls. *)
+ | Call of string * expr array
+
+ (* variant for if/then/else. *)
+ | If of expr * expr * expr
+
+ (* variant for for/in. *)
+ | For of string * expr * expr * expr option * expr
+
+(* 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
+ | BinOpPrototype of string * string array * int
+
+(* 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
+ * ::= ifexpr
+ * ::= forexpr *)
+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
+
+ (* ifexpr ::= 'if' expr 'then' expr 'else' expr *)
+ | [< 'Token.If; c=parse_expr;
+ 'Token.Then ?? "expected 'then'"; t=parse_expr;
+ 'Token.Else ?? "expected 'else'"; e=parse_expr >] ->
+ Ast.If (c, t, e)
+
+ (* forexpr
+ ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression *)
+ | [< 'Token.For;
+ 'Token.Ident id ?? "expected identifier after for";
+ 'Token.Kwd '=' ?? "expected '=' after for";
+ stream >] ->
+ begin parser
+ | [<
+ start=parse_expr;
+ 'Token.Kwd ',' ?? "expected ',' after for";
+ end_=parse_expr;
+ stream >] ->
+ let step =
+ begin parser
+ | [< 'Token.Kwd ','; step=parse_expr >] -> Some step
+ | [< >] -> None
+ end stream
+ in
+ begin parser
+ | [< 'Token.In; body=parse_expr >] ->
+ Ast.For (id, start, end_, step, body)
+ | [< >] ->
+ raise (Stream.Error "expected 'in' after for")
+ end stream
+ | [< >] ->
+ raise (Stream.Error "expected '=' after for")
+ end stream
+
+ | [< >] -> raise (Stream.Error "unknown token when expecting an expression.")
+
+(* unary
+ * ::= primary
+ * ::= '!' unary *)
+and parse_unary = parser
+ (* If this is a unary operator, read it. *)
+ | [< 'Token.Kwd op when op != '(' && op != ')'; operand=parse_expr >] ->
+ Ast.Unary (op, operand)
+
+ (* If the current token is not an operator, it must be a primary expr. *)
+ | [< stream >] -> parse_primary stream
+
+(* 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 unary expression after the binary operator. *)
+ let rhs = parse_unary 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_unary; stream >] -> parse_bin_rhs 0 lhs stream
+
+(* prototype
+ * ::= id '(' id* ')'
+ * ::= binary LETTER number? (id, id)
+ * ::= unary LETTER number? (id) *)
+let parse_prototype =
+ let rec parse_args accumulator = parser
+ | [< 'Token.Ident id; e=parse_args (id::accumulator) >] -> e
+ | [< >] -> accumulator
+ in
+ let parse_operator = parser
+ | [< 'Token.Unary >] -> "unary", 1
+ | [< 'Token.Binary >] -> "binary", 2
+ in
+ let parse_binary_precedence = parser
+ | [< 'Token.Number n >] -> int_of_float n
+ | [< >] -> 30
+ 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))
+ | [< (prefix, kind)=parse_operator;
+ 'Token.Kwd op ?? "expected an operator";
+ (* Read the precedence if present. *)
+ binary_precedence=parse_binary_precedence;
+ 'Token.Kwd '(' ?? "expected '(' in prototype";
+ args=parse_args [];
+ 'Token.Kwd ')' ?? "expected ')' in prototype" >] ->
+ let name = prefix ^ (String.make 1 op) in
+ let args = Array.of_list (List.rev args) in
+
+ (* Verify right number of arguments for operator. *)
+ if Array.length args != kind
+ then raise (Stream.Error "invalid number of operands for operator")
+ else
+ if kind == 1 then
+ Ast.Prototype (name, args)
+ else
+ Ast.BinOpPrototype (name, args, binary_precedence)
+ | [< >] ->
+ 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 ::= expression *)
+let parse_toplevel = parser
+ | [< e=parse_expr >] ->
+ (* Make an anonymous proto. *)
+ Ast.Function (Ast.Prototype ("", [||]), e)
+
+(* external ::= 'extern' prototype *)
+let parse_extern = parser
+ | [< 'Token.Extern; e=parse_prototype >] -> e
+</pre>
+</dd>
+
+<dt>codegen.ml:</dt>
+<dd class="doc_code">
+<pre>
+(*===----------------------------------------------------------------------===
+ * Code Generation
+ *===----------------------------------------------------------------------===*)
+
+open Llvm
+
+exception Error of string
+
+let the_module = create_module "my cool jit"
+let builder = builder ()
+let named_values:(string, llvalue) Hashtbl.t = Hashtbl.create 10
+
+let rec codegen_expr = function
+ | Ast.Number n -> const_float double_type n
+ | Ast.Variable name ->
+ (try Hashtbl.find named_values name with
+ | Not_found -> raise (Error "unknown variable name"))
+ | Ast.Unary (op, operand) ->
+ let operand = codegen_expr operand in
+ let callee = "unary" ^ (String.make 1 op) in
+ let callee =
+ match lookup_function callee the_module with
+ | Some callee -> callee
+ | None -> raise (Error "unknown unary operator")
+ in
+ build_call callee [|operand|] "unop" builder
+ | Ast.Binary (op, lhs, rhs) ->
+ let lhs_val = codegen_expr lhs in
+ let rhs_val = codegen_expr rhs in
+ begin
+ match op with
+ | '+' -> build_add lhs_val rhs_val "addtmp" builder
+ | '-' -> build_sub lhs_val rhs_val "subtmp" builder
+ | '*' -> build_mul 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
+ | _ ->
+ (* If it wasn't a builtin binary operator, it must be a user defined
+ * one. Emit a call to it. *)
+ let callee = "binary" ^ (String.make 1 op) in
+ let callee =
+ match lookup_function callee the_module with
+ | Some callee -> callee
+ | None -> raise (Error "binary operator not found!")
+ in
+ build_call callee [|lhs_val; rhs_val|] "binop" builder
+ end
+ | 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
+ | Ast.If (cond, then_, else_) ->
+ let cond = codegen_expr cond in
+
+ (* Convert condition to a bool by comparing equal to 0.0 *)
+ let zero = const_float double_type 0.0 in
+ let cond_val = build_fcmp Fcmp.One cond zero "ifcond" builder in
+
+ (* Grab the first block so that we might later add the conditional branch
+ * to it at the end of the function. *)
+ let start_bb = insertion_block builder in
+ let the_function = block_parent start_bb in
+
+ let then_bb = append_block "then" the_function in
+
+ (* Emit 'then' value. *)
+ position_at_end then_bb builder;
+ let then_val = codegen_expr then_ in
+
+ (* Codegen of 'then' can change the current block, update then_bb for the
+ * phi. We create a new name because one is used for the phi node, and the
+ * other is used for the conditional branch. *)
+ let new_then_bb = insertion_block builder in
+
+ (* Emit 'else' value. *)
+ let else_bb = append_block "else" the_function in
+ position_at_end else_bb builder;
+ let else_val = codegen_expr else_ in
+
+ (* Codegen of 'else' can change the current block, update else_bb for the
+ * phi. *)
+ let new_else_bb = insertion_block builder in
+
+ (* Emit merge block. *)
+ let merge_bb = append_block "ifcont" the_function in
+ position_at_end merge_bb builder;
+ let incoming = [(then_val, new_then_bb); (else_val, new_else_bb)] in
+ let phi = build_phi incoming "iftmp" builder in
+
+ (* Return to the start block to add the conditional branch. *)
+ position_at_end start_bb builder;
+ ignore (build_cond_br cond_val then_bb else_bb builder);
+
+ (* Set a unconditional branch at the end of the 'then' block and the
+ * 'else' block to the 'merge' block. *)
+ position_at_end new_then_bb builder; ignore (build_br merge_bb builder);
+ position_at_end new_else_bb builder; ignore (build_br merge_bb builder);
+
+ (* Finally, set the builder to the end of the merge block. *)
+ position_at_end merge_bb builder;
+
+ phi
+ | Ast.For (var_name, start, end_, step, body) ->
+ (* Emit the start code first, without 'variable' in scope. *)
+ let start_val = codegen_expr start in
+
+ (* Make the new basic block for the loop header, inserting after current
+ * block. *)
+ let preheader_bb = insertion_block builder in
+ let the_function = block_parent preheader_bb in
+ let loop_bb = append_block "loop" the_function in
+
+ (* Insert an explicit fall through from the current block to the
+ * loop_bb. *)
+ ignore (build_br loop_bb builder);
+
+ (* Start insertion in loop_bb. *)
+ position_at_end loop_bb builder;
+
+ (* Start the PHI node with an entry for start. *)
+ let variable = build_phi [(start_val, preheader_bb)] var_name builder in
+
+ (* Within the loop, the variable is defined equal to the PHI node. If it
+ * shadows an existing variable, we have to restore it, so save it
+ * now. *)
+ let old_val =
+ try Some (Hashtbl.find named_values var_name) with Not_found -> None
+ in
+ Hashtbl.add named_values var_name variable;
+
+ (* Emit the body of the loop. This, like any other expr, can change the
+ * current BB. Note that we ignore the value computed by the body, but
+ * don't allow an error *)
+ ignore (codegen_expr body);
+
+ (* Emit the step value. *)
+ let step_val =
+ match step with
+ | Some step -> codegen_expr step
+ (* If not specified, use 1.0. *)
+ | None -> const_float double_type 1.0
+ in
+
+ let next_var = build_add variable step_val "nextvar" builder in
+
+ (* Compute the end condition. *)
+ let end_cond = codegen_expr end_ in
+
+ (* Convert condition to a bool by comparing equal to 0.0. *)
+ let zero = const_float double_type 0.0 in
+ let end_cond = build_fcmp Fcmp.One end_cond zero "loopcond" builder in
+
+ (* Create the "after loop" block and insert it. *)
+ let loop_end_bb = insertion_block builder in
+ let after_bb = append_block "afterloop" the_function in
+
+ (* Insert the conditional branch into the end of loop_end_bb. *)
+ ignore (build_cond_br end_cond loop_bb after_bb builder);
+
+ (* Any new code will be inserted in after_bb. *)
+ position_at_end after_bb builder;
+
+ (* Add a new entry to the PHI node for the backedge. *)
+ add_incoming (next_var, loop_end_bb) variable;
+
+ (* Restore the unshadowed variable. *)
+ begin match old_val with
+ | Some old_val -> Hashtbl.add named_values var_name old_val
+ | None -> ()
+ end;
+
+ (* for expr always returns 0.0. *)
+ const_null double_type
+
+let codegen_proto = function
+ | Ast.Prototype (name, args) | Ast.BinOpPrototype (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
+ | None -> declare_function name ft the_module
+
+ (* 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 block_begin f <> At_end f then
+ raise (Error "redefinition of function");
+
+ (* If 'f' took a different number of arguments, reject. *)
+ if element_type (type_of f) <> ft then
+ raise (Error "redefinition of function with different # args");
+ f
+ in
+
+ (* 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
+
+let codegen_func the_fpm = function
+ | Ast.Function (proto, body) ->
+ Hashtbl.clear named_values;
+ let the_function = codegen_proto proto in
+
+ (* If this is an operator, install it. *)
+ begin match proto with
+ | Ast.BinOpPrototype (name, args, prec) ->
+ let op = name.[String.length name - 1] in
+ Hashtbl.add Parser.binop_precedence op prec;
+ | _ -> ()
+ end;
+
+ (* Create a new basic block to start insertion into. *)
+ let bb = append_block "entry" the_function in
+ position_at_end bb builder;
+
+ try
+ 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;
+
+ (* Optimize the function. *)
+ let _ = PassManager.run_function the_function the_fpm in
+
+ the_function
+ with e ->
+ delete_function the_function;
+ raise e
+</pre>
+</dd>
+
+<dt>toplevel.ml:</dt>
+<dd class="doc_code">
+<pre>
+(*===----------------------------------------------------------------------===
+ * Top-Level parsing and JIT Driver
+ *===----------------------------------------------------------------------===*)
+
+open Llvm
+open Llvm_executionengine
+
+(* top ::= definition | external | expression | ';' *)
+let rec main_loop the_fpm the_execution_engine stream =
+ match Stream.peek stream with
+ | None -> ()
+
+ (* ignore top-level semicolons. *)
+ | Some (Token.Kwd ';') ->
+ Stream.junk stream;
+ main_loop the_fpm the_execution_engine stream
+
+ | Some token ->
+ begin
+ try match token with
+ | Token.Def ->
+ let e = Parser.parse_definition stream in
+ print_endline "parsed a function definition.";
+ dump_value (Codegen.codegen_func the_fpm e);
+ | Token.Extern ->
+ let e = Parser.parse_extern stream in
+ print_endline "parsed an extern.";
+ dump_value (Codegen.codegen_proto e);
+ | _ ->
+ (* Evaluate a top-level expression into an anonymous function. *)
+ let e = Parser.parse_toplevel stream in
+ print_endline "parsed a top-level expr";
+ let the_function = Codegen.codegen_func the_fpm e in
+ dump_value the_function;
+
+ (* JIT the function, returning a function pointer. *)
+ let result = ExecutionEngine.run_function the_function [||]
+ the_execution_engine in
+
+ print_string "Evaluated to ";
+ print_float (GenericValue.as_float double_type result);
+ print_newline ();
+ with Stream.Error s | Codegen.Error s ->
+ (* Skip token for error recovery. *)
+ Stream.junk stream;
+ print_endline s;
+ end;
+ print_string "ready> "; flush stdout;
+ main_loop the_fpm the_execution_engine stream
+</pre>
+</dd>
+
+<dt>toy.ml:</dt>
+<dd class="doc_code">
+<pre>
+(*===----------------------------------------------------------------------===
+ * Main driver code.
+ *===----------------------------------------------------------------------===*)
+
+open Llvm
+open Llvm_executionengine
+open Llvm_target
+open Llvm_scalar_opts
+
+let main () =
+ (* Install standard binary operators.
+ * 1 is the lowest precedence. *)
+ Hashtbl.add Parser.binop_precedence '<' 10;
+ Hashtbl.add Parser.binop_precedence '+' 20;
+ Hashtbl.add Parser.binop_precedence '-' 20;
+ Hashtbl.add Parser.binop_precedence '*' 40; (* highest. *)
+
+ (* Prime the first token. *)
+ print_string "ready> "; flush stdout;
+ let stream = Lexer.lex (Stream.of_channel stdin) in
+
+ (* Create the JIT. *)
+ let the_module_provider = ModuleProvider.create Codegen.the_module in
+ let the_execution_engine = ExecutionEngine.create the_module_provider in
+ let the_fpm = PassManager.create_function the_module_provider in
+
+ (* Set up the optimizer pipeline. Start with registering info about how the
+ * target lays out data structures. *)
+ TargetData.add (ExecutionEngine.target_data the_execution_engine) the_fpm;
+
+ (* Do simple "peephole" optimizations and bit-twiddling optzn. *)
+ add_instruction_combining the_fpm;
+
+ (* reassociate expressions. *)
+ add_reassociation the_fpm;
+
+ (* Eliminate Common SubExpressions. *)
+ add_gvn the_fpm;
+
+ (* Simplify the control flow graph (deleting unreachable blocks, etc). *)
+ add_cfg_simplification the_fpm;
+
+ (* Run the main "interpreter loop" now. *)
+ Toplevel.main_loop the_fpm the_execution_engine stream;
+
+ (* Print out all the generated code. *)
+ dump_module Codegen.the_module
+;;
+
+main ()
+</pre>
+</dd>
+
+<dt>bindings.c</dt>
+<dd class="doc_code">
+<pre>
+#include <stdio.h>
+
+/* putchard - putchar that takes a double and returns 0. */
+extern double putchard(double X) {
+ putchar((char)X);
+ return 0;
+}
+
+/* printd - printf that takes a double prints it as "%f\n", returning 0. */
+extern double printd(double X) {
+ printf("%f\n", X);
+ return 0;
+}
+</pre>
+</dd>
+</dl>
+
+<a href="OCamlLangImpl7.html">Next: Extending the language: mutable variables /
+SSA construction</a>
+</div>
+
+<!-- *********************************************************************** -->
+<hr>
+<address>
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+
+ <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: 2007-10-17 11:05:13 -0700 (Wed, 17 Oct 2007) $
+</address>
+</body>
+</html>