Finish chapter 6, and add a spiffy demo that shows off the language.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43636 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/tutorial/LangImpl6.html b/docs/tutorial/LangImpl6.html
index a8ef28f..f679819 100644
--- a/docs/tutorial/LangImpl6.html
+++ b/docs/tutorial/LangImpl6.html
@@ -3,7 +3,7 @@
<html>
<head>
- <title>Kaleidoscope: Extending the Language: Operator Overloading</title>
+ <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">
<link rel="stylesheet" href="../llvm.css" type="text/css">
@@ -11,7 +11,7 @@
<body>
-<div class="doc_title">Kaleidoscope: Extending the Language: Operator Overloading</div>
+<div class="doc_title">Kaleidoscope: Extending the Language: User-defined Operators</div>
<div class="doc_author">
<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
@@ -29,30 +29,34 @@
with it though is that it doesn't have many useful operators (like division,
logical negation, or even any comparisons other than less-than.</p>
-<p>This chapter of the tutorial takes a wild digression into adding operator
-overloading to the simple and beautiful Kaleidoscope language, giving us a
+<p>This chapter of the tutorial takes a wild digression into adding user-defined
+operators to the simple and beautiful Kaleidoscope language, giving 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 and
use this as a way to show some interesting parsing techniques.</p>
+<p>At the end of this tutorial, we'll <a href="#example">run through a nice
+little example</a> that shows an example application that you can build with
+Kaleidoscope and the feature set it now has.</p>
+
</div>
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="idea">Operator Overloading: the Idea</a></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
+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 allow us to round out the set of
operators that are supported, culminating in a more interesting example app.</p>
-<p>The point of going into operator overloading in a tutorial like this is to
+<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. The parser we
are using so far is using recursive descent for most parts of the grammar, and
operator precedence parsing for the expressions. See <a
@@ -98,18 +102,18 @@
parts of the language in the library!</p>
<p>We will break down implementation of these features into two parts:
-implementing support for overloading of binary operators and adding unary
+implementing support for user-defined binary operators and adding unary
operators.</p>
</div>
<!-- *********************************************************************** -->
-<div class="doc_section"><a name="binary">Overloading Binary Operators</a></div>
+<div class="doc_section"><a name="binary">User-defined Binary Operators</a></div>
<!-- *********************************************************************** -->
<div class="doc_text">
-<p>Adding support for overloaded binary operators is pretty simple with our
+<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">
@@ -174,10 +178,604 @@
<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.</p>
+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)</b>
+static PrototypeAST *ParsePrototype() {
+ std::string FnName;
+
+ <b>int Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+ unsigned BinaryPrecedence = 30;</b>
+
+ switch (CurTok) {
+ default:
+ return ErrorP("Expected function name in prototype");
+ case tok_identifier:
+ FnName = IdentifierStr;
+ Kind = 0;
+ getNextToken();
+ break;
+ <b>case tok_binary:
+ getNextToken();
+ if (!isascii(CurTok))
+ return ErrorP("Expected binary operator");
+ FnName = "binary";
+ FnName += (char)CurTok;
+ Kind = 2;
+ getNextToken();
+
+ // Read the precedence if present.
+ if (CurTok == tok_number) {
+ if (NumVal < 1 || NumVal > 100)
+ return ErrorP("Invalid precedecnce: must be 1..100");
+ BinaryPrecedence = (unsigned)NumVal;
+ getNextToken();
+ }
+ break;</b>
+ }
+
+ if (CurTok != '(')
+ return ErrorP("Expected '(' in prototype");
+
+ std::vector<std::string> ArgNames;
+ while (getNextToken() == tok_identifier)
+ ArgNames.push_back(IdentifierStr);
+ if (CurTok != ')')
+ return ErrorP("Expected ')' in prototype");
+
+ // success.
+ getNextToken(); // eat ')'.
+
+ <b>// Verify right number of names for operator.
+ if (Kind && ArgNames.size() != Kind)
+ return ErrorP("Invalid number of operands for operator");
+
+ return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);</b>
+}
+</pre>
+</div>
+
+<p>This is all fairly straight-forward parsing code, and we have already seen
+a lot of similar code in the past. One interesting piece of this is the part
+that sets up <tt>FnName</tt> for binary operators. This builds names like
+"binary@" for a newly defined "@" operator. This takes advantage of the fact
+that symbol names in the LLVM symbol table are allowed to have any character in
+them, inluding embedded nul characters.</p>
+
+<p>The next interesting piece 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>
+Value *BinaryExprAST::Codegen() {
+ Value *L = LHS->Codegen();
+ Value *R = RHS->Codegen();
+ if (L == 0 || R == 0) return 0;
+
+ switch (Op) {
+ case '+': return Builder.CreateAdd(L, R, "addtmp");
+ case '-': return Builder.CreateSub(L, R, "subtmp");
+ case '*': return Builder.CreateMul(L, R, "multmp");
+ case '<':
+ L = Builder.CreateFCmpULT(L, R, "multmp");
+ // Convert bool 0/1 to double 0.0 or 1.0
+ return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp");
+ <b>default: break;</b>
+ }
+
+ <b>// If it wasn't a builtin binary operator, it must be a user defined one. Emit
+ // a call to it.
+ Function *F = TheModule->getFunction(std::string("binary")+Op);
+ assert(F && "binary operator not found!");
+
+ Value *Ops[] = { L, R };
+ return Builder.CreateCall(F, Ops, Ops+2, "binop");</b>
+}
+
+</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 into a function with the right
+name) everything falls into place.</p>
+
+<p>The final missing piece is a bit of top level magic, here:</p>
+
+<div class="doc_code">
+<pre>
+Function *FunctionAST::Codegen() {
+ NamedValues.clear();
+
+ Function *TheFunction = Proto->Codegen();
+ if (TheFunction == 0)
+ return 0;
+
+ <b>// If this is an operator, install it.
+ if (Proto->isBinaryOp())
+ BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();</b>
+
+ // Create a new basic block to start insertion into.
+ BasicBlock *BB = new BasicBlock("entry", TheFunction);
+ Builder.SetInsertPoint(BB);
+
+ if (Value *RetVal = Body->Codegen()) {
+ ...
+</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 to handle it. Since it is a fully-general operator
+precedence parser, this is all we need to do to "extend the grammar".</p>
+
+<p>With that, 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
+langugage, we'll need to add everything for 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>
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+ char Opcode;
+ ExprAST *Operand;
+public:
+ UnaryExprAST(char opcode, ExprAST *operand)
+ : Opcode(opcode), Operand(operand) {}
+ virtual Value *Codegen();
+};
+</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
+static ExprAST *ParseUnary() {
+ // If the current token is not an operator, it must be a primary expr.
+ if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+ return ParsePrimary();
+
+ // If this is a unary operator, read it.
+ int Opc = CurTok;
+ getNextToken();
+ if (ExprAST *Operand = ParseUnary())
+ return new UnaryExprAST(Opc, Operand);
+ return 0;
+}
+</pre>
+</div>
+
+<p>The grammar we add is pretty straight-forward 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 the above is that we need to call ParseUnary from somewhere.
+To do this, we change previous callers of ParsePrimary to call ParseUnary
+instead:</p>
+
+<div class="doc_code">
+<pre>
+/// binoprhs
+/// ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+ ...
+ <b>// Parse the unary expression after the binary operator.
+ ExprAST *RHS = ParseUnary();
+ if (!RHS) return 0;</b>
+ ...
+}
+/// expression
+/// ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+ <b>ExprAST *LHS = ParseUnary();</b>
+ if (!LHS) return 0;
+
+ return ParseBinOpRHS(0, LHS);
+}
+</pre>
+</div>
+
+<p>With these two simple changes, we now 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 (id)</b>
+static PrototypeAST *ParsePrototype() {
+ std::string FnName;
+
+ int Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+ unsigned BinaryPrecedence = 30;
+
+ switch (CurTok) {
+ default:
+ return ErrorP("Expected function name in prototype");
+ case tok_identifier:
+ FnName = IdentifierStr;
+ Kind = 0;
+ getNextToken();
+ break;
+ <b>case tok_unary:
+ getNextToken();
+ if (!isascii(CurTok))
+ return ErrorP("Expected unary operator");
+ FnName = "unary";
+ FnName += (char)CurTok;
+ Kind = 1;
+ getNextToken();
+ break;</b>
+ case tok_binary:
+ ...
+</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>
+Value *UnaryExprAST::Codegen() {
+ Value *OperandV = Operand->Codegen();
+ if (OperandV == 0) return 0;
+
+ Function *F = TheModule->getFunction(std::string("unary")+Opcode);
+ if (F == 0)
+ return ErrorV("Unknown unary operator");
+
+ return Builder.CreateCall(F, OperandV, "unop");
+}
+</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 realish 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 "primative" 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 >. We could also easily define
+# <= etc.
+def binary> 10 (LHS RHS)
+ !(LHS < RHS);
+
+# 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>...</p>
+<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 for 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^2 + 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 dimentional 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 successfully extended our language with the ability to extend the
+language in the library, and showed 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 at all.
+</p>
+
+<p>Strikingly, lack of this feature is an important limitation for some
+languages, and it is not at all obvious how to <a href="LangImpl7.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 this without building SSA in your front-end.</p>
</div>
@@ -206,6 +804,968 @@
<div class="doc_code">
<pre>
+#include "llvm/DerivedTypes.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/Module.h"
+#include "llvm/ModuleProvider.h"
+#include "llvm/PassManager.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/Target/TargetData.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Support/LLVMBuilder.h"
+#include <cstdio>
+#include <string>
+#include <map>
+#include <vector>
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+ tok_eof = -1,
+
+ // commands
+ tok_def = -2, tok_extern = -3,
+
+ // primary
+ tok_identifier = -4, tok_number = -5,
+
+ // control
+ tok_if = -6, tok_then = -7, tok_else = -8,
+ tok_for = -9, tok_in = -10,
+
+ // operators
+ tok_binary = -11, tok_unary = -12
+};
+
+static std::string IdentifierStr; // Filled in if tok_identifier
+static double NumVal; // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+ static int LastChar = ' ';
+
+ // Skip any whitespace.
+ while (isspace(LastChar))
+ LastChar = getchar();
+
+ if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+ IdentifierStr = LastChar;
+ while (isalnum((LastChar = getchar())))
+ IdentifierStr += LastChar;
+
+ if (IdentifierStr == "def") return tok_def;
+ if (IdentifierStr == "extern") return tok_extern;
+ if (IdentifierStr == "if") return tok_if;
+ if (IdentifierStr == "then") return tok_then;
+ if (IdentifierStr == "else") return tok_else;
+ if (IdentifierStr == "for") return tok_for;
+ if (IdentifierStr == "in") return tok_in;
+ if (IdentifierStr == "binary") return tok_binary;
+ if (IdentifierStr == "unary") return tok_unary;
+ return tok_identifier;
+ }
+
+ if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
+ std::string NumStr;
+ do {
+ NumStr += LastChar;
+ LastChar = getchar();
+ } while (isdigit(LastChar) || LastChar == '.');
+
+ NumVal = strtod(NumStr.c_str(), 0);
+ return tok_number;
+ }
+
+ if (LastChar == '#') {
+ // Comment until end of line.
+ do LastChar = getchar();
+ while (LastChar != EOF && LastChar != '\n' & LastChar != '\r');
+
+ if (LastChar != EOF)
+ return gettok();
+ }
+
+ // Check for end of file. Don't eat the EOF.
+ if (LastChar == EOF)
+ return tok_eof;
+
+ // Otherwise, just return the character as its ascii value.
+ int ThisChar = LastChar;
+ LastChar = getchar();
+ return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+/// ExprAST - Base class for all expression nodes.
+class ExprAST {
+public:
+ virtual ~ExprAST() {}
+ virtual Value *Codegen() = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+class NumberExprAST : public ExprAST {
+ double Val;
+public:
+ NumberExprAST(double val) : Val(val) {}
+ virtual Value *Codegen();
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+class VariableExprAST : public ExprAST {
+ std::string Name;
+public:
+ VariableExprAST(const std::string &name) : Name(name) {}
+ virtual Value *Codegen();
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+class UnaryExprAST : public ExprAST {
+ char Opcode;
+ ExprAST *Operand;
+public:
+ UnaryExprAST(char opcode, ExprAST *operand)
+ : Opcode(opcode), Operand(operand) {}
+ virtual Value *Codegen();
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+class BinaryExprAST : public ExprAST {
+ char Op;
+ ExprAST *LHS, *RHS;
+public:
+ BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
+ : Op(op), LHS(lhs), RHS(rhs) {}
+ virtual Value *Codegen();
+};
+
+/// CallExprAST - Expression class for function calls.
+class CallExprAST : public ExprAST {
+ std::string Callee;
+ std::vector<ExprAST*> Args;
+public:
+ CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
+ : Callee(callee), Args(args) {}
+ virtual Value *Codegen();
+};
+
+/// IfExprAST - Expression class for if/then/else.
+class IfExprAST : public ExprAST {
+ ExprAST *Cond, *Then, *Else;
+public:
+ IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
+ : Cond(cond), Then(then), Else(_else) {}
+ virtual Value *Codegen();
+};
+
+/// ForExprAST - Expression class for for/in.
+class ForExprAST : public ExprAST {
+ std::string VarName;
+ ExprAST *Start, *End, *Step, *Body;
+public:
+ ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
+ ExprAST *step, ExprAST *body)
+ : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
+ virtual Value *Codegen();
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+class PrototypeAST {
+ std::string Name;
+ std::vector<std::string> Args;
+ bool isOperator;
+ unsigned Precedence; // Precedence if a binary op.
+public:
+ PrototypeAST(const std::string &name, const std::vector<std::string> &args,
+ bool isoperator = false, unsigned prec = 0)
+ : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
+
+ bool isUnaryOp() const { return isOperator && Args.size() == 1; }
+ bool isBinaryOp() const { return isOperator && Args.size() == 2; }
+
+ char getOperatorName() const {
+ assert(isUnaryOp() || isBinaryOp());
+ return Name[Name.size()-1];
+ }
+
+ unsigned getBinaryPrecedence() const { return Precedence; }
+
+ Function *Codegen();
+};
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+ PrototypeAST *Proto;
+ ExprAST *Body;
+public:
+ FunctionAST(PrototypeAST *proto, ExprAST *body)
+ : Proto(proto), Body(body) {}
+
+ Function *Codegen();
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
+/// token the parser it looking at. getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+ return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+ if (!isascii(CurTok))
+ return -1;
+
+ // Make sure it's a declared binop.
+ int TokPrec = BinopPrecedence[CurTok];
+ if (TokPrec <= 0) return -1;
+ return TokPrec;
+}
+
+/// Error* - These are little helper functions for error handling.
+ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
+PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
+FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
+
+static ExprAST *ParseExpression();
+
+/// identifierexpr
+/// ::= identifer
+/// ::= identifer '(' expression* ')'
+static ExprAST *ParseIdentifierExpr() {
+ std::string IdName = IdentifierStr;
+
+ getNextToken(); // eat identifer.
+
+ if (CurTok != '(') // Simple variable ref.
+ return new VariableExprAST(IdName);
+
+ // Call.
+ getNextToken(); // eat (
+ std::vector<ExprAST*> Args;
+ if (CurTok != ')') {
+ while (1) {
+ ExprAST *Arg = ParseExpression();
+ if (!Arg) return 0;
+ Args.push_back(Arg);
+
+ if (CurTok == ')') break;
+
+ if (CurTok != ',')
+ return Error("Expected ')'");
+ getNextToken();
+ }
+ }
+
+ // Eat the ')'.
+ getNextToken();
+
+ return new CallExprAST(IdName, Args);
+}
+
+/// numberexpr ::= number
+static ExprAST *ParseNumberExpr() {
+ ExprAST *Result = new NumberExprAST(NumVal);
+ getNextToken(); // consume the number
+ return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static ExprAST *ParseParenExpr() {
+ getNextToken(); // eat (.
+ ExprAST *V = ParseExpression();
+ if (!V) return 0;
+
+ if (CurTok != ')')
+ return Error("expected ')'");
+ getNextToken(); // eat ).
+ return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static ExprAST *ParseIfExpr() {
+ getNextToken(); // eat the if.
+
+ // condition.
+ ExprAST *Cond = ParseExpression();
+ if (!Cond) return 0;
+
+ if (CurTok != tok_then)
+ return Error("expected then");
+ getNextToken(); // eat the then
+
+ ExprAST *Then = ParseExpression();
+ if (Then == 0) return 0;
+
+ if (CurTok != tok_else)
+ return Error("expected else");
+
+ getNextToken();
+
+ ExprAST *Else = ParseExpression();
+ if (!Else) return 0;
+
+ return new IfExprAST(Cond, Then, Else);
+}
+
+/// forexpr ::= 'for' identifer '=' expr ',' expr (',' expr)? 'in' expression
+static ExprAST *ParseForExpr() {
+ getNextToken(); // eat the for.
+
+ if (CurTok != tok_identifier)
+ return Error("expected identifier after for");
+
+ std::string IdName = IdentifierStr;
+ getNextToken(); // eat identifer.
+
+ if (CurTok != '=')
+ return Error("expected '=' after for");
+ getNextToken(); // eat '='.
+
+
+ ExprAST *Start = ParseExpression();
+ if (Start == 0) return 0;
+ if (CurTok != ',')
+ return Error("expected ',' after for start value");
+ getNextToken();
+
+ ExprAST *End = ParseExpression();
+ if (End == 0) return 0;
+
+ // The step value is optional.
+ ExprAST *Step = 0;
+ if (CurTok == ',') {
+ getNextToken();
+ Step = ParseExpression();
+ if (Step == 0) return 0;
+ }
+
+ if (CurTok != tok_in)
+ return Error("expected 'in' after for");
+ getNextToken(); // eat 'in'.
+
+ ExprAST *Body = ParseExpression();
+ if (Body == 0) return 0;
+
+ return new ForExprAST(IdName, Start, End, Step, Body);
+}
+
+
+/// primary
+/// ::= identifierexpr
+/// ::= numberexpr
+/// ::= parenexpr
+/// ::= ifexpr
+/// ::= forexpr
+static ExprAST *ParsePrimary() {
+ switch (CurTok) {
+ default: return Error("unknown token when expecting an expression");
+ case tok_identifier: return ParseIdentifierExpr();
+ case tok_number: return ParseNumberExpr();
+ case '(': return ParseParenExpr();
+ case tok_if: return ParseIfExpr();
+ case tok_for: return ParseForExpr();
+ }
+}
+
+/// unary
+/// ::= primary
+/// ::= '!' unary
+static ExprAST *ParseUnary() {
+ // If the current token is not an operator, it must be a primary expr.
+ if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
+ return ParsePrimary();
+
+ // If this is a unary operator, read it.
+ int Opc = CurTok;
+ getNextToken();
+ if (ExprAST *Operand = ParseUnary())
+ return new UnaryExprAST(Opc, Operand);
+ return 0;
+}
+
+/// binoprhs
+/// ::= ('+' unary)*
+static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
+ // If this is a binop, find its precedence.
+ while (1) {
+ int TokPrec = GetTokPrecedence();
+
+ // If this is a binop that binds at least as tightly as the current binop,
+ // consume it, otherwise we are done.
+ if (TokPrec < ExprPrec)
+ return LHS;
+
+ // Okay, we know this is a binop.
+ int BinOp = CurTok;
+ getNextToken(); // eat binop
+
+ // Parse the unary expression after the binary operator.
+ ExprAST *RHS = ParseUnary();
+ if (!RHS) return 0;
+
+ // If BinOp binds less tightly with RHS than the operator after RHS, let
+ // the pending operator take RHS as its LHS.
+ int NextPrec = GetTokPrecedence();
+ if (TokPrec < NextPrec) {
+ RHS = ParseBinOpRHS(TokPrec+1, RHS);
+ if (RHS == 0) return 0;
+ }
+
+ // Merge LHS/RHS.
+ LHS = new BinaryExprAST(BinOp, LHS, RHS);
+ }
+}
+
+/// expression
+/// ::= unary binoprhs
+///
+static ExprAST *ParseExpression() {
+ ExprAST *LHS = ParseUnary();
+ if (!LHS) return 0;
+
+ return ParseBinOpRHS(0, LHS);
+}
+
+/// prototype
+/// ::= id '(' id* ')'
+/// ::= binary LETTER number? (id, id)
+/// ::= unary LETTER (id)
+static PrototypeAST *ParsePrototype() {
+ std::string FnName;
+
+ int Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+ unsigned BinaryPrecedence = 30;
+
+ switch (CurTok) {
+ default:
+ return ErrorP("Expected function name in prototype");
+ case tok_identifier:
+ FnName = IdentifierStr;
+ Kind = 0;
+ getNextToken();
+ break;
+ case tok_unary:
+ getNextToken();
+ if (!isascii(CurTok))
+ return ErrorP("Expected unary operator");
+ FnName = "unary";
+ FnName += (char)CurTok;
+ Kind = 1;
+ getNextToken();
+ break;
+ case tok_binary:
+ getNextToken();
+ if (!isascii(CurTok))
+ return ErrorP("Expected binary operator");
+ FnName = "binary";
+ FnName += (char)CurTok;
+ Kind = 2;
+ getNextToken();
+
+ // Read the precedence if present.
+ if (CurTok == tok_number) {
+ if (NumVal < 1 || NumVal > 100)
+ return ErrorP("Invalid precedecnce: must be 1..100");
+ BinaryPrecedence = (unsigned)NumVal;
+ getNextToken();
+ }
+ break;
+ }
+
+ if (CurTok != '(')
+ return ErrorP("Expected '(' in prototype");
+
+ std::vector<std::string> ArgNames;
+ while (getNextToken() == tok_identifier)
+ ArgNames.push_back(IdentifierStr);
+ if (CurTok != ')')
+ return ErrorP("Expected ')' in prototype");
+
+ // success.
+ getNextToken(); // eat ')'.
+
+ // Verify right number of names for operator.
+ if (Kind && ArgNames.size() != Kind)
+ return ErrorP("Invalid number of operands for operator");
+
+ return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static FunctionAST *ParseDefinition() {
+ getNextToken(); // eat def.
+ PrototypeAST *Proto = ParsePrototype();
+ if (Proto == 0) return 0;
+
+ if (ExprAST *E = ParseExpression())
+ return new FunctionAST(Proto, E);
+ return 0;
+}
+
+/// toplevelexpr ::= expression
+static FunctionAST *ParseTopLevelExpr() {
+ if (ExprAST *E = ParseExpression()) {
+ // Make an anonymous proto.
+ PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
+ return new FunctionAST(Proto, E);
+ }
+ return 0;
+}
+
+/// external ::= 'extern' prototype
+static PrototypeAST *ParseExtern() {
+ getNextToken(); // eat extern.
+ return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+static Module *TheModule;
+static LLVMFoldingBuilder Builder;
+static std::map<std::string, Value*> NamedValues;
+static FunctionPassManager *TheFPM;
+
+Value *ErrorV(const char *Str) { Error(Str); return 0; }
+
+Value *NumberExprAST::Codegen() {
+ return ConstantFP::get(Type::DoubleTy, APFloat(Val));
+}
+
+Value *VariableExprAST::Codegen() {
+ // Look this variable up in the function.
+ Value *V = NamedValues[Name];
+ return V ? V : ErrorV("Unknown variable name");
+}
+
+Value *UnaryExprAST::Codegen() {
+ Value *OperandV = Operand->Codegen();
+ if (OperandV == 0) return 0;
+
+ Function *F = TheModule->getFunction(std::string("unary")+Opcode);
+ if (F == 0)
+ return ErrorV("Unknown unary operator");
+
+ return Builder.CreateCall(F, OperandV, "unop");
+}
+
+
+Value *BinaryExprAST::Codegen() {
+ Value *L = LHS->Codegen();
+ Value *R = RHS->Codegen();
+ if (L == 0 || R == 0) return 0;
+
+ switch (Op) {
+ case '+': return Builder.CreateAdd(L, R, "addtmp");
+ case '-': return Builder.CreateSub(L, R, "subtmp");
+ case '*': return Builder.CreateMul(L, R, "multmp");
+ case '<':
+ L = Builder.CreateFCmpULT(L, R, "multmp");
+ // Convert bool 0/1 to double 0.0 or 1.0
+ return Builder.CreateUIToFP(L, Type::DoubleTy, "booltmp");
+ default: break;
+ }
+
+ // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+ // a call to it.
+ Function *F = TheModule->getFunction(std::string("binary")+Op);
+ assert(F && "binary operator not found!");
+
+ Value *Ops[] = { L, R };
+ return Builder.CreateCall(F, Ops, Ops+2, "binop");
+}
+
+Value *CallExprAST::Codegen() {
+ // Look up the name in the global module table.
+ Function *CalleeF = TheModule->getFunction(Callee);
+ if (CalleeF == 0)
+ return ErrorV("Unknown function referenced");
+
+ // If argument mismatch error.
+ if (CalleeF->arg_size() != Args.size())
+ return ErrorV("Incorrect # arguments passed");
+
+ std::vector<Value*> ArgsV;
+ for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+ ArgsV.push_back(Args[i]->Codegen());
+ if (ArgsV.back() == 0) return 0;
+ }
+
+ return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
+}
+
+Value *IfExprAST::Codegen() {
+ Value *CondV = Cond->Codegen();
+ if (CondV == 0) return 0;
+
+ // Convert condition to a bool by comparing equal to 0.0.
+ CondV = Builder.CreateFCmpONE(CondV,
+ ConstantFP::get(Type::DoubleTy, APFloat(0.0)),
+ "ifcond");
+
+ Function *TheFunction = Builder.GetInsertBlock()->getParent();
+
+ // Create blocks for the then and else cases. Insert the 'then' block at the
+ // end of the function.
+ BasicBlock *ThenBB = new BasicBlock("then", TheFunction);
+ BasicBlock *ElseBB = new BasicBlock("else");
+ BasicBlock *MergeBB = new BasicBlock("ifcont");
+
+ Builder.CreateCondBr(CondV, ThenBB, ElseBB);
+
+ // Emit then value.
+ Builder.SetInsertPoint(ThenBB);
+
+ Value *ThenV = Then->Codegen();
+ if (ThenV == 0) return 0;
+
+ Builder.CreateBr(MergeBB);
+ // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+ ThenBB = Builder.GetInsertBlock();
+
+ // Emit else block.
+ TheFunction->getBasicBlockList().push_back(ElseBB);
+ Builder.SetInsertPoint(ElseBB);
+
+ Value *ElseV = Else->Codegen();
+ if (ElseV == 0) return 0;
+
+ Builder.CreateBr(MergeBB);
+ // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+ ElseBB = Builder.GetInsertBlock();
+
+ // Emit merge block.
+ TheFunction->getBasicBlockList().push_back(MergeBB);
+ Builder.SetInsertPoint(MergeBB);
+ PHINode *PN = Builder.CreatePHI(Type::DoubleTy, "iftmp");
+
+ PN->addIncoming(ThenV, ThenBB);
+ PN->addIncoming(ElseV, ElseBB);
+ return PN;
+}
+
+Value *ForExprAST::Codegen() {
+ // Output this as:
+ // ...
+ // start = startexpr
+ // goto loop
+ // loop:
+ // variable = phi [start, loopheader], [nextvariable, loopend]
+ // ...
+ // bodyexpr
+ // ...
+ // loopend:
+ // step = stepexpr
+ // nextvariable = variable + step
+ // endcond = endexpr
+ // br endcond, loop, endloop
+ // outloop:
+
+ // Emit the start code first, without 'variable' in scope.
+ Value *StartVal = Start->Codegen();
+ if (StartVal == 0) return 0;
+
+ // Make the new basic block for the loop header, inserting after current
+ // block.
+ Function *TheFunction = Builder.GetInsertBlock()->getParent();
+ BasicBlock *PreheaderBB = Builder.GetInsertBlock();
+ BasicBlock *LoopBB = new BasicBlock("loop", TheFunction);
+
+ // Insert an explicit fall through from the current block to the LoopBB.
+ Builder.CreateBr(LoopBB);
+
+ // Start insertion in LoopBB.
+ Builder.SetInsertPoint(LoopBB);
+
+ // Start the PHI node with an entry for Start.
+ PHINode *Variable = Builder.CreatePHI(Type::DoubleTy, VarName.c_str());
+ Variable->addIncoming(StartVal, PreheaderBB);
+
+ // 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.
+ Value *OldVal = NamedValues[VarName];
+ NamedValues[VarName] = 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.
+ if (Body->Codegen() == 0)
+ return 0;
+
+ // Emit the step value.
+ Value *StepVal;
+ if (Step) {
+ StepVal = Step->Codegen();
+ if (StepVal == 0) return 0;
+ } else {
+ // If not specified, use 1.0.
+ StepVal = ConstantFP::get(Type::DoubleTy, APFloat(1.0));
+ }
+
+ Value *NextVar = Builder.CreateAdd(Variable, StepVal, "nextvar");
+
+ // Compute the end condition.
+ Value *EndCond = End->Codegen();
+ if (EndCond == 0) return EndCond;
+
+ // Convert condition to a bool by comparing equal to 0.0.
+ EndCond = Builder.CreateFCmpONE(EndCond,
+ ConstantFP::get(Type::DoubleTy, APFloat(0.0)),
+ "loopcond");
+
+ // Create the "after loop" block and insert it.
+ BasicBlock *LoopEndBB = Builder.GetInsertBlock();
+ BasicBlock *AfterBB = new BasicBlock("afterloop", TheFunction);
+
+ // Insert the conditional branch into the end of LoopEndBB.
+ Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
+
+ // Any new code will be inserted in AfterBB.
+ Builder.SetInsertPoint(AfterBB);
+
+ // Add a new entry to the PHI node for the backedge.
+ Variable->addIncoming(NextVar, LoopEndBB);
+
+ // Restore the unshadowed variable.
+ if (OldVal)
+ NamedValues[VarName] = OldVal;
+ else
+ NamedValues.erase(VarName);
+
+
+ // for expr always returns 0.0.
+ return Constant::getNullValue(Type::DoubleTy);
+}
+
+Function *PrototypeAST::Codegen() {
+ // Make the function type: double(double,double) etc.
+ std::vector<const Type*> Doubles(Args.size(), Type::DoubleTy);
+ FunctionType *FT = FunctionType::get(Type::DoubleTy, Doubles, false);
+
+ Function *F = new Function(FT, Function::ExternalLinkage, Name, TheModule);
+
+ // If F conflicted, there was already something named 'Name'. If it has a
+ // body, don't allow redefinition or reextern.
+ if (F->getName() != Name) {
+ // Delete the one we just made and get the existing one.
+ F->eraseFromParent();
+ F = TheModule->getFunction(Name);
+
+ // If F already has a body, reject this.
+ if (!F->empty()) {
+ ErrorF("redefinition of function");
+ return 0;
+ }
+
+ // If F took a different number of args, reject.
+ if (F->arg_size() != Args.size()) {
+ ErrorF("redefinition of function with different # args");
+ return 0;
+ }
+ }
+
+ // Set names for all arguments.
+ unsigned Idx = 0;
+ for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+ ++AI, ++Idx) {
+ AI->setName(Args[Idx]);
+
+ // Add arguments to variable symbol table.
+ NamedValues[Args[Idx]] = AI;
+ }
+
+ return F;
+}
+
+Function *FunctionAST::Codegen() {
+ NamedValues.clear();
+
+ Function *TheFunction = Proto->Codegen();
+ if (TheFunction == 0)
+ return 0;
+
+ // If this is an operator, install it.
+ if (Proto->isBinaryOp())
+ BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
+
+ // Create a new basic block to start insertion into.
+ BasicBlock *BB = new BasicBlock("entry", TheFunction);
+ Builder.SetInsertPoint(BB);
+
+ if (Value *RetVal = Body->Codegen()) {
+ // Finish off the function.
+ Builder.CreateRet(RetVal);
+
+ // Validate the generated code, checking for consistency.
+ verifyFunction(*TheFunction);
+
+ // Optimize the function.
+ TheFPM->run(*TheFunction);
+
+ return TheFunction;
+ }
+
+ // Error reading body, remove function.
+ TheFunction->eraseFromParent();
+
+ if (Proto->isBinaryOp())
+ BinopPrecedence.erase(Proto->getOperatorName());
+ return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static ExecutionEngine *TheExecutionEngine;
+
+static void HandleDefinition() {
+ if (FunctionAST *F = ParseDefinition()) {
+ if (Function *LF = F->Codegen()) {
+ fprintf(stderr, "Read function definition:");
+ LF->dump();
+ }
+ } else {
+ // Skip token for error recovery.
+ getNextToken();
+ }
+}
+
+static void HandleExtern() {
+ if (PrototypeAST *P = ParseExtern()) {
+ if (Function *F = P->Codegen()) {
+ fprintf(stderr, "Read extern: ");
+ F->dump();
+ }
+ } else {
+ // Skip token for error recovery.
+ getNextToken();
+ }
+}
+
+static void HandleTopLevelExpression() {
+ // Evaluate a top level expression into an anonymous function.
+ if (FunctionAST *F = ParseTopLevelExpr()) {
+ if (Function *LF = F->Codegen()) {
+ // JIT the function, returning a function pointer.
+ void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
+
+ // Cast it to the right type (takes no arguments, returns a double) so we
+ // can call it as a native function.
+ double (*FP)() = (double (*)())FPtr;
+ fprintf(stderr, "Evaluated to %f\n", FP());
+ }
+ } else {
+ // Skip token for error recovery.
+ getNextToken();
+ }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+ while (1) {
+ fprintf(stderr, "ready> ");
+ switch (CurTok) {
+ case tok_eof: return;
+ case ';': getNextToken(); break; // ignore top level semicolons.
+ case tok_def: HandleDefinition(); break;
+ case tok_extern: HandleExtern(); break;
+ default: HandleTopLevelExpression(); break;
+ }
+ }
+}
+
+
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C"
+double putchard(double X) {
+ putchar((char)X);
+ return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C"
+double printd(double X) {
+ printf("%f\n", X);
+ return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main() {
+ // Install standard binary operators.
+ // 1 is lowest precedence.
+ BinopPrecedence['<'] = 10;
+ BinopPrecedence['+'] = 20;
+ BinopPrecedence['-'] = 20;
+ BinopPrecedence['*'] = 40; // highest.
+
+ // Prime the first token.
+ fprintf(stderr, "ready> ");
+ getNextToken();
+
+ // Make the module, which holds all the code.
+ TheModule = new Module("my cool jit");
+
+ // Create the JIT.
+ TheExecutionEngine = ExecutionEngine::create(TheModule);
+
+ {
+ ExistingModuleProvider OurModuleProvider(TheModule);
+ FunctionPassManager OurFPM(&OurModuleProvider);
+
+ // Set up the optimizer pipeline. Start with registering info about how the
+ // target lays out data structures.
+ OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData()));
+ // Do simple "peephole" optimizations and bit-twiddling optzns.
+ OurFPM.add(createInstructionCombiningPass());
+ // Reassociate expressions.
+ OurFPM.add(createReassociatePass());
+ // Eliminate Common SubExpressions.
+ OurFPM.add(createGVNPass());
+ // Simplify the control flow graph (deleting unreachable blocks, etc).
+ OurFPM.add(createCFGSimplificationPass());
+ // Set the global so the code gen can use this.
+ TheFPM = &OurFPM;
+
+ // Run the main "interpreter loop" now.
+ MainLoop();
+
+ TheFPM = 0;
+ } // Free module provider and pass manager.
+
+
+ // Print out all of the generated code.
+ TheModule->dump();
+ return 0;
+}
</pre>
</div>