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diff --git a/docs/main/tutorial/LangImpl6.html b/docs/main/tutorial/LangImpl6.html new file mode 100644 index 0000000..5fae906 --- /dev/null +++ b/docs/main/tutorial/LangImpl6.html @@ -0,0 +1,1814 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" + "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"> + <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="LangImpl7.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></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="LangImpl2.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> +enum Token { + ... + <b>// operators + tok_binary = -11, tok_unary = -12</b> +}; +... +static int gettok() { +... + if (IdentifierStr == "for") return tok_for; + if (IdentifierStr == "in") return tok_in; + <b>if (IdentifierStr == "binary") return tok_binary; + if (IdentifierStr == "unary") return tok_unary;</b> + return tok_identifier; +</pre> +</div> + +<p>This just adds lexer support for the unary and binary keywords, like we +did in <a href="LangImpl5.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>PrototypeAST</tt> AST node. To +represent our new user-defined operators as prototypes, we have to extend +the <tt>PrototypeAST</tt> AST node like this:</p> + +<div class="doc_code"> +<pre> +/// 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; + <b>bool isOperator; + unsigned Precedence; // Precedence if a binary op.</b> +public: + PrototypeAST(const std::string &name, const std::vector<std::string> &args, + <b>bool isoperator = false, unsigned prec = 0</b>) + : Name(name), Args(args), <b>isOperator(isoperator), Precedence(prec)</b> {} + + <b>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; }</b> + + Function *Codegen(); +}; +</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)</b> +static PrototypeAST *ParsePrototype() { + std::string FnName; + + <b>unsigned 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 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>FnName</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> +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, "cmptmp"); + // Convert bool 0/1 to double 0.0 or 1.0 + return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()), + "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 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> +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 = BasicBlock::Create(getGlobalContext(), "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 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> +/// 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 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 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 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 (id)</b> +static PrototypeAST *ParsePrototype() { + std::string FnName; + + unsigned 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 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="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 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 + g++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy + # Run + ./toy +</pre> +</div> + +<p>Here is the code:</p> + +<div class="doc_code"> +<pre> +#include "llvm/DerivedTypes.h" +#include "llvm/ExecutionEngine/ExecutionEngine.h" +#include "llvm/ExecutionEngine/JIT.h" +#include "llvm/LLVMContext.h" +#include "llvm/Module.h" +#include "llvm/PassManager.h" +#include "llvm/Analysis/Verifier.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Target/TargetSelect.h" +#include "llvm/Transforms/Scalar.h" +#include "llvm/Support/IRBuilder.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 name, and its argument names (thus implicitly the number +/// of arguments the function takes), 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 is 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 +/// ::= identifier +/// ::= identifier '(' expression* ')' +static ExprAST *ParseIdentifierExpr() { + std::string IdName = IdentifierStr; + + getNextToken(); // eat identifier. + + 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 ')' or ',' in argument list"); + 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' identifier '=' 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 identifier. + + 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; + + unsigned 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 IRBuilder<> Builder(getGlobalContext()); +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(getGlobalContext(), 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, "cmptmp"); + // Convert bool 0/1 to double 0.0 or 1.0 + return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()), + "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(getGlobalContext(), 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 = BasicBlock::Create(getGlobalContext(), "then", TheFunction); + BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else"); + BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "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::getDoubleTy(getGlobalContext()), + "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 = BasicBlock::Create(getGlobalContext(), "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::getDoubleTy(getGlobalContext()), 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(getGlobalContext(), 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(getGlobalContext(), APFloat(0.0)), + "loopcond"); + + // Create the "after loop" block and insert it. + BasicBlock *LoopEndBB = Builder.GetInsertBlock(); + BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "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::getDoubleTy(getGlobalContext())); +} + +Function *PrototypeAST::Codegen() { + // Make the function type: double(double,double) etc. + std::vector<const Type*> Doubles(Args.size(), + Type::getDoubleTy(getGlobalContext())); + FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()), + Doubles, false); + + Function *F = Function::Create(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 = BasicBlock::Create(getGlobalContext(), "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 (*)())(intptr_t)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() { + InitializeNativeTarget(); + LLVMContext &Context = getGlobalContext(); + + // 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", Context); + + // Create the JIT. This takes ownership of the module. + std::string ErrStr; + TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create(); + if (!TheExecutionEngine) { + fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str()); + exit(1); + } + + FunctionPassManager OurFPM(TheModule); + + // 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()); + + OurFPM.doInitialization(); + + // Set the global so the code gen can use this. + TheFPM = &OurFPM; + + // Run the main "interpreter loop" now. + MainLoop(); + + TheFPM = 0; + + // Print out all of the generated code. + TheModule->dump(); + + return 0; +} +</pre> +</div> + +<a href="LangImpl7.html">Next: Extending the language: mutable variables / SSA construction</a> +</div> + +<!-- *********************************************************************** --> +<hr> +<address> + <a href="http://jigsaw.w3.org/css-validator/check/referer"><img + src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a> + <a href="http://validator.w3.org/check/referer"><img + src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a> + + <a href="mailto:sabre@nondot.org">Chris Lattner</a><br> + <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br> + Last modified: $Date$ +</address> +</body> +</html> |