Kaleidoscope: Extending the Language: User-defined Operators

Date: Thu, 6 May 2010 23:45:43 +0000 Subject: Overhauled llvm/clang docs builds. Closes PR6613. NOTE: 2nd part changeset for cfe trunk to follow. *** PRE-PATCH ISSUES ADDRESSED - clang api docs fail build from objdir - clang/llvm api docs collide in install PREFIX/ - clang/llvm main docs collide in install - clang/llvm main docs have full of hard coded destination assumptions and make use of absolute root in static html files; namely CommandGuide tools hard codes a website destination for cross references and some html cross references assume website root paths *** IMPROVEMENTS - bumped Doxygen from 1.4.x -> 1.6.3 - splits llvm/clang docs into 'main' and 'api' (doxygen) build trees - provide consistent, reliable doc builds for both main+api docs - support buid vs. install vs. website intentions - support objdir builds - document targets with 'make help' - correct clean and uninstall operations - use recursive dir delete only where absolutely necessary - added call function fn.RMRF which safeguards against botched 'rm -rf'; if any target (or any variable is evaluated) which attempts to remove any dirs which match a hard-coded 'safelist', a verbose error will be printed and make will error-stop. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103213 91177308-0d34-0410-b5e6-96231b3b80d8 --- docs/tutorial/LangImpl6.html | 1814 ------------------------------------------ 1 file changed, 1814 deletions(-) delete mode 100644 docs/tutorial/LangImpl6.html (limited to 'docs/tutorial/LangImpl6.html') diff --git a/docs/tutorial/LangImpl6.html b/docs/tutorial/LangImpl6.html deleted file mode 100644 index 5fae906..0000000 --- a/docs/tutorial/LangImpl6.html +++ /dev/null @@ -1,1814 +0,0 @@ - - - - - Kaleidoscope: Extending the Language: User-defined Operators - - - - - - - -

- -

Up to Tutorial Index
Chapter 6 -
-
Chapter 7: Extending the Language: Mutable -Variables / SSA Construction

- -

Written by Chris Lattner

- - -

Chapter 6 Introduction

- - -

- -

Welcome to Chapter 6 of the "Implementing a language -with LLVM" 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).

- -

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.

- -

At the end of this tutorial, we'll run through an example Kaleidoscope -application that renders the Mandelbrot set. This gives -an example of what you can build with Kaleidoscope and its feature set.

- -

- - -

User-defined Operators: the Idea

- - -

- -

-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.

- -

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 Chapter 2 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.

- -

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:

- -

-# 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);
-

- -

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!

- -

We will break down implementation of these features into two parts: -implementing support for user-defined binary operators and adding unary -operators.

- -

- - -

User-defined Binary Operators

- - -

- -

Adding support for user-defined binary operators is pretty simple with our -current framework. We'll first add support for the unary/binary keywords:

- -

-enum Token {
-  ...
-  // operators
-  tok_binary = -11, tok_unary = -12
-};
-...
-static int gettok() {
-...
-    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;
-

- -

This just adds lexer support for the unary and binary keywords, like we -did in previous chapters. 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.

- -

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 PrototypeAST AST node. To -represent our new user-defined operators as prototypes, we have to extend -the PrototypeAST AST node like this:

- -

-/// 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();
-};
-

- -

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:

- -

-/// prototype
-///   ::= id '(' id* ')'
-///   ::= binary LETTER number? (id, 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_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);
-}
-

- -

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 FnName 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.

- -

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:

- -

-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");
-}
-
-

- -

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.

- -

The final piece of code we are missing, is a bit of top-level magic:

- -

-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()) {
-    ...
-

- -

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".

- -

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.

- -

- - -

User-defined Unary Operators

- - -

- -

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:

- -

-/// 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();
-};
-

- -

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:

- -

-/// 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;
-}
-

- -

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.

- -

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:

- -

-/// binoprhs
-///   ::= ('+' unary)*
-static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
-  ...
-    // Parse the unary expression after the binary operator.
-    ExprAST *RHS = ParseUnary();
-    if (!RHS) return 0;
-  ...
-}
-/// expression
-///   ::= unary binoprhs
-///
-static ExprAST *ParseExpression() {
-  ExprAST *LHS = ParseUnary();
-  if (!LHS) return 0;
-  
-  return ParseBinOpRHS(0, LHS);
-}
-

- -

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:

- -

-/// 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:
-    ...
-

- -

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:

- -

-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");
-}
-

- -

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. -

- -

- - -

Kicking the Tires

- - -

- -

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):

- -

-ready> extern printd(x);
-Read extern: declare double @printd(double)
-ready> def binary : 1 (x y) 0;  # Low-precedence operator that ignores operands.
-..
-ready> printd(123) : printd(456) : printd(789);
-123.000000
-456.000000
-789.000000
-Evaluated to 0.000000
-

- -

We can also define a bunch of other "primitive" operations, such as:

- -

-# 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);
-
-

- - -

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:

- -

-ready>
-
-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); # '*'
-...
-ready> printdensity(1): printdensity(2): printdensity(3) : 
-          printdensity(4): printdensity(5): printdensity(9): putchard(10);
-*++.. 
-Evaluated to 0.000000
-

- -

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:

- -

-# 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);
-

- -

This "z = z² + c" function is a beautiful little creature that is the basis -for computation of the Mandelbrot Set. Our -mandelconverge 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:

- -

-# 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);
-

- -

Given this, we can try plotting out the mandlebrot set! Lets try it out:

- -

-ready> mandel(-2.3, -1.3, 0.05, 0.07);
-*******************************+++++++++++*************************************
-*************************+++++++++++++++++++++++*******************************
-**********************+++++++++++++++++++++++++++++****************************
-*******************+++++++++++++++++++++.. ...++++++++*************************
-*****************++++++++++++++++++++++.... ...+++++++++***********************
-***************+++++++++++++++++++++++.....   ...+++++++++*********************
-**************+++++++++++++++++++++++....     ....+++++++++********************
-*************++++++++++++++++++++++......      .....++++++++*******************
-************+++++++++++++++++++++.......       .......+++++++******************
-***********+++++++++++++++++++....                ... .+++++++*****************
-**********+++++++++++++++++.......                     .+++++++****************
-*********++++++++++++++...........                    ...+++++++***************
-********++++++++++++............                      ...++++++++**************
-********++++++++++... ..........                        .++++++++**************
-*******+++++++++.....                                   .+++++++++*************
-*******++++++++......                                  ..+++++++++*************
-*******++++++.......                                   ..+++++++++*************
-*******+++++......                                     ..+++++++++*************
-*******.... ....                                      ...+++++++++*************
-*******.... .                                         ...+++++++++*************
-*******+++++......                                    ...+++++++++*************
-*******++++++.......                                   ..+++++++++*************
-*******++++++++......                                   .+++++++++*************
-*******+++++++++.....                                  ..+++++++++*************
-********++++++++++... ..........                        .++++++++**************
-********++++++++++++............                      ...++++++++**************
-*********++++++++++++++..........                     ...+++++++***************
-**********++++++++++++++++........                     .+++++++****************
-**********++++++++++++++++++++....                ... ..+++++++****************
-***********++++++++++++++++++++++.......       .......++++++++*****************
-************+++++++++++++++++++++++......      ......++++++++******************
-**************+++++++++++++++++++++++....      ....++++++++********************
-***************+++++++++++++++++++++++.....   ...+++++++++*********************
-*****************++++++++++++++++++++++....  ...++++++++***********************
-*******************+++++++++++++++++++++......++++++++*************************
-*********************++++++++++++++++++++++.++++++++***************************
-*************************+++++++++++++++++++++++*******************************
-******************************+++++++++++++************************************
-*******************************************************************************
-*******************************************************************************
-*******************************************************************************
-Evaluated to 0.000000
-ready> mandel(-2, -1, 0.02, 0.04);
-**************************+++++++++++++++++++++++++++++++++++++++++++++++++++++
-***********************++++++++++++++++++++++++++++++++++++++++++++++++++++++++
-*********************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
-*******************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++...
-*****************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++.....
-***************++++++++++++++++++++++++++++++++++++++++++++++++++++++++........
-**************++++++++++++++++++++++++++++++++++++++++++++++++++++++...........
-************+++++++++++++++++++++++++++++++++++++++++++++++++++++..............
-***********++++++++++++++++++++++++++++++++++++++++++++++++++........        . 
-**********++++++++++++++++++++++++++++++++++++++++++++++.............          
-********+++++++++++++++++++++++++++++++++++++++++++..................          
-*******+++++++++++++++++++++++++++++++++++++++.......................          
-******+++++++++++++++++++++++++++++++++++...........................           
-*****++++++++++++++++++++++++++++++++............................              
-*****++++++++++++++++++++++++++++...............................               
-****++++++++++++++++++++++++++......   .........................               
-***++++++++++++++++++++++++.........     ......    ...........                 
-***++++++++++++++++++++++............                                          
-**+++++++++++++++++++++..............                                          
-**+++++++++++++++++++................                                          
-*++++++++++++++++++.................                                           
-*++++++++++++++++............ ...                                              
-*++++++++++++++..............                                                  
-*+++....++++................                                                   
-*..........  ...........                                                       
-*                                                                              
-*..........  ...........                                                       
-*+++....++++................                                                   
-*++++++++++++++..............                                                  
-*++++++++++++++++............ ...                                              
-*++++++++++++++++++.................                                           
-**+++++++++++++++++++................                                          
-**+++++++++++++++++++++..............                                          
-***++++++++++++++++++++++............                                          
-***++++++++++++++++++++++++.........     ......    ...........                 
-****++++++++++++++++++++++++++......   .........................               
-*****++++++++++++++++++++++++++++...............................               
-*****++++++++++++++++++++++++++++++++............................              
-******+++++++++++++++++++++++++++++++++++...........................           
-*******+++++++++++++++++++++++++++++++++++++++.......................          
-********+++++++++++++++++++++++++++++++++++++++++++..................          
-Evaluated to 0.000000
-ready> mandel(-0.9, -1.4, 0.02, 0.03);
-*******************************************************************************
-*******************************************************************************
-*******************************************************************************
-**********+++++++++++++++++++++************************************************
-*+++++++++++++++++++++++++++++++++++++++***************************************
-+++++++++++++++++++++++++++++++++++++++++++++**********************************
-++++++++++++++++++++++++++++++++++++++++++++++++++*****************************
-++++++++++++++++++++++++++++++++++++++++++++++++++++++*************************
-+++++++++++++++++++++++++++++++++++++++++++++++++++++++++**********************
-+++++++++++++++++++++++++++++++++.........++++++++++++++++++*******************
-+++++++++++++++++++++++++++++++....   ......+++++++++++++++++++****************
-+++++++++++++++++++++++++++++.......  ........+++++++++++++++++++**************
-++++++++++++++++++++++++++++........   ........++++++++++++++++++++************
-+++++++++++++++++++++++++++.........     ..  ...+++++++++++++++++++++**********
-++++++++++++++++++++++++++...........        ....++++++++++++++++++++++********
-++++++++++++++++++++++++.............       .......++++++++++++++++++++++******
-+++++++++++++++++++++++.............        ........+++++++++++++++++++++++****
-++++++++++++++++++++++...........           ..........++++++++++++++++++++++***
-++++++++++++++++++++...........                .........++++++++++++++++++++++*
-++++++++++++++++++............                  ...........++++++++++++++++++++
-++++++++++++++++...............                 .............++++++++++++++++++
-++++++++++++++.................                 ...............++++++++++++++++
-++++++++++++..................                  .................++++++++++++++
-+++++++++..................                      .................+++++++++++++
-++++++........        .                               .........  ..++++++++++++
-++............                                         ......    ....++++++++++
-..............                                                    ...++++++++++
-..............                                                    ....+++++++++
-..............                                                    .....++++++++
-.............                                                    ......++++++++
-...........                                                     .......++++++++
-.........                                                       ........+++++++
-.........                                                       ........+++++++
-.........                                                           ....+++++++
-........                                                             ...+++++++
-.......                                                              ...+++++++
-                                                                    ....+++++++
-                                                                   .....+++++++
-                                                                    ....+++++++
-                                                                    ....+++++++
-                                                                    ....+++++++
-Evaluated to 0.000000
-ready> ^D
-

- -

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!

- -

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. -

- -

Strikingly, variable mutation is an important feature of some -languages, and it is not at all obvious how to add -support for mutable variables 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.

- -

- - -

Full Code Listing

- - -

- -

-Here is the complete code listing for our running example, enhanced with the -if/then/else and for expressions.. To build this example, use: -

- -

-   # Compile
-   g++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy
-   # Run
-   ./toy
-

- -

Here is the code:

- -

-#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;
-}
-

- -Next: Extending the language: mutable variables / SSA construction -

- - -

- - Chris Lattner
- The LLVM Compiler Infrastructure
- Last modified: $Date$ -

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