--- /dev/null
+============================================================
+Kaleidoscope: Extending the Language: User-defined Operators
+============================================================
+
+.. contents::
+ :local:
+
+Written by `Chris Lattner <mailto:sabre@nondot.org>`_
+
+Chapter 6 Introduction
+======================
+
+Welcome to Chapter 6 of the "`Implementing a language with
+LLVM <index.html>`_" 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 <#example>`_. 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 <LangImpl2.html>`_ 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:
+
+.. code-block:: c++
+
+ 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 <LangImpl5.html#iflexer>`_. 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:
+
+.. code-block:: c++
+
+ /// 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:
+
+.. code-block:: c++
+
+ /// 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:
+
+.. code-block:: c++
+
+ Value *BinaryExprAST::Codegen() {
+ Value *L = LHS->Codegen();
+ Value *R = RHS->Codegen();
+ if (L == 0 || R == 0) return 0;
+
+ switch (Op) {
+ case '+': return Builder.CreateFAdd(L, R, "addtmp");
+ case '-': return Builder.CreateFSub(L, R, "subtmp");
+ case '*': return Builder.CreateFMul(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[2] = { L, R };
+ return Builder.CreateCall(F, Ops, "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:
+
+.. code-block:: c++
+
+ 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:
+
+.. code-block:: c++
+
+ /// 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:
+
+.. code-block:: c++
+
+ /// 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:
+
+.. code-block:: c++
+
+ /// 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:
+
+.. code-block:: c++
+
+ /// 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:
+
+.. code-block:: c++
+
+ 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);
+
+ # Define ':' for sequencing: as a low-precedence operator that ignores operands
+ # and just returns the RHS.
+ def binary : 1 (x y) y;
+
+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 <http://en.wikipedia.org/wiki/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 plotting 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 <LangImpl7.html>`_ 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:
+
+.. code-block:: bash
+
+ # Compile
+ clang++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy
+ # Run
+ ./toy
+
+On some platforms, you will need to specify -rdynamic or
+-Wl,--export-dynamic when linking. This ensures that symbols defined in
+the main executable are exported to the dynamic linker and so are
+available for symbol resolution at run time. This is not needed if you
+compile your support code into a shared library, although doing that
+will cause problems on Windows.
+
+Here is the code:
+
+.. code-block:: c++
+
+ #include "llvm/DerivedTypes.h"
+ #include "llvm/ExecutionEngine/ExecutionEngine.h"
+ #include "llvm/ExecutionEngine/JIT.h"
+ #include "llvm/IRBuilder.h"
+ #include "llvm/LLVMContext.h"
+ #include "llvm/Module.h"
+ #include "llvm/PassManager.h"
+ #include "llvm/Analysis/Verifier.h"
+ #include "llvm/Analysis/Passes.h"
+ #include "llvm/DataLayout.h"
+ #include "llvm/Transforms/Scalar.h"
+ #include "llvm/Support/TargetSelect.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.CreateFAdd(L, R, "addtmp");
+ case '-': return Builder.CreateFSub(L, R, "subtmp");
+ case '*': return Builder.CreateFMul(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[2] = { L, R };
+ return Builder.CreateCall(F, Ops, "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, "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()), 2,
+ "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()), 2, 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.CreateFAdd(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<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 DataLayout(*TheExecutionEngine->getDataLayout()));
+ // Provide basic AliasAnalysis support for GVN.
+ OurFPM.add(createBasicAliasAnalysisPass());
+ // 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 <LangImpl7.html>`_
+
projects / oota-llvm.git / blobdiff