1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
2 "http://www.w3.org/TR/html4/strict.dtd">
6 <title>Kaleidoscope: Extending the Language: User-defined Operators</title>
7 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
8 <meta name="author" content="Chris Lattner">
9 <link rel="stylesheet" href="../llvm.css" type="text/css">
14 <div class="doc_title">Kaleidoscope: Extending the Language: User-defined Operators</div>
17 <li><a href="index.html">Up to Tutorial Index</a></li>
20 <li><a href="#intro">Chapter 6 Introduction</a></li>
21 <li><a href="#idea">User-defined Operators: the Idea</a></li>
22 <li><a href="#binary">User-defined Binary Operators</a></li>
23 <li><a href="#unary">User-defined Unary Operators</a></li>
24 <li><a href="#example">Kicking the Tires</a></li>
25 <li><a href="#code">Full Code Listing</a></li>
28 <li><a href="LangImpl7.html">Chapter 7</a>: Extending the Language: Mutable
29 Variables / SSA Construction</li>
32 <div class="doc_author">
33 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></p>
36 <!-- *********************************************************************** -->
37 <div class="doc_section"><a name="intro">Chapter 6 Introduction</a></div>
38 <!-- *********************************************************************** -->
40 <div class="doc_text">
42 <p>Welcome to Chapter 6 of the "<a href="index.html">Implementing a language
43 with LLVM</a>" tutorial. At this point in our tutorial, we now have a fully
44 functional language that is fairly minimal, but also useful. There
45 is still one big problem with it, however. Our language doesn't have many
46 useful operators (like division, logical negation, or even any comparisons
47 besides less-than).</p>
49 <p>This chapter of the tutorial takes a wild digression into adding user-defined
50 operators to the simple and beautiful Kaleidoscope language. This digression now gives
51 us a simple and ugly language in some ways, but also a powerful one at the same time.
52 One of the great things about creating your own language is that you get to
53 decide what is good or bad. In this tutorial we'll assume that it is okay to
54 use this as a way to show some interesting parsing techniques.</p>
56 <p>At the end of this tutorial, we'll run through an example Kaleidoscope
57 application that <a href="#example">renders the Mandelbrot set</a>. This gives
58 an example of what you can build with Kaleidoscope and its feature set.</p>
62 <!-- *********************************************************************** -->
63 <div class="doc_section"><a name="idea">User-defined Operators: the Idea</a></div>
64 <!-- *********************************************************************** -->
66 <div class="doc_text">
69 The "operator overloading" that we will add to Kaleidoscope is more general than
70 languages like C++. In C++, you are only allowed to redefine existing
71 operators: you can't programatically change the grammar, introduce new
72 operators, change precedence levels, etc. In this chapter, we will add this
73 capability to Kaleidoscope, which will let the user round out the set of
74 operators that are supported.</p>
76 <p>The point of going into user-defined operators in a tutorial like this is to
77 show the power and flexibility of using a hand-written parser. Thus far, the parser
78 we have been implementing uses recursive descent for most parts of the grammar and
79 operator precedence parsing for the expressions. See <a
80 href="LangImpl2.html">Chapter 2</a> for details. Without using operator
81 precedence parsing, it would be very difficult to allow the programmer to
82 introduce new operators into the grammar: the grammar is dynamically extensible
85 <p>The two specific features we'll add are programmable unary operators (right
86 now, Kaleidoscope has no unary operators at all) as well as binary operators.
87 An example of this is:</p>
89 <div class="doc_code">
98 # Define > with the same precedence as <.
99 def binary> 10 (LHS RHS)
102 # Binary "logical or", (note that it does not "short circuit")
103 def binary| 5 (LHS RHS)
111 # Define = with slightly lower precedence than relationals.
112 def binary= 9 (LHS RHS)
113 !(LHS < RHS | LHS > RHS);
117 <p>Many languages aspire to being able to implement their standard runtime
118 library in the language itself. In Kaleidoscope, we can implement significant
119 parts of the language in the library!</p>
121 <p>We will break down implementation of these features into two parts:
122 implementing support for user-defined binary operators and adding unary
127 <!-- *********************************************************************** -->
128 <div class="doc_section"><a name="binary">User-defined Binary Operators</a></div>
129 <!-- *********************************************************************** -->
131 <div class="doc_text">
133 <p>Adding support for user-defined binary operators is pretty simple with our
134 current framework. We'll first add support for the unary/binary keywords:</p>
136 <div class="doc_code">
141 tok_binary = -11, tok_unary = -12</b>
144 static int gettok() {
146 if (IdentifierStr == "for") return tok_for;
147 if (IdentifierStr == "in") return tok_in;
148 <b>if (IdentifierStr == "binary") return tok_binary;
149 if (IdentifierStr == "unary") return tok_unary;</b>
150 return tok_identifier;
154 <p>This just adds lexer support for the unary and binary keywords, like we
155 did in <a href="LangImpl5.html#iflexer">previous chapters</a>. One nice thing
156 about our current AST, is that we represent binary operators with full generalisation
157 by using their ASCII code as the opcode. For our extended operators, we'll use this
158 same representation, so we don't need any new AST or parser support.</p>
160 <p>On the other hand, we have to be able to represent the definitions of these
161 new operators, in the "def binary| 5" part of the function definition. In our
162 grammar so far, the "name" for the function definition is parsed as the
163 "prototype" production and into the <tt>PrototypeAST</tt> AST node. To
164 represent our new user-defined operators as prototypes, we have to extend
165 the <tt>PrototypeAST</tt> AST node like this:</p>
167 <div class="doc_code">
169 /// PrototypeAST - This class represents the "prototype" for a function,
170 /// which captures its argument names as well as if it is an operator.
173 std::vector<std::string> Args;
175 unsigned Precedence; // Precedence if a binary op.</b>
177 PrototypeAST(const std::string &name, const std::vector<std::string> &args,
178 <b>bool isoperator = false, unsigned prec = 0</b>)
179 : Name(name), Args(args), <b>isOperator(isoperator), Precedence(prec)</b> {}
181 <b>bool isUnaryOp() const { return isOperator && Args.size() == 1; }
182 bool isBinaryOp() const { return isOperator && Args.size() == 2; }
184 char getOperatorName() const {
185 assert(isUnaryOp() || isBinaryOp());
186 return Name[Name.size()-1];
189 unsigned getBinaryPrecedence() const { return Precedence; }</b>
196 <p>Basically, in addition to knowing a name for the prototype, we now keep track
197 of whether it was an operator, and if it was, what precedence level the operator
198 is at. The precedence is only used for binary operators (as you'll see below,
199 it just doesn't apply for unary operators). Now that we have a way to represent
200 the prototype for a user-defined operator, we need to parse it:</p>
202 <div class="doc_code">
205 /// ::= id '(' id* ')'
206 <b>/// ::= binary LETTER number? (id, id)</b>
207 static PrototypeAST *ParsePrototype() {
210 <b>unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
211 unsigned BinaryPrecedence = 30;</b>
215 return ErrorP("Expected function name in prototype");
217 FnName = IdentifierStr;
223 if (!isascii(CurTok))
224 return ErrorP("Expected binary operator");
226 FnName += (char)CurTok;
230 // Read the precedence if present.
231 if (CurTok == tok_number) {
232 if (NumVal < 1 || NumVal > 100)
233 return ErrorP("Invalid precedecnce: must be 1..100");
234 BinaryPrecedence = (unsigned)NumVal;
241 return ErrorP("Expected '(' in prototype");
243 std::vector<std::string> ArgNames;
244 while (getNextToken() == tok_identifier)
245 ArgNames.push_back(IdentifierStr);
247 return ErrorP("Expected ')' in prototype");
250 getNextToken(); // eat ')'.
252 <b>// Verify right number of names for operator.
253 if (Kind && ArgNames.size() != Kind)
254 return ErrorP("Invalid number of operands for operator");
256 return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);</b>
261 <p>This is all fairly straightforward parsing code, and we have already seen
262 a lot of similar code in the past. One interesting part about the code above is
263 the couple lines that set up <tt>FnName</tt> for binary operators. This builds names
264 like "binary@" for a newly defined "@" operator. This then takes advantage of the
265 fact that symbol names in the LLVM symbol table are allowed to have any character in
266 them, including embedded nul characters.</p>
268 <p>The next interesting thing to add, is codegen support for these binary operators.
269 Given our current structure, this is a simple addition of a default case for our
270 existing binary operator node:</p>
272 <div class="doc_code">
274 Value *BinaryExprAST::Codegen() {
275 Value *L = LHS->Codegen();
276 Value *R = RHS->Codegen();
277 if (L == 0 || R == 0) return 0;
280 case '+': return Builder.CreateAdd(L, R, "addtmp");
281 case '-': return Builder.CreateSub(L, R, "subtmp");
282 case '*': return Builder.CreateMul(L, R, "multmp");
284 L = Builder.CreateFCmpULT(L, R, "cmptmp");
285 // Convert bool 0/1 to double 0.0 or 1.0
286 return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
288 <b>default: break;</b>
291 <b>// If it wasn't a builtin binary operator, it must be a user defined one. Emit
293 Function *F = TheModule->getFunction(std::string("binary")+Op);
294 assert(F && "binary operator not found!");
296 Value *Ops[] = { L, R };
297 return Builder.CreateCall(F, Ops, Ops+2, "binop");</b>
303 <p>As you can see above, the new code is actually really simple. It just does
304 a lookup for the appropriate operator in the symbol table and generates a
305 function call to it. Since user-defined operators are just built as normal
306 functions (because the "prototype" boils down to a function with the right
307 name) everything falls into place.</p>
309 <p>The final piece of code we are missing, is a bit of top-level magic:</p>
311 <div class="doc_code">
313 Function *FunctionAST::Codegen() {
316 Function *TheFunction = Proto->Codegen();
317 if (TheFunction == 0)
320 <b>// If this is an operator, install it.
321 if (Proto->isBinaryOp())
322 BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();</b>
324 // Create a new basic block to start insertion into.
325 BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
326 Builder.SetInsertPoint(BB);
328 if (Value *RetVal = Body->Codegen()) {
333 <p>Basically, before codegening a function, if it is a user-defined operator, we
334 register it in the precedence table. This allows the binary operator parsing
335 logic we already have in place to handle it. Since we are working on a fully-general operator precedence parser, this is all we need to do to "extend the grammar".</p>
337 <p>Now we have useful user-defined binary operators. This builds a lot
338 on the previous framework we built for other operators. Adding unary operators
339 is a bit more challenging, because we don't have any framework for it yet - lets
340 see what it takes.</p>
344 <!-- *********************************************************************** -->
345 <div class="doc_section"><a name="unary">User-defined Unary Operators</a></div>
346 <!-- *********************************************************************** -->
348 <div class="doc_text">
350 <p>Since we don't currently support unary operators in the Kaleidoscope
351 language, we'll need to add everything to support them. Above, we added simple
352 support for the 'unary' keyword to the lexer. In addition to that, we need an
355 <div class="doc_code">
357 /// UnaryExprAST - Expression class for a unary operator.
358 class UnaryExprAST : public ExprAST {
362 UnaryExprAST(char opcode, ExprAST *operand)
363 : Opcode(opcode), Operand(operand) {}
364 virtual Value *Codegen();
369 <p>This AST node is very simple and obvious by now. It directly mirrors the
370 binary operator AST node, except that it only has one child. With this, we
371 need to add the parsing logic. Parsing a unary operator is pretty simple: we'll
372 add a new function to do it:</p>
374 <div class="doc_code">
379 static ExprAST *ParseUnary() {
380 // If the current token is not an operator, it must be a primary expr.
381 if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
382 return ParsePrimary();
384 // If this is a unary operator, read it.
387 if (ExprAST *Operand = ParseUnary())
388 return new UnaryExprAST(Opc, Operand);
394 <p>The grammar we add is pretty straightforward here. If we see a unary
395 operator when parsing a primary operator, we eat the operator as a prefix and
396 parse the remaining piece as another unary operator. This allows us to handle
397 multiple unary operators (e.g. "!!x"). Note that unary operators can't have
398 ambiguous parses like binary operators can, so there is no need for precedence
401 <p>The problem with this function, is that we need to call ParseUnary from somewhere.
402 To do this, we change previous callers of ParsePrimary to call ParseUnary
405 <div class="doc_code">
409 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
411 <b>// Parse the unary expression after the binary operator.
412 ExprAST *RHS = ParseUnary();
413 if (!RHS) return 0;</b>
417 /// ::= unary binoprhs
419 static ExprAST *ParseExpression() {
420 <b>ExprAST *LHS = ParseUnary();</b>
423 return ParseBinOpRHS(0, LHS);
428 <p>With these two simple changes, we are now able to parse unary operators and build the
429 AST for them. Next up, we need to add parser support for prototypes, to parse
430 the unary operator prototype. We extend the binary operator code above
433 <div class="doc_code">
436 /// ::= id '(' id* ')'
437 /// ::= binary LETTER number? (id, id)
438 <b>/// ::= unary LETTER (id)</b>
439 static PrototypeAST *ParsePrototype() {
442 unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
443 unsigned BinaryPrecedence = 30;
447 return ErrorP("Expected function name in prototype");
449 FnName = IdentifierStr;
455 if (!isascii(CurTok))
456 return ErrorP("Expected unary operator");
458 FnName += (char)CurTok;
467 <p>As with binary operators, we name unary operators with a name that includes
468 the operator character. This assists us at code generation time. Speaking of,
469 the final piece we need to add is codegen support for unary operators. It looks
472 <div class="doc_code">
474 Value *UnaryExprAST::Codegen() {
475 Value *OperandV = Operand->Codegen();
476 if (OperandV == 0) return 0;
478 Function *F = TheModule->getFunction(std::string("unary")+Opcode);
480 return ErrorV("Unknown unary operator");
482 return Builder.CreateCall(F, OperandV, "unop");
487 <p>This code is similar to, but simpler than, the code for binary operators. It
488 is simpler primarily because it doesn't need to handle any predefined operators.
493 <!-- *********************************************************************** -->
494 <div class="doc_section"><a name="example">Kicking the Tires</a></div>
495 <!-- *********************************************************************** -->
497 <div class="doc_text">
499 <p>It is somewhat hard to believe, but with a few simple extensions we've
500 covered in the last chapters, we have grown a real-ish language. With this, we
501 can do a lot of interesting things, including I/O, math, and a bunch of other
502 things. For example, we can now add a nice sequencing operator (printd is
503 defined to print out the specified value and a newline):</p>
505 <div class="doc_code">
507 ready> <b>extern printd(x);</b>
508 Read extern: declare double @printd(double)
509 ready> <b>def binary : 1 (x y) 0; # Low-precedence operator that ignores operands.</b>
511 ready> <b>printd(123) : printd(456) : printd(789);</b>
515 Evaluated to 0.000000
519 <p>We can also define a bunch of other "primitive" operations, such as:</p>
521 <div class="doc_code">
534 # Define > with the same precedence as >.
535 def binary> 10 (LHS RHS)
538 # Binary logical or, which does not short circuit.
539 def binary| 5 (LHS RHS)
547 # Binary logical and, which does not short circuit.
548 def binary& 6 (LHS RHS)
554 # Define = with slightly lower precedence than relationals.
555 def binary = 9 (LHS RHS)
556 !(LHS < RHS | LHS > RHS);
562 <p>Given the previous if/then/else support, we can also define interesting
563 functions for I/O. For example, the following prints out a character whose
564 "density" reflects the value passed in: the lower the value, the denser the
567 <div class="doc_code">
571 extern putchard(char)
575 else if d > 4 then
577 else if d > 2 then
580 putchard(42); # '*'</b>
582 ready> <b>printdensity(1): printdensity(2): printdensity(3) :
583 printdensity(4): printdensity(5): printdensity(9): putchard(10);</b>
585 Evaluated to 0.000000
589 <p>Based on these simple primitive operations, we can start to define more
590 interesting things. For example, here's a little function that solves for the
591 number of iterations it takes a function in the complex plane to
594 <div class="doc_code">
596 # determine whether the specific location diverges.
597 # Solve for z = z^2 + c in the complex plane.
598 def mandleconverger(real imag iters creal cimag)
599 if iters > 255 | (real*real + imag*imag > 4) then
602 mandleconverger(real*real - imag*imag + creal,
604 iters+1, creal, cimag);
606 # return the number of iterations required for the iteration to escape
607 def mandleconverge(real imag)
608 mandleconverger(real, imag, 0, real, imag);
612 <p>This "z = z<sup>2</sup> + c" function is a beautiful little creature that is the basis
613 for computation of the <a
614 href="http://en.wikipedia.org/wiki/Mandelbrot_set">Mandelbrot Set</a>. Our
615 <tt>mandelconverge</tt> function returns the number of iterations that it takes
616 for a complex orbit to escape, saturating to 255. This is not a very useful
617 function by itself, but if you plot its value over a two-dimensional plane,
618 you can see the Mandelbrot set. Given that we are limited to using putchard
619 here, our amazing graphical output is limited, but we can whip together
620 something using the density plotter above:</p>
622 <div class="doc_code">
624 # compute and plot the mandlebrot set with the specified 2 dimensional range
626 def mandelhelp(xmin xmax xstep ymin ymax ystep)
627 for y = ymin, y < ymax, ystep in (
628 (for x = xmin, x < xmax, xstep in
629 printdensity(mandleconverge(x,y)))
633 # mandel - This is a convenient helper function for ploting the mandelbrot set
634 # from the specified position with the specified Magnification.
635 def mandel(realstart imagstart realmag imagmag)
636 mandelhelp(realstart, realstart+realmag*78, realmag,
637 imagstart, imagstart+imagmag*40, imagmag);
641 <p>Given this, we can try plotting out the mandlebrot set! Lets try it out:</p>
643 <div class="doc_code">
645 ready> <b>mandel(-2.3, -1.3, 0.05, 0.07);</b>
646 *******************************+++++++++++*************************************
647 *************************+++++++++++++++++++++++*******************************
648 **********************+++++++++++++++++++++++++++++****************************
649 *******************+++++++++++++++++++++.. ...++++++++*************************
650 *****************++++++++++++++++++++++.... ...+++++++++***********************
651 ***************+++++++++++++++++++++++..... ...+++++++++*********************
652 **************+++++++++++++++++++++++.... ....+++++++++********************
653 *************++++++++++++++++++++++...... .....++++++++*******************
654 ************+++++++++++++++++++++....... .......+++++++******************
655 ***********+++++++++++++++++++.... ... .+++++++*****************
656 **********+++++++++++++++++....... .+++++++****************
657 *********++++++++++++++........... ...+++++++***************
658 ********++++++++++++............ ...++++++++**************
659 ********++++++++++... .......... .++++++++**************
660 *******+++++++++..... .+++++++++*************
661 *******++++++++...... ..+++++++++*************
662 *******++++++....... ..+++++++++*************
663 *******+++++...... ..+++++++++*************
664 *******.... .... ...+++++++++*************
665 *******.... . ...+++++++++*************
666 *******+++++...... ...+++++++++*************
667 *******++++++....... ..+++++++++*************
668 *******++++++++...... .+++++++++*************
669 *******+++++++++..... ..+++++++++*************
670 ********++++++++++... .......... .++++++++**************
671 ********++++++++++++............ ...++++++++**************
672 *********++++++++++++++.......... ...+++++++***************
673 **********++++++++++++++++........ .+++++++****************
674 **********++++++++++++++++++++.... ... ..+++++++****************
675 ***********++++++++++++++++++++++....... .......++++++++*****************
676 ************+++++++++++++++++++++++...... ......++++++++******************
677 **************+++++++++++++++++++++++.... ....++++++++********************
678 ***************+++++++++++++++++++++++..... ...+++++++++*********************
679 *****************++++++++++++++++++++++.... ...++++++++***********************
680 *******************+++++++++++++++++++++......++++++++*************************
681 *********************++++++++++++++++++++++.++++++++***************************
682 *************************+++++++++++++++++++++++*******************************
683 ******************************+++++++++++++************************************
684 *******************************************************************************
685 *******************************************************************************
686 *******************************************************************************
687 Evaluated to 0.000000
688 ready> <b>mandel(-2, -1, 0.02, 0.04);</b>
689 **************************+++++++++++++++++++++++++++++++++++++++++++++++++++++
690 ***********************++++++++++++++++++++++++++++++++++++++++++++++++++++++++
691 *********************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++.
692 *******************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++...
693 *****************+++++++++++++++++++++++++++++++++++++++++++++++++++++++++.....
694 ***************++++++++++++++++++++++++++++++++++++++++++++++++++++++++........
695 **************++++++++++++++++++++++++++++++++++++++++++++++++++++++...........
696 ************+++++++++++++++++++++++++++++++++++++++++++++++++++++..............
697 ***********++++++++++++++++++++++++++++++++++++++++++++++++++........ .
698 **********++++++++++++++++++++++++++++++++++++++++++++++.............
699 ********+++++++++++++++++++++++++++++++++++++++++++..................
700 *******+++++++++++++++++++++++++++++++++++++++.......................
701 ******+++++++++++++++++++++++++++++++++++...........................
702 *****++++++++++++++++++++++++++++++++............................
703 *****++++++++++++++++++++++++++++...............................
704 ****++++++++++++++++++++++++++...... .........................
705 ***++++++++++++++++++++++++......... ...... ...........
706 ***++++++++++++++++++++++............
707 **+++++++++++++++++++++..............
708 **+++++++++++++++++++................
709 *++++++++++++++++++.................
710 *++++++++++++++++............ ...
711 *++++++++++++++..............
712 *+++....++++................
713 *.......... ...........
715 *.......... ...........
716 *+++....++++................
717 *++++++++++++++..............
718 *++++++++++++++++............ ...
719 *++++++++++++++++++.................
720 **+++++++++++++++++++................
721 **+++++++++++++++++++++..............
722 ***++++++++++++++++++++++............
723 ***++++++++++++++++++++++++......... ...... ...........
724 ****++++++++++++++++++++++++++...... .........................
725 *****++++++++++++++++++++++++++++...............................
726 *****++++++++++++++++++++++++++++++++............................
727 ******+++++++++++++++++++++++++++++++++++...........................
728 *******+++++++++++++++++++++++++++++++++++++++.......................
729 ********+++++++++++++++++++++++++++++++++++++++++++..................
730 Evaluated to 0.000000
731 ready> <b>mandel(-0.9, -1.4, 0.02, 0.03);</b>
732 *******************************************************************************
733 *******************************************************************************
734 *******************************************************************************
735 **********+++++++++++++++++++++************************************************
736 *+++++++++++++++++++++++++++++++++++++++***************************************
737 +++++++++++++++++++++++++++++++++++++++++++++**********************************
738 ++++++++++++++++++++++++++++++++++++++++++++++++++*****************************
739 ++++++++++++++++++++++++++++++++++++++++++++++++++++++*************************
740 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++**********************
741 +++++++++++++++++++++++++++++++++.........++++++++++++++++++*******************
742 +++++++++++++++++++++++++++++++.... ......+++++++++++++++++++****************
743 +++++++++++++++++++++++++++++....... ........+++++++++++++++++++**************
744 ++++++++++++++++++++++++++++........ ........++++++++++++++++++++************
745 +++++++++++++++++++++++++++......... .. ...+++++++++++++++++++++**********
746 ++++++++++++++++++++++++++........... ....++++++++++++++++++++++********
747 ++++++++++++++++++++++++............. .......++++++++++++++++++++++******
748 +++++++++++++++++++++++............. ........+++++++++++++++++++++++****
749 ++++++++++++++++++++++........... ..........++++++++++++++++++++++***
750 ++++++++++++++++++++........... .........++++++++++++++++++++++*
751 ++++++++++++++++++............ ...........++++++++++++++++++++
752 ++++++++++++++++............... .............++++++++++++++++++
753 ++++++++++++++................. ...............++++++++++++++++
754 ++++++++++++.................. .................++++++++++++++
755 +++++++++.................. .................+++++++++++++
756 ++++++........ . ......... ..++++++++++++
757 ++............ ...... ....++++++++++
758 .............. ...++++++++++
759 .............. ....+++++++++
760 .............. .....++++++++
761 ............. ......++++++++
762 ........... .......++++++++
763 ......... ........+++++++
764 ......... ........+++++++
765 ......... ....+++++++
773 Evaluated to 0.000000
778 <p>At this point, you may be starting to realize that Kaleidoscope is a real
779 and powerful language. It may not be self-similar :), but it can be used to
780 plot things that are!</p>
782 <p>With this, we conclude the "adding user-defined operators" chapter of the
783 tutorial. We have successfully augmented our language, adding the ability to extend the
784 language in the library, and we have shown how this can be used to build a simple but
785 interesting end-user application in Kaleidoscope. At this point, Kaleidoscope
786 can build a variety of applications that are functional and can call functions
787 with side-effects, but it can't actually define and mutate a variable itself.
790 <p>Strikingly, variable mutation is an important feature of some
791 languages, and it is not at all obvious how to <a href="LangImpl7.html">add
792 support for mutable variables</a> without having to add an "SSA construction"
793 phase to your front-end. In the next chapter, we will describe how you can
794 add variable mutation without building SSA in your front-end.</p>
798 <!-- *********************************************************************** -->
799 <div class="doc_section"><a name="code">Full Code Listing</a></div>
800 <!-- *********************************************************************** -->
802 <div class="doc_text">
805 Here is the complete code listing for our running example, enhanced with the
806 if/then/else and for expressions.. To build this example, use:
809 <div class="doc_code">
812 g++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy
818 <p>Here is the code:</p>
820 <div class="doc_code">
822 #include "llvm/DerivedTypes.h"
823 #include "llvm/ExecutionEngine/ExecutionEngine.h"
824 #include "llvm/ExecutionEngine/Interpreter.h"
825 #include "llvm/ExecutionEngine/JIT.h"
826 #include "llvm/LLVMContext.h"
827 #include "llvm/Module.h"
828 #include "llvm/ModuleProvider.h"
829 #include "llvm/PassManager.h"
830 #include "llvm/Analysis/Verifier.h"
831 #include "llvm/Target/TargetData.h"
832 #include "llvm/Target/TargetSelect.h"
833 #include "llvm/Transforms/Scalar.h"
834 #include "llvm/Support/IRBuilder.h"
835 #include <cstdio>
836 #include <string>
838 #include <vector>
839 using namespace llvm;
841 //===----------------------------------------------------------------------===//
843 //===----------------------------------------------------------------------===//
845 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
846 // of these for known things.
851 tok_def = -2, tok_extern = -3,
854 tok_identifier = -4, tok_number = -5,
857 tok_if = -6, tok_then = -7, tok_else = -8,
858 tok_for = -9, tok_in = -10,
861 tok_binary = -11, tok_unary = -12
864 static std::string IdentifierStr; // Filled in if tok_identifier
865 static double NumVal; // Filled in if tok_number
867 /// gettok - Return the next token from standard input.
868 static int gettok() {
869 static int LastChar = ' ';
871 // Skip any whitespace.
872 while (isspace(LastChar))
873 LastChar = getchar();
875 if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
876 IdentifierStr = LastChar;
877 while (isalnum((LastChar = getchar())))
878 IdentifierStr += LastChar;
880 if (IdentifierStr == "def") return tok_def;
881 if (IdentifierStr == "extern") return tok_extern;
882 if (IdentifierStr == "if") return tok_if;
883 if (IdentifierStr == "then") return tok_then;
884 if (IdentifierStr == "else") return tok_else;
885 if (IdentifierStr == "for") return tok_for;
886 if (IdentifierStr == "in") return tok_in;
887 if (IdentifierStr == "binary") return tok_binary;
888 if (IdentifierStr == "unary") return tok_unary;
889 return tok_identifier;
892 if (isdigit(LastChar) || LastChar == '.') { // Number: [0-9.]+
896 LastChar = getchar();
897 } while (isdigit(LastChar) || LastChar == '.');
899 NumVal = strtod(NumStr.c_str(), 0);
903 if (LastChar == '#') {
904 // Comment until end of line.
905 do LastChar = getchar();
906 while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
912 // Check for end of file. Don't eat the EOF.
916 // Otherwise, just return the character as its ascii value.
917 int ThisChar = LastChar;
918 LastChar = getchar();
922 //===----------------------------------------------------------------------===//
923 // Abstract Syntax Tree (aka Parse Tree)
924 //===----------------------------------------------------------------------===//
926 /// ExprAST - Base class for all expression nodes.
929 virtual ~ExprAST() {}
930 virtual Value *Codegen() = 0;
933 /// NumberExprAST - Expression class for numeric literals like "1.0".
934 class NumberExprAST : public ExprAST {
937 NumberExprAST(double val) : Val(val) {}
938 virtual Value *Codegen();
941 /// VariableExprAST - Expression class for referencing a variable, like "a".
942 class VariableExprAST : public ExprAST {
945 VariableExprAST(const std::string &name) : Name(name) {}
946 virtual Value *Codegen();
949 /// UnaryExprAST - Expression class for a unary operator.
950 class UnaryExprAST : public ExprAST {
954 UnaryExprAST(char opcode, ExprAST *operand)
955 : Opcode(opcode), Operand(operand) {}
956 virtual Value *Codegen();
959 /// BinaryExprAST - Expression class for a binary operator.
960 class BinaryExprAST : public ExprAST {
964 BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
965 : Op(op), LHS(lhs), RHS(rhs) {}
966 virtual Value *Codegen();
969 /// CallExprAST - Expression class for function calls.
970 class CallExprAST : public ExprAST {
972 std::vector<ExprAST*> Args;
974 CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
975 : Callee(callee), Args(args) {}
976 virtual Value *Codegen();
979 /// IfExprAST - Expression class for if/then/else.
980 class IfExprAST : public ExprAST {
981 ExprAST *Cond, *Then, *Else;
983 IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
984 : Cond(cond), Then(then), Else(_else) {}
985 virtual Value *Codegen();
988 /// ForExprAST - Expression class for for/in.
989 class ForExprAST : public ExprAST {
991 ExprAST *Start, *End, *Step, *Body;
993 ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
994 ExprAST *step, ExprAST *body)
995 : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
996 virtual Value *Codegen();
999 /// PrototypeAST - This class represents the "prototype" for a function,
1000 /// which captures its name, and its argument names (thus implicitly the number
1001 /// of arguments the function takes), as well as if it is an operator.
1002 class PrototypeAST {
1004 std::vector<std::string> Args;
1006 unsigned Precedence; // Precedence if a binary op.
1008 PrototypeAST(const std::string &name, const std::vector<std::string> &args,
1009 bool isoperator = false, unsigned prec = 0)
1010 : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
1012 bool isUnaryOp() const { return isOperator && Args.size() == 1; }
1013 bool isBinaryOp() const { return isOperator && Args.size() == 2; }
1015 char getOperatorName() const {
1016 assert(isUnaryOp() || isBinaryOp());
1017 return Name[Name.size()-1];
1020 unsigned getBinaryPrecedence() const { return Precedence; }
1022 Function *Codegen();
1025 /// FunctionAST - This class represents a function definition itself.
1027 PrototypeAST *Proto;
1030 FunctionAST(PrototypeAST *proto, ExprAST *body)
1031 : Proto(proto), Body(body) {}
1033 Function *Codegen();
1036 //===----------------------------------------------------------------------===//
1038 //===----------------------------------------------------------------------===//
1040 /// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
1041 /// token the parser is looking at. getNextToken reads another token from the
1042 /// lexer and updates CurTok with its results.
1044 static int getNextToken() {
1045 return CurTok = gettok();
1048 /// BinopPrecedence - This holds the precedence for each binary operator that is
1050 static std::map<char, int> BinopPrecedence;
1052 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
1053 static int GetTokPrecedence() {
1054 if (!isascii(CurTok))
1057 // Make sure it's a declared binop.
1058 int TokPrec = BinopPrecedence[CurTok];
1059 if (TokPrec <= 0) return -1;
1063 /// Error* - These are little helper functions for error handling.
1064 ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
1065 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
1066 FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
1068 static ExprAST *ParseExpression();
1072 /// ::= identifier '(' expression* ')'
1073 static ExprAST *ParseIdentifierExpr() {
1074 std::string IdName = IdentifierStr;
1076 getNextToken(); // eat identifier.
1078 if (CurTok != '(') // Simple variable ref.
1079 return new VariableExprAST(IdName);
1082 getNextToken(); // eat (
1083 std::vector<ExprAST*> Args;
1084 if (CurTok != ')') {
1086 ExprAST *Arg = ParseExpression();
1088 Args.push_back(Arg);
1090 if (CurTok == ')') break;
1093 return Error("Expected ')' or ',' in argument list");
1101 return new CallExprAST(IdName, Args);
1104 /// numberexpr ::= number
1105 static ExprAST *ParseNumberExpr() {
1106 ExprAST *Result = new NumberExprAST(NumVal);
1107 getNextToken(); // consume the number
1111 /// parenexpr ::= '(' expression ')'
1112 static ExprAST *ParseParenExpr() {
1113 getNextToken(); // eat (.
1114 ExprAST *V = ParseExpression();
1118 return Error("expected ')'");
1119 getNextToken(); // eat ).
1123 /// ifexpr ::= 'if' expression 'then' expression 'else' expression
1124 static ExprAST *ParseIfExpr() {
1125 getNextToken(); // eat the if.
1128 ExprAST *Cond = ParseExpression();
1129 if (!Cond) return 0;
1131 if (CurTok != tok_then)
1132 return Error("expected then");
1133 getNextToken(); // eat the then
1135 ExprAST *Then = ParseExpression();
1136 if (Then == 0) return 0;
1138 if (CurTok != tok_else)
1139 return Error("expected else");
1143 ExprAST *Else = ParseExpression();
1144 if (!Else) return 0;
1146 return new IfExprAST(Cond, Then, Else);
1149 /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
1150 static ExprAST *ParseForExpr() {
1151 getNextToken(); // eat the for.
1153 if (CurTok != tok_identifier)
1154 return Error("expected identifier after for");
1156 std::string IdName = IdentifierStr;
1157 getNextToken(); // eat identifier.
1160 return Error("expected '=' after for");
1161 getNextToken(); // eat '='.
1164 ExprAST *Start = ParseExpression();
1165 if (Start == 0) return 0;
1167 return Error("expected ',' after for start value");
1170 ExprAST *End = ParseExpression();
1171 if (End == 0) return 0;
1173 // The step value is optional.
1175 if (CurTok == ',') {
1177 Step = ParseExpression();
1178 if (Step == 0) return 0;
1181 if (CurTok != tok_in)
1182 return Error("expected 'in' after for");
1183 getNextToken(); // eat 'in'.
1185 ExprAST *Body = ParseExpression();
1186 if (Body == 0) return 0;
1188 return new ForExprAST(IdName, Start, End, Step, Body);
1192 /// ::= identifierexpr
1197 static ExprAST *ParsePrimary() {
1199 default: return Error("unknown token when expecting an expression");
1200 case tok_identifier: return ParseIdentifierExpr();
1201 case tok_number: return ParseNumberExpr();
1202 case '(': return ParseParenExpr();
1203 case tok_if: return ParseIfExpr();
1204 case tok_for: return ParseForExpr();
1211 static ExprAST *ParseUnary() {
1212 // If the current token is not an operator, it must be a primary expr.
1213 if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
1214 return ParsePrimary();
1216 // If this is a unary operator, read it.
1219 if (ExprAST *Operand = ParseUnary())
1220 return new UnaryExprAST(Opc, Operand);
1225 /// ::= ('+' unary)*
1226 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
1227 // If this is a binop, find its precedence.
1229 int TokPrec = GetTokPrecedence();
1231 // If this is a binop that binds at least as tightly as the current binop,
1232 // consume it, otherwise we are done.
1233 if (TokPrec < ExprPrec)
1236 // Okay, we know this is a binop.
1238 getNextToken(); // eat binop
1240 // Parse the unary expression after the binary operator.
1241 ExprAST *RHS = ParseUnary();
1244 // If BinOp binds less tightly with RHS than the operator after RHS, let
1245 // the pending operator take RHS as its LHS.
1246 int NextPrec = GetTokPrecedence();
1247 if (TokPrec < NextPrec) {
1248 RHS = ParseBinOpRHS(TokPrec+1, RHS);
1249 if (RHS == 0) return 0;
1253 LHS = new BinaryExprAST(BinOp, LHS, RHS);
1258 /// ::= unary binoprhs
1260 static ExprAST *ParseExpression() {
1261 ExprAST *LHS = ParseUnary();
1264 return ParseBinOpRHS(0, LHS);
1268 /// ::= id '(' id* ')'
1269 /// ::= binary LETTER number? (id, id)
1270 /// ::= unary LETTER (id)
1271 static PrototypeAST *ParsePrototype() {
1274 unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
1275 unsigned BinaryPrecedence = 30;
1279 return ErrorP("Expected function name in prototype");
1280 case tok_identifier:
1281 FnName = IdentifierStr;
1287 if (!isascii(CurTok))
1288 return ErrorP("Expected unary operator");
1290 FnName += (char)CurTok;
1296 if (!isascii(CurTok))
1297 return ErrorP("Expected binary operator");
1299 FnName += (char)CurTok;
1303 // Read the precedence if present.
1304 if (CurTok == tok_number) {
1305 if (NumVal < 1 || NumVal > 100)
1306 return ErrorP("Invalid precedecnce: must be 1..100");
1307 BinaryPrecedence = (unsigned)NumVal;
1314 return ErrorP("Expected '(' in prototype");
1316 std::vector<std::string> ArgNames;
1317 while (getNextToken() == tok_identifier)
1318 ArgNames.push_back(IdentifierStr);
1320 return ErrorP("Expected ')' in prototype");
1323 getNextToken(); // eat ')'.
1325 // Verify right number of names for operator.
1326 if (Kind && ArgNames.size() != Kind)
1327 return ErrorP("Invalid number of operands for operator");
1329 return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
1332 /// definition ::= 'def' prototype expression
1333 static FunctionAST *ParseDefinition() {
1334 getNextToken(); // eat def.
1335 PrototypeAST *Proto = ParsePrototype();
1336 if (Proto == 0) return 0;
1338 if (ExprAST *E = ParseExpression())
1339 return new FunctionAST(Proto, E);
1343 /// toplevelexpr ::= expression
1344 static FunctionAST *ParseTopLevelExpr() {
1345 if (ExprAST *E = ParseExpression()) {
1346 // Make an anonymous proto.
1347 PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
1348 return new FunctionAST(Proto, E);
1353 /// external ::= 'extern' prototype
1354 static PrototypeAST *ParseExtern() {
1355 getNextToken(); // eat extern.
1356 return ParsePrototype();
1359 //===----------------------------------------------------------------------===//
1361 //===----------------------------------------------------------------------===//
1363 static Module *TheModule;
1364 static IRBuilder<> Builder(getGlobalContext());
1365 static std::map<std::string, Value*> NamedValues;
1366 static FunctionPassManager *TheFPM;
1368 Value *ErrorV(const char *Str) { Error(Str); return 0; }
1370 Value *NumberExprAST::Codegen() {
1371 return ConstantFP::get(getGlobalContext(), APFloat(Val));
1374 Value *VariableExprAST::Codegen() {
1375 // Look this variable up in the function.
1376 Value *V = NamedValues[Name];
1377 return V ? V : ErrorV("Unknown variable name");
1380 Value *UnaryExprAST::Codegen() {
1381 Value *OperandV = Operand->Codegen();
1382 if (OperandV == 0) return 0;
1384 Function *F = TheModule->getFunction(std::string("unary")+Opcode);
1386 return ErrorV("Unknown unary operator");
1388 return Builder.CreateCall(F, OperandV, "unop");
1391 Value *BinaryExprAST::Codegen() {
1392 Value *L = LHS->Codegen();
1393 Value *R = RHS->Codegen();
1394 if (L == 0 || R == 0) return 0;
1397 case '+': return Builder.CreateAdd(L, R, "addtmp");
1398 case '-': return Builder.CreateSub(L, R, "subtmp");
1399 case '*': return Builder.CreateMul(L, R, "multmp");
1401 L = Builder.CreateFCmpULT(L, R, "cmptmp");
1402 // Convert bool 0/1 to double 0.0 or 1.0
1403 return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
1408 // If it wasn't a builtin binary operator, it must be a user defined one. Emit
1410 Function *F = TheModule->getFunction(std::string("binary")+Op);
1411 assert(F && "binary operator not found!");
1413 Value *Ops[] = { L, R };
1414 return Builder.CreateCall(F, Ops, Ops+2, "binop");
1417 Value *CallExprAST::Codegen() {
1418 // Look up the name in the global module table.
1419 Function *CalleeF = TheModule->getFunction(Callee);
1421 return ErrorV("Unknown function referenced");
1423 // If argument mismatch error.
1424 if (CalleeF->arg_size() != Args.size())
1425 return ErrorV("Incorrect # arguments passed");
1427 std::vector<Value*> ArgsV;
1428 for (unsigned i = 0, e = Args.size(); i != e; ++i) {
1429 ArgsV.push_back(Args[i]->Codegen());
1430 if (ArgsV.back() == 0) return 0;
1433 return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
1436 Value *IfExprAST::Codegen() {
1437 Value *CondV = Cond->Codegen();
1438 if (CondV == 0) return 0;
1440 // Convert condition to a bool by comparing equal to 0.0.
1441 CondV = Builder.CreateFCmpONE(CondV,
1442 ConstantFP::get(getGlobalContext(), APFloat(0.0)),
1445 Function *TheFunction = Builder.GetInsertBlock()->getParent();
1447 // Create blocks for the then and else cases. Insert the 'then' block at the
1448 // end of the function.
1449 BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
1450 BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
1451 BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
1453 Builder.CreateCondBr(CondV, ThenBB, ElseBB);
1456 Builder.SetInsertPoint(ThenBB);
1458 Value *ThenV = Then->Codegen();
1459 if (ThenV == 0) return 0;
1461 Builder.CreateBr(MergeBB);
1462 // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
1463 ThenBB = Builder.GetInsertBlock();
1466 TheFunction->getBasicBlockList().push_back(ElseBB);
1467 Builder.SetInsertPoint(ElseBB);
1469 Value *ElseV = Else->Codegen();
1470 if (ElseV == 0) return 0;
1472 Builder.CreateBr(MergeBB);
1473 // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
1474 ElseBB = Builder.GetInsertBlock();
1476 // Emit merge block.
1477 TheFunction->getBasicBlockList().push_back(MergeBB);
1478 Builder.SetInsertPoint(MergeBB);
1479 PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()),
1482 PN->addIncoming(ThenV, ThenBB);
1483 PN->addIncoming(ElseV, ElseBB);
1487 Value *ForExprAST::Codegen() {
1490 // start = startexpr
1493 // variable = phi [start, loopheader], [nextvariable, loopend]
1499 // nextvariable = variable + step
1500 // endcond = endexpr
1501 // br endcond, loop, endloop
1504 // Emit the start code first, without 'variable' in scope.
1505 Value *StartVal = Start->Codegen();
1506 if (StartVal == 0) return 0;
1508 // Make the new basic block for the loop header, inserting after current
1510 Function *TheFunction = Builder.GetInsertBlock()->getParent();
1511 BasicBlock *PreheaderBB = Builder.GetInsertBlock();
1512 BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
1514 // Insert an explicit fall through from the current block to the LoopBB.
1515 Builder.CreateBr(LoopBB);
1517 // Start insertion in LoopBB.
1518 Builder.SetInsertPoint(LoopBB);
1520 // Start the PHI node with an entry for Start.
1521 PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), VarName.c_str());
1522 Variable->addIncoming(StartVal, PreheaderBB);
1524 // Within the loop, the variable is defined equal to the PHI node. If it
1525 // shadows an existing variable, we have to restore it, so save it now.
1526 Value *OldVal = NamedValues[VarName];
1527 NamedValues[VarName] = Variable;
1529 // Emit the body of the loop. This, like any other expr, can change the
1530 // current BB. Note that we ignore the value computed by the body, but don't
1532 if (Body->Codegen() == 0)
1535 // Emit the step value.
1538 StepVal = Step->Codegen();
1539 if (StepVal == 0) return 0;
1541 // If not specified, use 1.0.
1542 StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
1545 Value *NextVar = Builder.CreateAdd(Variable, StepVal, "nextvar");
1547 // Compute the end condition.
1548 Value *EndCond = End->Codegen();
1549 if (EndCond == 0) return EndCond;
1551 // Convert condition to a bool by comparing equal to 0.0.
1552 EndCond = Builder.CreateFCmpONE(EndCond,
1553 ConstantFP::get(getGlobalContext(), APFloat(0.0)),
1556 // Create the "after loop" block and insert it.
1557 BasicBlock *LoopEndBB = Builder.GetInsertBlock();
1558 BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
1560 // Insert the conditional branch into the end of LoopEndBB.
1561 Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
1563 // Any new code will be inserted in AfterBB.
1564 Builder.SetInsertPoint(AfterBB);
1566 // Add a new entry to the PHI node for the backedge.
1567 Variable->addIncoming(NextVar, LoopEndBB);
1569 // Restore the unshadowed variable.
1571 NamedValues[VarName] = OldVal;
1573 NamedValues.erase(VarName);
1576 // for expr always returns 0.0.
1577 return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
1580 Function *PrototypeAST::Codegen() {
1581 // Make the function type: double(double,double) etc.
1582 std::vector<const Type*> Doubles(Args.size(),
1583 Type::getDoubleTy(getGlobalContext()));
1584 FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
1587 Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
1589 // If F conflicted, there was already something named 'Name'. If it has a
1590 // body, don't allow redefinition or reextern.
1591 if (F->getName() != Name) {
1592 // Delete the one we just made and get the existing one.
1593 F->eraseFromParent();
1594 F = TheModule->getFunction(Name);
1596 // If F already has a body, reject this.
1597 if (!F->empty()) {
1598 ErrorF("redefinition of function");
1602 // If F took a different number of args, reject.
1603 if (F->arg_size() != Args.size()) {
1604 ErrorF("redefinition of function with different # args");
1609 // Set names for all arguments.
1611 for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
1613 AI->setName(Args[Idx]);
1615 // Add arguments to variable symbol table.
1616 NamedValues[Args[Idx]] = AI;
1622 Function *FunctionAST::Codegen() {
1623 NamedValues.clear();
1625 Function *TheFunction = Proto->Codegen();
1626 if (TheFunction == 0)
1629 // If this is an operator, install it.
1630 if (Proto->isBinaryOp())
1631 BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
1633 // Create a new basic block to start insertion into.
1634 BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
1635 Builder.SetInsertPoint(BB);
1637 if (Value *RetVal = Body->Codegen()) {
1638 // Finish off the function.
1639 Builder.CreateRet(RetVal);
1641 // Validate the generated code, checking for consistency.
1642 verifyFunction(*TheFunction);
1644 // Optimize the function.
1645 TheFPM->run(*TheFunction);
1650 // Error reading body, remove function.
1651 TheFunction->eraseFromParent();
1653 if (Proto->isBinaryOp())
1654 BinopPrecedence.erase(Proto->getOperatorName());
1658 //===----------------------------------------------------------------------===//
1659 // Top-Level parsing and JIT Driver
1660 //===----------------------------------------------------------------------===//
1662 static ExecutionEngine *TheExecutionEngine;
1664 static void HandleDefinition() {
1665 if (FunctionAST *F = ParseDefinition()) {
1666 if (Function *LF = F->Codegen()) {
1667 fprintf(stderr, "Read function definition:");
1671 // Skip token for error recovery.
1676 static void HandleExtern() {
1677 if (PrototypeAST *P = ParseExtern()) {
1678 if (Function *F = P->Codegen()) {
1679 fprintf(stderr, "Read extern: ");
1683 // Skip token for error recovery.
1688 static void HandleTopLevelExpression() {
1689 // Evaluate a top-level expression into an anonymous function.
1690 if (FunctionAST *F = ParseTopLevelExpr()) {
1691 if (Function *LF = F->Codegen()) {
1692 // JIT the function, returning a function pointer.
1693 void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
1695 // Cast it to the right type (takes no arguments, returns a double) so we
1696 // can call it as a native function.
1697 double (*FP)() = (double (*)())(intptr_t)FPtr;
1698 fprintf(stderr, "Evaluated to %f\n", FP());
1701 // Skip token for error recovery.
1706 /// top ::= definition | external | expression | ';'
1707 static void MainLoop() {
1709 fprintf(stderr, "ready> ");
1711 case tok_eof: return;
1712 case ';': getNextToken(); break; // ignore top-level semicolons.
1713 case tok_def: HandleDefinition(); break;
1714 case tok_extern: HandleExtern(); break;
1715 default: HandleTopLevelExpression(); break;
1720 //===----------------------------------------------------------------------===//
1721 // "Library" functions that can be "extern'd" from user code.
1722 //===----------------------------------------------------------------------===//
1724 /// putchard - putchar that takes a double and returns 0.
1726 double putchard(double X) {
1731 /// printd - printf that takes a double prints it as "%f\n", returning 0.
1733 double printd(double X) {
1738 //===----------------------------------------------------------------------===//
1739 // Main driver code.
1740 //===----------------------------------------------------------------------===//
1743 InitializeNativeTarget();
1744 LLVMContext &Context = getGlobalContext();
1746 // Install standard binary operators.
1747 // 1 is lowest precedence.
1748 BinopPrecedence['<'] = 10;
1749 BinopPrecedence['+'] = 20;
1750 BinopPrecedence['-'] = 20;
1751 BinopPrecedence['*'] = 40; // highest.
1753 // Prime the first token.
1754 fprintf(stderr, "ready> ");
1757 // Make the module, which holds all the code.
1758 TheModule = new Module("my cool jit", Context);
1760 ExistingModuleProvider *OurModuleProvider =
1761 new ExistingModuleProvider(TheModule);
1763 // Create the JIT. This takes ownership of the module and module provider.
1764 TheExecutionEngine = EngineBuilder(OurModuleProvider).create();
1766 FunctionPassManager OurFPM(OurModuleProvider);
1768 // Set up the optimizer pipeline. Start with registering info about how the
1769 // target lays out data structures.
1770 OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData()));
1771 // Do simple "peephole" optimizations and bit-twiddling optzns.
1772 OurFPM.add(createInstructionCombiningPass());
1773 // Reassociate expressions.
1774 OurFPM.add(createReassociatePass());
1775 // Eliminate Common SubExpressions.
1776 OurFPM.add(createGVNPass());
1777 // Simplify the control flow graph (deleting unreachable blocks, etc).
1778 OurFPM.add(createCFGSimplificationPass());
1780 OurFPM.doInitialization();
1782 // Set the global so the code gen can use this.
1783 TheFPM = &OurFPM;
1785 // Run the main "interpreter loop" now.
1790 // Print out all of the generated code.
1791 TheModule->dump();
1798 <a href="LangImpl7.html">Next: Extending the language: mutable variables / SSA construction</a>
1801 <!-- *********************************************************************** -->
1804 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
1805 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
1806 <a href="http://validator.w3.org/check/referer"><img
1807 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!"></a>
1809 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1810 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
1811 Last modified: $Date: 2007-10-17 11:05:13 -0700 (Wed, 17 Oct 2007) $