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16 <ul>
19 <ol>
26 </ol>
27 </li>
29 Variables / SSA Construction</li>
30 </ul>
34 </div>
36 <!-- *********************************************************************** -->
38 <!-- *********************************************************************** -->
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
58 an example of what you can build with Kaleidoscope and its feature set.</p>
60 </div>
62 <!-- *********************************************************************** -->
64 <!-- *********************************************************************** -->
68 <p>
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
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
83 as the JIT runs.</p>
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>
90 <pre>
91 # Logical unary not.
92 def unary!(v)
93 if v then
94 0
95 else
96 1;
100 RHS < LHS;
103 def binary| 5 (LHS RHS)
104 if LHS then
105 1
106 else if RHS then
107 1
108 else
109 0;
111 # Define = with slightly lower precedence than relationals.
112 def binary= 9 (LHS RHS)
114 </pre>
115 </div>
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
123 operators.</p>
125 </div>
127 <!-- *********************************************************************** -->
129 <!-- *********************************************************************** -->
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>
137 <pre>
138 enum Token {
139 ...
140 <b>// operators
142 };
143 ...
144 static int gettok() {
145 ...
146 if (IdentifierStr == "for") return tok_for;
147 if (IdentifierStr == "in") return tok_in;
150 return tok_identifier;
151 </pre>
152 </div>
154 <p>This just adds lexer support for the unary and binary keywords, like we
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
164 represent our new user-defined operators as prototypes, we have to extend
168 <pre>
169 /// PrototypeAST - This class represents the "prototype" for a function,
170 /// which captures its argument names as well as if it is an operator.
171 class PrototypeAST {
172 std::string Name;
174 <b>bool isOperator;
175 unsigned Precedence; // Precedence if a binary op.</b>
176 public:
184 char getOperatorName() const {
185 assert(isUnaryOp() || isBinaryOp());
186 return Name[Name.size()-1];
187 }
189 unsigned getBinaryPrecedence() const { return Precedence; }</b>
191 Function *Codegen();
192 };
193 </pre>
194 </div>
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>
203 <pre>
204 /// prototype
205 /// ::= id '(' id* ')'
207 static PrototypeAST *ParsePrototype() {
208 std::string FnName;
213 switch (CurTok) {
214 default:
215 return ErrorP("Expected function name in prototype");
216 case tok_identifier:
217 FnName = IdentifierStr;
218 Kind = 0;
219 getNextToken();
220 break;
221 <b>case tok_binary:
222 getNextToken();
223 if (!isascii(CurTok))
224 return ErrorP("Expected binary operator");
225 FnName = "binary";
226 FnName += (char)CurTok;
227 Kind = 2;
228 getNextToken();
230 // Read the precedence if present.
231 if (CurTok == tok_number) {
233 return ErrorP("Invalid precedecnce: must be 1..100");
234 BinaryPrecedence = (unsigned)NumVal;
235 getNextToken();
236 }
237 break;</b>
238 }
240 if (CurTok != '(')
241 return ErrorP("Expected '(' in prototype");
244 while (getNextToken() == tok_identifier)
245 ArgNames.push_back(IdentifierStr);
246 if (CurTok != ')')
247 return ErrorP("Expected ')' in prototype");
249 // success.
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");
257 }
258 </pre>
259 </div>
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
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>
273 <pre>
274 Value *BinaryExprAST::Codegen() {
275 Value *L = LHS->Codegen();
276 Value *R = RHS->Codegen();
279 switch (Op) {
280 case '+': return Builder.CreateAdd(L, R, "addtmp");
281 case '-': return Builder.CreateSub(L, R, "subtmp");
282 case '*': return Builder.CreateMul(L, R, "multmp");
283 case '<':
284 L = Builder.CreateFCmpULT(L, R, "cmptmp");
286 return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
287 "booltmp");
289 }
291 <b>// If it wasn't a builtin binary operator, it must be a user defined one. Emit
292 // a call to it.
296 Value *Ops[] = { L, R };
298 }
300 </pre>
301 </div>
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>
312 <pre>
313 Function *FunctionAST::Codegen() {
314 NamedValues.clear();
316 Function *TheFunction = Proto->Codegen();
317 if (TheFunction == 0)
318 return 0;
320 <b>// If this is an operator, install it.
321 if (Proto->isBinaryOp())
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()) {
329 ...
330 </pre>
331 </div>
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>
342 </div>
344 <!-- *********************************************************************** -->
346 <!-- *********************************************************************** -->
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
353 AST node:</p>
356 <pre>
357 /// UnaryExprAST - Expression class for a unary operator.
358 class UnaryExprAST : public ExprAST {
359 char Opcode;
360 ExprAST *Operand;
361 public:
362 UnaryExprAST(char opcode, ExprAST *operand)
363 : Opcode(opcode), Operand(operand) {}
364 virtual Value *Codegen();
365 };
366 </pre>
367 </div>
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>
375 <pre>
376 /// unary
377 /// ::= primary
378 /// ::= '!' unary
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.
385 int Opc = CurTok;
386 getNextToken();
387 if (ExprAST *Operand = ParseUnary())
388 return new UnaryExprAST(Opc, Operand);
389 return 0;
390 }
391 </pre>
392 </div>
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
399 information.</p>
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
403 instead:</p>
406 <pre>
407 /// binoprhs
408 /// ::= ('+' unary)*
409 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
410 ...
411 <b>// Parse the unary expression after the binary operator.
412 ExprAST *RHS = ParseUnary();
414 ...
415 }
416 /// expression
417 /// ::= unary binoprhs
418 ///
419 static ExprAST *ParseExpression() {
421 if (!LHS) return 0;
423 return ParseBinOpRHS(0, LHS);
424 }
425 </pre>
426 </div>
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
431 with:</p>
434 <pre>
435 /// prototype
436 /// ::= id '(' id* ')'
437 /// ::= binary LETTER number? (id, id)
439 static PrototypeAST *ParsePrototype() {
440 std::string FnName;
443 unsigned BinaryPrecedence = 30;
445 switch (CurTok) {
446 default:
447 return ErrorP("Expected function name in prototype");
448 case tok_identifier:
449 FnName = IdentifierStr;
450 Kind = 0;
451 getNextToken();
452 break;
453 <b>case tok_unary:
454 getNextToken();
455 if (!isascii(CurTok))
456 return ErrorP("Expected unary operator");
457 FnName = "unary";
458 FnName += (char)CurTok;
459 Kind = 1;
460 getNextToken();
461 break;</b>
462 case tok_binary:
463 ...
464 </pre>
465 </div>
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
470 like this:</p>
473 <pre>
474 Value *UnaryExprAST::Codegen() {
475 Value *OperandV = Operand->Codegen();
479 if (F == 0)
480 return ErrorV("Unknown unary operator");
482 return Builder.CreateCall(F, OperandV, "unop");
483 }
484 </pre>
485 </div>
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.
489 </p>
491 </div>
493 <!-- *********************************************************************** -->
495 <!-- *********************************************************************** -->
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>
506 <pre>
508 Read extern: declare double @printd(double)
510 ..
512 123.000000
513 456.000000
514 789.000000
515 Evaluated to 0.000000
516 </pre>
517 </div>
522 <pre>
523 # Logical unary not.
524 def unary!(v)
525 if v then
526 0
527 else
528 1;
530 # Unary negate.
531 def unary-(v)
532 0-v;
536 RHS < LHS;
538 # Binary logical or, which does not short circuit.
539 def binary| 5 (LHS RHS)
540 if LHS then
541 1
542 else if RHS then
543 1
544 else
545 0;
547 # Binary logical and, which does not short circuit.
549 if !LHS then
550 0
551 else
552 !!RHS;
554 # Define = with slightly lower precedence than relationals.
555 def binary = 9 (LHS RHS)
558 </pre>
559 </div>
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
565 character:</p>
568 <pre>
569 ready>
570 <b>
571 extern putchard(char)
572 def printdensity(d)
574 putchard(32) # ' '
576 putchard(46) # '.'
578 putchard(43) # '+'
579 else
581 ...
584 *++..
585 Evaluated to 0.000000
586 </pre>
587 </div>
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
592 converge:</p>
595 <pre>
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)
600 iters
601 else
602 mandleconverger(real*real - imag*imag + creal,
603 2*real*imag + cimag,
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);
609 </pre>
610 </div>
613 for computation of the <a
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>
623 <pre>
624 # compute and plot the mandlebrot set with the specified 2 dimensional range
625 # info.
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)))
630 : putchard(10)
631 )
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);
638 </pre>
639 </div>
644 <pre>
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
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 *.......... ...........
714 *
715 *.......... ...........
716 *+++....++++................
717 *++++++++++++++..............
718 *++++++++++++++++............ ...
719 *++++++++++++++++++.................
720 **+++++++++++++++++++................
721 **+++++++++++++++++++++..............
722 ***++++++++++++++++++++++............
723 ***++++++++++++++++++++++++......... ...... ...........
724 ****++++++++++++++++++++++++++...... .........................
725 *****++++++++++++++++++++++++++++...............................
726 *****++++++++++++++++++++++++++++++++............................
727 ******+++++++++++++++++++++++++++++++++++...........................
728 *******+++++++++++++++++++++++++++++++++++++++.......................
729 ********+++++++++++++++++++++++++++++++++++++++++++..................
730 Evaluated to 0.000000
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 ......... ....+++++++
766 ........ ...+++++++
767 ....... ...+++++++
768 ....+++++++
769 .....+++++++
770 ....+++++++
771 ....+++++++
772 ....+++++++
773 Evaluated to 0.000000
775 </pre>
776 </div>
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>
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.
788 </p>
790 <p>Strikingly, variable mutation is an important feature of some
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>
796 </div>
799 <!-- *********************************************************************** -->
801 <!-- *********************************************************************** -->
805 <p>
806 Here is the complete code listing for our running example, enhanced with the
807 if/then/else and for expressions.. To build this example, use:
808 </p>
811 <pre>
812 # Compile
813 g++ -g toy.cpp `llvm-config --cppflags --ldflags --libs core jit native` -O3 -o toy
814 # Run
815 ./toy
816 </pre>
817 </div>
822 <pre>
823 #include "llvm/DerivedTypes.h"
824 #include "llvm/ExecutionEngine/ExecutionEngine.h"
825 #include "llvm/ExecutionEngine/Interpreter.h"
826 #include "llvm/ExecutionEngine/JIT.h"
827 #include "llvm/LLVMContext.h"
828 #include "llvm/Module.h"
829 #include "llvm/ModuleProvider.h"
830 #include "llvm/PassManager.h"
831 #include "llvm/Analysis/Verifier.h"
832 #include "llvm/Target/TargetData.h"
833 #include "llvm/Target/TargetSelect.h"
834 #include "llvm/Transforms/Scalar.h"
835 #include "llvm/Support/IRBuilder.h"
840 using namespace llvm;
842 //===----------------------------------------------------------------------===//
843 // Lexer
844 //===----------------------------------------------------------------------===//
847 // of these for known things.
848 enum Token {
849 tok_eof = -1,
851 // commands
854 // primary
857 // control
861 // operators
863 };
865 static std::string IdentifierStr; // Filled in if tok_identifier
866 static double NumVal; // Filled in if tok_number
868 /// gettok - Return the next token from standard input.
869 static int gettok() {
870 static int LastChar = ' ';
872 // Skip any whitespace.
873 while (isspace(LastChar))
874 LastChar = getchar();
876 if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
877 IdentifierStr = LastChar;
878 while (isalnum((LastChar = getchar())))
879 IdentifierStr += LastChar;
881 if (IdentifierStr == "def") return tok_def;
882 if (IdentifierStr == "extern") return tok_extern;
883 if (IdentifierStr == "if") return tok_if;
884 if (IdentifierStr == "then") return tok_then;
885 if (IdentifierStr == "else") return tok_else;
886 if (IdentifierStr == "for") return tok_for;
887 if (IdentifierStr == "in") return tok_in;
888 if (IdentifierStr == "binary") return tok_binary;
889 if (IdentifierStr == "unary") return tok_unary;
890 return tok_identifier;
891 }
894 std::string NumStr;
895 do {
896 NumStr += LastChar;
897 LastChar = getchar();
898 } while (isdigit(LastChar) || LastChar == '.');
900 NumVal = strtod(NumStr.c_str(), 0);
901 return tok_number;
902 }
904 if (LastChar == '#') {
905 // Comment until end of line.
906 do LastChar = getchar();
909 if (LastChar != EOF)
910 return gettok();
911 }
913 // Check for end of file. Don't eat the EOF.
914 if (LastChar == EOF)
915 return tok_eof;
917 // Otherwise, just return the character as its ascii value.
918 int ThisChar = LastChar;
919 LastChar = getchar();
920 return ThisChar;
921 }
923 //===----------------------------------------------------------------------===//
924 // Abstract Syntax Tree (aka Parse Tree)
925 //===----------------------------------------------------------------------===//
927 /// ExprAST - Base class for all expression nodes.
928 class ExprAST {
929 public:
930 virtual ~ExprAST() {}
931 virtual Value *Codegen() = 0;
932 };
934 /// NumberExprAST - Expression class for numeric literals like "1.0".
935 class NumberExprAST : public ExprAST {
936 double Val;
937 public:
938 NumberExprAST(double val) : Val(val) {}
939 virtual Value *Codegen();
940 };
942 /// VariableExprAST - Expression class for referencing a variable, like "a".
943 class VariableExprAST : public ExprAST {
944 std::string Name;
945 public:
946 VariableExprAST(const std::string &name) : Name(name) {}
947 virtual Value *Codegen();
948 };
950 /// UnaryExprAST - Expression class for a unary operator.
951 class UnaryExprAST : public ExprAST {
952 char Opcode;
953 ExprAST *Operand;
954 public:
955 UnaryExprAST(char opcode, ExprAST *operand)
956 : Opcode(opcode), Operand(operand) {}
957 virtual Value *Codegen();
958 };
960 /// BinaryExprAST - Expression class for a binary operator.
961 class BinaryExprAST : public ExprAST {
962 char Op;
963 ExprAST *LHS, *RHS;
964 public:
965 BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
966 : Op(op), LHS(lhs), RHS(rhs) {}
967 virtual Value *Codegen();
968 };
970 /// CallExprAST - Expression class for function calls.
971 class CallExprAST : public ExprAST {
972 std::string Callee;
974 public:
976 : Callee(callee), Args(args) {}
977 virtual Value *Codegen();
978 };
980 /// IfExprAST - Expression class for if/then/else.
981 class IfExprAST : public ExprAST {
982 ExprAST *Cond, *Then, *Else;
983 public:
984 IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
985 : Cond(cond), Then(then), Else(_else) {}
986 virtual Value *Codegen();
987 };
989 /// ForExprAST - Expression class for for/in.
990 class ForExprAST : public ExprAST {
991 std::string VarName;
992 ExprAST *Start, *End, *Step, *Body;
993 public:
994 ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
995 ExprAST *step, ExprAST *body)
996 : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
997 virtual Value *Codegen();
998 };
1000 /// PrototypeAST - This class represents the "prototype" for a function,
1001 /// which captures its argument names as well as if it is an operator.
1002 class PrototypeAST {
1003 std::string Name;
1005 bool isOperator;
1006 unsigned Precedence; // Precedence if a binary op.
1007 public:
1009 bool isoperator = false, unsigned prec = 0)
1010 : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
1015 char getOperatorName() const {
1016 assert(isUnaryOp() || isBinaryOp());
1017 return Name[Name.size()-1];
1018 }
1020 unsigned getBinaryPrecedence() const { return Precedence; }
1022 Function *Codegen();
1023 };
1025 /// FunctionAST - This class represents a function definition itself.
1026 class FunctionAST {
1027 PrototypeAST *Proto;
1028 ExprAST *Body;
1029 public:
1030 FunctionAST(PrototypeAST *proto, ExprAST *body)
1031 : Proto(proto), Body(body) {}
1033 Function *Codegen();
1034 };
1036 //===----------------------------------------------------------------------===//
1037 // Parser
1038 //===----------------------------------------------------------------------===//
1040 /// CurTok/getNextToken - Provide a simple token buffer. CurTok is the current
1041 /// token the parser it looking at. getNextToken reads another token from the
1042 /// lexer and updates CurTok with its results.
1043 static int CurTok;
1044 static int getNextToken() {
1045 return CurTok = gettok();
1046 }
1048 /// BinopPrecedence - This holds the precedence for each binary operator that is
1049 /// defined.
1052 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
1053 static int GetTokPrecedence() {
1054 if (!isascii(CurTok))
1055 return -1;
1057 // Make sure it's a declared binop.
1058 int TokPrec = BinopPrecedence[CurTok];
1060 return TokPrec;
1061 }
1063 /// Error* - These are little helper functions for error handling.
1065 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
1066 FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
1068 static ExprAST *ParseExpression();
1070 /// identifierexpr
1071 /// ::= identifier
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);
1081 // Call.
1082 getNextToken(); // eat (
1084 if (CurTok != ')') {
1085 while (1) {
1086 ExprAST *Arg = ParseExpression();
1087 if (!Arg) return 0;
1088 Args.push_back(Arg);
1090 if (CurTok == ')') break;
1092 if (CurTok != ',')
1093 return Error("Expected ')' or ',' in argument list");
1094 getNextToken();
1095 }
1096 }
1098 // Eat the ')'.
1099 getNextToken();
1101 return new CallExprAST(IdName, Args);
1102 }
1104 /// numberexpr ::= number
1105 static ExprAST *ParseNumberExpr() {
1106 ExprAST *Result = new NumberExprAST(NumVal);
1107 getNextToken(); // consume the number
1108 return Result;
1109 }
1111 /// parenexpr ::= '(' expression ')'
1112 static ExprAST *ParseParenExpr() {
1113 getNextToken(); // eat (.
1114 ExprAST *V = ParseExpression();
1115 if (!V) return 0;
1117 if (CurTok != ')')
1118 return Error("expected ')'");
1119 getNextToken(); // eat ).
1120 return V;
1121 }
1123 /// ifexpr ::= 'if' expression 'then' expression 'else' expression
1124 static ExprAST *ParseIfExpr() {
1125 getNextToken(); // eat the if.
1127 // condition.
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();
1138 if (CurTok != tok_else)
1139 return Error("expected else");
1141 getNextToken();
1143 ExprAST *Else = ParseExpression();
1144 if (!Else) return 0;
1146 return new IfExprAST(Cond, Then, Else);
1147 }
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.
1159 if (CurTok != '=')
1160 return Error("expected '=' after for");
1161 getNextToken(); // eat '='.
1164 ExprAST *Start = ParseExpression();
1166 if (CurTok != ',')
1167 return Error("expected ',' after for start value");
1168 getNextToken();
1170 ExprAST *End = ParseExpression();
1173 // The step value is optional.
1174 ExprAST *Step = 0;
1175 if (CurTok == ',') {
1176 getNextToken();
1177 Step = ParseExpression();
1179 }
1181 if (CurTok != tok_in)
1182 return Error("expected 'in' after for");
1183 getNextToken(); // eat 'in'.
1185 ExprAST *Body = ParseExpression();
1188 return new ForExprAST(IdName, Start, End, Step, Body);
1189 }
1192 /// primary
1193 /// ::= identifierexpr
1194 /// ::= numberexpr
1195 /// ::= parenexpr
1196 /// ::= ifexpr
1197 /// ::= forexpr
1198 static ExprAST *ParsePrimary() {
1199 switch (CurTok) {
1200 default: return Error("unknown token when expecting an expression");
1201 case tok_identifier: return ParseIdentifierExpr();
1202 case tok_number: return ParseNumberExpr();
1203 case '(': return ParseParenExpr();
1204 case tok_if: return ParseIfExpr();
1205 case tok_for: return ParseForExpr();
1206 }
1207 }
1209 /// unary
1210 /// ::= primary
1211 /// ::= '!' unary
1212 static ExprAST *ParseUnary() {
1213 // If the current token is not an operator, it must be a primary expr.
1214 if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
1215 return ParsePrimary();
1217 // If this is a unary operator, read it.
1218 int Opc = CurTok;
1219 getNextToken();
1220 if (ExprAST *Operand = ParseUnary())
1221 return new UnaryExprAST(Opc, Operand);
1222 return 0;
1223 }
1225 /// binoprhs
1226 /// ::= ('+' unary)*
1227 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
1228 // If this is a binop, find its precedence.
1229 while (1) {
1230 int TokPrec = GetTokPrecedence();
1232 // If this is a binop that binds at least as tightly as the current binop,
1233 // consume it, otherwise we are done.
1234 if (TokPrec < ExprPrec)
1235 return LHS;
1237 // Okay, we know this is a binop.
1238 int BinOp = CurTok;
1239 getNextToken(); // eat binop
1241 // Parse the unary expression after the binary operator.
1242 ExprAST *RHS = ParseUnary();
1243 if (!RHS) return 0;
1245 // If BinOp binds less tightly with RHS than the operator after RHS, let
1246 // the pending operator take RHS as its LHS.
1247 int NextPrec = GetTokPrecedence();
1248 if (TokPrec < NextPrec) {
1249 RHS = ParseBinOpRHS(TokPrec+1, RHS);
1251 }
1253 // Merge LHS/RHS.
1254 LHS = new BinaryExprAST(BinOp, LHS, RHS);
1255 }
1256 }
1258 /// expression
1259 /// ::= unary binoprhs
1260 ///
1261 static ExprAST *ParseExpression() {
1262 ExprAST *LHS = ParseUnary();
1263 if (!LHS) return 0;
1265 return ParseBinOpRHS(0, LHS);
1266 }
1268 /// prototype
1269 /// ::= id '(' id* ')'
1270 /// ::= binary LETTER number? (id, id)
1271 /// ::= unary LETTER (id)
1272 static PrototypeAST *ParsePrototype() {
1273 std::string FnName;
1276 unsigned BinaryPrecedence = 30;
1278 switch (CurTok) {
1279 default:
1280 return ErrorP("Expected function name in prototype");
1281 case tok_identifier:
1282 FnName = IdentifierStr;
1283 Kind = 0;
1284 getNextToken();
1285 break;
1286 case tok_unary:
1287 getNextToken();
1288 if (!isascii(CurTok))
1289 return ErrorP("Expected unary operator");
1290 FnName = "unary";
1291 FnName += (char)CurTok;
1292 Kind = 1;
1293 getNextToken();
1294 break;
1295 case tok_binary:
1296 getNextToken();
1297 if (!isascii(CurTok))
1298 return ErrorP("Expected binary operator");
1299 FnName = "binary";
1300 FnName += (char)CurTok;
1301 Kind = 2;
1302 getNextToken();
1304 // Read the precedence if present.
1305 if (CurTok == tok_number) {
1307 return ErrorP("Invalid precedecnce: must be 1..100");
1308 BinaryPrecedence = (unsigned)NumVal;
1309 getNextToken();
1310 }
1311 break;
1312 }
1314 if (CurTok != '(')
1315 return ErrorP("Expected '(' in prototype");
1318 while (getNextToken() == tok_identifier)
1319 ArgNames.push_back(IdentifierStr);
1320 if (CurTok != ')')
1321 return ErrorP("Expected ')' in prototype");
1323 // success.
1324 getNextToken(); // eat ')'.
1326 // Verify right number of names for operator.
1327 if (Kind && ArgNames.size() != Kind)
1328 return ErrorP("Invalid number of operands for operator");
1330 return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
1331 }
1333 /// definition ::= 'def' prototype expression
1334 static FunctionAST *ParseDefinition() {
1335 getNextToken(); // eat def.
1336 PrototypeAST *Proto = ParsePrototype();
1339 if (ExprAST *E = ParseExpression())
1340 return new FunctionAST(Proto, E);
1341 return 0;
1342 }
1344 /// toplevelexpr ::= expression
1345 static FunctionAST *ParseTopLevelExpr() {
1346 if (ExprAST *E = ParseExpression()) {
1347 // Make an anonymous proto.
1349 return new FunctionAST(Proto, E);
1350 }
1351 return 0;
1352 }
1354 /// external ::= 'extern' prototype
1355 static PrototypeAST *ParseExtern() {
1356 getNextToken(); // eat extern.
1357 return ParsePrototype();
1358 }
1360 //===----------------------------------------------------------------------===//
1361 // Code Generation
1362 //===----------------------------------------------------------------------===//
1364 static Module *TheModule;
1365 static IRBuilder<> Builder(getGlobalContext());
1367 static FunctionPassManager *TheFPM;
1369 Value *ErrorV(const char *Str) { Error(Str); return 0; }
1371 Value *NumberExprAST::Codegen() {
1372 return ConstantFP::get(getGlobalContext(), APFloat(Val));
1373 }
1375 Value *VariableExprAST::Codegen() {
1376 // Look this variable up in the function.
1377 Value *V = NamedValues[Name];
1378 return V ? V : ErrorV("Unknown variable name");
1379 }
1381 Value *UnaryExprAST::Codegen() {
1382 Value *OperandV = Operand->Codegen();
1386 if (F == 0)
1387 return ErrorV("Unknown unary operator");
1389 return Builder.CreateCall(F, OperandV, "unop");
1390 }
1393 Value *BinaryExprAST::Codegen() {
1394 Value *L = LHS->Codegen();
1395 Value *R = RHS->Codegen();
1398 switch (Op) {
1399 case '+': return Builder.CreateAdd(L, R, "addtmp");
1400 case '-': return Builder.CreateSub(L, R, "subtmp");
1401 case '*': return Builder.CreateMul(L, R, "multmp");
1402 case '<':
1403 L = Builder.CreateFCmpULT(L, R, "cmptmp");
1405 return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()), "booltmp");
1406 default: break;
1407 }
1409 // If it wasn't a builtin binary operator, it must be a user defined one. Emit
1410 // a call to it.
1414 Value *Ops[] = { L, R };
1416 }
1418 Value *CallExprAST::Codegen() {
1419 // Look up the name in the global module table.
1420 Function *CalleeF = TheModule->getFunction(Callee);
1421 if (CalleeF == 0)
1422 return ErrorV("Unknown function referenced");
1424 // If argument mismatch error.
1425 if (CalleeF->arg_size() != Args.size())
1426 return ErrorV("Incorrect # arguments passed");
1429 for (unsigned i = 0, e = Args.size(); i != e; ++i) {
1430 ArgsV.push_back(Args[i]->Codegen());
1432 }
1434 return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
1435 }
1437 Value *IfExprAST::Codegen() {
1438 Value *CondV = Cond->Codegen();
1441 // Convert condition to a bool by comparing equal to 0.0.
1442 CondV = Builder.CreateFCmpONE(CondV,
1443 ConstantFP::get(getGlobalContext(), APFloat(0.0)),
1444 "ifcond");
1446 Function *TheFunction = Builder.GetInsertBlock()->getParent();
1448 // Create blocks for the then and else cases. Insert the 'then' block at the
1449 // end of the function.
1450 BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
1451 BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
1452 BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
1454 Builder.CreateCondBr(CondV, ThenBB, ElseBB);
1456 // Emit then value.
1457 Builder.SetInsertPoint(ThenBB);
1459 Value *ThenV = Then->Codegen();
1462 Builder.CreateBr(MergeBB);
1463 // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
1464 ThenBB = Builder.GetInsertBlock();
1466 // Emit else block.
1467 TheFunction->getBasicBlockList().push_back(ElseBB);
1468 Builder.SetInsertPoint(ElseBB);
1470 Value *ElseV = Else->Codegen();
1473 Builder.CreateBr(MergeBB);
1474 // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
1475 ElseBB = Builder.GetInsertBlock();
1477 // Emit merge block.
1478 TheFunction->getBasicBlockList().push_back(MergeBB);
1479 Builder.SetInsertPoint(MergeBB);
1480 PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()),
1481 "iftmp");
1483 PN->addIncoming(ThenV, ThenBB);
1484 PN->addIncoming(ElseV, ElseBB);
1485 return PN;
1486 }
1488 Value *ForExprAST::Codegen() {
1489 // Output this as:
1490 // ...
1491 // start = startexpr
1492 // goto loop
1493 // loop:
1494 // variable = phi [start, loopheader], [nextvariable, loopend]
1495 // ...
1496 // bodyexpr
1497 // ...
1498 // loopend:
1499 // step = stepexpr
1500 // nextvariable = variable + step
1501 // endcond = endexpr
1502 // br endcond, loop, endloop
1503 // outloop:
1505 // Emit the start code first, without 'variable' in scope.
1506 Value *StartVal = Start->Codegen();
1509 // Make the new basic block for the loop header, inserting after current
1510 // block.
1511 Function *TheFunction = Builder.GetInsertBlock()->getParent();
1512 BasicBlock *PreheaderBB = Builder.GetInsertBlock();
1513 BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
1515 // Insert an explicit fall through from the current block to the LoopBB.
1516 Builder.CreateBr(LoopBB);
1518 // Start insertion in LoopBB.
1519 Builder.SetInsertPoint(LoopBB);
1521 // Start the PHI node with an entry for Start.
1522 PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), VarName.c_str());
1523 Variable->addIncoming(StartVal, PreheaderBB);
1525 // Within the loop, the variable is defined equal to the PHI node. If it
1526 // shadows an existing variable, we have to restore it, so save it now.
1527 Value *OldVal = NamedValues[VarName];
1528 NamedValues[VarName] = Variable;
1530 // Emit the body of the loop. This, like any other expr, can change the
1531 // current BB. Note that we ignore the value computed by the body, but don't
1532 // allow an error.
1534 return 0;
1536 // Emit the step value.
1537 Value *StepVal;
1538 if (Step) {
1539 StepVal = Step->Codegen();
1541 } else {
1542 // If not specified, use 1.0.
1543 StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
1544 }
1546 Value *NextVar = Builder.CreateAdd(Variable, StepVal, "nextvar");
1548 // Compute the end condition.
1549 Value *EndCond = End->Codegen();
1550 if (EndCond == 0) return EndCond;
1552 // Convert condition to a bool by comparing equal to 0.0.
1553 EndCond = Builder.CreateFCmpONE(EndCond,
1554 ConstantFP::get(getGlobalContext(), APFloat(0.0)),
1555 "loopcond");
1557 // Create the "after loop" block and insert it.
1558 BasicBlock *LoopEndBB = Builder.GetInsertBlock();
1559 BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
1561 // Insert the conditional branch into the end of LoopEndBB.
1562 Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
1564 // Any new code will be inserted in AfterBB.
1565 Builder.SetInsertPoint(AfterBB);
1567 // Add a new entry to the PHI node for the backedge.
1568 Variable->addIncoming(NextVar, LoopEndBB);
1570 // Restore the unshadowed variable.
1571 if (OldVal)
1572 NamedValues[VarName] = OldVal;
1573 else
1574 NamedValues.erase(VarName);
1577 // for expr always returns 0.0.
1578 return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
1579 }
1581 Function *PrototypeAST::Codegen() {
1582 // Make the function type: double(double,double) etc.
1584 Type::getDoubleTy(getGlobalContext()));
1585 FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
1586 Doubles, false);
1588 Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
1590 // If F conflicted, there was already something named 'Name'. If it has a
1591 // body, don't allow redefinition or reextern.
1592 if (F->getName() != Name) {
1593 // Delete the one we just made and get the existing one.
1594 F->eraseFromParent();
1595 F = TheModule->getFunction(Name);
1597 // If F already has a body, reject this.
1598 if (!F->empty()) {
1599 ErrorF("redefinition of function");
1600 return 0;
1601 }
1603 // If F took a different number of args, reject.
1604 if (F->arg_size() != Args.size()) {
1605 ErrorF("redefinition of function with different # args");
1606 return 0;
1607 }
1608 }
1610 // Set names for all arguments.
1611 unsigned Idx = 0;
1612 for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
1613 ++AI, ++Idx) {
1614 AI->setName(Args[Idx]);
1616 // Add arguments to variable symbol table.
1617 NamedValues[Args[Idx]] = AI;
1618 }
1620 return F;
1621 }
1623 Function *FunctionAST::Codegen() {
1624 NamedValues.clear();
1626 Function *TheFunction = Proto->Codegen();
1627 if (TheFunction == 0)
1628 return 0;
1630 // If this is an operator, install it.
1631 if (Proto->isBinaryOp())
1634 // Create a new basic block to start insertion into.
1635 BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
1636 Builder.SetInsertPoint(BB);
1638 if (Value *RetVal = Body->Codegen()) {
1639 // Finish off the function.
1640 Builder.CreateRet(RetVal);
1642 // Validate the generated code, checking for consistency.
1643 verifyFunction(*TheFunction);
1645 // Optimize the function.
1646 TheFPM->run(*TheFunction);
1648 return TheFunction;
1649 }
1651 // Error reading body, remove function.
1652 TheFunction->eraseFromParent();
1654 if (Proto->isBinaryOp())
1655 BinopPrecedence.erase(Proto->getOperatorName());
1656 return 0;
1657 }
1659 //===----------------------------------------------------------------------===//
1660 // Top-Level parsing and JIT Driver
1661 //===----------------------------------------------------------------------===//
1663 static ExecutionEngine *TheExecutionEngine;
1665 static void HandleDefinition() {
1666 if (FunctionAST *F = ParseDefinition()) {
1667 if (Function *LF = F->Codegen()) {
1668 fprintf(stderr, "Read function definition:");
1669 LF->dump();
1670 }
1671 } else {
1672 // Skip token for error recovery.
1673 getNextToken();
1674 }
1675 }
1677 static void HandleExtern() {
1678 if (PrototypeAST *P = ParseExtern()) {
1679 if (Function *F = P->Codegen()) {
1680 fprintf(stderr, "Read extern: ");
1681 F->dump();
1682 }
1683 } else {
1684 // Skip token for error recovery.
1685 getNextToken();
1686 }
1687 }
1689 static void HandleTopLevelExpression() {
1690 // Evaluate a top level expression into an anonymous function.
1691 if (FunctionAST *F = ParseTopLevelExpr()) {
1692 if (Function *LF = F->Codegen()) {
1693 // JIT the function, returning a function pointer.
1694 void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
1696 // Cast it to the right type (takes no arguments, returns a double) so we
1697 // can call it as a native function.
1698 double (*FP)() = (double (*)())(intptr_t)FPtr;
1699 fprintf(stderr, "Evaluated to %f\n", FP());
1700 }
1701 } else {
1702 // Skip token for error recovery.
1703 getNextToken();
1704 }
1705 }
1707 /// top ::= definition | external | expression | ';'
1708 static void MainLoop() {
1709 while (1) {
1710 fprintf(stderr, "ready> ");
1711 switch (CurTok) {
1712 case tok_eof: return;
1713 case ';': getNextToken(); break; // ignore top level semicolons.
1714 case tok_def: HandleDefinition(); break;
1715 case tok_extern: HandleExtern(); break;
1716 default: HandleTopLevelExpression(); break;
1717 }
1718 }
1719 }
1723 //===----------------------------------------------------------------------===//
1725 //===----------------------------------------------------------------------===//
1727 /// putchard - putchar that takes a double and returns 0.
1728 extern "C"
1729 double putchard(double X) {
1730 putchar((char)X);
1731 return 0;
1732 }
1735 extern "C"
1736 double printd(double X) {
1737 printf("%f\n", X);
1738 return 0;
1739 }
1741 //===----------------------------------------------------------------------===//
1742 // Main driver code.
1743 //===----------------------------------------------------------------------===//
1745 int main() {
1746 // Install standard binary operators.
1747 // 1 is lowest precedence.
1749 BinopPrecedence['+'] = 20;
1750 BinopPrecedence['-'] = 20;
1751 BinopPrecedence['*'] = 40; // highest.
1753 // Prime the first token.
1754 fprintf(stderr, "ready> ");
1755 getNextToken();
1757 // Make the module, which holds all the code.
1758 TheModule = new Module("my cool jit", getGlobalContext());
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.
1786 MainLoop();
1788 TheFPM = 0;
1790 // Print out all of the generated code.
1791 TheModule->dump();
1793 return 0;
1794 }
1795 </pre>
1796 </div>
1798 <a href="LangImpl7.html">Next: Extending the language: mutable variables / SSA construction</a>
1799 </div>
1801 <!-- *********************************************************************** -->
1802 <hr>
1803 <address>
1812 </address>
1813 </body>
1814 </html>