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1 #include "llvm/IR/Verifier.h"
2 #include "llvm/IR/DerivedTypes.h"
3 #include "llvm/IR/IRBuilder.h"
4 #include "llvm/IR/LLVMContext.h"
5 #include "llvm/IR/Module.h"
6 #include <cctype>
7 #include <cstdio>
8 #include <map>
9 #include <string>
10 #include <vector>
11 using namespace llvm;
12 
13 //===----------------------------------------------------------------------===//
14 // Lexer
15 //===----------------------------------------------------------------------===//
16 
17 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
18 // of these for known things.
19 enum Token {
20   tok_eof = -1,
21 
22   // commands
23   tok_def = -2, tok_extern = -3,
24 
25   // primary
26   tok_identifier = -4, tok_number = -5
27 };
28 
29 static std::string IdentifierStr;  // Filled in if tok_identifier
30 static double NumVal;              // Filled in if tok_number
31 
32 /// gettok - Return the next token from standard input.
gettok()33 static int gettok() {
34   static int LastChar = ' ';
35 
36   // Skip any whitespace.
37   while (isspace(LastChar))
38     LastChar = getchar();
39 
40   if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
41     IdentifierStr = LastChar;
42     while (isalnum((LastChar = getchar())))
43       IdentifierStr += LastChar;
44 
45     if (IdentifierStr == "def") return tok_def;
46     if (IdentifierStr == "extern") return tok_extern;
47     return tok_identifier;
48   }
49 
50   if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
51     std::string NumStr;
52     do {
53       NumStr += LastChar;
54       LastChar = getchar();
55     } while (isdigit(LastChar) || LastChar == '.');
56 
57     NumVal = strtod(NumStr.c_str(), 0);
58     return tok_number;
59   }
60 
61   if (LastChar == '#') {
62     // Comment until end of line.
63     do LastChar = getchar();
64     while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
65 
66     if (LastChar != EOF)
67       return gettok();
68   }
69 
70   // Check for end of file.  Don't eat the EOF.
71   if (LastChar == EOF)
72     return tok_eof;
73 
74   // Otherwise, just return the character as its ascii value.
75   int ThisChar = LastChar;
76   LastChar = getchar();
77   return ThisChar;
78 }
79 
80 //===----------------------------------------------------------------------===//
81 // Abstract Syntax Tree (aka Parse Tree)
82 //===----------------------------------------------------------------------===//
83 namespace {
84 /// ExprAST - Base class for all expression nodes.
85 class ExprAST {
86 public:
~ExprAST()87   virtual ~ExprAST() {}
88   virtual Value *Codegen() = 0;
89 };
90 
91 /// NumberExprAST - Expression class for numeric literals like "1.0".
92 class NumberExprAST : public ExprAST {
93   double Val;
94 public:
NumberExprAST(double val)95   NumberExprAST(double val) : Val(val) {}
96   virtual Value *Codegen();
97 };
98 
99 /// VariableExprAST - Expression class for referencing a variable, like "a".
100 class VariableExprAST : public ExprAST {
101   std::string Name;
102 public:
VariableExprAST(const std::string & name)103   VariableExprAST(const std::string &name) : Name(name) {}
104   virtual Value *Codegen();
105 };
106 
107 /// BinaryExprAST - Expression class for a binary operator.
108 class BinaryExprAST : public ExprAST {
109   char Op;
110   ExprAST *LHS, *RHS;
111 public:
BinaryExprAST(char op,ExprAST * lhs,ExprAST * rhs)112   BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
113     : Op(op), LHS(lhs), RHS(rhs) {}
114   virtual Value *Codegen();
115 };
116 
117 /// CallExprAST - Expression class for function calls.
118 class CallExprAST : public ExprAST {
119   std::string Callee;
120   std::vector<ExprAST*> Args;
121 public:
CallExprAST(const std::string & callee,std::vector<ExprAST * > & args)122   CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
123     : Callee(callee), Args(args) {}
124   virtual Value *Codegen();
125 };
126 
127 /// PrototypeAST - This class represents the "prototype" for a function,
128 /// which captures its name, and its argument names (thus implicitly the number
129 /// of arguments the function takes).
130 class PrototypeAST {
131   std::string Name;
132   std::vector<std::string> Args;
133 public:
PrototypeAST(const std::string & name,const std::vector<std::string> & args)134   PrototypeAST(const std::string &name, const std::vector<std::string> &args)
135     : Name(name), Args(args) {}
136 
137   Function *Codegen();
138 };
139 
140 /// FunctionAST - This class represents a function definition itself.
141 class FunctionAST {
142   PrototypeAST *Proto;
143   ExprAST *Body;
144 public:
FunctionAST(PrototypeAST * proto,ExprAST * body)145   FunctionAST(PrototypeAST *proto, ExprAST *body)
146     : Proto(proto), Body(body) {}
147 
148   Function *Codegen();
149 };
150 } // end anonymous namespace
151 
152 //===----------------------------------------------------------------------===//
153 // Parser
154 //===----------------------------------------------------------------------===//
155 
156 /// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
157 /// token the parser is looking at.  getNextToken reads another token from the
158 /// lexer and updates CurTok with its results.
159 static int CurTok;
getNextToken()160 static int getNextToken() {
161   return CurTok = gettok();
162 }
163 
164 /// BinopPrecedence - This holds the precedence for each binary operator that is
165 /// defined.
166 static std::map<char, int> BinopPrecedence;
167 
168 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
GetTokPrecedence()169 static int GetTokPrecedence() {
170   if (!isascii(CurTok))
171     return -1;
172 
173   // Make sure it's a declared binop.
174   int TokPrec = BinopPrecedence[CurTok];
175   if (TokPrec <= 0) return -1;
176   return TokPrec;
177 }
178 
179 /// Error* - These are little helper functions for error handling.
Error(const char * Str)180 ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
ErrorP(const char * Str)181 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
ErrorF(const char * Str)182 FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
183 
184 static ExprAST *ParseExpression();
185 
186 /// identifierexpr
187 ///   ::= identifier
188 ///   ::= identifier '(' expression* ')'
ParseIdentifierExpr()189 static ExprAST *ParseIdentifierExpr() {
190   std::string IdName = IdentifierStr;
191 
192   getNextToken();  // eat identifier.
193 
194   if (CurTok != '(') // Simple variable ref.
195     return new VariableExprAST(IdName);
196 
197   // Call.
198   getNextToken();  // eat (
199   std::vector<ExprAST*> Args;
200   if (CurTok != ')') {
201     while (1) {
202       ExprAST *Arg = ParseExpression();
203       if (!Arg) return 0;
204       Args.push_back(Arg);
205 
206       if (CurTok == ')') break;
207 
208       if (CurTok != ',')
209         return Error("Expected ')' or ',' in argument list");
210       getNextToken();
211     }
212   }
213 
214   // Eat the ')'.
215   getNextToken();
216 
217   return new CallExprAST(IdName, Args);
218 }
219 
220 /// numberexpr ::= number
ParseNumberExpr()221 static ExprAST *ParseNumberExpr() {
222   ExprAST *Result = new NumberExprAST(NumVal);
223   getNextToken(); // consume the number
224   return Result;
225 }
226 
227 /// parenexpr ::= '(' expression ')'
ParseParenExpr()228 static ExprAST *ParseParenExpr() {
229   getNextToken();  // eat (.
230   ExprAST *V = ParseExpression();
231   if (!V) return 0;
232 
233   if (CurTok != ')')
234     return Error("expected ')'");
235   getNextToken();  // eat ).
236   return V;
237 }
238 
239 /// primary
240 ///   ::= identifierexpr
241 ///   ::= numberexpr
242 ///   ::= parenexpr
ParsePrimary()243 static ExprAST *ParsePrimary() {
244   switch (CurTok) {
245   default: return Error("unknown token when expecting an expression");
246   case tok_identifier: return ParseIdentifierExpr();
247   case tok_number:     return ParseNumberExpr();
248   case '(':            return ParseParenExpr();
249   }
250 }
251 
252 /// binoprhs
253 ///   ::= ('+' primary)*
ParseBinOpRHS(int ExprPrec,ExprAST * LHS)254 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
255   // If this is a binop, find its precedence.
256   while (1) {
257     int TokPrec = GetTokPrecedence();
258 
259     // If this is a binop that binds at least as tightly as the current binop,
260     // consume it, otherwise we are done.
261     if (TokPrec < ExprPrec)
262       return LHS;
263 
264     // Okay, we know this is a binop.
265     int BinOp = CurTok;
266     getNextToken();  // eat binop
267 
268     // Parse the primary expression after the binary operator.
269     ExprAST *RHS = ParsePrimary();
270     if (!RHS) return 0;
271 
272     // If BinOp binds less tightly with RHS than the operator after RHS, let
273     // the pending operator take RHS as its LHS.
274     int NextPrec = GetTokPrecedence();
275     if (TokPrec < NextPrec) {
276       RHS = ParseBinOpRHS(TokPrec+1, RHS);
277       if (RHS == 0) return 0;
278     }
279 
280     // Merge LHS/RHS.
281     LHS = new BinaryExprAST(BinOp, LHS, RHS);
282   }
283 }
284 
285 /// expression
286 ///   ::= primary binoprhs
287 ///
ParseExpression()288 static ExprAST *ParseExpression() {
289   ExprAST *LHS = ParsePrimary();
290   if (!LHS) return 0;
291 
292   return ParseBinOpRHS(0, LHS);
293 }
294 
295 /// prototype
296 ///   ::= id '(' id* ')'
ParsePrototype()297 static PrototypeAST *ParsePrototype() {
298   if (CurTok != tok_identifier)
299     return ErrorP("Expected function name in prototype");
300 
301   std::string FnName = IdentifierStr;
302   getNextToken();
303 
304   if (CurTok != '(')
305     return ErrorP("Expected '(' in prototype");
306 
307   std::vector<std::string> ArgNames;
308   while (getNextToken() == tok_identifier)
309     ArgNames.push_back(IdentifierStr);
310   if (CurTok != ')')
311     return ErrorP("Expected ')' in prototype");
312 
313   // success.
314   getNextToken();  // eat ')'.
315 
316   return new PrototypeAST(FnName, ArgNames);
317 }
318 
319 /// definition ::= 'def' prototype expression
ParseDefinition()320 static FunctionAST *ParseDefinition() {
321   getNextToken();  // eat def.
322   PrototypeAST *Proto = ParsePrototype();
323   if (Proto == 0) return 0;
324 
325   if (ExprAST *E = ParseExpression())
326     return new FunctionAST(Proto, E);
327   return 0;
328 }
329 
330 /// toplevelexpr ::= expression
ParseTopLevelExpr()331 static FunctionAST *ParseTopLevelExpr() {
332   if (ExprAST *E = ParseExpression()) {
333     // Make an anonymous proto.
334     PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
335     return new FunctionAST(Proto, E);
336   }
337   return 0;
338 }
339 
340 /// external ::= 'extern' prototype
ParseExtern()341 static PrototypeAST *ParseExtern() {
342   getNextToken();  // eat extern.
343   return ParsePrototype();
344 }
345 
346 //===----------------------------------------------------------------------===//
347 // Code Generation
348 //===----------------------------------------------------------------------===//
349 
350 static Module *TheModule;
351 static IRBuilder<> Builder(getGlobalContext());
352 static std::map<std::string, Value*> NamedValues;
353 
ErrorV(const char * Str)354 Value *ErrorV(const char *Str) { Error(Str); return 0; }
355 
Codegen()356 Value *NumberExprAST::Codegen() {
357   return ConstantFP::get(getGlobalContext(), APFloat(Val));
358 }
359 
Codegen()360 Value *VariableExprAST::Codegen() {
361   // Look this variable up in the function.
362   Value *V = NamedValues[Name];
363   return V ? V : ErrorV("Unknown variable name");
364 }
365 
Codegen()366 Value *BinaryExprAST::Codegen() {
367   Value *L = LHS->Codegen();
368   Value *R = RHS->Codegen();
369   if (L == 0 || R == 0) return 0;
370 
371   switch (Op) {
372   case '+': return Builder.CreateFAdd(L, R, "addtmp");
373   case '-': return Builder.CreateFSub(L, R, "subtmp");
374   case '*': return Builder.CreateFMul(L, R, "multmp");
375   case '<':
376     L = Builder.CreateFCmpULT(L, R, "cmptmp");
377     // Convert bool 0/1 to double 0.0 or 1.0
378     return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
379                                 "booltmp");
380   default: return ErrorV("invalid binary operator");
381   }
382 }
383 
Codegen()384 Value *CallExprAST::Codegen() {
385   // Look up the name in the global module table.
386   Function *CalleeF = TheModule->getFunction(Callee);
387   if (CalleeF == 0)
388     return ErrorV("Unknown function referenced");
389 
390   // If argument mismatch error.
391   if (CalleeF->arg_size() != Args.size())
392     return ErrorV("Incorrect # arguments passed");
393 
394   std::vector<Value*> ArgsV;
395   for (unsigned i = 0, e = Args.size(); i != e; ++i) {
396     ArgsV.push_back(Args[i]->Codegen());
397     if (ArgsV.back() == 0) return 0;
398   }
399 
400   return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
401 }
402 
Codegen()403 Function *PrototypeAST::Codegen() {
404   // Make the function type:  double(double,double) etc.
405   std::vector<Type*> Doubles(Args.size(),
406                              Type::getDoubleTy(getGlobalContext()));
407   FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
408                                        Doubles, false);
409 
410   Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
411 
412   // If F conflicted, there was already something named 'Name'.  If it has a
413   // body, don't allow redefinition or reextern.
414   if (F->getName() != Name) {
415     // Delete the one we just made and get the existing one.
416     F->eraseFromParent();
417     F = TheModule->getFunction(Name);
418 
419     // If F already has a body, reject this.
420     if (!F->empty()) {
421       ErrorF("redefinition of function");
422       return 0;
423     }
424 
425     // If F took a different number of args, reject.
426     if (F->arg_size() != Args.size()) {
427       ErrorF("redefinition of function with different # args");
428       return 0;
429     }
430   }
431 
432   // Set names for all arguments.
433   unsigned Idx = 0;
434   for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
435        ++AI, ++Idx) {
436     AI->setName(Args[Idx]);
437 
438     // Add arguments to variable symbol table.
439     NamedValues[Args[Idx]] = AI;
440   }
441 
442   return F;
443 }
444 
Codegen()445 Function *FunctionAST::Codegen() {
446   NamedValues.clear();
447 
448   Function *TheFunction = Proto->Codegen();
449   if (TheFunction == 0)
450     return 0;
451 
452   // Create a new basic block to start insertion into.
453   BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
454   Builder.SetInsertPoint(BB);
455 
456   if (Value *RetVal = Body->Codegen()) {
457     // Finish off the function.
458     Builder.CreateRet(RetVal);
459 
460     // Validate the generated code, checking for consistency.
461     verifyFunction(*TheFunction);
462 
463     return TheFunction;
464   }
465 
466   // Error reading body, remove function.
467   TheFunction->eraseFromParent();
468   return 0;
469 }
470 
471 //===----------------------------------------------------------------------===//
472 // Top-Level parsing and JIT Driver
473 //===----------------------------------------------------------------------===//
474 
HandleDefinition()475 static void HandleDefinition() {
476   if (FunctionAST *F = ParseDefinition()) {
477     if (Function *LF = F->Codegen()) {
478       fprintf(stderr, "Read function definition:");
479       LF->dump();
480     }
481   } else {
482     // Skip token for error recovery.
483     getNextToken();
484   }
485 }
486 
HandleExtern()487 static void HandleExtern() {
488   if (PrototypeAST *P = ParseExtern()) {
489     if (Function *F = P->Codegen()) {
490       fprintf(stderr, "Read extern: ");
491       F->dump();
492     }
493   } else {
494     // Skip token for error recovery.
495     getNextToken();
496   }
497 }
498 
HandleTopLevelExpression()499 static void HandleTopLevelExpression() {
500   // Evaluate a top-level expression into an anonymous function.
501   if (FunctionAST *F = ParseTopLevelExpr()) {
502     if (Function *LF = F->Codegen()) {
503       fprintf(stderr, "Read top-level expression:");
504       LF->dump();
505     }
506   } else {
507     // Skip token for error recovery.
508     getNextToken();
509   }
510 }
511 
512 /// top ::= definition | external | expression | ';'
MainLoop()513 static void MainLoop() {
514   while (1) {
515     fprintf(stderr, "ready> ");
516     switch (CurTok) {
517     case tok_eof:    return;
518     case ';':        getNextToken(); break;  // ignore top-level semicolons.
519     case tok_def:    HandleDefinition(); break;
520     case tok_extern: HandleExtern(); break;
521     default:         HandleTopLevelExpression(); break;
522     }
523   }
524 }
525 
526 //===----------------------------------------------------------------------===//
527 // "Library" functions that can be "extern'd" from user code.
528 //===----------------------------------------------------------------------===//
529 
530 /// putchard - putchar that takes a double and returns 0.
531 extern "C"
putchard(double X)532 double putchard(double X) {
533   putchar((char)X);
534   return 0;
535 }
536 
537 //===----------------------------------------------------------------------===//
538 // Main driver code.
539 //===----------------------------------------------------------------------===//
540 
main()541 int main() {
542   LLVMContext &Context = getGlobalContext();
543 
544   // Install standard binary operators.
545   // 1 is lowest precedence.
546   BinopPrecedence['<'] = 10;
547   BinopPrecedence['+'] = 20;
548   BinopPrecedence['-'] = 20;
549   BinopPrecedence['*'] = 40;  // highest.
550 
551   // Prime the first token.
552   fprintf(stderr, "ready> ");
553   getNextToken();
554 
555   // Make the module, which holds all the code.
556   TheModule = new Module("my cool jit", Context);
557 
558   // Run the main "interpreter loop" now.
559   MainLoop();
560 
561   // Print out all of the generated code.
562   TheModule->dump();
563 
564   return 0;
565 }
566