examples/Kaleidoscope/Chapter5/toy.cpp

   1 #include "llvm/DerivedTypes.h"
   2 #include "llvm/ExecutionEngine/ExecutionEngine.h"
   3 #include "llvm/ExecutionEngine/JIT.h"
   4 #include "llvm/LLVMContext.h"
   5 #include "llvm/Module.h"
   6 #include "llvm/PassManager.h"
   7 #include "llvm/Analysis/Verifier.h"
   8 #include "llvm/Target/TargetData.h"
   9 #include "llvm/Target/TargetSelect.h"
  10 #include "llvm/Transforms/Scalar.h"
  11 #include "llvm/Support/IRBuilder.h"
  12 #include <cstdio>
  13 #include <string>
  14 #include <map>
  15 #include <vector>
  16 using namespace llvm;
  17
  18 //===----------------------------------------------------------------------===//
  19 // Lexer
  20 //===----------------------------------------------------------------------===//
  21
  22 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
  23 // of these for known things.
  24 enum Token {
  25   tok_eof = -1,
  26
  27   // commands
  28   tok_def = -2, tok_extern = -3,
  29
  30   // primary
  31   tok_identifier = -4, tok_number = -5,
  32
  33   // control
  34   tok_if = -6, tok_then = -7, tok_else = -8,
  35   tok_for = -9, tok_in = -10
  36 };
  37
  38 static std::string IdentifierStr;  // Filled in if tok_identifier
  39 static double NumVal;              // Filled in if tok_number
  40
  41 /// gettok - Return the next token from standard input.
  42 static int gettok() {
  43   static int LastChar = ' ';
  44
  45   // Skip any whitespace.
  46   while (isspace(LastChar))
  47     LastChar = getchar();
  48
  49   if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
  50     IdentifierStr = LastChar;
  51     while (isalnum((LastChar = getchar())))
  52       IdentifierStr += LastChar;
  53
  54     if (IdentifierStr == "def") return tok_def;
  55     if (IdentifierStr == "extern") return tok_extern;
  56     if (IdentifierStr == "if") return tok_if;
  57     if (IdentifierStr == "then") return tok_then;
  58     if (IdentifierStr == "else") return tok_else;
  59     if (IdentifierStr == "for") return tok_for;
  60     if (IdentifierStr == "in") return tok_in;
  61     return tok_identifier;
  62   }
  63
  64   if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
  65     std::string NumStr;
  66     do {
  67       NumStr += LastChar;
  68       LastChar = getchar();
  69     } while (isdigit(LastChar) || LastChar == '.');
  70
  71     NumVal = strtod(NumStr.c_str(), 0);
  72     return tok_number;
  73   }
  74
  75   if (LastChar == '#') {
  76     // Comment until end of line.
  77     do LastChar = getchar();
  78     while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
  79
  80     if (LastChar != EOF)
  81       return gettok();
  82   }
  83
  84   // Check for end of file.  Don't eat the EOF.
  85   if (LastChar == EOF)
  86     return tok_eof;
  87
  88   // Otherwise, just return the character as its ascii value.
  89   int ThisChar = LastChar;
  90   LastChar = getchar();
  91   return ThisChar;
  92 }
  93
  94 //===----------------------------------------------------------------------===//
  95 // Abstract Syntax Tree (aka Parse Tree)
  96 //===----------------------------------------------------------------------===//
  97
  98 /// ExprAST - Base class for all expression nodes.
  99 class ExprAST {
 100 public:
 101   virtual ~ExprAST() {}
 102   virtual Value *Codegen() = 0;
 103 };
 104
 105 /// NumberExprAST - Expression class for numeric literals like "1.0".
 106 class NumberExprAST : public ExprAST {
 107   double Val;
 108 public:
 109   NumberExprAST(double val) : Val(val) {}
 110   virtual Value *Codegen();
 111 };
 112
 113 /// VariableExprAST - Expression class for referencing a variable, like "a".
 114 class VariableExprAST : public ExprAST {
 115   std::string Name;
 116 public:
 117   VariableExprAST(const std::string &name) : Name(name) {}
 118   virtual Value *Codegen();
 119 };
 120
 121 /// BinaryExprAST - Expression class for a binary operator.
 122 class BinaryExprAST : public ExprAST {
 123   char Op;
 124   ExprAST *LHS, *RHS;
 125 public:
 126   BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
 127     : Op(op), LHS(lhs), RHS(rhs) {}
 128   virtual Value *Codegen();
 129 };
 130
 131 /// CallExprAST - Expression class for function calls.
 132 class CallExprAST : public ExprAST {
 133   std::string Callee;
 134   std::vector<ExprAST*> Args;
 135 public:
 136   CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
 137     : Callee(callee), Args(args) {}
 138   virtual Value *Codegen();
 139 };
 140
 141 /// IfExprAST - Expression class for if/then/else.
 142 class IfExprAST : public ExprAST {
 143   ExprAST *Cond, *Then, *Else;
 144 public:
 145   IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
 146   : Cond(cond), Then(then), Else(_else) {}
 147   virtual Value *Codegen();
 148 };
 149
 150 /// ForExprAST - Expression class for for/in.
 151 class ForExprAST : public ExprAST {
 152   std::string VarName;
 153   ExprAST *Start, *End, *Step, *Body;
 154 public:
 155   ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
 156              ExprAST *step, ExprAST *body)
 157     : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
 158   virtual Value *Codegen();
 159 };
 160
 161 /// PrototypeAST - This class represents the "prototype" for a function,
 162 /// which captures its name, and its argument names (thus implicitly the number
 163 /// of arguments the function takes).
 164 class PrototypeAST {
 165   std::string Name;
 166   std::vector<std::string> Args;
 167 public:
 168   PrototypeAST(const std::string &name, const std::vector<std::string> &args)
 169     : Name(name), Args(args) {}
 170
 171   Function *Codegen();
 172 };
 173
 174 /// FunctionAST - This class represents a function definition itself.
 175 class FunctionAST {
 176   PrototypeAST *Proto;
 177   ExprAST *Body;
 178 public:
 179   FunctionAST(PrototypeAST *proto, ExprAST *body)
 180     : Proto(proto), Body(body) {}
 181
 182   Function *Codegen();
 183 };
 184
 185 //===----------------------------------------------------------------------===//
 186 // Parser
 187 //===----------------------------------------------------------------------===//
 188
 189 /// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
 190 /// token the parser is looking at.  getNextToken reads another token from the
 191 /// lexer and updates CurTok with its results.
 192 static int CurTok;
 193 static int getNextToken() {
 194   return CurTok = gettok();
 195 }
 196
 197 /// BinopPrecedence - This holds the precedence for each binary operator that is
 198 /// defined.
 199 static std::map<char, int> BinopPrecedence;
 200
 201 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
 202 static int GetTokPrecedence() {
 203   if (!isascii(CurTok))
 204     return -1;
 205
 206   // Make sure it's a declared binop.
 207   int TokPrec = BinopPrecedence[CurTok];
 208   if (TokPrec <= 0) return -1;
 209   return TokPrec;
 210 }
 211
 212 /// Error* - These are little helper functions for error handling.
 213 ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
 214 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
 215 FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
 216
 217 static ExprAST *ParseExpression();
 218
 219 /// identifierexpr
 220 ///   ::= identifier
 221 ///   ::= identifier '(' expression* ')'
 222 static ExprAST *ParseIdentifierExpr() {
 223   std::string IdName = IdentifierStr;
 224
 225   getNextToken();  // eat identifier.
 226
 227   if (CurTok != '(') // Simple variable ref.
 228     return new VariableExprAST(IdName);
 229
 230   // Call.
 231   getNextToken();  // eat (
 232   std::vector<ExprAST*> Args;
 233   if (CurTok != ')') {
 234     while (1) {
 235       ExprAST *Arg = ParseExpression();
 236       if (!Arg) return 0;
 237       Args.push_back(Arg);
 238
 239       if (CurTok == ')') break;
 240
 241       if (CurTok != ',')
 242         return Error("Expected ')' or ',' in argument list");
 243       getNextToken();
 244     }
 245   }
 246
 247   // Eat the ')'.
 248   getNextToken();
 249
 250   return new CallExprAST(IdName, Args);
 251 }
 252
 253 /// numberexpr ::= number
 254 static ExprAST *ParseNumberExpr() {
 255   ExprAST *Result = new NumberExprAST(NumVal);
 256   getNextToken(); // consume the number
 257   return Result;
 258 }
 259
 260 /// parenexpr ::= '(' expression ')'
 261 static ExprAST *ParseParenExpr() {
 262   getNextToken();  // eat (.
 263   ExprAST *V = ParseExpression();
 264   if (!V) return 0;
 265
 266   if (CurTok != ')')
 267     return Error("expected ')'");
 268   getNextToken();  // eat ).
 269   return V;
 270 }
 271
 272 /// ifexpr ::= 'if' expression 'then' expression 'else' expression
 273 static ExprAST *ParseIfExpr() {
 274   getNextToken();  // eat the if.
 275
 276   // condition.
 277   ExprAST *Cond = ParseExpression();
 278   if (!Cond) return 0;
 279
 280   if (CurTok != tok_then)
 281     return Error("expected then");
 282   getNextToken();  // eat the then
 283
 284   ExprAST *Then = ParseExpression();
 285   if (Then == 0) return 0;
 286
 287   if (CurTok != tok_else)
 288     return Error("expected else");
 289
 290   getNextToken();
 291
 292   ExprAST *Else = ParseExpression();
 293   if (!Else) return 0;
 294
 295   return new IfExprAST(Cond, Then, Else);
 296 }
 297
 298 /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
 299 static ExprAST *ParseForExpr() {
 300   getNextToken();  // eat the for.
 301
 302   if (CurTok != tok_identifier)
 303     return Error("expected identifier after for");
 304
 305   std::string IdName = IdentifierStr;
 306   getNextToken();  // eat identifier.
 307
 308   if (CurTok != '=')
 309     return Error("expected '=' after for");
 310   getNextToken();  // eat '='.
 311
 312
 313   ExprAST *Start = ParseExpression();
 314   if (Start == 0) return 0;
 315   if (CurTok != ',')
 316     return Error("expected ',' after for start value");
 317   getNextToken();
 318
 319   ExprAST *End = ParseExpression();
 320   if (End == 0) return 0;
 321
 322   // The step value is optional.
 323   ExprAST *Step = 0;
 324   if (CurTok == ',') {
 325     getNextToken();
 326     Step = ParseExpression();
 327     if (Step == 0) return 0;
 328   }
 329
 330   if (CurTok != tok_in)
 331     return Error("expected 'in' after for");
 332   getNextToken();  // eat 'in'.
 333
 334   ExprAST *Body = ParseExpression();
 335   if (Body == 0) return 0;
 336
 337   return new ForExprAST(IdName, Start, End, Step, Body);
 338 }
 339
 340 /// primary
 341 ///   ::= identifierexpr
 342 ///   ::= numberexpr
 343 ///   ::= parenexpr
 344 ///   ::= ifexpr
 345 ///   ::= forexpr
 346 static ExprAST *ParsePrimary() {
 347   switch (CurTok) {
 348   default: return Error("unknown token when expecting an expression");
 349   case tok_identifier: return ParseIdentifierExpr();
 350   case tok_number:     return ParseNumberExpr();
 351   case '(':            return ParseParenExpr();
 352   case tok_if:         return ParseIfExpr();
 353   case tok_for:        return ParseForExpr();
 354   }
 355 }
 356
 357 /// binoprhs
 358 ///   ::= ('+' primary)*
 359 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
 360   // If this is a binop, find its precedence.
 361   while (1) {
 362     int TokPrec = GetTokPrecedence();
 363
 364     // If this is a binop that binds at least as tightly as the current binop,
 365     // consume it, otherwise we are done.
 366     if (TokPrec < ExprPrec)
 367       return LHS;
 368
 369     // Okay, we know this is a binop.
 370     int BinOp = CurTok;
 371     getNextToken();  // eat binop
 372
 373     // Parse the primary expression after the binary operator.
 374     ExprAST *RHS = ParsePrimary();
 375     if (!RHS) return 0;
 376
 377     // If BinOp binds less tightly with RHS than the operator after RHS, let
 378     // the pending operator take RHS as its LHS.
 379     int NextPrec = GetTokPrecedence();
 380     if (TokPrec < NextPrec) {
 381       RHS = ParseBinOpRHS(TokPrec+1, RHS);
 382       if (RHS == 0) return 0;
 383     }
 384
 385     // Merge LHS/RHS.
 386     LHS = new BinaryExprAST(BinOp, LHS, RHS);
 387   }
 388 }
 389
 390 /// expression
 391 ///   ::= primary binoprhs
 392 ///
 393 static ExprAST *ParseExpression() {
 394   ExprAST *LHS = ParsePrimary();
 395   if (!LHS) return 0;
 396
 397   return ParseBinOpRHS(0, LHS);
 398 }
 399
 400 /// prototype
 401 ///   ::= id '(' id* ')'
 402 static PrototypeAST *ParsePrototype() {
 403   if (CurTok != tok_identifier)
 404     return ErrorP("Expected function name in prototype");
 405
 406   std::string FnName = IdentifierStr;
 407   getNextToken();
 408
 409   if (CurTok != '(')
 410     return ErrorP("Expected '(' in prototype");
 411
 412   std::vector<std::string> ArgNames;
 413   while (getNextToken() == tok_identifier)
 414     ArgNames.push_back(IdentifierStr);
 415   if (CurTok != ')')
 416     return ErrorP("Expected ')' in prototype");
 417
 418   // success.
 419   getNextToken();  // eat ')'.
 420
 421   return new PrototypeAST(FnName, ArgNames);
 422 }
 423
 424 /// definition ::= 'def' prototype expression
 425 static FunctionAST *ParseDefinition() {
 426   getNextToken();  // eat def.
 427   PrototypeAST *Proto = ParsePrototype();
 428   if (Proto == 0) return 0;
 429
 430   if (ExprAST *E = ParseExpression())
 431     return new FunctionAST(Proto, E);
 432   return 0;
 433 }
 434
 435 /// toplevelexpr ::= expression
 436 static FunctionAST *ParseTopLevelExpr() {
 437   if (ExprAST *E = ParseExpression()) {
 438     // Make an anonymous proto.
 439     PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
 440     return new FunctionAST(Proto, E);
 441   }
 442   return 0;
 443 }
 444
 445 /// external ::= 'extern' prototype
 446 static PrototypeAST *ParseExtern() {
 447   getNextToken();  // eat extern.
 448   return ParsePrototype();
 449 }
 450
 451 //===----------------------------------------------------------------------===//
 452 // Code Generation
 453 //===----------------------------------------------------------------------===//
 454
 455 static Module *TheModule;
 456 static IRBuilder<> Builder(getGlobalContext());
 457 static std::map<std::string, Value*> NamedValues;
 458 static FunctionPassManager *TheFPM;
 459
 460 Value *ErrorV(const char *Str) { Error(Str); return 0; }
 461
 462 Value *NumberExprAST::Codegen() {
 463   return ConstantFP::get(getGlobalContext(), APFloat(Val));
 464 }
 465
 466 Value *VariableExprAST::Codegen() {
 467   // Look this variable up in the function.
 468   Value *V = NamedValues[Name];
 469   return V ? V : ErrorV("Unknown variable name");
 470 }
 471
 472 Value *BinaryExprAST::Codegen() {
 473   Value *L = LHS->Codegen();
 474   Value *R = RHS->Codegen();
 475   if (L == 0 || R == 0) return 0;
 476
 477   switch (Op) {
 478   case '+': return Builder.CreateFAdd(L, R, "addtmp");
 479   case '-': return Builder.CreateFSub(L, R, "subtmp");
 480   case '*': return Builder.CreateFMul(L, R, "multmp");
 481   case '<':
 482     L = Builder.CreateFCmpULT(L, R, "cmptmp");
 483     // Convert bool 0/1 to double 0.0 or 1.0
 484     return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
 485                                 "booltmp");
 486   default: return ErrorV("invalid binary operator");
 487   }
 488 }
 489
 490 Value *CallExprAST::Codegen() {
 491   // Look up the name in the global module table.
 492   Function *CalleeF = TheModule->getFunction(Callee);
 493   if (CalleeF == 0)
 494     return ErrorV("Unknown function referenced");
 495
 496   // If argument mismatch error.
 497   if (CalleeF->arg_size() != Args.size())
 498     return ErrorV("Incorrect # arguments passed");
 499
 500   std::vector<Value*> ArgsV;
 501   for (unsigned i = 0, e = Args.size(); i != e; ++i) {
 502     ArgsV.push_back(Args[i]->Codegen());
 503     if (ArgsV.back() == 0) return 0;
 504   }
 505
 506   return Builder.CreateCall(CalleeF, ArgsV.begin(), ArgsV.end(), "calltmp");
 507 }
 508
 509 Value *IfExprAST::Codegen() {
 510   Value *CondV = Cond->Codegen();
 511   if (CondV == 0) return 0;
 512
 513   // Convert condition to a bool by comparing equal to 0.0.
 514   CondV = Builder.CreateFCmpONE(CondV,
 515                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
 516                                 "ifcond");
 517
 518   Function *TheFunction = Builder.GetInsertBlock()->getParent();
 519
 520   // Create blocks for the then and else cases.  Insert the 'then' block at the
 521   // end of the function.
 522   BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
 523   BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
 524   BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
 525
 526   Builder.CreateCondBr(CondV, ThenBB, ElseBB);
 527
 528   // Emit then value.
 529   Builder.SetInsertPoint(ThenBB);
 530
 531   Value *ThenV = Then->Codegen();
 532   if (ThenV == 0) return 0;
 533
 534   Builder.CreateBr(MergeBB);
 535   // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
 536   ThenBB = Builder.GetInsertBlock();
 537
 538   // Emit else block.
 539   TheFunction->getBasicBlockList().push_back(ElseBB);
 540   Builder.SetInsertPoint(ElseBB);
 541
 542   Value *ElseV = Else->Codegen();
 543   if (ElseV == 0) return 0;
 544
 545   Builder.CreateBr(MergeBB);
 546   // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
 547   ElseBB = Builder.GetInsertBlock();
 548
 549   // Emit merge block.
 550   TheFunction->getBasicBlockList().push_back(MergeBB);
 551   Builder.SetInsertPoint(MergeBB);
 552   PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()),
 553                                   "iftmp");
 554
 555   PN->addIncoming(ThenV, ThenBB);
 556   PN->addIncoming(ElseV, ElseBB);
 557   return PN;
 558 }
 559
 560 Value *ForExprAST::Codegen() {
 561   // Output this as:
 562   //   ...
 563   //   start = startexpr
 564   //   goto loop
 565   // loop:
 566   //   variable = phi [start, loopheader], [nextvariable, loopend]
 567   //   ...
 568   //   bodyexpr
 569   //   ...
 570   // loopend:
 571   //   step = stepexpr
 572   //   nextvariable = variable + step
 573   //   endcond = endexpr
 574   //   br endcond, loop, endloop
 575   // outloop:
 576
 577   // Emit the start code first, without 'variable' in scope.
 578   Value *StartVal = Start->Codegen();
 579   if (StartVal == 0) return 0;
 580
 581   // Make the new basic block for the loop header, inserting after current
 582   // block.
 583   Function *TheFunction = Builder.GetInsertBlock()->getParent();
 584   BasicBlock *PreheaderBB = Builder.GetInsertBlock();
 585   BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
 586
 587   // Insert an explicit fall through from the current block to the LoopBB.
 588   Builder.CreateBr(LoopBB);
 589
 590   // Start insertion in LoopBB.
 591   Builder.SetInsertPoint(LoopBB);
 592
 593   // Start the PHI node with an entry for Start.
 594   PHINode *Variable = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), VarName.c_str());
 595   Variable->addIncoming(StartVal, PreheaderBB);
 596
 597   // Within the loop, the variable is defined equal to the PHI node.  If it
 598   // shadows an existing variable, we have to restore it, so save it now.
 599   Value *OldVal = NamedValues[VarName];
 600   NamedValues[VarName] = Variable;
 601
 602   // Emit the body of the loop.  This, like any other expr, can change the
 603   // current BB.  Note that we ignore the value computed by the body, but don't
 604   // allow an error.
 605   if (Body->Codegen() == 0)
 606     return 0;
 607
 608   // Emit the step value.
 609   Value *StepVal;
 610   if (Step) {
 611     StepVal = Step->Codegen();
 612     if (StepVal == 0) return 0;
 613   } else {
 614     // If not specified, use 1.0.
 615     StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
 616   }
 617
 618   Value *NextVar = Builder.CreateFAdd(Variable, StepVal, "nextvar");
 619
 620   // Compute the end condition.
 621   Value *EndCond = End->Codegen();
 622   if (EndCond == 0) return EndCond;
 623
 624   // Convert condition to a bool by comparing equal to 0.0.
 625   EndCond = Builder.CreateFCmpONE(EndCond,
 626                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
 627                                   "loopcond");
 628
 629   // Create the "after loop" block and insert it.
 630   BasicBlock *LoopEndBB = Builder.GetInsertBlock();
 631   BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
 632
 633   // Insert the conditional branch into the end of LoopEndBB.
 634   Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
 635
 636   // Any new code will be inserted in AfterBB.
 637   Builder.SetInsertPoint(AfterBB);
 638
 639   // Add a new entry to the PHI node for the backedge.
 640   Variable->addIncoming(NextVar, LoopEndBB);
 641
 642   // Restore the unshadowed variable.
 643   if (OldVal)
 644     NamedValues[VarName] = OldVal;
 645   else
 646     NamedValues.erase(VarName);
 647
 648
 649   // for expr always returns 0.0.
 650   return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
 651 }
 652
 653 Function *PrototypeAST::Codegen() {
 654   // Make the function type:  double(double,double) etc.
 655   std::vector<const Type*> Doubles(Args.size(),
 656                                    Type::getDoubleTy(getGlobalContext()));
 657   FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
 658                                        Doubles, false);
 659
 660   Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
 661
 662   // If F conflicted, there was already something named 'Name'.  If it has a
 663   // body, don't allow redefinition or reextern.
 664   if (F->getName() != Name) {
 665     // Delete the one we just made and get the existing one.
 666     F->eraseFromParent();
 667     F = TheModule->getFunction(Name);
 668
 669     // If F already has a body, reject this.
 670     if (!F->empty()) {
 671       ErrorF("redefinition of function");
 672       return 0;
 673     }
 674
 675     // If F took a different number of args, reject.
 676     if (F->arg_size() != Args.size()) {
 677       ErrorF("redefinition of function with different # args");
 678       return 0;
 679     }
 680   }
 681
 682   // Set names for all arguments.
 683   unsigned Idx = 0;
 684   for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
 685        ++AI, ++Idx) {
 686     AI->setName(Args[Idx]);
 687
 688     // Add arguments to variable symbol table.
 689     NamedValues[Args[Idx]] = AI;
 690   }
 691
 692   return F;
 693 }
 694
 695 Function *FunctionAST::Codegen() {
 696   NamedValues.clear();
 697
 698   Function *TheFunction = Proto->Codegen();
 699   if (TheFunction == 0)
 700     return 0;
 701
 702   // Create a new basic block to start insertion into.
 703   BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
 704   Builder.SetInsertPoint(BB);
 705
 706   if (Value *RetVal = Body->Codegen()) {
 707     // Finish off the function.
 708     Builder.CreateRet(RetVal);
 709
 710     // Validate the generated code, checking for consistency.
 711     verifyFunction(*TheFunction);
 712
 713     // Optimize the function.
 714     TheFPM->run(*TheFunction);
 715
 716     return TheFunction;
 717   }
 718
 719   // Error reading body, remove function.
 720   TheFunction->eraseFromParent();
 721   return 0;
 722 }
 723
 724 //===----------------------------------------------------------------------===//
 725 // Top-Level parsing and JIT Driver
 726 //===----------------------------------------------------------------------===//
 727
 728 static ExecutionEngine *TheExecutionEngine;
 729
 730 static void HandleDefinition() {
 731   if (FunctionAST *F = ParseDefinition()) {
 732     if (Function *LF = F->Codegen()) {
 733       fprintf(stderr, "Read function definition:");
 734       LF->dump();
 735     }
 736   } else {
 737     // Skip token for error recovery.
 738     getNextToken();
 739   }
 740 }
 741
 742 static void HandleExtern() {
 743   if (PrototypeAST *P = ParseExtern()) {
 744     if (Function *F = P->Codegen()) {
 745       fprintf(stderr, "Read extern: ");
 746       F->dump();
 747     }
 748   } else {
 749     // Skip token for error recovery.
 750     getNextToken();
 751   }
 752 }
 753
 754 static void HandleTopLevelExpression() {
 755   // Evaluate a top-level expression into an anonymous function.
 756   if (FunctionAST *F = ParseTopLevelExpr()) {
 757     if (Function *LF = F->Codegen()) {
 758       // JIT the function, returning a function pointer.
 759       void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
 760
 761       // Cast it to the right type (takes no arguments, returns a double) so we
 762       // can call it as a native function.
 763       double (*FP)() = (double (*)())(intptr_t)FPtr;
 764       fprintf(stderr, "Evaluated to %f\n", FP());
 765     }
 766   } else {
 767     // Skip token for error recovery.
 768     getNextToken();
 769   }
 770 }
 771
 772 /// top ::= definition | external | expression | ';'
 773 static void MainLoop() {
 774   while (1) {
 775     fprintf(stderr, "ready> ");
 776     switch (CurTok) {
 777     case tok_eof:    return;
 778     case ';':        getNextToken(); break;  // ignore top-level semicolons.
 779     case tok_def:    HandleDefinition(); break;
 780     case tok_extern: HandleExtern(); break;
 781     default:         HandleTopLevelExpression(); break;
 782     }
 783   }
 784 }
 785
 786 //===----------------------------------------------------------------------===//
 787 // "Library" functions that can be "extern'd" from user code.
 788 //===----------------------------------------------------------------------===//
 789
 790 /// putchard - putchar that takes a double and returns 0.
 791 extern "C"
 792 double putchard(double X) {
 793   putchar((char)X);
 794   return 0;
 795 }
 796
 797 //===----------------------------------------------------------------------===//
 798 // Main driver code.
 799 //===----------------------------------------------------------------------===//
 800
 801 int main() {
 802   InitializeNativeTarget();
 803   LLVMContext &Context = getGlobalContext();
 804
 805   // Install standard binary operators.
 806   // 1 is lowest precedence.
 807   BinopPrecedence['<'] = 10;
 808   BinopPrecedence['+'] = 20;
 809   BinopPrecedence['-'] = 20;
 810   BinopPrecedence['*'] = 40;  // highest.
 811
 812   // Prime the first token.
 813   fprintf(stderr, "ready> ");
 814   getNextToken();
 815
 816   // Make the module, which holds all the code.
 817   TheModule = new Module("my cool jit", Context);
 818
 819   // Create the JIT.  This takes ownership of the module.
 820   std::string ErrStr;
 821   TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create();
 822   if (!TheExecutionEngine) {
 823     fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
 824     exit(1);
 825   }
 826
 827   FunctionPassManager OurFPM(TheModule);
 828
 829   // Set up the optimizer pipeline.  Start with registering info about how the
 830   // target lays out data structures.
 831   OurFPM.add(new TargetData(*TheExecutionEngine->getTargetData()));
 832   // Do simple "peephole" optimizations and bit-twiddling optzns.
 833   OurFPM.add(createInstructionCombiningPass());
 834   // Reassociate expressions.
 835   OurFPM.add(createReassociatePass());
 836   // Eliminate Common SubExpressions.
 837   OurFPM.add(createGVNPass());
 838   // Simplify the control flow graph (deleting unreachable blocks, etc).
 839   OurFPM.add(createCFGSimplificationPass());
 840
 841   OurFPM.doInitialization();
 842
 843   // Set the global so the code gen can use this.
 844   TheFPM = &OurFPM;
 845
 846   // Run the main "interpreter loop" now.
 847   MainLoop();
 848
 849   TheFPM = 0;
 850
 851   // Print out all of the generated code.
 852   TheModule->dump();
 853
 854   return 0;
 855 }