1#include "llvm/Analysis/Passes.h"
2#include "llvm/ExecutionEngine/ExecutionEngine.h"
3#include "llvm/ExecutionEngine/JIT.h"
4#include "llvm/IR/DataLayout.h"
5#include "llvm/IR/DerivedTypes.h"
6#include "llvm/IR/IRBuilder.h"
7#include "llvm/IR/LLVMContext.h"
8#include "llvm/IR/Module.h"
9#include "llvm/IR/Verifier.h"
10#include "llvm/PassManager.h"
11#include "llvm/Support/TargetSelect.h"
12#include "llvm/Transforms/Scalar.h"
13#include <cctype>
14#include <cstdio>
15#include <map>
16#include <string>
17#include <vector>
18using namespace llvm;
19
20//===----------------------------------------------------------------------===//
21// Lexer
22//===----------------------------------------------------------------------===//
23
24// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
25// of these for known things.
26enum Token {
27  tok_eof = -1,
28
29  // commands
30  tok_def = -2, tok_extern = -3,
31
32  // primary
33  tok_identifier = -4, tok_number = -5,
34
35  // control
36  tok_if = -6, tok_then = -7, tok_else = -8,
37  tok_for = -9, tok_in = -10,
38
39  // operators
40  tok_binary = -11, tok_unary = -12,
41
42  // var definition
43  tok_var = -13
44};
45
46static std::string IdentifierStr;  // Filled in if tok_identifier
47static double NumVal;              // Filled in if tok_number
48
49/// gettok - Return the next token from standard input.
50static int gettok() {
51  static int LastChar = ' ';
52
53  // Skip any whitespace.
54  while (isspace(LastChar))
55    LastChar = getchar();
56
57  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
58    IdentifierStr = LastChar;
59    while (isalnum((LastChar = getchar())))
60      IdentifierStr += LastChar;
61
62    if (IdentifierStr == "def") return tok_def;
63    if (IdentifierStr == "extern") return tok_extern;
64    if (IdentifierStr == "if") return tok_if;
65    if (IdentifierStr == "then") return tok_then;
66    if (IdentifierStr == "else") return tok_else;
67    if (IdentifierStr == "for") return tok_for;
68    if (IdentifierStr == "in") return tok_in;
69    if (IdentifierStr == "binary") return tok_binary;
70    if (IdentifierStr == "unary") return tok_unary;
71    if (IdentifierStr == "var") return tok_var;
72    return tok_identifier;
73  }
74
75  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
76    std::string NumStr;
77    do {
78      NumStr += LastChar;
79      LastChar = getchar();
80    } while (isdigit(LastChar) || LastChar == '.');
81
82    NumVal = strtod(NumStr.c_str(), 0);
83    return tok_number;
84  }
85
86  if (LastChar == '#') {
87    // Comment until end of line.
88    do LastChar = getchar();
89    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
90
91    if (LastChar != EOF)
92      return gettok();
93  }
94
95  // Check for end of file.  Don't eat the EOF.
96  if (LastChar == EOF)
97    return tok_eof;
98
99  // Otherwise, just return the character as its ascii value.
100  int ThisChar = LastChar;
101  LastChar = getchar();
102  return ThisChar;
103}
104
105//===----------------------------------------------------------------------===//
106// Abstract Syntax Tree (aka Parse Tree)
107//===----------------------------------------------------------------------===//
108namespace {
109/// ExprAST - Base class for all expression nodes.
110class ExprAST {
111public:
112  virtual ~ExprAST() {}
113  virtual Value *Codegen() = 0;
114};
115
116/// NumberExprAST - Expression class for numeric literals like "1.0".
117class NumberExprAST : public ExprAST {
118  double Val;
119public:
120  NumberExprAST(double val) : Val(val) {}
121  virtual Value *Codegen();
122};
123
124/// VariableExprAST - Expression class for referencing a variable, like "a".
125class VariableExprAST : public ExprAST {
126  std::string Name;
127public:
128  VariableExprAST(const std::string &name) : Name(name) {}
129  const std::string &getName() const { return Name; }
130  virtual Value *Codegen();
131};
132
133/// UnaryExprAST - Expression class for a unary operator.
134class UnaryExprAST : public ExprAST {
135  char Opcode;
136  ExprAST *Operand;
137public:
138  UnaryExprAST(char opcode, ExprAST *operand)
139    : Opcode(opcode), Operand(operand) {}
140  virtual Value *Codegen();
141};
142
143/// BinaryExprAST - Expression class for a binary operator.
144class BinaryExprAST : public ExprAST {
145  char Op;
146  ExprAST *LHS, *RHS;
147public:
148  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
149    : Op(op), LHS(lhs), RHS(rhs) {}
150  virtual Value *Codegen();
151};
152
153/// CallExprAST - Expression class for function calls.
154class CallExprAST : public ExprAST {
155  std::string Callee;
156  std::vector<ExprAST*> Args;
157public:
158  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
159    : Callee(callee), Args(args) {}
160  virtual Value *Codegen();
161};
162
163/// IfExprAST - Expression class for if/then/else.
164class IfExprAST : public ExprAST {
165  ExprAST *Cond, *Then, *Else;
166public:
167  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
168  : Cond(cond), Then(then), Else(_else) {}
169  virtual Value *Codegen();
170};
171
172/// ForExprAST - Expression class for for/in.
173class ForExprAST : public ExprAST {
174  std::string VarName;
175  ExprAST *Start, *End, *Step, *Body;
176public:
177  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
178             ExprAST *step, ExprAST *body)
179    : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
180  virtual Value *Codegen();
181};
182
183/// VarExprAST - Expression class for var/in
184class VarExprAST : public ExprAST {
185  std::vector<std::pair<std::string, ExprAST*> > VarNames;
186  ExprAST *Body;
187public:
188  VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
189             ExprAST *body)
190  : VarNames(varnames), Body(body) {}
191
192  virtual Value *Codegen();
193};
194
195/// PrototypeAST - This class represents the "prototype" for a function,
196/// which captures its argument names as well as if it is an operator.
197class PrototypeAST {
198  std::string Name;
199  std::vector<std::string> Args;
200  bool isOperator;
201  unsigned Precedence;  // Precedence if a binary op.
202public:
203  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
204               bool isoperator = false, unsigned prec = 0)
205  : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
206
207  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
208  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
209
210  char getOperatorName() const {
211    assert(isUnaryOp() || isBinaryOp());
212    return Name[Name.size()-1];
213  }
214
215  unsigned getBinaryPrecedence() const { return Precedence; }
216
217  Function *Codegen();
218
219  void CreateArgumentAllocas(Function *F);
220};
221
222/// FunctionAST - This class represents a function definition itself.
223class FunctionAST {
224  PrototypeAST *Proto;
225  ExprAST *Body;
226public:
227  FunctionAST(PrototypeAST *proto, ExprAST *body)
228    : Proto(proto), Body(body) {}
229
230  Function *Codegen();
231};
232} // end anonymous namespace
233
234//===----------------------------------------------------------------------===//
235// Parser
236//===----------------------------------------------------------------------===//
237
238/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
239/// token the parser is looking at.  getNextToken reads another token from the
240/// lexer and updates CurTok with its results.
241static int CurTok;
242static int getNextToken() {
243  return CurTok = gettok();
244}
245
246/// BinopPrecedence - This holds the precedence for each binary operator that is
247/// defined.
248static std::map<char, int> BinopPrecedence;
249
250/// GetTokPrecedence - Get the precedence of the pending binary operator token.
251static int GetTokPrecedence() {
252  if (!isascii(CurTok))
253    return -1;
254
255  // Make sure it's a declared binop.
256  int TokPrec = BinopPrecedence[CurTok];
257  if (TokPrec <= 0) return -1;
258  return TokPrec;
259}
260
261/// Error* - These are little helper functions for error handling.
262ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
263PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
264FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
265
266static ExprAST *ParseExpression();
267
268/// identifierexpr
269///   ::= identifier
270///   ::= identifier '(' expression* ')'
271static ExprAST *ParseIdentifierExpr() {
272  std::string IdName = IdentifierStr;
273
274  getNextToken();  // eat identifier.
275
276  if (CurTok != '(') // Simple variable ref.
277    return new VariableExprAST(IdName);
278
279  // Call.
280  getNextToken();  // eat (
281  std::vector<ExprAST*> Args;
282  if (CurTok != ')') {
283    while (1) {
284      ExprAST *Arg = ParseExpression();
285      if (!Arg) return 0;
286      Args.push_back(Arg);
287
288      if (CurTok == ')') break;
289
290      if (CurTok != ',')
291        return Error("Expected ')' or ',' in argument list");
292      getNextToken();
293    }
294  }
295
296  // Eat the ')'.
297  getNextToken();
298
299  return new CallExprAST(IdName, Args);
300}
301
302/// numberexpr ::= number
303static ExprAST *ParseNumberExpr() {
304  ExprAST *Result = new NumberExprAST(NumVal);
305  getNextToken(); // consume the number
306  return Result;
307}
308
309/// parenexpr ::= '(' expression ')'
310static ExprAST *ParseParenExpr() {
311  getNextToken();  // eat (.
312  ExprAST *V = ParseExpression();
313  if (!V) return 0;
314
315  if (CurTok != ')')
316    return Error("expected ')'");
317  getNextToken();  // eat ).
318  return V;
319}
320
321/// ifexpr ::= 'if' expression 'then' expression 'else' expression
322static ExprAST *ParseIfExpr() {
323  getNextToken();  // eat the if.
324
325  // condition.
326  ExprAST *Cond = ParseExpression();
327  if (!Cond) return 0;
328
329  if (CurTok != tok_then)
330    return Error("expected then");
331  getNextToken();  // eat the then
332
333  ExprAST *Then = ParseExpression();
334  if (Then == 0) return 0;
335
336  if (CurTok != tok_else)
337    return Error("expected else");
338
339  getNextToken();
340
341  ExprAST *Else = ParseExpression();
342  if (!Else) return 0;
343
344  return new IfExprAST(Cond, Then, Else);
345}
346
347/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
348static ExprAST *ParseForExpr() {
349  getNextToken();  // eat the for.
350
351  if (CurTok != tok_identifier)
352    return Error("expected identifier after for");
353
354  std::string IdName = IdentifierStr;
355  getNextToken();  // eat identifier.
356
357  if (CurTok != '=')
358    return Error("expected '=' after for");
359  getNextToken();  // eat '='.
360
361
362  ExprAST *Start = ParseExpression();
363  if (Start == 0) return 0;
364  if (CurTok != ',')
365    return Error("expected ',' after for start value");
366  getNextToken();
367
368  ExprAST *End = ParseExpression();
369  if (End == 0) return 0;
370
371  // The step value is optional.
372  ExprAST *Step = 0;
373  if (CurTok == ',') {
374    getNextToken();
375    Step = ParseExpression();
376    if (Step == 0) return 0;
377  }
378
379  if (CurTok != tok_in)
380    return Error("expected 'in' after for");
381  getNextToken();  // eat 'in'.
382
383  ExprAST *Body = ParseExpression();
384  if (Body == 0) return 0;
385
386  return new ForExprAST(IdName, Start, End, Step, Body);
387}
388
389/// varexpr ::= 'var' identifier ('=' expression)?
390//                    (',' identifier ('=' expression)?)* 'in' expression
391static ExprAST *ParseVarExpr() {
392  getNextToken();  // eat the var.
393
394  std::vector<std::pair<std::string, ExprAST*> > VarNames;
395
396  // At least one variable name is required.
397  if (CurTok != tok_identifier)
398    return Error("expected identifier after var");
399
400  while (1) {
401    std::string Name = IdentifierStr;
402    getNextToken();  // eat identifier.
403
404    // Read the optional initializer.
405    ExprAST *Init = 0;
406    if (CurTok == '=') {
407      getNextToken(); // eat the '='.
408
409      Init = ParseExpression();
410      if (Init == 0) return 0;
411    }
412
413    VarNames.push_back(std::make_pair(Name, Init));
414
415    // End of var list, exit loop.
416    if (CurTok != ',') break;
417    getNextToken(); // eat the ','.
418
419    if (CurTok != tok_identifier)
420      return Error("expected identifier list after var");
421  }
422
423  // At this point, we have to have 'in'.
424  if (CurTok != tok_in)
425    return Error("expected 'in' keyword after 'var'");
426  getNextToken();  // eat 'in'.
427
428  ExprAST *Body = ParseExpression();
429  if (Body == 0) return 0;
430
431  return new VarExprAST(VarNames, Body);
432}
433
434/// primary
435///   ::= identifierexpr
436///   ::= numberexpr
437///   ::= parenexpr
438///   ::= ifexpr
439///   ::= forexpr
440///   ::= varexpr
441static ExprAST *ParsePrimary() {
442  switch (CurTok) {
443  default: return Error("unknown token when expecting an expression");
444  case tok_identifier: return ParseIdentifierExpr();
445  case tok_number:     return ParseNumberExpr();
446  case '(':            return ParseParenExpr();
447  case tok_if:         return ParseIfExpr();
448  case tok_for:        return ParseForExpr();
449  case tok_var:        return ParseVarExpr();
450  }
451}
452
453/// unary
454///   ::= primary
455///   ::= '!' unary
456static ExprAST *ParseUnary() {
457  // If the current token is not an operator, it must be a primary expr.
458  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
459    return ParsePrimary();
460
461  // If this is a unary operator, read it.
462  int Opc = CurTok;
463  getNextToken();
464  if (ExprAST *Operand = ParseUnary())
465    return new UnaryExprAST(Opc, Operand);
466  return 0;
467}
468
469/// binoprhs
470///   ::= ('+' unary)*
471static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
472  // If this is a binop, find its precedence.
473  while (1) {
474    int TokPrec = GetTokPrecedence();
475
476    // If this is a binop that binds at least as tightly as the current binop,
477    // consume it, otherwise we are done.
478    if (TokPrec < ExprPrec)
479      return LHS;
480
481    // Okay, we know this is a binop.
482    int BinOp = CurTok;
483    getNextToken();  // eat binop
484
485    // Parse the unary expression after the binary operator.
486    ExprAST *RHS = ParseUnary();
487    if (!RHS) return 0;
488
489    // If BinOp binds less tightly with RHS than the operator after RHS, let
490    // the pending operator take RHS as its LHS.
491    int NextPrec = GetTokPrecedence();
492    if (TokPrec < NextPrec) {
493      RHS = ParseBinOpRHS(TokPrec+1, RHS);
494      if (RHS == 0) return 0;
495    }
496
497    // Merge LHS/RHS.
498    LHS = new BinaryExprAST(BinOp, LHS, RHS);
499  }
500}
501
502/// expression
503///   ::= unary binoprhs
504///
505static ExprAST *ParseExpression() {
506  ExprAST *LHS = ParseUnary();
507  if (!LHS) return 0;
508
509  return ParseBinOpRHS(0, LHS);
510}
511
512/// prototype
513///   ::= id '(' id* ')'
514///   ::= binary LETTER number? (id, id)
515///   ::= unary LETTER (id)
516static PrototypeAST *ParsePrototype() {
517  std::string FnName;
518
519  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
520  unsigned BinaryPrecedence = 30;
521
522  switch (CurTok) {
523  default:
524    return ErrorP("Expected function name in prototype");
525  case tok_identifier:
526    FnName = IdentifierStr;
527    Kind = 0;
528    getNextToken();
529    break;
530  case tok_unary:
531    getNextToken();
532    if (!isascii(CurTok))
533      return ErrorP("Expected unary operator");
534    FnName = "unary";
535    FnName += (char)CurTok;
536    Kind = 1;
537    getNextToken();
538    break;
539  case tok_binary:
540    getNextToken();
541    if (!isascii(CurTok))
542      return ErrorP("Expected binary operator");
543    FnName = "binary";
544    FnName += (char)CurTok;
545    Kind = 2;
546    getNextToken();
547
548    // Read the precedence if present.
549    if (CurTok == tok_number) {
550      if (NumVal < 1 || NumVal > 100)
551        return ErrorP("Invalid precedecnce: must be 1..100");
552      BinaryPrecedence = (unsigned)NumVal;
553      getNextToken();
554    }
555    break;
556  }
557
558  if (CurTok != '(')
559    return ErrorP("Expected '(' in prototype");
560
561  std::vector<std::string> ArgNames;
562  while (getNextToken() == tok_identifier)
563    ArgNames.push_back(IdentifierStr);
564  if (CurTok != ')')
565    return ErrorP("Expected ')' in prototype");
566
567  // success.
568  getNextToken();  // eat ')'.
569
570  // Verify right number of names for operator.
571  if (Kind && ArgNames.size() != Kind)
572    return ErrorP("Invalid number of operands for operator");
573
574  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
575}
576
577/// definition ::= 'def' prototype expression
578static FunctionAST *ParseDefinition() {
579  getNextToken();  // eat def.
580  PrototypeAST *Proto = ParsePrototype();
581  if (Proto == 0) return 0;
582
583  if (ExprAST *E = ParseExpression())
584    return new FunctionAST(Proto, E);
585  return 0;
586}
587
588/// toplevelexpr ::= expression
589static FunctionAST *ParseTopLevelExpr() {
590  if (ExprAST *E = ParseExpression()) {
591    // Make an anonymous proto.
592    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
593    return new FunctionAST(Proto, E);
594  }
595  return 0;
596}
597
598/// external ::= 'extern' prototype
599static PrototypeAST *ParseExtern() {
600  getNextToken();  // eat extern.
601  return ParsePrototype();
602}
603
604//===----------------------------------------------------------------------===//
605// Code Generation
606//===----------------------------------------------------------------------===//
607
608static Module *TheModule;
609static IRBuilder<> Builder(getGlobalContext());
610static std::map<std::string, AllocaInst*> NamedValues;
611static FunctionPassManager *TheFPM;
612
613Value *ErrorV(const char *Str) { Error(Str); return 0; }
614
615/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
616/// the function.  This is used for mutable variables etc.
617static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
618                                          const std::string &VarName) {
619  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
620                 TheFunction->getEntryBlock().begin());
621  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
622                           VarName.c_str());
623}
624
625Value *NumberExprAST::Codegen() {
626  return ConstantFP::get(getGlobalContext(), APFloat(Val));
627}
628
629Value *VariableExprAST::Codegen() {
630  // Look this variable up in the function.
631  Value *V = NamedValues[Name];
632  if (V == 0) return ErrorV("Unknown variable name");
633
634  // Load the value.
635  return Builder.CreateLoad(V, Name.c_str());
636}
637
638Value *UnaryExprAST::Codegen() {
639  Value *OperandV = Operand->Codegen();
640  if (OperandV == 0) return 0;
641
642  Function *F = TheModule->getFunction(std::string("unary")+Opcode);
643  if (F == 0)
644    return ErrorV("Unknown unary operator");
645
646  return Builder.CreateCall(F, OperandV, "unop");
647}
648
649Value *BinaryExprAST::Codegen() {
650  // Special case '=' because we don't want to emit the LHS as an expression.
651  if (Op == '=') {
652    // Assignment requires the LHS to be an identifier.
653    VariableExprAST *LHSE = dynamic_cast<VariableExprAST*>(LHS);
654    if (!LHSE)
655      return ErrorV("destination of '=' must be a variable");
656    // Codegen the RHS.
657    Value *Val = RHS->Codegen();
658    if (Val == 0) return 0;
659
660    // Look up the name.
661    Value *Variable = NamedValues[LHSE->getName()];
662    if (Variable == 0) return ErrorV("Unknown variable name");
663
664    Builder.CreateStore(Val, Variable);
665    return Val;
666  }
667
668  Value *L = LHS->Codegen();
669  Value *R = RHS->Codegen();
670  if (L == 0 || R == 0) return 0;
671
672  switch (Op) {
673  case '+': return Builder.CreateFAdd(L, R, "addtmp");
674  case '-': return Builder.CreateFSub(L, R, "subtmp");
675  case '*': return Builder.CreateFMul(L, R, "multmp");
676  case '<':
677    L = Builder.CreateFCmpULT(L, R, "cmptmp");
678    // Convert bool 0/1 to double 0.0 or 1.0
679    return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
680                                "booltmp");
681  default: break;
682  }
683
684  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
685  // a call to it.
686  Function *F = TheModule->getFunction(std::string("binary")+Op);
687  assert(F && "binary operator not found!");
688
689  Value *Ops[] = { L, R };
690  return Builder.CreateCall(F, Ops, "binop");
691}
692
693Value *CallExprAST::Codegen() {
694  // Look up the name in the global module table.
695  Function *CalleeF = TheModule->getFunction(Callee);
696  if (CalleeF == 0)
697    return ErrorV("Unknown function referenced");
698
699  // If argument mismatch error.
700  if (CalleeF->arg_size() != Args.size())
701    return ErrorV("Incorrect # arguments passed");
702
703  std::vector<Value*> ArgsV;
704  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
705    ArgsV.push_back(Args[i]->Codegen());
706    if (ArgsV.back() == 0) return 0;
707  }
708
709  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
710}
711
712Value *IfExprAST::Codegen() {
713  Value *CondV = Cond->Codegen();
714  if (CondV == 0) return 0;
715
716  // Convert condition to a bool by comparing equal to 0.0.
717  CondV = Builder.CreateFCmpONE(CondV,
718                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
719                                "ifcond");
720
721  Function *TheFunction = Builder.GetInsertBlock()->getParent();
722
723  // Create blocks for the then and else cases.  Insert the 'then' block at the
724  // end of the function.
725  BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
726  BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
727  BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
728
729  Builder.CreateCondBr(CondV, ThenBB, ElseBB);
730
731  // Emit then value.
732  Builder.SetInsertPoint(ThenBB);
733
734  Value *ThenV = Then->Codegen();
735  if (ThenV == 0) return 0;
736
737  Builder.CreateBr(MergeBB);
738  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
739  ThenBB = Builder.GetInsertBlock();
740
741  // Emit else block.
742  TheFunction->getBasicBlockList().push_back(ElseBB);
743  Builder.SetInsertPoint(ElseBB);
744
745  Value *ElseV = Else->Codegen();
746  if (ElseV == 0) return 0;
747
748  Builder.CreateBr(MergeBB);
749  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
750  ElseBB = Builder.GetInsertBlock();
751
752  // Emit merge block.
753  TheFunction->getBasicBlockList().push_back(MergeBB);
754  Builder.SetInsertPoint(MergeBB);
755  PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
756                                  "iftmp");
757
758  PN->addIncoming(ThenV, ThenBB);
759  PN->addIncoming(ElseV, ElseBB);
760  return PN;
761}
762
763Value *ForExprAST::Codegen() {
764  // Output this as:
765  //   var = alloca double
766  //   ...
767  //   start = startexpr
768  //   store start -> var
769  //   goto loop
770  // loop:
771  //   ...
772  //   bodyexpr
773  //   ...
774  // loopend:
775  //   step = stepexpr
776  //   endcond = endexpr
777  //
778  //   curvar = load var
779  //   nextvar = curvar + step
780  //   store nextvar -> var
781  //   br endcond, loop, endloop
782  // outloop:
783
784  Function *TheFunction = Builder.GetInsertBlock()->getParent();
785
786  // Create an alloca for the variable in the entry block.
787  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
788
789  // Emit the start code first, without 'variable' in scope.
790  Value *StartVal = Start->Codegen();
791  if (StartVal == 0) return 0;
792
793  // Store the value into the alloca.
794  Builder.CreateStore(StartVal, Alloca);
795
796  // Make the new basic block for the loop header, inserting after current
797  // block.
798  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
799
800  // Insert an explicit fall through from the current block to the LoopBB.
801  Builder.CreateBr(LoopBB);
802
803  // Start insertion in LoopBB.
804  Builder.SetInsertPoint(LoopBB);
805
806  // Within the loop, the variable is defined equal to the PHI node.  If it
807  // shadows an existing variable, we have to restore it, so save it now.
808  AllocaInst *OldVal = NamedValues[VarName];
809  NamedValues[VarName] = Alloca;
810
811  // Emit the body of the loop.  This, like any other expr, can change the
812  // current BB.  Note that we ignore the value computed by the body, but don't
813  // allow an error.
814  if (Body->Codegen() == 0)
815    return 0;
816
817  // Emit the step value.
818  Value *StepVal;
819  if (Step) {
820    StepVal = Step->Codegen();
821    if (StepVal == 0) return 0;
822  } else {
823    // If not specified, use 1.0.
824    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
825  }
826
827  // Compute the end condition.
828  Value *EndCond = End->Codegen();
829  if (EndCond == 0) return EndCond;
830
831  // Reload, increment, and restore the alloca.  This handles the case where
832  // the body of the loop mutates the variable.
833  Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
834  Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
835  Builder.CreateStore(NextVar, Alloca);
836
837  // Convert condition to a bool by comparing equal to 0.0.
838  EndCond = Builder.CreateFCmpONE(EndCond,
839                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
840                                  "loopcond");
841
842  // Create the "after loop" block and insert it.
843  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
844
845  // Insert the conditional branch into the end of LoopEndBB.
846  Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
847
848  // Any new code will be inserted in AfterBB.
849  Builder.SetInsertPoint(AfterBB);
850
851  // Restore the unshadowed variable.
852  if (OldVal)
853    NamedValues[VarName] = OldVal;
854  else
855    NamedValues.erase(VarName);
856
857
858  // for expr always returns 0.0.
859  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
860}
861
862Value *VarExprAST::Codegen() {
863  std::vector<AllocaInst *> OldBindings;
864
865  Function *TheFunction = Builder.GetInsertBlock()->getParent();
866
867  // Register all variables and emit their initializer.
868  for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
869    const std::string &VarName = VarNames[i].first;
870    ExprAST *Init = VarNames[i].second;
871
872    // Emit the initializer before adding the variable to scope, this prevents
873    // the initializer from referencing the variable itself, and permits stuff
874    // like this:
875    //  var a = 1 in
876    //    var a = a in ...   # refers to outer 'a'.
877    Value *InitVal;
878    if (Init) {
879      InitVal = Init->Codegen();
880      if (InitVal == 0) return 0;
881    } else { // If not specified, use 0.0.
882      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
883    }
884
885    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
886    Builder.CreateStore(InitVal, Alloca);
887
888    // Remember the old variable binding so that we can restore the binding when
889    // we unrecurse.
890    OldBindings.push_back(NamedValues[VarName]);
891
892    // Remember this binding.
893    NamedValues[VarName] = Alloca;
894  }
895
896  // Codegen the body, now that all vars are in scope.
897  Value *BodyVal = Body->Codegen();
898  if (BodyVal == 0) return 0;
899
900  // Pop all our variables from scope.
901  for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
902    NamedValues[VarNames[i].first] = OldBindings[i];
903
904  // Return the body computation.
905  return BodyVal;
906}
907
908Function *PrototypeAST::Codegen() {
909  // Make the function type:  double(double,double) etc.
910  std::vector<Type*> Doubles(Args.size(),
911                             Type::getDoubleTy(getGlobalContext()));
912  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
913                                       Doubles, false);
914
915  Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
916
917  // If F conflicted, there was already something named 'Name'.  If it has a
918  // body, don't allow redefinition or reextern.
919  if (F->getName() != Name) {
920    // Delete the one we just made and get the existing one.
921    F->eraseFromParent();
922    F = TheModule->getFunction(Name);
923
924    // If F already has a body, reject this.
925    if (!F->empty()) {
926      ErrorF("redefinition of function");
927      return 0;
928    }
929
930    // If F took a different number of args, reject.
931    if (F->arg_size() != Args.size()) {
932      ErrorF("redefinition of function with different # args");
933      return 0;
934    }
935  }
936
937  // Set names for all arguments.
938  unsigned Idx = 0;
939  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
940       ++AI, ++Idx)
941    AI->setName(Args[Idx]);
942
943  return F;
944}
945
946/// CreateArgumentAllocas - Create an alloca for each argument and register the
947/// argument in the symbol table so that references to it will succeed.
948void PrototypeAST::CreateArgumentAllocas(Function *F) {
949  Function::arg_iterator AI = F->arg_begin();
950  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
951    // Create an alloca for this variable.
952    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
953
954    // Store the initial value into the alloca.
955    Builder.CreateStore(AI, Alloca);
956
957    // Add arguments to variable symbol table.
958    NamedValues[Args[Idx]] = Alloca;
959  }
960}
961
962Function *FunctionAST::Codegen() {
963  NamedValues.clear();
964
965  Function *TheFunction = Proto->Codegen();
966  if (TheFunction == 0)
967    return 0;
968
969  // If this is an operator, install it.
970  if (Proto->isBinaryOp())
971    BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
972
973  // Create a new basic block to start insertion into.
974  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
975  Builder.SetInsertPoint(BB);
976
977  // Add all arguments to the symbol table and create their allocas.
978  Proto->CreateArgumentAllocas(TheFunction);
979
980  if (Value *RetVal = Body->Codegen()) {
981    // Finish off the function.
982    Builder.CreateRet(RetVal);
983
984    // Validate the generated code, checking for consistency.
985    verifyFunction(*TheFunction);
986
987    // Optimize the function.
988    TheFPM->run(*TheFunction);
989
990    return TheFunction;
991  }
992
993  // Error reading body, remove function.
994  TheFunction->eraseFromParent();
995
996  if (Proto->isBinaryOp())
997    BinopPrecedence.erase(Proto->getOperatorName());
998  return 0;
999}
1000
1001//===----------------------------------------------------------------------===//
1002// Top-Level parsing and JIT Driver
1003//===----------------------------------------------------------------------===//
1004
1005static ExecutionEngine *TheExecutionEngine;
1006
1007static void HandleDefinition() {
1008  if (FunctionAST *F = ParseDefinition()) {
1009    if (Function *LF = F->Codegen()) {
1010      fprintf(stderr, "Read function definition:");
1011      LF->dump();
1012    }
1013  } else {
1014    // Skip token for error recovery.
1015    getNextToken();
1016  }
1017}
1018
1019static void HandleExtern() {
1020  if (PrototypeAST *P = ParseExtern()) {
1021    if (Function *F = P->Codegen()) {
1022      fprintf(stderr, "Read extern: ");
1023      F->dump();
1024    }
1025  } else {
1026    // Skip token for error recovery.
1027    getNextToken();
1028  }
1029}
1030
1031static void HandleTopLevelExpression() {
1032  // Evaluate a top-level expression into an anonymous function.
1033  if (FunctionAST *F = ParseTopLevelExpr()) {
1034    if (Function *LF = F->Codegen()) {
1035      // JIT the function, returning a function pointer.
1036      void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
1037
1038      // Cast it to the right type (takes no arguments, returns a double) so we
1039      // can call it as a native function.
1040      double (*FP)() = (double (*)())(intptr_t)FPtr;
1041      fprintf(stderr, "Evaluated to %f\n", FP());
1042    }
1043  } else {
1044    // Skip token for error recovery.
1045    getNextToken();
1046  }
1047}
1048
1049/// top ::= definition | external | expression | ';'
1050static void MainLoop() {
1051  while (1) {
1052    fprintf(stderr, "ready> ");
1053    switch (CurTok) {
1054    case tok_eof:    return;
1055    case ';':        getNextToken(); break;  // ignore top-level semicolons.
1056    case tok_def:    HandleDefinition(); break;
1057    case tok_extern: HandleExtern(); break;
1058    default:         HandleTopLevelExpression(); break;
1059    }
1060  }
1061}
1062
1063//===----------------------------------------------------------------------===//
1064// "Library" functions that can be "extern'd" from user code.
1065//===----------------------------------------------------------------------===//
1066
1067/// putchard - putchar that takes a double and returns 0.
1068extern "C"
1069double putchard(double X) {
1070  putchar((char)X);
1071  return 0;
1072}
1073
1074/// printd - printf that takes a double prints it as "%f\n", returning 0.
1075extern "C"
1076double printd(double X) {
1077  printf("%f\n", X);
1078  return 0;
1079}
1080
1081//===----------------------------------------------------------------------===//
1082// Main driver code.
1083//===----------------------------------------------------------------------===//
1084
1085int main() {
1086  InitializeNativeTarget();
1087  LLVMContext &Context = getGlobalContext();
1088
1089  // Install standard binary operators.
1090  // 1 is lowest precedence.
1091  BinopPrecedence['='] = 2;
1092  BinopPrecedence['<'] = 10;
1093  BinopPrecedence['+'] = 20;
1094  BinopPrecedence['-'] = 20;
1095  BinopPrecedence['*'] = 40;  // highest.
1096
1097  // Prime the first token.
1098  fprintf(stderr, "ready> ");
1099  getNextToken();
1100
1101  // Make the module, which holds all the code.
1102  TheModule = new Module("my cool jit", Context);
1103
1104  // Create the JIT.  This takes ownership of the module.
1105  std::string ErrStr;
1106  TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create();
1107  if (!TheExecutionEngine) {
1108    fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
1109    exit(1);
1110  }
1111
1112  FunctionPassManager OurFPM(TheModule);
1113
1114  // Set up the optimizer pipeline.  Start with registering info about how the
1115  // target lays out data structures.
1116  TheModule->setDataLayout(TheExecutionEngine->getDataLayout());
1117  OurFPM.add(new DataLayoutPass(TheModule));
1118  // Provide basic AliasAnalysis support for GVN.
1119  OurFPM.add(createBasicAliasAnalysisPass());
1120  // Promote allocas to registers.
1121  OurFPM.add(createPromoteMemoryToRegisterPass());
1122  // Do simple "peephole" optimizations and bit-twiddling optzns.
1123  OurFPM.add(createInstructionCombiningPass());
1124  // Reassociate expressions.
1125  OurFPM.add(createReassociatePass());
1126  // Eliminate Common SubExpressions.
1127  OurFPM.add(createGVNPass());
1128  // Simplify the control flow graph (deleting unreachable blocks, etc).
1129  OurFPM.add(createCFGSimplificationPass());
1130
1131  OurFPM.doInitialization();
1132
1133  // Set the global so the code gen can use this.
1134  TheFPM = &OurFPM;
1135
1136  // Run the main "interpreter loop" now.
1137  MainLoop();
1138
1139  TheFPM = 0;
1140
1141  // Print out all of the generated code.
1142  TheModule->dump();
1143
1144  return 0;
1145}
1146