1#include "llvm/Analysis/Passes.h"
2#include "llvm/ExecutionEngine/Orc/CompileUtils.h"
3#include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
4#include "llvm/ExecutionEngine/Orc/LambdaResolver.h"
5#include "llvm/ExecutionEngine/Orc/LazyEmittingLayer.h"
6#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
7#include "llvm/IR/DataLayout.h"
8#include "llvm/IR/DerivedTypes.h"
9#include "llvm/IR/IRBuilder.h"
10#include "llvm/IR/LegacyPassManager.h"
11#include "llvm/IR/LLVMContext.h"
12#include "llvm/IR/Module.h"
13#include "llvm/IR/Verifier.h"
14#include "llvm/Support/TargetSelect.h"
15#include "llvm/Transforms/Scalar.h"
16#include <cctype>
17#include <iomanip>
18#include <iostream>
19#include <map>
20#include <sstream>
21#include <string>
22#include <vector>
23
24using namespace llvm;
25using namespace llvm::orc;
26
27//===----------------------------------------------------------------------===//
28// Lexer
29//===----------------------------------------------------------------------===//
30
31// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
32// of these for known things.
33enum Token {
34  tok_eof = -1,
35
36  // commands
37  tok_def = -2, tok_extern = -3,
38
39  // primary
40  tok_identifier = -4, tok_number = -5,
41
42  // control
43  tok_if = -6, tok_then = -7, tok_else = -8,
44  tok_for = -9, tok_in = -10,
45
46  // operators
47  tok_binary = -11, tok_unary = -12,
48
49  // var definition
50  tok_var = -13
51};
52
53static std::string IdentifierStr;  // Filled in if tok_identifier
54static double NumVal;              // Filled in if tok_number
55
56/// gettok - Return the next token from standard input.
57static int gettok() {
58  static int LastChar = ' ';
59
60  // Skip any whitespace.
61  while (isspace(LastChar))
62    LastChar = getchar();
63
64  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
65    IdentifierStr = LastChar;
66    while (isalnum((LastChar = getchar())))
67      IdentifierStr += LastChar;
68
69    if (IdentifierStr == "def") return tok_def;
70    if (IdentifierStr == "extern") return tok_extern;
71    if (IdentifierStr == "if") return tok_if;
72    if (IdentifierStr == "then") return tok_then;
73    if (IdentifierStr == "else") return tok_else;
74    if (IdentifierStr == "for") return tok_for;
75    if (IdentifierStr == "in") return tok_in;
76    if (IdentifierStr == "binary") return tok_binary;
77    if (IdentifierStr == "unary") return tok_unary;
78    if (IdentifierStr == "var") return tok_var;
79    return tok_identifier;
80  }
81
82  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
83    std::string NumStr;
84    do {
85      NumStr += LastChar;
86      LastChar = getchar();
87    } while (isdigit(LastChar) || LastChar == '.');
88
89    NumVal = strtod(NumStr.c_str(), nullptr);
90    return tok_number;
91  }
92
93  if (LastChar == '#') {
94    // Comment until end of line.
95    do LastChar = getchar();
96    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
97
98    if (LastChar != EOF)
99      return gettok();
100  }
101
102  // Check for end of file.  Don't eat the EOF.
103  if (LastChar == EOF)
104    return tok_eof;
105
106  // Otherwise, just return the character as its ascii value.
107  int ThisChar = LastChar;
108  LastChar = getchar();
109  return ThisChar;
110}
111
112//===----------------------------------------------------------------------===//
113// Abstract Syntax Tree (aka Parse Tree)
114//===----------------------------------------------------------------------===//
115
116class IRGenContext;
117
118/// ExprAST - Base class for all expression nodes.
119struct ExprAST {
120  virtual ~ExprAST() {}
121  virtual Value *IRGen(IRGenContext &C) const = 0;
122};
123
124/// NumberExprAST - Expression class for numeric literals like "1.0".
125struct NumberExprAST : public ExprAST {
126  NumberExprAST(double Val) : Val(Val) {}
127  Value *IRGen(IRGenContext &C) const override;
128
129  double Val;
130};
131
132/// VariableExprAST - Expression class for referencing a variable, like "a".
133struct VariableExprAST : public ExprAST {
134  VariableExprAST(std::string Name) : Name(std::move(Name)) {}
135  Value *IRGen(IRGenContext &C) const override;
136
137  std::string Name;
138};
139
140/// UnaryExprAST - Expression class for a unary operator.
141struct UnaryExprAST : public ExprAST {
142  UnaryExprAST(char Opcode, std::unique_ptr<ExprAST> Operand)
143    : Opcode(std::move(Opcode)), Operand(std::move(Operand)) {}
144
145  Value *IRGen(IRGenContext &C) const override;
146
147  char Opcode;
148  std::unique_ptr<ExprAST> Operand;
149};
150
151/// BinaryExprAST - Expression class for a binary operator.
152struct BinaryExprAST : public ExprAST {
153  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
154                std::unique_ptr<ExprAST> RHS)
155    : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
156
157  Value *IRGen(IRGenContext &C) const override;
158
159  char Op;
160  std::unique_ptr<ExprAST> LHS, RHS;
161};
162
163/// CallExprAST - Expression class for function calls.
164struct CallExprAST : public ExprAST {
165  CallExprAST(std::string CalleeName,
166              std::vector<std::unique_ptr<ExprAST>> Args)
167    : CalleeName(std::move(CalleeName)), Args(std::move(Args)) {}
168
169  Value *IRGen(IRGenContext &C) const override;
170
171  std::string CalleeName;
172  std::vector<std::unique_ptr<ExprAST>> Args;
173};
174
175/// IfExprAST - Expression class for if/then/else.
176struct IfExprAST : public ExprAST {
177  IfExprAST(std::unique_ptr<ExprAST> Cond, std::unique_ptr<ExprAST> Then,
178            std::unique_ptr<ExprAST> Else)
179    : Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}
180  Value *IRGen(IRGenContext &C) const override;
181
182  std::unique_ptr<ExprAST> Cond, Then, Else;
183};
184
185/// ForExprAST - Expression class for for/in.
186struct ForExprAST : public ExprAST {
187  ForExprAST(std::string VarName, std::unique_ptr<ExprAST> Start,
188             std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
189             std::unique_ptr<ExprAST> Body)
190    : VarName(std::move(VarName)), Start(std::move(Start)), End(std::move(End)),
191      Step(std::move(Step)), Body(std::move(Body)) {}
192
193  Value *IRGen(IRGenContext &C) const override;
194
195  std::string VarName;
196  std::unique_ptr<ExprAST> Start, End, Step, Body;
197};
198
199/// VarExprAST - Expression class for var/in
200struct VarExprAST : public ExprAST {
201  typedef std::pair<std::string, std::unique_ptr<ExprAST>> Binding;
202  typedef std::vector<Binding> BindingList;
203
204  VarExprAST(BindingList VarBindings, std::unique_ptr<ExprAST> Body)
205    : VarBindings(std::move(VarBindings)), Body(std::move(Body)) {}
206
207  Value *IRGen(IRGenContext &C) const override;
208
209  BindingList VarBindings;
210  std::unique_ptr<ExprAST> Body;
211};
212
213/// PrototypeAST - This class represents the "prototype" for a function,
214/// which captures its argument names as well as if it is an operator.
215struct PrototypeAST {
216  PrototypeAST(std::string Name, std::vector<std::string> Args,
217               bool IsOperator = false, unsigned Precedence = 0)
218    : Name(std::move(Name)), Args(std::move(Args)), IsOperator(IsOperator),
219      Precedence(Precedence) {}
220
221  Function *IRGen(IRGenContext &C) const;
222  void CreateArgumentAllocas(Function *F, IRGenContext &C);
223
224  bool isUnaryOp() const { return IsOperator && Args.size() == 1; }
225  bool isBinaryOp() const { return IsOperator && Args.size() == 2; }
226
227  char getOperatorName() const {
228    assert(isUnaryOp() || isBinaryOp());
229    return Name[Name.size()-1];
230  }
231
232  std::string Name;
233  std::vector<std::string> Args;
234  bool IsOperator;
235  unsigned Precedence;  // Precedence if a binary op.
236};
237
238/// FunctionAST - This class represents a function definition itself.
239struct FunctionAST {
240  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
241              std::unique_ptr<ExprAST> Body)
242    : Proto(std::move(Proto)), Body(std::move(Body)) {}
243
244  Function *IRGen(IRGenContext &C) const;
245
246  std::unique_ptr<PrototypeAST> Proto;
247  std::unique_ptr<ExprAST> Body;
248};
249
250//===----------------------------------------------------------------------===//
251// Parser
252//===----------------------------------------------------------------------===//
253
254/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
255/// token the parser is looking at.  getNextToken reads another token from the
256/// lexer and updates CurTok with its results.
257static int CurTok;
258static int getNextToken() {
259  return CurTok = gettok();
260}
261
262/// BinopPrecedence - This holds the precedence for each binary operator that is
263/// defined.
264static std::map<char, int> BinopPrecedence;
265
266/// GetTokPrecedence - Get the precedence of the pending binary operator token.
267static int GetTokPrecedence() {
268  if (!isascii(CurTok))
269    return -1;
270
271  // Make sure it's a declared binop.
272  int TokPrec = BinopPrecedence[CurTok];
273  if (TokPrec <= 0) return -1;
274  return TokPrec;
275}
276
277template <typename T>
278std::unique_ptr<T> ErrorU(const std::string &Str) {
279  std::cerr << "Error: " << Str << "\n";
280  return nullptr;
281}
282
283template <typename T>
284T* ErrorP(const std::string &Str) {
285  std::cerr << "Error: " << Str << "\n";
286  return nullptr;
287}
288
289static std::unique_ptr<ExprAST> ParseExpression();
290
291/// identifierexpr
292///   ::= identifier
293///   ::= identifier '(' expression* ')'
294static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
295  std::string IdName = IdentifierStr;
296
297  getNextToken();  // eat identifier.
298
299  if (CurTok != '(') // Simple variable ref.
300    return llvm::make_unique<VariableExprAST>(IdName);
301
302  // Call.
303  getNextToken();  // eat (
304  std::vector<std::unique_ptr<ExprAST>> Args;
305  if (CurTok != ')') {
306    while (1) {
307      auto Arg = ParseExpression();
308      if (!Arg) return nullptr;
309      Args.push_back(std::move(Arg));
310
311      if (CurTok == ')') break;
312
313      if (CurTok != ',')
314        return ErrorU<CallExprAST>("Expected ')' or ',' in argument list");
315      getNextToken();
316    }
317  }
318
319  // Eat the ')'.
320  getNextToken();
321
322  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
323}
324
325/// numberexpr ::= number
326static std::unique_ptr<NumberExprAST> ParseNumberExpr() {
327  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
328  getNextToken(); // consume the number
329  return Result;
330}
331
332/// parenexpr ::= '(' expression ')'
333static std::unique_ptr<ExprAST> ParseParenExpr() {
334  getNextToken();  // eat (.
335  auto V = ParseExpression();
336  if (!V)
337    return nullptr;
338
339  if (CurTok != ')')
340    return ErrorU<ExprAST>("expected ')'");
341  getNextToken();  // eat ).
342  return V;
343}
344
345/// ifexpr ::= 'if' expression 'then' expression 'else' expression
346static std::unique_ptr<ExprAST> ParseIfExpr() {
347  getNextToken();  // eat the if.
348
349  // condition.
350  auto Cond = ParseExpression();
351  if (!Cond)
352    return nullptr;
353
354  if (CurTok != tok_then)
355    return ErrorU<ExprAST>("expected then");
356  getNextToken();  // eat the then
357
358  auto Then = ParseExpression();
359  if (!Then)
360    return nullptr;
361
362  if (CurTok != tok_else)
363    return ErrorU<ExprAST>("expected else");
364
365  getNextToken();
366
367  auto Else = ParseExpression();
368  if (!Else)
369    return nullptr;
370
371  return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
372                                      std::move(Else));
373}
374
375/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
376static std::unique_ptr<ForExprAST> ParseForExpr() {
377  getNextToken();  // eat the for.
378
379  if (CurTok != tok_identifier)
380    return ErrorU<ForExprAST>("expected identifier after for");
381
382  std::string IdName = IdentifierStr;
383  getNextToken();  // eat identifier.
384
385  if (CurTok != '=')
386    return ErrorU<ForExprAST>("expected '=' after for");
387  getNextToken();  // eat '='.
388
389  auto Start = ParseExpression();
390  if (!Start)
391    return nullptr;
392  if (CurTok != ',')
393    return ErrorU<ForExprAST>("expected ',' after for start value");
394  getNextToken();
395
396  auto End = ParseExpression();
397  if (!End)
398    return nullptr;
399
400  // The step value is optional.
401  std::unique_ptr<ExprAST> Step;
402  if (CurTok == ',') {
403    getNextToken();
404    Step = ParseExpression();
405    if (!Step)
406      return nullptr;
407  }
408
409  if (CurTok != tok_in)
410    return ErrorU<ForExprAST>("expected 'in' after for");
411  getNextToken();  // eat 'in'.
412
413  auto Body = ParseExpression();
414  if (Body)
415    return nullptr;
416
417  return llvm::make_unique<ForExprAST>(IdName, std::move(Start), std::move(End),
418                                       std::move(Step), std::move(Body));
419}
420
421/// varexpr ::= 'var' identifier ('=' expression)?
422//                    (',' identifier ('=' expression)?)* 'in' expression
423static std::unique_ptr<VarExprAST> ParseVarExpr() {
424  getNextToken();  // eat the var.
425
426  VarExprAST::BindingList VarBindings;
427
428  // At least one variable name is required.
429  if (CurTok != tok_identifier)
430    return ErrorU<VarExprAST>("expected identifier after var");
431
432  while (1) {
433    std::string Name = IdentifierStr;
434    getNextToken();  // eat identifier.
435
436    // Read the optional initializer.
437    std::unique_ptr<ExprAST> Init;
438    if (CurTok == '=') {
439      getNextToken(); // eat the '='.
440
441      Init = ParseExpression();
442      if (!Init)
443        return nullptr;
444    }
445
446    VarBindings.push_back(VarExprAST::Binding(Name, std::move(Init)));
447
448    // End of var list, exit loop.
449    if (CurTok != ',') break;
450    getNextToken(); // eat the ','.
451
452    if (CurTok != tok_identifier)
453      return ErrorU<VarExprAST>("expected identifier list after var");
454  }
455
456  // At this point, we have to have 'in'.
457  if (CurTok != tok_in)
458    return ErrorU<VarExprAST>("expected 'in' keyword after 'var'");
459  getNextToken();  // eat 'in'.
460
461  auto Body = ParseExpression();
462  if (!Body)
463    return nullptr;
464
465  return llvm::make_unique<VarExprAST>(std::move(VarBindings), std::move(Body));
466}
467
468/// primary
469///   ::= identifierexpr
470///   ::= numberexpr
471///   ::= parenexpr
472///   ::= ifexpr
473///   ::= forexpr
474///   ::= varexpr
475static std::unique_ptr<ExprAST> ParsePrimary() {
476  switch (CurTok) {
477  default: return ErrorU<ExprAST>("unknown token when expecting an expression");
478  case tok_identifier: return ParseIdentifierExpr();
479  case tok_number:     return ParseNumberExpr();
480  case '(':            return ParseParenExpr();
481  case tok_if:         return ParseIfExpr();
482  case tok_for:        return ParseForExpr();
483  case tok_var:        return ParseVarExpr();
484  }
485}
486
487/// unary
488///   ::= primary
489///   ::= '!' unary
490static std::unique_ptr<ExprAST> ParseUnary() {
491  // If the current token is not an operator, it must be a primary expr.
492  if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
493    return ParsePrimary();
494
495  // If this is a unary operator, read it.
496  int Opc = CurTok;
497  getNextToken();
498  if (auto Operand = ParseUnary())
499    return llvm::make_unique<UnaryExprAST>(Opc, std::move(Operand));
500  return nullptr;
501}
502
503/// binoprhs
504///   ::= ('+' unary)*
505static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
506                                              std::unique_ptr<ExprAST> LHS) {
507  // If this is a binop, find its precedence.
508  while (1) {
509    int TokPrec = GetTokPrecedence();
510
511    // If this is a binop that binds at least as tightly as the current binop,
512    // consume it, otherwise we are done.
513    if (TokPrec < ExprPrec)
514      return LHS;
515
516    // Okay, we know this is a binop.
517    int BinOp = CurTok;
518    getNextToken();  // eat binop
519
520    // Parse the unary expression after the binary operator.
521    auto RHS = ParseUnary();
522    if (!RHS)
523      return nullptr;
524
525    // If BinOp binds less tightly with RHS than the operator after RHS, let
526    // the pending operator take RHS as its LHS.
527    int NextPrec = GetTokPrecedence();
528    if (TokPrec < NextPrec) {
529      RHS = ParseBinOpRHS(TokPrec+1, std::move(RHS));
530      if (!RHS)
531        return nullptr;
532    }
533
534    // Merge LHS/RHS.
535    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS), std::move(RHS));
536  }
537}
538
539/// expression
540///   ::= unary binoprhs
541///
542static std::unique_ptr<ExprAST> ParseExpression() {
543  auto LHS = ParseUnary();
544  if (!LHS)
545    return nullptr;
546
547  return ParseBinOpRHS(0, std::move(LHS));
548}
549
550/// prototype
551///   ::= id '(' id* ')'
552///   ::= binary LETTER number? (id, id)
553///   ::= unary LETTER (id)
554static std::unique_ptr<PrototypeAST> ParsePrototype() {
555  std::string FnName;
556
557  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
558  unsigned BinaryPrecedence = 30;
559
560  switch (CurTok) {
561  default:
562    return ErrorU<PrototypeAST>("Expected function name in prototype");
563  case tok_identifier:
564    FnName = IdentifierStr;
565    Kind = 0;
566    getNextToken();
567    break;
568  case tok_unary:
569    getNextToken();
570    if (!isascii(CurTok))
571      return ErrorU<PrototypeAST>("Expected unary operator");
572    FnName = "unary";
573    FnName += (char)CurTok;
574    Kind = 1;
575    getNextToken();
576    break;
577  case tok_binary:
578    getNextToken();
579    if (!isascii(CurTok))
580      return ErrorU<PrototypeAST>("Expected binary operator");
581    FnName = "binary";
582    FnName += (char)CurTok;
583    Kind = 2;
584    getNextToken();
585
586    // Read the precedence if present.
587    if (CurTok == tok_number) {
588      if (NumVal < 1 || NumVal > 100)
589        return ErrorU<PrototypeAST>("Invalid precedecnce: must be 1..100");
590      BinaryPrecedence = (unsigned)NumVal;
591      getNextToken();
592    }
593    break;
594  }
595
596  if (CurTok != '(')
597    return ErrorU<PrototypeAST>("Expected '(' in prototype");
598
599  std::vector<std::string> ArgNames;
600  while (getNextToken() == tok_identifier)
601    ArgNames.push_back(IdentifierStr);
602  if (CurTok != ')')
603    return ErrorU<PrototypeAST>("Expected ')' in prototype");
604
605  // success.
606  getNextToken();  // eat ')'.
607
608  // Verify right number of names for operator.
609  if (Kind && ArgNames.size() != Kind)
610    return ErrorU<PrototypeAST>("Invalid number of operands for operator");
611
612  return llvm::make_unique<PrototypeAST>(FnName, std::move(ArgNames), Kind != 0,
613                                         BinaryPrecedence);
614}
615
616/// definition ::= 'def' prototype expression
617static std::unique_ptr<FunctionAST> ParseDefinition() {
618  getNextToken();  // eat def.
619  auto Proto = ParsePrototype();
620  if (!Proto)
621    return nullptr;
622
623  if (auto Body = ParseExpression())
624    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(Body));
625  return nullptr;
626}
627
628/// toplevelexpr ::= expression
629static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
630  if (auto E = ParseExpression()) {
631    // Make an anonymous proto.
632    auto Proto =
633      llvm::make_unique<PrototypeAST>("__anon_expr", std::vector<std::string>());
634    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
635  }
636  return nullptr;
637}
638
639/// external ::= 'extern' prototype
640static std::unique_ptr<PrototypeAST> ParseExtern() {
641  getNextToken();  // eat extern.
642  return ParsePrototype();
643}
644
645//===----------------------------------------------------------------------===//
646// Code Generation
647//===----------------------------------------------------------------------===//
648
649// FIXME: Obviously we can do better than this
650std::string GenerateUniqueName(const std::string &Root) {
651  static int i = 0;
652  std::ostringstream NameStream;
653  NameStream << Root << ++i;
654  return NameStream.str();
655}
656
657std::string MakeLegalFunctionName(std::string Name)
658{
659  std::string NewName;
660  assert(!Name.empty() && "Base name must not be empty");
661
662  // Start with what we have
663  NewName = Name;
664
665  // Look for a numberic first character
666  if (NewName.find_first_of("0123456789") == 0) {
667    NewName.insert(0, 1, 'n');
668  }
669
670  // Replace illegal characters with their ASCII equivalent
671  std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
672  size_t pos;
673  while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
674    std::ostringstream NumStream;
675    NumStream << (int)NewName.at(pos);
676    NewName = NewName.replace(pos, 1, NumStream.str());
677  }
678
679  return NewName;
680}
681
682class SessionContext {
683public:
684  SessionContext(LLVMContext &C)
685    : Context(C), TM(EngineBuilder().selectTarget()) {}
686  LLVMContext& getLLVMContext() const { return Context; }
687  TargetMachine& getTarget() { return *TM; }
688  void addPrototypeAST(std::unique_ptr<PrototypeAST> P);
689  PrototypeAST* getPrototypeAST(const std::string &Name);
690private:
691  typedef std::map<std::string, std::unique_ptr<PrototypeAST>> PrototypeMap;
692
693  LLVMContext &Context;
694  std::unique_ptr<TargetMachine> TM;
695
696  PrototypeMap Prototypes;
697};
698
699void SessionContext::addPrototypeAST(std::unique_ptr<PrototypeAST> P) {
700  Prototypes[P->Name] = std::move(P);
701}
702
703PrototypeAST* SessionContext::getPrototypeAST(const std::string &Name) {
704  PrototypeMap::iterator I = Prototypes.find(Name);
705  if (I != Prototypes.end())
706    return I->second.get();
707  return nullptr;
708}
709
710class IRGenContext {
711public:
712
713  IRGenContext(SessionContext &S)
714    : Session(S),
715      M(new Module(GenerateUniqueName("jit_module_"),
716                   Session.getLLVMContext())),
717      Builder(Session.getLLVMContext()) {
718    M->setDataLayout(Session.getTarget().createDataLayout());
719  }
720
721  SessionContext& getSession() { return Session; }
722  Module& getM() const { return *M; }
723  std::unique_ptr<Module> takeM() { return std::move(M); }
724  IRBuilder<>& getBuilder() { return Builder; }
725  LLVMContext& getLLVMContext() { return Session.getLLVMContext(); }
726  Function* getPrototype(const std::string &Name);
727
728  std::map<std::string, AllocaInst*> NamedValues;
729private:
730  SessionContext &Session;
731  std::unique_ptr<Module> M;
732  IRBuilder<> Builder;
733};
734
735Function* IRGenContext::getPrototype(const std::string &Name) {
736  if (Function *ExistingProto = M->getFunction(Name))
737    return ExistingProto;
738  if (PrototypeAST *ProtoAST = Session.getPrototypeAST(Name))
739    return ProtoAST->IRGen(*this);
740  return nullptr;
741}
742
743/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
744/// the function.  This is used for mutable variables etc.
745static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
746                                          const std::string &VarName) {
747  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
748                 TheFunction->getEntryBlock().begin());
749  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), nullptr,
750                           VarName.c_str());
751}
752
753Value *NumberExprAST::IRGen(IRGenContext &C) const {
754  return ConstantFP::get(C.getLLVMContext(), APFloat(Val));
755}
756
757Value *VariableExprAST::IRGen(IRGenContext &C) const {
758  // Look this variable up in the function.
759  Value *V = C.NamedValues[Name];
760
761  if (!V)
762    return ErrorP<Value>("Unknown variable name '" + Name + "'");
763
764  // Load the value.
765  return C.getBuilder().CreateLoad(V, Name.c_str());
766}
767
768Value *UnaryExprAST::IRGen(IRGenContext &C) const {
769  if (Value *OperandV = Operand->IRGen(C)) {
770    std::string FnName = MakeLegalFunctionName(std::string("unary")+Opcode);
771    if (Function *F = C.getPrototype(FnName))
772      return C.getBuilder().CreateCall(F, OperandV, "unop");
773    return ErrorP<Value>("Unknown unary operator");
774  }
775
776  // Could not codegen operand - return null.
777  return nullptr;
778}
779
780Value *BinaryExprAST::IRGen(IRGenContext &C) const {
781  // Special case '=' because we don't want to emit the LHS as an expression.
782  if (Op == '=') {
783    // Assignment requires the LHS to be an identifier.
784    auto &LHSVar = static_cast<VariableExprAST &>(*LHS);
785    // Codegen the RHS.
786    Value *Val = RHS->IRGen(C);
787    if (!Val) return nullptr;
788
789    // Look up the name.
790    if (auto Variable = C.NamedValues[LHSVar.Name]) {
791      C.getBuilder().CreateStore(Val, Variable);
792      return Val;
793    }
794    return ErrorP<Value>("Unknown variable name");
795  }
796
797  Value *L = LHS->IRGen(C);
798  Value *R = RHS->IRGen(C);
799  if (!L || !R) return nullptr;
800
801  switch (Op) {
802  case '+': return C.getBuilder().CreateFAdd(L, R, "addtmp");
803  case '-': return C.getBuilder().CreateFSub(L, R, "subtmp");
804  case '*': return C.getBuilder().CreateFMul(L, R, "multmp");
805  case '/': return C.getBuilder().CreateFDiv(L, R, "divtmp");
806  case '<':
807    L = C.getBuilder().CreateFCmpULT(L, R, "cmptmp");
808    // Convert bool 0/1 to double 0.0 or 1.0
809    return C.getBuilder().CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
810                                "booltmp");
811  default: break;
812  }
813
814  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
815  // a call to it.
816  std::string FnName = MakeLegalFunctionName(std::string("binary")+Op);
817  if (Function *F = C.getPrototype(FnName)) {
818    Value *Ops[] = { L, R };
819    return C.getBuilder().CreateCall(F, Ops, "binop");
820  }
821
822  return ErrorP<Value>("Unknown binary operator");
823}
824
825Value *CallExprAST::IRGen(IRGenContext &C) const {
826  // Look up the name in the global module table.
827  if (auto CalleeF = C.getPrototype(CalleeName)) {
828    // If argument mismatch error.
829    if (CalleeF->arg_size() != Args.size())
830      return ErrorP<Value>("Incorrect # arguments passed");
831
832    std::vector<Value*> ArgsV;
833    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
834      ArgsV.push_back(Args[i]->IRGen(C));
835      if (!ArgsV.back()) return nullptr;
836    }
837
838    return C.getBuilder().CreateCall(CalleeF, ArgsV, "calltmp");
839  }
840
841  return ErrorP<Value>("Unknown function referenced");
842}
843
844Value *IfExprAST::IRGen(IRGenContext &C) const {
845  Value *CondV = Cond->IRGen(C);
846  if (!CondV) return nullptr;
847
848  // Convert condition to a bool by comparing equal to 0.0.
849  ConstantFP *FPZero =
850    ConstantFP::get(C.getLLVMContext(), APFloat(0.0));
851  CondV = C.getBuilder().CreateFCmpONE(CondV, FPZero, "ifcond");
852
853  Function *TheFunction = C.getBuilder().GetInsertBlock()->getParent();
854
855  // Create blocks for the then and else cases.  Insert the 'then' block at the
856  // end of the function.
857  BasicBlock *ThenBB = BasicBlock::Create(C.getLLVMContext(), "then", TheFunction);
858  BasicBlock *ElseBB = BasicBlock::Create(C.getLLVMContext(), "else");
859  BasicBlock *MergeBB = BasicBlock::Create(C.getLLVMContext(), "ifcont");
860
861  C.getBuilder().CreateCondBr(CondV, ThenBB, ElseBB);
862
863  // Emit then value.
864  C.getBuilder().SetInsertPoint(ThenBB);
865
866  Value *ThenV = Then->IRGen(C);
867  if (!ThenV) return nullptr;
868
869  C.getBuilder().CreateBr(MergeBB);
870  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
871  ThenBB = C.getBuilder().GetInsertBlock();
872
873  // Emit else block.
874  TheFunction->getBasicBlockList().push_back(ElseBB);
875  C.getBuilder().SetInsertPoint(ElseBB);
876
877  Value *ElseV = Else->IRGen(C);
878  if (!ElseV) return nullptr;
879
880  C.getBuilder().CreateBr(MergeBB);
881  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
882  ElseBB = C.getBuilder().GetInsertBlock();
883
884  // Emit merge block.
885  TheFunction->getBasicBlockList().push_back(MergeBB);
886  C.getBuilder().SetInsertPoint(MergeBB);
887  PHINode *PN = C.getBuilder().CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
888                                  "iftmp");
889
890  PN->addIncoming(ThenV, ThenBB);
891  PN->addIncoming(ElseV, ElseBB);
892  return PN;
893}
894
895Value *ForExprAST::IRGen(IRGenContext &C) const {
896  // Output this as:
897  //   var = alloca double
898  //   ...
899  //   start = startexpr
900  //   store start -> var
901  //   goto loop
902  // loop:
903  //   ...
904  //   bodyexpr
905  //   ...
906  // loopend:
907  //   step = stepexpr
908  //   endcond = endexpr
909  //
910  //   curvar = load var
911  //   nextvar = curvar + step
912  //   store nextvar -> var
913  //   br endcond, loop, endloop
914  // outloop:
915
916  Function *TheFunction = C.getBuilder().GetInsertBlock()->getParent();
917
918  // Create an alloca for the variable in the entry block.
919  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
920
921  // Emit the start code first, without 'variable' in scope.
922  Value *StartVal = Start->IRGen(C);
923  if (!StartVal) return nullptr;
924
925  // Store the value into the alloca.
926  C.getBuilder().CreateStore(StartVal, Alloca);
927
928  // Make the new basic block for the loop header, inserting after current
929  // block.
930  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
931
932  // Insert an explicit fall through from the current block to the LoopBB.
933  C.getBuilder().CreateBr(LoopBB);
934
935  // Start insertion in LoopBB.
936  C.getBuilder().SetInsertPoint(LoopBB);
937
938  // Within the loop, the variable is defined equal to the PHI node.  If it
939  // shadows an existing variable, we have to restore it, so save it now.
940  AllocaInst *OldVal = C.NamedValues[VarName];
941  C.NamedValues[VarName] = Alloca;
942
943  // Emit the body of the loop.  This, like any other expr, can change the
944  // current BB.  Note that we ignore the value computed by the body, but don't
945  // allow an error.
946  if (!Body->IRGen(C))
947    return nullptr;
948
949  // Emit the step value.
950  Value *StepVal;
951  if (Step) {
952    StepVal = Step->IRGen(C);
953    if (!StepVal) return nullptr;
954  } else {
955    // If not specified, use 1.0.
956    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
957  }
958
959  // Compute the end condition.
960  Value *EndCond = End->IRGen(C);
961  if (!EndCond) return nullptr;
962
963  // Reload, increment, and restore the alloca.  This handles the case where
964  // the body of the loop mutates the variable.
965  Value *CurVar = C.getBuilder().CreateLoad(Alloca, VarName.c_str());
966  Value *NextVar = C.getBuilder().CreateFAdd(CurVar, StepVal, "nextvar");
967  C.getBuilder().CreateStore(NextVar, Alloca);
968
969  // Convert condition to a bool by comparing equal to 0.0.
970  EndCond = C.getBuilder().CreateFCmpONE(EndCond,
971                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
972                                  "loopcond");
973
974  // Create the "after loop" block and insert it.
975  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
976
977  // Insert the conditional branch into the end of LoopEndBB.
978  C.getBuilder().CreateCondBr(EndCond, LoopBB, AfterBB);
979
980  // Any new code will be inserted in AfterBB.
981  C.getBuilder().SetInsertPoint(AfterBB);
982
983  // Restore the unshadowed variable.
984  if (OldVal)
985    C.NamedValues[VarName] = OldVal;
986  else
987    C.NamedValues.erase(VarName);
988
989  // for expr always returns 0.0.
990  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
991}
992
993Value *VarExprAST::IRGen(IRGenContext &C) const {
994  std::vector<AllocaInst *> OldBindings;
995
996  Function *TheFunction = C.getBuilder().GetInsertBlock()->getParent();
997
998  // Register all variables and emit their initializer.
999  for (unsigned i = 0, e = VarBindings.size(); i != e; ++i) {
1000    auto &VarName = VarBindings[i].first;
1001    auto &Init = VarBindings[i].second;
1002
1003    // Emit the initializer before adding the variable to scope, this prevents
1004    // the initializer from referencing the variable itself, and permits stuff
1005    // like this:
1006    //  var a = 1 in
1007    //    var a = a in ...   # refers to outer 'a'.
1008    Value *InitVal;
1009    if (Init) {
1010      InitVal = Init->IRGen(C);
1011      if (!InitVal) return nullptr;
1012    } else // If not specified, use 0.0.
1013      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
1014
1015    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
1016    C.getBuilder().CreateStore(InitVal, Alloca);
1017
1018    // Remember the old variable binding so that we can restore the binding when
1019    // we unrecurse.
1020    OldBindings.push_back(C.NamedValues[VarName]);
1021
1022    // Remember this binding.
1023    C.NamedValues[VarName] = Alloca;
1024  }
1025
1026  // Codegen the body, now that all vars are in scope.
1027  Value *BodyVal = Body->IRGen(C);
1028  if (!BodyVal) return nullptr;
1029
1030  // Pop all our variables from scope.
1031  for (unsigned i = 0, e = VarBindings.size(); i != e; ++i)
1032    C.NamedValues[VarBindings[i].first] = OldBindings[i];
1033
1034  // Return the body computation.
1035  return BodyVal;
1036}
1037
1038Function *PrototypeAST::IRGen(IRGenContext &C) const {
1039  std::string FnName = MakeLegalFunctionName(Name);
1040
1041  // Make the function type:  double(double,double) etc.
1042  std::vector<Type*> Doubles(Args.size(),
1043                             Type::getDoubleTy(getGlobalContext()));
1044  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
1045                                       Doubles, false);
1046  Function *F = Function::Create(FT, Function::ExternalLinkage, FnName,
1047                                 &C.getM());
1048
1049  // If F conflicted, there was already something named 'FnName'.  If it has a
1050  // body, don't allow redefinition or reextern.
1051  if (F->getName() != FnName) {
1052    // Delete the one we just made and get the existing one.
1053    F->eraseFromParent();
1054    F = C.getM().getFunction(Name);
1055
1056    // If F already has a body, reject this.
1057    if (!F->empty()) {
1058      ErrorP<Function>("redefinition of function");
1059      return nullptr;
1060    }
1061
1062    // If F took a different number of args, reject.
1063    if (F->arg_size() != Args.size()) {
1064      ErrorP<Function>("redefinition of function with different # args");
1065      return nullptr;
1066    }
1067  }
1068
1069  // Set names for all arguments.
1070  unsigned Idx = 0;
1071  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
1072       ++AI, ++Idx)
1073    AI->setName(Args[Idx]);
1074
1075  return F;
1076}
1077
1078/// CreateArgumentAllocas - Create an alloca for each argument and register the
1079/// argument in the symbol table so that references to it will succeed.
1080void PrototypeAST::CreateArgumentAllocas(Function *F, IRGenContext &C) {
1081  Function::arg_iterator AI = F->arg_begin();
1082  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
1083    // Create an alloca for this variable.
1084    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
1085
1086    // Store the initial value into the alloca.
1087    C.getBuilder().CreateStore(&*AI, Alloca);
1088
1089    // Add arguments to variable symbol table.
1090    C.NamedValues[Args[Idx]] = Alloca;
1091  }
1092}
1093
1094Function *FunctionAST::IRGen(IRGenContext &C) const {
1095  C.NamedValues.clear();
1096
1097  Function *TheFunction = Proto->IRGen(C);
1098  if (!TheFunction)
1099    return nullptr;
1100
1101  // If this is an operator, install it.
1102  if (Proto->isBinaryOp())
1103    BinopPrecedence[Proto->getOperatorName()] = Proto->Precedence;
1104
1105  // Create a new basic block to start insertion into.
1106  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
1107  C.getBuilder().SetInsertPoint(BB);
1108
1109  // Add all arguments to the symbol table and create their allocas.
1110  Proto->CreateArgumentAllocas(TheFunction, C);
1111
1112  if (Value *RetVal = Body->IRGen(C)) {
1113    // Finish off the function.
1114    C.getBuilder().CreateRet(RetVal);
1115
1116    // Validate the generated code, checking for consistency.
1117    verifyFunction(*TheFunction);
1118
1119    return TheFunction;
1120  }
1121
1122  // Error reading body, remove function.
1123  TheFunction->eraseFromParent();
1124
1125  if (Proto->isBinaryOp())
1126    BinopPrecedence.erase(Proto->getOperatorName());
1127  return nullptr;
1128}
1129
1130//===----------------------------------------------------------------------===//
1131// Top-Level parsing and JIT Driver
1132//===----------------------------------------------------------------------===//
1133
1134static std::unique_ptr<llvm::Module> IRGen(SessionContext &S,
1135                                           const FunctionAST &F) {
1136  IRGenContext C(S);
1137  auto LF = F.IRGen(C);
1138  if (!LF)
1139    return nullptr;
1140#ifndef MINIMAL_STDERR_OUTPUT
1141  fprintf(stderr, "Read function definition:");
1142  LF->dump();
1143#endif
1144  return C.takeM();
1145}
1146
1147template <typename T>
1148static std::vector<T> singletonSet(T t) {
1149  std::vector<T> Vec;
1150  Vec.push_back(std::move(t));
1151  return Vec;
1152}
1153
1154class KaleidoscopeJIT {
1155public:
1156  typedef ObjectLinkingLayer<> ObjLayerT;
1157  typedef IRCompileLayer<ObjLayerT> CompileLayerT;
1158  typedef LazyEmittingLayer<CompileLayerT> LazyEmitLayerT;
1159  typedef LazyEmitLayerT::ModuleSetHandleT ModuleHandleT;
1160
1161  KaleidoscopeJIT(SessionContext &Session)
1162    : Session(Session),
1163      CompileLayer(ObjectLayer, SimpleCompiler(Session.getTarget())),
1164      LazyEmitLayer(CompileLayer) {}
1165
1166  std::string mangle(const std::string &Name) {
1167    std::string MangledName;
1168    {
1169      raw_string_ostream MangledNameStream(MangledName);
1170      Mangler::getNameWithPrefix(MangledNameStream, Name,
1171                                 Session.getTarget().createDataLayout());
1172    }
1173    return MangledName;
1174  }
1175
1176  void addFunctionAST(std::unique_ptr<FunctionAST> FnAST) {
1177    std::cerr << "Adding AST: " << FnAST->Proto->Name << "\n";
1178    FunctionDefs[mangle(FnAST->Proto->Name)] = std::move(FnAST);
1179  }
1180
1181  ModuleHandleT addModule(std::unique_ptr<Module> M) {
1182    // We need a memory manager to allocate memory and resolve symbols for this
1183    // new module. Create one that resolves symbols by looking back into the
1184    // JIT.
1185    auto Resolver = createLambdaResolver(
1186                      [&](const std::string &Name) {
1187                        // First try to find 'Name' within the JIT.
1188                        if (auto Symbol = findSymbol(Name))
1189                          return RuntimeDyld::SymbolInfo(Symbol.getAddress(),
1190                                                         Symbol.getFlags());
1191
1192                        // If we don't already have a definition of 'Name' then search
1193                        // the ASTs.
1194                        return searchFunctionASTs(Name);
1195                      },
1196                      [](const std::string &S) { return nullptr; } );
1197
1198    return LazyEmitLayer.addModuleSet(singletonSet(std::move(M)),
1199                                      make_unique<SectionMemoryManager>(),
1200                                      std::move(Resolver));
1201  }
1202
1203  void removeModule(ModuleHandleT H) { LazyEmitLayer.removeModuleSet(H); }
1204
1205  JITSymbol findSymbol(const std::string &Name) {
1206    return LazyEmitLayer.findSymbol(Name, true);
1207  }
1208
1209  JITSymbol findSymbolIn(ModuleHandleT H, const std::string &Name) {
1210    return LazyEmitLayer.findSymbolIn(H, Name, true);
1211  }
1212
1213  JITSymbol findUnmangledSymbol(const std::string &Name) {
1214    return findSymbol(mangle(Name));
1215  }
1216
1217private:
1218
1219  // This method searches the FunctionDefs map for a definition of 'Name'. If it
1220  // finds one it generates a stub for it and returns the address of the stub.
1221  RuntimeDyld::SymbolInfo searchFunctionASTs(const std::string &Name) {
1222    auto DefI = FunctionDefs.find(Name);
1223    if (DefI == FunctionDefs.end())
1224      return nullptr;
1225
1226    // Take the FunctionAST out of the map.
1227    auto FnAST = std::move(DefI->second);
1228    FunctionDefs.erase(DefI);
1229
1230    // IRGen the AST, add it to the JIT, and return the address for it.
1231    auto H = addModule(IRGen(Session, *FnAST));
1232    auto Sym = findSymbolIn(H, Name);
1233    return RuntimeDyld::SymbolInfo(Sym.getAddress(), Sym.getFlags());
1234  }
1235
1236  SessionContext &Session;
1237  ObjLayerT ObjectLayer;
1238  CompileLayerT CompileLayer;
1239  LazyEmitLayerT LazyEmitLayer;
1240
1241  std::map<std::string, std::unique_ptr<FunctionAST>> FunctionDefs;
1242};
1243
1244static void HandleDefinition(SessionContext &S, KaleidoscopeJIT &J) {
1245  if (auto F = ParseDefinition()) {
1246    S.addPrototypeAST(llvm::make_unique<PrototypeAST>(*F->Proto));
1247    J.addFunctionAST(std::move(F));
1248  } else {
1249    // Skip token for error recovery.
1250    getNextToken();
1251  }
1252}
1253
1254static void HandleExtern(SessionContext &S) {
1255  if (auto P = ParseExtern())
1256    S.addPrototypeAST(std::move(P));
1257  else {
1258    // Skip token for error recovery.
1259    getNextToken();
1260  }
1261}
1262
1263static void HandleTopLevelExpression(SessionContext &S, KaleidoscopeJIT &J) {
1264  // Evaluate a top-level expression into an anonymous function.
1265  if (auto F = ParseTopLevelExpr()) {
1266    IRGenContext C(S);
1267    if (auto ExprFunc = F->IRGen(C)) {
1268#ifndef MINIMAL_STDERR_OUTPUT
1269      std::cerr << "Expression function:\n";
1270      ExprFunc->dump();
1271#endif
1272      // Add the CodeGen'd module to the JIT. Keep a handle to it: We can remove
1273      // this module as soon as we've executed Function ExprFunc.
1274      auto H = J.addModule(C.takeM());
1275
1276      // Get the address of the JIT'd function in memory.
1277      auto ExprSymbol = J.findUnmangledSymbol("__anon_expr");
1278
1279      // Cast it to the right type (takes no arguments, returns a double) so we
1280      // can call it as a native function.
1281      double (*FP)() = (double (*)())(intptr_t)ExprSymbol.getAddress();
1282#ifdef MINIMAL_STDERR_OUTPUT
1283      FP();
1284#else
1285      std::cerr << "Evaluated to " << FP() << "\n";
1286#endif
1287
1288      // Remove the function.
1289      J.removeModule(H);
1290    }
1291  } else {
1292    // Skip token for error recovery.
1293    getNextToken();
1294  }
1295}
1296
1297/// top ::= definition | external | expression | ';'
1298static void MainLoop() {
1299  SessionContext S(getGlobalContext());
1300  KaleidoscopeJIT J(S);
1301
1302  while (1) {
1303    switch (CurTok) {
1304    case tok_eof:    return;
1305    case ';':        getNextToken(); continue;  // ignore top-level semicolons.
1306    case tok_def:    HandleDefinition(S, J); break;
1307    case tok_extern: HandleExtern(S); break;
1308    default:         HandleTopLevelExpression(S, J); break;
1309    }
1310#ifndef MINIMAL_STDERR_OUTPUT
1311    std::cerr << "ready> ";
1312#endif
1313  }
1314}
1315
1316//===----------------------------------------------------------------------===//
1317// "Library" functions that can be "extern'd" from user code.
1318//===----------------------------------------------------------------------===//
1319
1320/// putchard - putchar that takes a double and returns 0.
1321extern "C"
1322double putchard(double X) {
1323  putchar((char)X);
1324  return 0;
1325}
1326
1327/// printd - printf that takes a double prints it as "%f\n", returning 0.
1328extern "C"
1329double printd(double X) {
1330  printf("%f", X);
1331  return 0;
1332}
1333
1334extern "C"
1335double printlf() {
1336  printf("\n");
1337  return 0;
1338}
1339
1340//===----------------------------------------------------------------------===//
1341// Main driver code.
1342//===----------------------------------------------------------------------===//
1343
1344int main() {
1345  InitializeNativeTarget();
1346  InitializeNativeTargetAsmPrinter();
1347  InitializeNativeTargetAsmParser();
1348
1349  // Install standard binary operators.
1350  // 1 is lowest precedence.
1351  BinopPrecedence['='] = 2;
1352  BinopPrecedence['<'] = 10;
1353  BinopPrecedence['+'] = 20;
1354  BinopPrecedence['-'] = 20;
1355  BinopPrecedence['/'] = 40;
1356  BinopPrecedence['*'] = 40;  // highest.
1357
1358  // Prime the first token.
1359#ifndef MINIMAL_STDERR_OUTPUT
1360  std::cerr << "ready> ";
1361#endif
1362  getNextToken();
1363
1364  std::cerr << std::fixed;
1365
1366  // Run the main "interpreter loop" now.
1367  MainLoop();
1368
1369  return 0;
1370}
1371