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      1 #define MINIMAL_STDERR_OUTPUT
      2 
      3 #include "llvm/Analysis/Passes.h"
      4 #include "llvm/ExecutionEngine/ExecutionEngine.h"
      5 #include "llvm/ExecutionEngine/MCJIT.h"
      6 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
      7 #include "llvm/IR/DataLayout.h"
      8 #include "llvm/IR/DerivedTypes.h"
      9 #include "llvm/IR/IRBuilder.h"
     10 #include "llvm/IR/LLVMContext.h"
     11 #include "llvm/IR/LegacyPassManager.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 <cstdio>
     18 #include <map>
     19 #include <string>
     20 #include <vector>
     21 using namespace llvm;
     22 
     23 //===----------------------------------------------------------------------===//
     24 // Lexer
     25 //===----------------------------------------------------------------------===//
     26 
     27 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
     28 // of these for known things.
     29 enum Token {
     30   tok_eof = -1,
     31 
     32   // commands
     33   tok_def = -2, tok_extern = -3,
     34 
     35   // primary
     36   tok_identifier = -4, tok_number = -5,
     37 
     38   // control
     39   tok_if = -6, tok_then = -7, tok_else = -8,
     40   tok_for = -9, tok_in = -10,
     41 
     42   // operators
     43   tok_binary = -11, tok_unary = -12,
     44 
     45   // var definition
     46   tok_var = -13
     47 };
     48 
     49 static std::string IdentifierStr;  // Filled in if tok_identifier
     50 static double NumVal;              // Filled in if tok_number
     51 
     52 /// gettok - Return the next token from standard input.
     53 static int gettok() {
     54   static int LastChar = ' ';
     55 
     56   // Skip any whitespace.
     57   while (isspace(LastChar))
     58     LastChar = getchar();
     59 
     60   if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
     61     IdentifierStr = LastChar;
     62     while (isalnum((LastChar = getchar())))
     63       IdentifierStr += LastChar;
     64 
     65     if (IdentifierStr == "def") return tok_def;
     66     if (IdentifierStr == "extern") return tok_extern;
     67     if (IdentifierStr == "if") return tok_if;
     68     if (IdentifierStr == "then") return tok_then;
     69     if (IdentifierStr == "else") return tok_else;
     70     if (IdentifierStr == "for") return tok_for;
     71     if (IdentifierStr == "in") return tok_in;
     72     if (IdentifierStr == "binary") return tok_binary;
     73     if (IdentifierStr == "unary") return tok_unary;
     74     if (IdentifierStr == "var") return tok_var;
     75     return tok_identifier;
     76   }
     77 
     78   if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
     79     std::string NumStr;
     80     do {
     81       NumStr += LastChar;
     82       LastChar = getchar();
     83     } while (isdigit(LastChar) || LastChar == '.');
     84 
     85     NumVal = strtod(NumStr.c_str(), 0);
     86     return tok_number;
     87   }
     88 
     89   if (LastChar == '#') {
     90     // Comment until end of line.
     91     do LastChar = getchar();
     92     while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
     93 
     94     if (LastChar != EOF)
     95       return gettok();
     96   }
     97 
     98   // Check for end of file.  Don't eat the EOF.
     99   if (LastChar == EOF)
    100     return tok_eof;
    101 
    102   // Otherwise, just return the character as its ascii value.
    103   int ThisChar = LastChar;
    104   LastChar = getchar();
    105   return ThisChar;
    106 }
    107 
    108 //===----------------------------------------------------------------------===//
    109 // Abstract Syntax Tree (aka Parse Tree)
    110 //===----------------------------------------------------------------------===//
    111 
    112 /// ExprAST - Base class for all expression nodes.
    113 class ExprAST {
    114 public:
    115   virtual ~ExprAST() {}
    116   virtual Value *Codegen() = 0;
    117 };
    118 
    119 /// NumberExprAST - Expression class for numeric literals like "1.0".
    120 class NumberExprAST : public ExprAST {
    121   double Val;
    122 public:
    123   NumberExprAST(double val) : Val(val) {}
    124   virtual Value *Codegen();
    125 };
    126 
    127 /// VariableExprAST - Expression class for referencing a variable, like "a".
    128 class VariableExprAST : public ExprAST {
    129   std::string Name;
    130 public:
    131   VariableExprAST(const std::string &name) : Name(name) {}
    132   const std::string &getName() const { return Name; }
    133   virtual Value *Codegen();
    134 };
    135 
    136 /// UnaryExprAST - Expression class for a unary operator.
    137 class UnaryExprAST : public ExprAST {
    138   char Opcode;
    139   ExprAST *Operand;
    140 public:
    141   UnaryExprAST(char opcode, ExprAST *operand)
    142     : Opcode(opcode), Operand(operand) {}
    143   virtual Value *Codegen();
    144 };
    145 
    146 /// BinaryExprAST - Expression class for a binary operator.
    147 class BinaryExprAST : public ExprAST {
    148   char Op;
    149   ExprAST *LHS, *RHS;
    150 public:
    151   BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
    152     : Op(op), LHS(lhs), RHS(rhs) {}
    153   virtual Value *Codegen();
    154 };
    155 
    156 /// CallExprAST - Expression class for function calls.
    157 class CallExprAST : public ExprAST {
    158   std::string Callee;
    159   std::vector<ExprAST*> Args;
    160 public:
    161   CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
    162     : Callee(callee), Args(args) {}
    163   virtual Value *Codegen();
    164 };
    165 
    166 /// IfExprAST - Expression class for if/then/else.
    167 class IfExprAST : public ExprAST {
    168   ExprAST *Cond, *Then, *Else;
    169 public:
    170   IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
    171   : Cond(cond), Then(then), Else(_else) {}
    172   virtual Value *Codegen();
    173 };
    174 
    175 /// ForExprAST - Expression class for for/in.
    176 class ForExprAST : public ExprAST {
    177   std::string VarName;
    178   ExprAST *Start, *End, *Step, *Body;
    179 public:
    180   ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
    181              ExprAST *step, ExprAST *body)
    182     : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
    183   virtual Value *Codegen();
    184 };
    185 
    186 /// VarExprAST - Expression class for var/in
    187 class VarExprAST : public ExprAST {
    188   std::vector<std::pair<std::string, ExprAST*> > VarNames;
    189   ExprAST *Body;
    190 public:
    191   VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
    192              ExprAST *body)
    193   : VarNames(varnames), Body(body) {}
    194 
    195   virtual Value *Codegen();
    196 };
    197 
    198 /// PrototypeAST - This class represents the "prototype" for a function,
    199 /// which captures its argument names as well as if it is an operator.
    200 class PrototypeAST {
    201   std::string Name;
    202   std::vector<std::string> Args;
    203   bool isOperator;
    204   unsigned Precedence;  // Precedence if a binary op.
    205 public:
    206   PrototypeAST(const std::string &name, const std::vector<std::string> &args,
    207                bool isoperator = false, unsigned prec = 0)
    208   : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
    209 
    210   bool isUnaryOp() const { return isOperator && Args.size() == 1; }
    211   bool isBinaryOp() const { return isOperator && Args.size() == 2; }
    212 
    213   char getOperatorName() const {
    214     assert(isUnaryOp() || isBinaryOp());
    215     return Name[Name.size()-1];
    216   }
    217 
    218   unsigned getBinaryPrecedence() const { return Precedence; }
    219 
    220   Function *Codegen();
    221 
    222   void CreateArgumentAllocas(Function *F);
    223 };
    224 
    225 /// FunctionAST - This class represents a function definition itself.
    226 class FunctionAST {
    227   PrototypeAST *Proto;
    228   ExprAST *Body;
    229 public:
    230   FunctionAST(PrototypeAST *proto, ExprAST *body)
    231     : Proto(proto), Body(body) {}
    232 
    233   Function *Codegen();
    234 };
    235 
    236 //===----------------------------------------------------------------------===//
    237 // Parser
    238 //===----------------------------------------------------------------------===//
    239 
    240 /// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
    241 /// token the parser is looking at.  getNextToken reads another token from the
    242 /// lexer and updates CurTok with its results.
    243 static int CurTok;
    244 static int getNextToken() {
    245   return CurTok = gettok();
    246 }
    247 
    248 /// BinopPrecedence - This holds the precedence for each binary operator that is
    249 /// defined.
    250 static std::map<char, int> BinopPrecedence;
    251 
    252 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
    253 static int GetTokPrecedence() {
    254   if (!isascii(CurTok))
    255     return -1;
    256 
    257   // Make sure it's a declared binop.
    258   int TokPrec = BinopPrecedence[CurTok];
    259   if (TokPrec <= 0) return -1;
    260   return TokPrec;
    261 }
    262 
    263 /// Error* - These are little helper functions for error handling.
    264 ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
    265 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
    266 FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
    267 
    268 static ExprAST *ParseExpression();
    269 
    270 /// identifierexpr
    271 ///   ::= identifier
    272 ///   ::= identifier '(' expression* ')'
    273 static ExprAST *ParseIdentifierExpr() {
    274   std::string IdName = IdentifierStr;
    275 
    276   getNextToken();  // eat identifier.
    277 
    278   if (CurTok != '(') // Simple variable ref.
    279     return new VariableExprAST(IdName);
    280 
    281   // Call.
    282   getNextToken();  // eat (
    283   std::vector<ExprAST*> Args;
    284   if (CurTok != ')') {
    285     while (1) {
    286       ExprAST *Arg = ParseExpression();
    287       if (!Arg) return 0;
    288       Args.push_back(Arg);
    289 
    290       if (CurTok == ')') break;
    291 
    292       if (CurTok != ',')
    293         return Error("Expected ')' or ',' in argument list");
    294       getNextToken();
    295     }
    296   }
    297 
    298   // Eat the ')'.
    299   getNextToken();
    300 
    301   return new CallExprAST(IdName, Args);
    302 }
    303 
    304 /// numberexpr ::= number
    305 static ExprAST *ParseNumberExpr() {
    306   ExprAST *Result = new NumberExprAST(NumVal);
    307   getNextToken(); // consume the number
    308   return Result;
    309 }
    310 
    311 /// parenexpr ::= '(' expression ')'
    312 static ExprAST *ParseParenExpr() {
    313   getNextToken();  // eat (.
    314   ExprAST *V = ParseExpression();
    315   if (!V) return 0;
    316 
    317   if (CurTok != ')')
    318     return Error("expected ')'");
    319   getNextToken();  // eat ).
    320   return V;
    321 }
    322 
    323 /// ifexpr ::= 'if' expression 'then' expression 'else' expression
    324 static ExprAST *ParseIfExpr() {
    325   getNextToken();  // eat the if.
    326 
    327   // condition.
    328   ExprAST *Cond = ParseExpression();
    329   if (!Cond) return 0;
    330 
    331   if (CurTok != tok_then)
    332     return Error("expected then");
    333   getNextToken();  // eat the then
    334 
    335   ExprAST *Then = ParseExpression();
    336   if (Then == 0) return 0;
    337 
    338   if (CurTok != tok_else)
    339     return Error("expected else");
    340 
    341   getNextToken();
    342 
    343   ExprAST *Else = ParseExpression();
    344   if (!Else) return 0;
    345 
    346   return new IfExprAST(Cond, Then, Else);
    347 }
    348 
    349 /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
    350 static ExprAST *ParseForExpr() {
    351   getNextToken();  // eat the for.
    352 
    353   if (CurTok != tok_identifier)
    354     return Error("expected identifier after for");
    355 
    356   std::string IdName = IdentifierStr;
    357   getNextToken();  // eat identifier.
    358 
    359   if (CurTok != '=')
    360     return Error("expected '=' after for");
    361   getNextToken();  // eat '='.
    362 
    363 
    364   ExprAST *Start = ParseExpression();
    365   if (Start == 0) return 0;
    366   if (CurTok != ',')
    367     return Error("expected ',' after for start value");
    368   getNextToken();
    369 
    370   ExprAST *End = ParseExpression();
    371   if (End == 0) return 0;
    372 
    373   // The step value is optional.
    374   ExprAST *Step = 0;
    375   if (CurTok == ',') {
    376     getNextToken();
    377     Step = ParseExpression();
    378     if (Step == 0) return 0;
    379   }
    380 
    381   if (CurTok != tok_in)
    382     return Error("expected 'in' after for");
    383   getNextToken();  // eat 'in'.
    384 
    385   ExprAST *Body = ParseExpression();
    386   if (Body == 0) return 0;
    387 
    388   return new ForExprAST(IdName, Start, End, Step, Body);
    389 }
    390 
    391 /// varexpr ::= 'var' identifier ('=' expression)?
    392 //                    (',' identifier ('=' expression)?)* 'in' expression
    393 static ExprAST *ParseVarExpr() {
    394   getNextToken();  // eat the var.
    395 
    396   std::vector<std::pair<std::string, ExprAST*> > VarNames;
    397 
    398   // At least one variable name is required.
    399   if (CurTok != tok_identifier)
    400     return Error("expected identifier after var");
    401 
    402   while (1) {
    403     std::string Name = IdentifierStr;
    404     getNextToken();  // eat identifier.
    405 
    406     // Read the optional initializer.
    407     ExprAST *Init = 0;
    408     if (CurTok == '=') {
    409       getNextToken(); // eat the '='.
    410 
    411       Init = ParseExpression();
    412       if (Init == 0) return 0;
    413     }
    414 
    415     VarNames.push_back(std::make_pair(Name, Init));
    416 
    417     // End of var list, exit loop.
    418     if (CurTok != ',') break;
    419     getNextToken(); // eat the ','.
    420 
    421     if (CurTok != tok_identifier)
    422       return Error("expected identifier list after var");
    423   }
    424 
    425   // At this point, we have to have 'in'.
    426   if (CurTok != tok_in)
    427     return Error("expected 'in' keyword after 'var'");
    428   getNextToken();  // eat 'in'.
    429 
    430   ExprAST *Body = ParseExpression();
    431   if (Body == 0) return 0;
    432 
    433   return new VarExprAST(VarNames, Body);
    434 }
    435 
    436 /// primary
    437 ///   ::= identifierexpr
    438 ///   ::= numberexpr
    439 ///   ::= parenexpr
    440 ///   ::= ifexpr
    441 ///   ::= forexpr
    442 ///   ::= varexpr
    443 static ExprAST *ParsePrimary() {
    444   switch (CurTok) {
    445   default: return Error("unknown token when expecting an expression");
    446   case tok_identifier: return ParseIdentifierExpr();
    447   case tok_number:     return ParseNumberExpr();
    448   case '(':            return ParseParenExpr();
    449   case tok_if:         return ParseIfExpr();
    450   case tok_for:        return ParseForExpr();
    451   case tok_var:        return ParseVarExpr();
    452   }
    453 }
    454 
    455 /// unary
    456 ///   ::= primary
    457 ///   ::= '!' unary
    458 static ExprAST *ParseUnary() {
    459   // If the current token is not an operator, it must be a primary expr.
    460   if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
    461     return ParsePrimary();
    462 
    463   // If this is a unary operator, read it.
    464   int Opc = CurTok;
    465   getNextToken();
    466   if (ExprAST *Operand = ParseUnary())
    467     return new UnaryExprAST(Opc, Operand);
    468   return 0;
    469 }
    470 
    471 /// binoprhs
    472 ///   ::= ('+' unary)*
    473 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
    474   // If this is a binop, find its precedence.
    475   while (1) {
    476     int TokPrec = GetTokPrecedence();
    477 
    478     // If this is a binop that binds at least as tightly as the current binop,
    479     // consume it, otherwise we are done.
    480     if (TokPrec < ExprPrec)
    481       return LHS;
    482 
    483     // Okay, we know this is a binop.
    484     int BinOp = CurTok;
    485     getNextToken();  // eat binop
    486 
    487     // Parse the unary expression after the binary operator.
    488     ExprAST *RHS = ParseUnary();
    489     if (!RHS) return 0;
    490 
    491     // If BinOp binds less tightly with RHS than the operator after RHS, let
    492     // the pending operator take RHS as its LHS.
    493     int NextPrec = GetTokPrecedence();
    494     if (TokPrec < NextPrec) {
    495       RHS = ParseBinOpRHS(TokPrec+1, RHS);
    496       if (RHS == 0) return 0;
    497     }
    498 
    499     // Merge LHS/RHS.
    500     LHS = new BinaryExprAST(BinOp, LHS, RHS);
    501   }
    502 }
    503 
    504 /// expression
    505 ///   ::= unary binoprhs
    506 ///
    507 static ExprAST *ParseExpression() {
    508   ExprAST *LHS = ParseUnary();
    509   if (!LHS) return 0;
    510 
    511   return ParseBinOpRHS(0, LHS);
    512 }
    513 
    514 /// prototype
    515 ///   ::= id '(' id* ')'
    516 ///   ::= binary LETTER number? (id, id)
    517 ///   ::= unary LETTER (id)
    518 static PrototypeAST *ParsePrototype() {
    519   std::string FnName;
    520 
    521   unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
    522   unsigned BinaryPrecedence = 30;
    523 
    524   switch (CurTok) {
    525   default:
    526     return ErrorP("Expected function name in prototype");
    527   case tok_identifier:
    528     FnName = IdentifierStr;
    529     Kind = 0;
    530     getNextToken();
    531     break;
    532   case tok_unary:
    533     getNextToken();
    534     if (!isascii(CurTok))
    535       return ErrorP("Expected unary operator");
    536     FnName = "unary";
    537     FnName += (char)CurTok;
    538     Kind = 1;
    539     getNextToken();
    540     break;
    541   case tok_binary:
    542     getNextToken();
    543     if (!isascii(CurTok))
    544       return ErrorP("Expected binary operator");
    545     FnName = "binary";
    546     FnName += (char)CurTok;
    547     Kind = 2;
    548     getNextToken();
    549 
    550     // Read the precedence if present.
    551     if (CurTok == tok_number) {
    552       if (NumVal < 1 || NumVal > 100)
    553         return ErrorP("Invalid precedecnce: must be 1..100");
    554       BinaryPrecedence = (unsigned)NumVal;
    555       getNextToken();
    556     }
    557     break;
    558   }
    559 
    560   if (CurTok != '(')
    561     return ErrorP("Expected '(' in prototype");
    562 
    563   std::vector<std::string> ArgNames;
    564   while (getNextToken() == tok_identifier)
    565     ArgNames.push_back(IdentifierStr);
    566   if (CurTok != ')')
    567     return ErrorP("Expected ')' in prototype");
    568 
    569   // success.
    570   getNextToken();  // eat ')'.
    571 
    572   // Verify right number of names for operator.
    573   if (Kind && ArgNames.size() != Kind)
    574     return ErrorP("Invalid number of operands for operator");
    575 
    576   return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
    577 }
    578 
    579 /// definition ::= 'def' prototype expression
    580 static FunctionAST *ParseDefinition() {
    581   getNextToken();  // eat def.
    582   PrototypeAST *Proto = ParsePrototype();
    583   if (Proto == 0) return 0;
    584 
    585   if (ExprAST *E = ParseExpression())
    586     return new FunctionAST(Proto, E);
    587   return 0;
    588 }
    589 
    590 /// toplevelexpr ::= expression
    591 static FunctionAST *ParseTopLevelExpr() {
    592   if (ExprAST *E = ParseExpression()) {
    593     // Make an anonymous proto.
    594     PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
    595     return new FunctionAST(Proto, E);
    596   }
    597   return 0;
    598 }
    599 
    600 /// external ::= 'extern' prototype
    601 static PrototypeAST *ParseExtern() {
    602   getNextToken();  // eat extern.
    603   return ParsePrototype();
    604 }
    605 
    606 //===----------------------------------------------------------------------===//
    607 // Quick and dirty hack
    608 //===----------------------------------------------------------------------===//
    609 
    610 // FIXME: Obviously we can do better than this
    611 std::string GenerateUniqueName(const char *root)
    612 {
    613   static int i = 0;
    614   char s[16];
    615   sprintf(s, "%s%d", root, i++);
    616   std::string S = s;
    617   return S;
    618 }
    619 
    620 std::string MakeLegalFunctionName(std::string Name)
    621 {
    622   std::string NewName;
    623   if (!Name.length())
    624       return GenerateUniqueName("anon_func_");
    625 
    626   // Start with what we have
    627   NewName = Name;
    628 
    629   // Look for a numberic first character
    630   if (NewName.find_first_of("0123456789") == 0) {
    631     NewName.insert(0, 1, 'n');
    632   }
    633 
    634   // Replace illegal characters with their ASCII equivalent
    635   std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    636   size_t pos;
    637   while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
    638     char old_c = NewName.at(pos);
    639     char new_str[16];
    640     sprintf(new_str, "%d", (int)old_c);
    641     NewName = NewName.replace(pos, 1, new_str);
    642   }
    643 
    644   return NewName;
    645 }
    646 
    647 //===----------------------------------------------------------------------===//
    648 // MCJIT helper class
    649 //===----------------------------------------------------------------------===//
    650 
    651 class MCJITHelper
    652 {
    653 public:
    654   MCJITHelper(LLVMContext& C) : Context(C), OpenModule(NULL) {}
    655   ~MCJITHelper();
    656 
    657   Function *getFunction(const std::string FnName);
    658   Module *getModuleForNewFunction();
    659   void *getPointerToFunction(Function* F);
    660   void *getPointerToNamedFunction(const std::string &Name);
    661   ExecutionEngine *compileModule(Module *M);
    662   void closeCurrentModule();
    663   void dump();
    664 
    665 private:
    666   typedef std::vector<Module*> ModuleVector;
    667 
    668   LLVMContext  &Context;
    669   Module       *OpenModule;
    670   ModuleVector  Modules;
    671   std::map<Module *, ExecutionEngine *> EngineMap;
    672 };
    673 
    674 class HelpingMemoryManager : public SectionMemoryManager
    675 {
    676   HelpingMemoryManager(const HelpingMemoryManager&) = delete;
    677   void operator=(const HelpingMemoryManager&) = delete;
    678 
    679 public:
    680   HelpingMemoryManager(MCJITHelper *Helper) : MasterHelper(Helper) {}
    681   virtual ~HelpingMemoryManager() {}
    682 
    683   /// This method returns the address of the specified function.
    684   /// Our implementation will attempt to find functions in other
    685   /// modules associated with the MCJITHelper to cross link functions
    686   /// from one generated module to another.
    687   ///
    688   /// If \p AbortOnFailure is false and no function with the given name is
    689   /// found, this function returns a null pointer. Otherwise, it prints a
    690   /// message to stderr and aborts.
    691   virtual void *getPointerToNamedFunction(const std::string &Name,
    692                                           bool AbortOnFailure = true);
    693 private:
    694   MCJITHelper *MasterHelper;
    695 };
    696 
    697 void *HelpingMemoryManager::getPointerToNamedFunction(const std::string &Name,
    698                                         bool AbortOnFailure)
    699 {
    700   // Try the standard symbol resolution first, but ask it not to abort.
    701   void *pfn = SectionMemoryManager::getPointerToNamedFunction(Name, false);
    702   if (pfn)
    703     return pfn;
    704 
    705   pfn = MasterHelper->getPointerToNamedFunction(Name);
    706   if (!pfn && AbortOnFailure)
    707     report_fatal_error("Program used external function '" + Name +
    708                         "' which could not be resolved!");
    709   return pfn;
    710 }
    711 
    712 MCJITHelper::~MCJITHelper()
    713 {
    714   // Walk the vector of modules.
    715   ModuleVector::iterator it, end;
    716   for (it = Modules.begin(), end = Modules.end();
    717        it != end; ++it) {
    718     // See if we have an execution engine for this module.
    719     std::map<Module*, ExecutionEngine*>::iterator mapIt = EngineMap.find(*it);
    720     // If we have an EE, the EE owns the module so just delete the EE.
    721     if (mapIt != EngineMap.end()) {
    722       delete mapIt->second;
    723     } else {
    724       // Otherwise, we still own the module.  Delete it now.
    725       delete *it;
    726     }
    727   }
    728 }
    729 
    730 Function *MCJITHelper::getFunction(const std::string FnName) {
    731   ModuleVector::iterator begin = Modules.begin();
    732   ModuleVector::iterator end = Modules.end();
    733   ModuleVector::iterator it;
    734   for (it = begin; it != end; ++it) {
    735     Function *F = (*it)->getFunction(FnName);
    736     if (F) {
    737       if (*it == OpenModule)
    738           return F;
    739 
    740       assert(OpenModule != NULL);
    741 
    742       // This function is in a module that has already been JITed.
    743       // We need to generate a new prototype for external linkage.
    744       Function *PF = OpenModule->getFunction(FnName);
    745       if (PF && !PF->empty()) {
    746         ErrorF("redefinition of function across modules");
    747         return 0;
    748       }
    749 
    750       // If we don't have a prototype yet, create one.
    751       if (!PF)
    752         PF = Function::Create(F->getFunctionType(),
    753                                       Function::ExternalLinkage,
    754                                       FnName,
    755                                       OpenModule);
    756       return PF;
    757     }
    758   }
    759   return NULL;
    760 }
    761 
    762 Module *MCJITHelper::getModuleForNewFunction() {
    763   // If we have a Module that hasn't been JITed, use that.
    764   if (OpenModule)
    765     return OpenModule;
    766 
    767   // Otherwise create a new Module.
    768   std::string ModName = GenerateUniqueName("mcjit_module_");
    769   Module *M = new Module(ModName, Context);
    770   Modules.push_back(M);
    771   OpenModule = M;
    772   return M;
    773 }
    774 
    775 void *MCJITHelper::getPointerToFunction(Function* F) {
    776   // Look for this function in an existing module
    777   ModuleVector::iterator begin = Modules.begin();
    778   ModuleVector::iterator end = Modules.end();
    779   ModuleVector::iterator it;
    780   std::string FnName = F->getName();
    781   for (it = begin; it != end; ++it) {
    782     Function *MF = (*it)->getFunction(FnName);
    783     if (MF == F) {
    784       std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
    785       if (eeIt != EngineMap.end()) {
    786         void *P = eeIt->second->getPointerToFunction(F);
    787         if (P)
    788           return P;
    789       } else {
    790         ExecutionEngine *EE = compileModule(*it);
    791         void *P = EE->getPointerToFunction(F);
    792         if (P)
    793           return P;
    794       }
    795     }
    796   }
    797   return NULL;
    798 }
    799 
    800 void MCJITHelper::closeCurrentModule() {
    801   OpenModule = NULL;
    802 }
    803 
    804 ExecutionEngine *MCJITHelper::compileModule(Module *M) {
    805   if (M == OpenModule)
    806     closeCurrentModule();
    807 
    808   std::string ErrStr;
    809   ExecutionEngine *NewEngine = EngineBuilder(M)
    810                                             .setErrorStr(&ErrStr)
    811                                             .setMCJITMemoryManager(new HelpingMemoryManager(this))
    812                                             .create();
    813   if (!NewEngine) {
    814     fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
    815     exit(1);
    816   }
    817 
    818   // Create a function pass manager for this engine
    819   FunctionPassManager *FPM = new FunctionPassManager(M);
    820 
    821   // Set up the optimizer pipeline.  Start with registering info about how the
    822   // target lays out data structures.
    823   FPM->add(new DataLayout(*NewEngine->getDataLayout()));
    824   // Provide basic AliasAnalysis support for GVN.
    825   FPM->add(createBasicAliasAnalysisPass());
    826   // Promote allocas to registers.
    827   FPM->add(createPromoteMemoryToRegisterPass());
    828   // Do simple "peephole" optimizations and bit-twiddling optzns.
    829   FPM->add(createInstructionCombiningPass());
    830   // Reassociate expressions.
    831   FPM->add(createReassociatePass());
    832   // Eliminate Common SubExpressions.
    833   FPM->add(createGVNPass());
    834   // Simplify the control flow graph (deleting unreachable blocks, etc).
    835   FPM->add(createCFGSimplificationPass());
    836   FPM->doInitialization();
    837 
    838   // For each function in the module
    839   Module::iterator it;
    840   Module::iterator end = M->end();
    841   for (it = M->begin(); it != end; ++it) {
    842     // Run the FPM on this function
    843     FPM->run(*it);
    844   }
    845 
    846   // We don't need this anymore
    847   delete FPM;
    848 
    849   // Store this engine
    850   EngineMap[M] = NewEngine;
    851   NewEngine->finalizeObject();
    852 
    853   return NewEngine;
    854 }
    855 
    856 void *MCJITHelper::getPointerToNamedFunction(const std::string &Name)
    857 {
    858   // Look for the functions in our modules, compiling only as necessary
    859   ModuleVector::iterator begin = Modules.begin();
    860   ModuleVector::iterator end = Modules.end();
    861   ModuleVector::iterator it;
    862   for (it = begin; it != end; ++it) {
    863     Function *F = (*it)->getFunction(Name);
    864     if (F && !F->empty()) {
    865       std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
    866       if (eeIt != EngineMap.end()) {
    867         void *P = eeIt->second->getPointerToFunction(F);
    868         if (P)
    869           return P;
    870       } else {
    871         ExecutionEngine *EE = compileModule(*it);
    872         void *P = EE->getPointerToFunction(F);
    873         if (P)
    874           return P;
    875       }
    876     }
    877   }
    878   return NULL;
    879 }
    880 
    881 void MCJITHelper::dump()
    882 {
    883   ModuleVector::iterator begin = Modules.begin();
    884   ModuleVector::iterator end = Modules.end();
    885   ModuleVector::iterator it;
    886   for (it = begin; it != end; ++it)
    887     (*it)->dump();
    888 }
    889 
    890 //===----------------------------------------------------------------------===//
    891 // Code Generation
    892 //===----------------------------------------------------------------------===//
    893 
    894 static MCJITHelper *TheHelper;
    895 static IRBuilder<> Builder(getGlobalContext());
    896 static std::map<std::string, AllocaInst*> NamedValues;
    897 
    898 Value *ErrorV(const char *Str) { Error(Str); return 0; }
    899 
    900 /// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
    901 /// the function.  This is used for mutable variables etc.
    902 static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
    903                                           const std::string &VarName) {
    904   IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
    905                  TheFunction->getEntryBlock().begin());
    906   return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
    907                            VarName.c_str());
    908 }
    909 
    910 Value *NumberExprAST::Codegen() {
    911   return ConstantFP::get(getGlobalContext(), APFloat(Val));
    912 }
    913 
    914 Value *VariableExprAST::Codegen() {
    915   // Look this variable up in the function.
    916   Value *V = NamedValues[Name];
    917   char ErrStr[256];
    918   sprintf(ErrStr, "Unknown variable name %s", Name.c_str());
    919   if (V == 0) return ErrorV(ErrStr);
    920 
    921   // Load the value.
    922   return Builder.CreateLoad(V, Name.c_str());
    923 }
    924 
    925 Value *UnaryExprAST::Codegen() {
    926   Value *OperandV = Operand->Codegen();
    927   if (OperandV == 0) return 0;
    928 
    929   Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
    930   if (F == 0)
    931     return ErrorV("Unknown unary operator");
    932 
    933   return Builder.CreateCall(F, OperandV, "unop");
    934 }
    935 
    936 Value *BinaryExprAST::Codegen() {
    937   // Special case '=' because we don't want to emit the LHS as an expression.
    938   if (Op == '=') {
    939     // Assignment requires the LHS to be an identifier.
    940     VariableExprAST *LHSE = static_cast<VariableExprAST*>(LHS);
    941     if (!LHSE)
    942       return ErrorV("destination of '=' must be a variable");
    943     // Codegen the RHS.
    944     Value *Val = RHS->Codegen();
    945     if (Val == 0) return 0;
    946 
    947     // Look up the name.
    948     Value *Variable = NamedValues[LHSE->getName()];
    949     if (Variable == 0) return ErrorV("Unknown variable name");
    950 
    951     Builder.CreateStore(Val, Variable);
    952     return Val;
    953   }
    954 
    955   Value *L = LHS->Codegen();
    956   Value *R = RHS->Codegen();
    957   if (L == 0 || R == 0) return 0;
    958 
    959   switch (Op) {
    960   case '+': return Builder.CreateFAdd(L, R, "addtmp");
    961   case '-': return Builder.CreateFSub(L, R, "subtmp");
    962   case '*': return Builder.CreateFMul(L, R, "multmp");
    963   case '/': return Builder.CreateFDiv(L, R, "divtmp");
    964   case '<':
    965     L = Builder.CreateFCmpULT(L, R, "cmptmp");
    966     // Convert bool 0/1 to double 0.0 or 1.0
    967     return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
    968                                 "booltmp");
    969   default: break;
    970   }
    971 
    972   // If it wasn't a builtin binary operator, it must be a user defined one. Emit
    973   // a call to it.
    974   Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("binary")+Op));
    975   assert(F && "binary operator not found!");
    976 
    977   Value *Ops[] = { L, R };
    978   return Builder.CreateCall(F, Ops, "binop");
    979 }
    980 
    981 Value *CallExprAST::Codegen() {
    982   // Look up the name in the global module table.
    983   Function *CalleeF = TheHelper->getFunction(Callee);
    984   if (CalleeF == 0)
    985     return ErrorV("Unknown function referenced");
    986 
    987   // If argument mismatch error.
    988   if (CalleeF->arg_size() != Args.size())
    989     return ErrorV("Incorrect # arguments passed");
    990 
    991   std::vector<Value*> ArgsV;
    992   for (unsigned i = 0, e = Args.size(); i != e; ++i) {
    993     ArgsV.push_back(Args[i]->Codegen());
    994     if (ArgsV.back() == 0) return 0;
    995   }
    996 
    997   return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
    998 }
    999 
   1000 Value *IfExprAST::Codegen() {
   1001   Value *CondV = Cond->Codegen();
   1002   if (CondV == 0) return 0;
   1003 
   1004   // Convert condition to a bool by comparing equal to 0.0.
   1005   CondV = Builder.CreateFCmpONE(CondV,
   1006                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
   1007                                 "ifcond");
   1008 
   1009   Function *TheFunction = Builder.GetInsertBlock()->getParent();
   1010 
   1011   // Create blocks for the then and else cases.  Insert the 'then' block at the
   1012   // end of the function.
   1013   BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
   1014   BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
   1015   BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
   1016 
   1017   Builder.CreateCondBr(CondV, ThenBB, ElseBB);
   1018 
   1019   // Emit then value.
   1020   Builder.SetInsertPoint(ThenBB);
   1021 
   1022   Value *ThenV = Then->Codegen();
   1023   if (ThenV == 0) return 0;
   1024 
   1025   Builder.CreateBr(MergeBB);
   1026   // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
   1027   ThenBB = Builder.GetInsertBlock();
   1028 
   1029   // Emit else block.
   1030   TheFunction->getBasicBlockList().push_back(ElseBB);
   1031   Builder.SetInsertPoint(ElseBB);
   1032 
   1033   Value *ElseV = Else->Codegen();
   1034   if (ElseV == 0) return 0;
   1035 
   1036   Builder.CreateBr(MergeBB);
   1037   // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
   1038   ElseBB = Builder.GetInsertBlock();
   1039 
   1040   // Emit merge block.
   1041   TheFunction->getBasicBlockList().push_back(MergeBB);
   1042   Builder.SetInsertPoint(MergeBB);
   1043   PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
   1044                                   "iftmp");
   1045 
   1046   PN->addIncoming(ThenV, ThenBB);
   1047   PN->addIncoming(ElseV, ElseBB);
   1048   return PN;
   1049 }
   1050 
   1051 Value *ForExprAST::Codegen() {
   1052   // Output this as:
   1053   //   var = alloca double
   1054   //   ...
   1055   //   start = startexpr
   1056   //   store start -> var
   1057   //   goto loop
   1058   // loop:
   1059   //   ...
   1060   //   bodyexpr
   1061   //   ...
   1062   // loopend:
   1063   //   step = stepexpr
   1064   //   endcond = endexpr
   1065   //
   1066   //   curvar = load var
   1067   //   nextvar = curvar + step
   1068   //   store nextvar -> var
   1069   //   br endcond, loop, endloop
   1070   // outloop:
   1071 
   1072   Function *TheFunction = Builder.GetInsertBlock()->getParent();
   1073 
   1074   // Create an alloca for the variable in the entry block.
   1075   AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
   1076 
   1077   // Emit the start code first, without 'variable' in scope.
   1078   Value *StartVal = Start->Codegen();
   1079   if (StartVal == 0) return 0;
   1080 
   1081   // Store the value into the alloca.
   1082   Builder.CreateStore(StartVal, Alloca);
   1083 
   1084   // Make the new basic block for the loop header, inserting after current
   1085   // block.
   1086   BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
   1087 
   1088   // Insert an explicit fall through from the current block to the LoopBB.
   1089   Builder.CreateBr(LoopBB);
   1090 
   1091   // Start insertion in LoopBB.
   1092   Builder.SetInsertPoint(LoopBB);
   1093 
   1094   // Within the loop, the variable is defined equal to the PHI node.  If it
   1095   // shadows an existing variable, we have to restore it, so save it now.
   1096   AllocaInst *OldVal = NamedValues[VarName];
   1097   NamedValues[VarName] = Alloca;
   1098 
   1099   // Emit the body of the loop.  This, like any other expr, can change the
   1100   // current BB.  Note that we ignore the value computed by the body, but don't
   1101   // allow an error.
   1102   if (Body->Codegen() == 0)
   1103     return 0;
   1104 
   1105   // Emit the step value.
   1106   Value *StepVal;
   1107   if (Step) {
   1108     StepVal = Step->Codegen();
   1109     if (StepVal == 0) return 0;
   1110   } else {
   1111     // If not specified, use 1.0.
   1112     StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
   1113   }
   1114 
   1115   // Compute the end condition.
   1116   Value *EndCond = End->Codegen();
   1117   if (EndCond == 0) return EndCond;
   1118 
   1119   // Reload, increment, and restore the alloca.  This handles the case where
   1120   // the body of the loop mutates the variable.
   1121   Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
   1122   Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
   1123   Builder.CreateStore(NextVar, Alloca);
   1124 
   1125   // Convert condition to a bool by comparing equal to 0.0.
   1126   EndCond = Builder.CreateFCmpONE(EndCond,
   1127                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
   1128                                   "loopcond");
   1129 
   1130   // Create the "after loop" block and insert it.
   1131   BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
   1132 
   1133   // Insert the conditional branch into the end of LoopEndBB.
   1134   Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
   1135 
   1136   // Any new code will be inserted in AfterBB.
   1137   Builder.SetInsertPoint(AfterBB);
   1138 
   1139   // Restore the unshadowed variable.
   1140   if (OldVal)
   1141     NamedValues[VarName] = OldVal;
   1142   else
   1143     NamedValues.erase(VarName);
   1144 
   1145 
   1146   // for expr always returns 0.0.
   1147   return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
   1148 }
   1149 
   1150 Value *VarExprAST::Codegen() {
   1151   std::vector<AllocaInst *> OldBindings;
   1152 
   1153   Function *TheFunction = Builder.GetInsertBlock()->getParent();
   1154 
   1155   // Register all variables and emit their initializer.
   1156   for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
   1157     const std::string &VarName = VarNames[i].first;
   1158     ExprAST *Init = VarNames[i].second;
   1159 
   1160     // Emit the initializer before adding the variable to scope, this prevents
   1161     // the initializer from referencing the variable itself, and permits stuff
   1162     // like this:
   1163     //  var a = 1 in
   1164     //    var a = a in ...   # refers to outer 'a'.
   1165     Value *InitVal;
   1166     if (Init) {
   1167       InitVal = Init->Codegen();
   1168       if (InitVal == 0) return 0;
   1169     } else { // If not specified, use 0.0.
   1170       InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
   1171     }
   1172 
   1173     AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
   1174     Builder.CreateStore(InitVal, Alloca);
   1175 
   1176     // Remember the old variable binding so that we can restore the binding when
   1177     // we unrecurse.
   1178     OldBindings.push_back(NamedValues[VarName]);
   1179 
   1180     // Remember this binding.
   1181     NamedValues[VarName] = Alloca;
   1182   }
   1183 
   1184   // Codegen the body, now that all vars are in scope.
   1185   Value *BodyVal = Body->Codegen();
   1186   if (BodyVal == 0) return 0;
   1187 
   1188   // Pop all our variables from scope.
   1189   for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
   1190     NamedValues[VarNames[i].first] = OldBindings[i];
   1191 
   1192   // Return the body computation.
   1193   return BodyVal;
   1194 }
   1195 
   1196 Function *PrototypeAST::Codegen() {
   1197   // Make the function type:  double(double,double) etc.
   1198   std::vector<Type*> Doubles(Args.size(),
   1199                              Type::getDoubleTy(getGlobalContext()));
   1200   FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
   1201                                        Doubles, false);
   1202 
   1203   std::string FnName = MakeLegalFunctionName(Name);
   1204 
   1205   Module* M = TheHelper->getModuleForNewFunction();
   1206 
   1207   Function *F = Function::Create(FT, Function::ExternalLinkage, FnName, M);
   1208 
   1209   // If F conflicted, there was already something named 'FnName'.  If it has a
   1210   // body, don't allow redefinition or reextern.
   1211   if (F->getName() != FnName) {
   1212     // Delete the one we just made and get the existing one.
   1213     F->eraseFromParent();
   1214     F = M->getFunction(Name);
   1215 
   1216     // If F already has a body, reject this.
   1217     if (!F->empty()) {
   1218       ErrorF("redefinition of function");
   1219       return 0;
   1220     }
   1221 
   1222     // If F took a different number of args, reject.
   1223     if (F->arg_size() != Args.size()) {
   1224       ErrorF("redefinition of function with different # args");
   1225       return 0;
   1226     }
   1227   }
   1228 
   1229   // Set names for all arguments.
   1230   unsigned Idx = 0;
   1231   for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
   1232        ++AI, ++Idx)
   1233     AI->setName(Args[Idx]);
   1234 
   1235   return F;
   1236 }
   1237 
   1238 /// CreateArgumentAllocas - Create an alloca for each argument and register the
   1239 /// argument in the symbol table so that references to it will succeed.
   1240 void PrototypeAST::CreateArgumentAllocas(Function *F) {
   1241   Function::arg_iterator AI = F->arg_begin();
   1242   for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
   1243     // Create an alloca for this variable.
   1244     AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
   1245 
   1246     // Store the initial value into the alloca.
   1247     Builder.CreateStore(AI, Alloca);
   1248 
   1249     // Add arguments to variable symbol table.
   1250     NamedValues[Args[Idx]] = Alloca;
   1251   }
   1252 }
   1253 
   1254 Function *FunctionAST::Codegen() {
   1255   NamedValues.clear();
   1256 
   1257   Function *TheFunction = Proto->Codegen();
   1258   if (TheFunction == 0)
   1259     return 0;
   1260 
   1261   // If this is an operator, install it.
   1262   if (Proto->isBinaryOp())
   1263     BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
   1264 
   1265   // Create a new basic block to start insertion into.
   1266   BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
   1267   Builder.SetInsertPoint(BB);
   1268 
   1269   // Add all arguments to the symbol table and create their allocas.
   1270   Proto->CreateArgumentAllocas(TheFunction);
   1271 
   1272   if (Value *RetVal = Body->Codegen()) {
   1273     // Finish off the function.
   1274     Builder.CreateRet(RetVal);
   1275 
   1276     // Validate the generated code, checking for consistency.
   1277     verifyFunction(*TheFunction);
   1278 
   1279     return TheFunction;
   1280   }
   1281 
   1282   // Error reading body, remove function.
   1283   TheFunction->eraseFromParent();
   1284 
   1285   if (Proto->isBinaryOp())
   1286     BinopPrecedence.erase(Proto->getOperatorName());
   1287   return 0;
   1288 }
   1289 
   1290 //===----------------------------------------------------------------------===//
   1291 // Top-Level parsing and JIT Driver
   1292 //===----------------------------------------------------------------------===//
   1293 
   1294 static void HandleDefinition() {
   1295   if (FunctionAST *F = ParseDefinition()) {
   1296     TheHelper->closeCurrentModule();
   1297     if (Function *LF = F->Codegen()) {
   1298 #ifndef MINIMAL_STDERR_OUTPUT
   1299       fprintf(stderr, "Read function definition:");
   1300       LF->dump();
   1301 #endif
   1302     }
   1303   } else {
   1304     // Skip token for error recovery.
   1305     getNextToken();
   1306   }
   1307 }
   1308 
   1309 static void HandleExtern() {
   1310   if (PrototypeAST *P = ParseExtern()) {
   1311     if (Function *F = P->Codegen()) {
   1312 #ifndef MINIMAL_STDERR_OUTPUT
   1313       fprintf(stderr, "Read extern: ");
   1314       F->dump();
   1315 #endif
   1316     }
   1317   } else {
   1318     // Skip token for error recovery.
   1319     getNextToken();
   1320   }
   1321 }
   1322 
   1323 static void HandleTopLevelExpression() {
   1324   // Evaluate a top-level expression into an anonymous function.
   1325   if (FunctionAST *F = ParseTopLevelExpr()) {
   1326     if (Function *LF = F->Codegen()) {
   1327       // JIT the function, returning a function pointer.
   1328       void *FPtr = TheHelper->getPointerToFunction(LF);
   1329 
   1330       // Cast it to the right type (takes no arguments, returns a double) so we
   1331       // can call it as a native function.
   1332       double (*FP)() = (double (*)())(intptr_t)FPtr;
   1333 #ifdef MINIMAL_STDERR_OUTPUT
   1334       FP();
   1335 #else
   1336       fprintf(stderr, "Evaluated to %f\n", FP());
   1337 #endif
   1338     }
   1339   } else {
   1340     // Skip token for error recovery.
   1341     getNextToken();
   1342   }
   1343 }
   1344 
   1345 /// top ::= definition | external | expression | ';'
   1346 static void MainLoop() {
   1347   while (1) {
   1348 #ifndef MINIMAL_STDERR_OUTPUT
   1349     fprintf(stderr, "ready> ");
   1350 #endif
   1351     switch (CurTok) {
   1352     case tok_eof:    return;
   1353     case ';':        getNextToken(); break;  // ignore top-level semicolons.
   1354     case tok_def:    HandleDefinition(); break;
   1355     case tok_extern: HandleExtern(); break;
   1356     default:         HandleTopLevelExpression(); break;
   1357     }
   1358   }
   1359 }
   1360 
   1361 //===----------------------------------------------------------------------===//
   1362 // "Library" functions that can be "extern'd" from user code.
   1363 //===----------------------------------------------------------------------===//
   1364 
   1365 /// putchard - putchar that takes a double and returns 0.
   1366 extern "C"
   1367 double putchard(double X) {
   1368   putchar((char)X);
   1369   return 0;
   1370 }
   1371 
   1372 /// printd - printf that takes a double prints it as "%f\n", returning 0.
   1373 extern "C"
   1374 double printd(double X) {
   1375   printf("%f", X);
   1376   return 0;
   1377 }
   1378 
   1379 extern "C"
   1380 double printlf() {
   1381   printf("\n");
   1382   return 0;
   1383 }
   1384 
   1385 //===----------------------------------------------------------------------===//
   1386 // Main driver code.
   1387 //===----------------------------------------------------------------------===//
   1388 
   1389 int main() {
   1390   InitializeNativeTarget();
   1391   InitializeNativeTargetAsmPrinter();
   1392   InitializeNativeTargetAsmParser();
   1393   LLVMContext &Context = getGlobalContext();
   1394 
   1395   // Install standard binary operators.
   1396   // 1 is lowest precedence.
   1397   BinopPrecedence['='] = 2;
   1398   BinopPrecedence['<'] = 10;
   1399   BinopPrecedence['+'] = 20;
   1400   BinopPrecedence['-'] = 20;
   1401   BinopPrecedence['/'] = 40;
   1402   BinopPrecedence['*'] = 40;  // highest.
   1403 
   1404   // Prime the first token.
   1405 #ifndef MINIMAL_STDERR_OUTPUT
   1406   fprintf(stderr, "ready> ");
   1407 #endif
   1408   getNextToken();
   1409 
   1410   // Make the helper, which holds all the code.
   1411   TheHelper = new MCJITHelper(Context);
   1412 
   1413   // Run the main "interpreter loop" now.
   1414   MainLoop();
   1415 
   1416 #ifndef MINIMAL_STDERR_OUTPUT
   1417   // Print out all of the generated code.
   1418   TheHelper->dump();
   1419 #endif
   1420 
   1421   return 0;
   1422 }
   1423