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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/ObjectCache.h"
      7 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
      8 #include "llvm/IR/DataLayout.h"
      9 #include "llvm/IR/DerivedTypes.h"
     10 #include "llvm/IR/IRBuilder.h"
     11 #include "llvm/IR/LLVMContext.h"
     12 #include "llvm/IR/LegacyPassManager.h"
     13 #include "llvm/IR/Module.h"
     14 #include "llvm/IR/Verifier.h"
     15 #include "llvm/IRReader/IRReader.h"
     16 #include "llvm/Support/CommandLine.h"
     17 #include "llvm/Support/FileSystem.h"
     18 #include "llvm/Support/Path.h"
     19 #include "llvm/Support/SourceMgr.h"
     20 #include "llvm/Support/TargetSelect.h"
     21 #include "llvm/Support/raw_ostream.h"
     22 #include "llvm/Transforms/Scalar.h"
     23 #include <cctype>
     24 #include <cstdio>
     25 #include <map>
     26 #include <string>
     27 #include <vector>
     28 using namespace llvm;
     29 
     30 //===----------------------------------------------------------------------===//
     31 // Command-line options
     32 //===----------------------------------------------------------------------===//
     33 
     34 cl::opt<std::string>
     35 InputIR("input-IR",
     36         cl::desc("Specify the name of an IR file to load for function definitions"),
     37         cl::value_desc("input IR file name"));
     38 
     39 cl::opt<bool>
     40 UseObjectCache("use-object-cache",
     41                cl::desc("Enable use of the MCJIT object caching"),
     42                cl::init(false));
     43 
     44 //===----------------------------------------------------------------------===//
     45 // Lexer
     46 //===----------------------------------------------------------------------===//
     47 
     48 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
     49 // of these for known things.
     50 enum Token {
     51   tok_eof = -1,
     52 
     53   // commands
     54   tok_def = -2, tok_extern = -3,
     55 
     56   // primary
     57   tok_identifier = -4, tok_number = -5,
     58 
     59   // control
     60   tok_if = -6, tok_then = -7, tok_else = -8,
     61   tok_for = -9, tok_in = -10,
     62 
     63   // operators
     64   tok_binary = -11, tok_unary = -12,
     65 
     66   // var definition
     67   tok_var = -13
     68 };
     69 
     70 static std::string IdentifierStr;  // Filled in if tok_identifier
     71 static double NumVal;              // Filled in if tok_number
     72 
     73 /// gettok - Return the next token from standard input.
     74 static int gettok() {
     75   static int LastChar = ' ';
     76 
     77   // Skip any whitespace.
     78   while (isspace(LastChar))
     79     LastChar = getchar();
     80 
     81   if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
     82     IdentifierStr = LastChar;
     83     while (isalnum((LastChar = getchar())))
     84       IdentifierStr += LastChar;
     85 
     86     if (IdentifierStr == "def") return tok_def;
     87     if (IdentifierStr == "extern") return tok_extern;
     88     if (IdentifierStr == "if") return tok_if;
     89     if (IdentifierStr == "then") return tok_then;
     90     if (IdentifierStr == "else") return tok_else;
     91     if (IdentifierStr == "for") return tok_for;
     92     if (IdentifierStr == "in") return tok_in;
     93     if (IdentifierStr == "binary") return tok_binary;
     94     if (IdentifierStr == "unary") return tok_unary;
     95     if (IdentifierStr == "var") return tok_var;
     96     return tok_identifier;
     97   }
     98 
     99   if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
    100     std::string NumStr;
    101     do {
    102       NumStr += LastChar;
    103       LastChar = getchar();
    104     } while (isdigit(LastChar) || LastChar == '.');
    105 
    106     NumVal = strtod(NumStr.c_str(), 0);
    107     return tok_number;
    108   }
    109 
    110   if (LastChar == '#') {
    111     // Comment until end of line.
    112     do LastChar = getchar();
    113     while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
    114 
    115     if (LastChar != EOF)
    116       return gettok();
    117   }
    118 
    119   // Check for end of file.  Don't eat the EOF.
    120   if (LastChar == EOF)
    121     return tok_eof;
    122 
    123   // Otherwise, just return the character as its ascii value.
    124   int ThisChar = LastChar;
    125   LastChar = getchar();
    126   return ThisChar;
    127 }
    128 
    129 //===----------------------------------------------------------------------===//
    130 // Abstract Syntax Tree (aka Parse Tree)
    131 //===----------------------------------------------------------------------===//
    132 
    133 /// ExprAST - Base class for all expression nodes.
    134 class ExprAST {
    135 public:
    136   virtual ~ExprAST() {}
    137   virtual Value *Codegen() = 0;
    138 };
    139 
    140 /// NumberExprAST - Expression class for numeric literals like "1.0".
    141 class NumberExprAST : public ExprAST {
    142   double Val;
    143 public:
    144   NumberExprAST(double val) : Val(val) {}
    145   virtual Value *Codegen();
    146 };
    147 
    148 /// VariableExprAST - Expression class for referencing a variable, like "a".
    149 class VariableExprAST : public ExprAST {
    150   std::string Name;
    151 public:
    152   VariableExprAST(const std::string &name) : Name(name) {}
    153   const std::string &getName() const { return Name; }
    154   virtual Value *Codegen();
    155 };
    156 
    157 /// UnaryExprAST - Expression class for a unary operator.
    158 class UnaryExprAST : public ExprAST {
    159   char Opcode;
    160   ExprAST *Operand;
    161 public:
    162   UnaryExprAST(char opcode, ExprAST *operand)
    163     : Opcode(opcode), Operand(operand) {}
    164   virtual Value *Codegen();
    165 };
    166 
    167 /// BinaryExprAST - Expression class for a binary operator.
    168 class BinaryExprAST : public ExprAST {
    169   char Op;
    170   ExprAST *LHS, *RHS;
    171 public:
    172   BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
    173     : Op(op), LHS(lhs), RHS(rhs) {}
    174   virtual Value *Codegen();
    175 };
    176 
    177 /// CallExprAST - Expression class for function calls.
    178 class CallExprAST : public ExprAST {
    179   std::string Callee;
    180   std::vector<ExprAST*> Args;
    181 public:
    182   CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
    183     : Callee(callee), Args(args) {}
    184   virtual Value *Codegen();
    185 };
    186 
    187 /// IfExprAST - Expression class for if/then/else.
    188 class IfExprAST : public ExprAST {
    189   ExprAST *Cond, *Then, *Else;
    190 public:
    191   IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
    192   : Cond(cond), Then(then), Else(_else) {}
    193   virtual Value *Codegen();
    194 };
    195 
    196 /// ForExprAST - Expression class for for/in.
    197 class ForExprAST : public ExprAST {
    198   std::string VarName;
    199   ExprAST *Start, *End, *Step, *Body;
    200 public:
    201   ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
    202              ExprAST *step, ExprAST *body)
    203     : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
    204   virtual Value *Codegen();
    205 };
    206 
    207 /// VarExprAST - Expression class for var/in
    208 class VarExprAST : public ExprAST {
    209   std::vector<std::pair<std::string, ExprAST*> > VarNames;
    210   ExprAST *Body;
    211 public:
    212   VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
    213              ExprAST *body)
    214   : VarNames(varnames), Body(body) {}
    215 
    216   virtual Value *Codegen();
    217 };
    218 
    219 /// PrototypeAST - This class represents the "prototype" for a function,
    220 /// which captures its argument names as well as if it is an operator.
    221 class PrototypeAST {
    222   std::string Name;
    223   std::vector<std::string> Args;
    224   bool isOperator;
    225   unsigned Precedence;  // Precedence if a binary op.
    226 public:
    227   PrototypeAST(const std::string &name, const std::vector<std::string> &args,
    228                bool isoperator = false, unsigned prec = 0)
    229   : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
    230 
    231   bool isUnaryOp() const { return isOperator && Args.size() == 1; }
    232   bool isBinaryOp() const { return isOperator && Args.size() == 2; }
    233 
    234   char getOperatorName() const {
    235     assert(isUnaryOp() || isBinaryOp());
    236     return Name[Name.size()-1];
    237   }
    238 
    239   unsigned getBinaryPrecedence() const { return Precedence; }
    240 
    241   Function *Codegen();
    242 
    243   void CreateArgumentAllocas(Function *F);
    244 };
    245 
    246 /// FunctionAST - This class represents a function definition itself.
    247 class FunctionAST {
    248   PrototypeAST *Proto;
    249   ExprAST *Body;
    250 public:
    251   FunctionAST(PrototypeAST *proto, ExprAST *body)
    252     : Proto(proto), Body(body) {}
    253 
    254   Function *Codegen();
    255 };
    256 
    257 //===----------------------------------------------------------------------===//
    258 // Parser
    259 //===----------------------------------------------------------------------===//
    260 
    261 /// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
    262 /// token the parser is looking at.  getNextToken reads another token from the
    263 /// lexer and updates CurTok with its results.
    264 static int CurTok;
    265 static int getNextToken() {
    266   return CurTok = gettok();
    267 }
    268 
    269 /// BinopPrecedence - This holds the precedence for each binary operator that is
    270 /// defined.
    271 static std::map<char, int> BinopPrecedence;
    272 
    273 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
    274 static int GetTokPrecedence() {
    275   if (!isascii(CurTok))
    276     return -1;
    277 
    278   // Make sure it's a declared binop.
    279   int TokPrec = BinopPrecedence[CurTok];
    280   if (TokPrec <= 0) return -1;
    281   return TokPrec;
    282 }
    283 
    284 /// Error* - These are little helper functions for error handling.
    285 ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
    286 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
    287 FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
    288 
    289 static ExprAST *ParseExpression();
    290 
    291 /// identifierexpr
    292 ///   ::= identifier
    293 ///   ::= identifier '(' expression* ')'
    294 static ExprAST *ParseIdentifierExpr() {
    295   std::string IdName = IdentifierStr;
    296 
    297   getNextToken();  // eat identifier.
    298 
    299   if (CurTok != '(') // Simple variable ref.
    300     return new VariableExprAST(IdName);
    301 
    302   // Call.
    303   getNextToken();  // eat (
    304   std::vector<ExprAST*> Args;
    305   if (CurTok != ')') {
    306     while (1) {
    307       ExprAST *Arg = ParseExpression();
    308       if (!Arg) return 0;
    309       Args.push_back(Arg);
    310 
    311       if (CurTok == ')') break;
    312 
    313       if (CurTok != ',')
    314         return Error("Expected ')' or ',' in argument list");
    315       getNextToken();
    316     }
    317   }
    318 
    319   // Eat the ')'.
    320   getNextToken();
    321 
    322   return new CallExprAST(IdName, Args);
    323 }
    324 
    325 /// numberexpr ::= number
    326 static ExprAST *ParseNumberExpr() {
    327   ExprAST *Result = new NumberExprAST(NumVal);
    328   getNextToken(); // consume the number
    329   return Result;
    330 }
    331 
    332 /// parenexpr ::= '(' expression ')'
    333 static ExprAST *ParseParenExpr() {
    334   getNextToken();  // eat (.
    335   ExprAST *V = ParseExpression();
    336   if (!V) return 0;
    337 
    338   if (CurTok != ')')
    339     return Error("expected ')'");
    340   getNextToken();  // eat ).
    341   return V;
    342 }
    343 
    344 /// ifexpr ::= 'if' expression 'then' expression 'else' expression
    345 static ExprAST *ParseIfExpr() {
    346   getNextToken();  // eat the if.
    347 
    348   // condition.
    349   ExprAST *Cond = ParseExpression();
    350   if (!Cond) return 0;
    351 
    352   if (CurTok != tok_then)
    353     return Error("expected then");
    354   getNextToken();  // eat the then
    355 
    356   ExprAST *Then = ParseExpression();
    357   if (Then == 0) return 0;
    358 
    359   if (CurTok != tok_else)
    360     return Error("expected else");
    361 
    362   getNextToken();
    363 
    364   ExprAST *Else = ParseExpression();
    365   if (!Else) return 0;
    366 
    367   return new IfExprAST(Cond, Then, Else);
    368 }
    369 
    370 /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
    371 static ExprAST *ParseForExpr() {
    372   getNextToken();  // eat the for.
    373 
    374   if (CurTok != tok_identifier)
    375     return Error("expected identifier after for");
    376 
    377   std::string IdName = IdentifierStr;
    378   getNextToken();  // eat identifier.
    379 
    380   if (CurTok != '=')
    381     return Error("expected '=' after for");
    382   getNextToken();  // eat '='.
    383 
    384 
    385   ExprAST *Start = ParseExpression();
    386   if (Start == 0) return 0;
    387   if (CurTok != ',')
    388     return Error("expected ',' after for start value");
    389   getNextToken();
    390 
    391   ExprAST *End = ParseExpression();
    392   if (End == 0) return 0;
    393 
    394   // The step value is optional.
    395   ExprAST *Step = 0;
    396   if (CurTok == ',') {
    397     getNextToken();
    398     Step = ParseExpression();
    399     if (Step == 0) return 0;
    400   }
    401 
    402   if (CurTok != tok_in)
    403     return Error("expected 'in' after for");
    404   getNextToken();  // eat 'in'.
    405 
    406   ExprAST *Body = ParseExpression();
    407   if (Body == 0) return 0;
    408 
    409   return new ForExprAST(IdName, Start, End, Step, Body);
    410 }
    411 
    412 /// varexpr ::= 'var' identifier ('=' expression)?
    413 //                    (',' identifier ('=' expression)?)* 'in' expression
    414 static ExprAST *ParseVarExpr() {
    415   getNextToken();  // eat the var.
    416 
    417   std::vector<std::pair<std::string, ExprAST*> > VarNames;
    418 
    419   // At least one variable name is required.
    420   if (CurTok != tok_identifier)
    421     return Error("expected identifier after var");
    422 
    423   while (1) {
    424     std::string Name = IdentifierStr;
    425     getNextToken();  // eat identifier.
    426 
    427     // Read the optional initializer.
    428     ExprAST *Init = 0;
    429     if (CurTok == '=') {
    430       getNextToken(); // eat the '='.
    431 
    432       Init = ParseExpression();
    433       if (Init == 0) return 0;
    434     }
    435 
    436     VarNames.push_back(std::make_pair(Name, Init));
    437 
    438     // End of var list, exit loop.
    439     if (CurTok != ',') break;
    440     getNextToken(); // eat the ','.
    441 
    442     if (CurTok != tok_identifier)
    443       return Error("expected identifier list after var");
    444   }
    445 
    446   // At this point, we have to have 'in'.
    447   if (CurTok != tok_in)
    448     return Error("expected 'in' keyword after 'var'");
    449   getNextToken();  // eat 'in'.
    450 
    451   ExprAST *Body = ParseExpression();
    452   if (Body == 0) return 0;
    453 
    454   return new VarExprAST(VarNames, Body);
    455 }
    456 
    457 /// primary
    458 ///   ::= identifierexpr
    459 ///   ::= numberexpr
    460 ///   ::= parenexpr
    461 ///   ::= ifexpr
    462 ///   ::= forexpr
    463 ///   ::= varexpr
    464 static ExprAST *ParsePrimary() {
    465   switch (CurTok) {
    466   default: return Error("unknown token when expecting an expression");
    467   case tok_identifier: return ParseIdentifierExpr();
    468   case tok_number:     return ParseNumberExpr();
    469   case '(':            return ParseParenExpr();
    470   case tok_if:         return ParseIfExpr();
    471   case tok_for:        return ParseForExpr();
    472   case tok_var:        return ParseVarExpr();
    473   }
    474 }
    475 
    476 /// unary
    477 ///   ::= primary
    478 ///   ::= '!' unary
    479 static ExprAST *ParseUnary() {
    480   // If the current token is not an operator, it must be a primary expr.
    481   if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
    482     return ParsePrimary();
    483 
    484   // If this is a unary operator, read it.
    485   int Opc = CurTok;
    486   getNextToken();
    487   if (ExprAST *Operand = ParseUnary())
    488     return new UnaryExprAST(Opc, Operand);
    489   return 0;
    490 }
    491 
    492 /// binoprhs
    493 ///   ::= ('+' unary)*
    494 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
    495   // If this is a binop, find its precedence.
    496   while (1) {
    497     int TokPrec = GetTokPrecedence();
    498 
    499     // If this is a binop that binds at least as tightly as the current binop,
    500     // consume it, otherwise we are done.
    501     if (TokPrec < ExprPrec)
    502       return LHS;
    503 
    504     // Okay, we know this is a binop.
    505     int BinOp = CurTok;
    506     getNextToken();  // eat binop
    507 
    508     // Parse the unary expression after the binary operator.
    509     ExprAST *RHS = ParseUnary();
    510     if (!RHS) return 0;
    511 
    512     // If BinOp binds less tightly with RHS than the operator after RHS, let
    513     // the pending operator take RHS as its LHS.
    514     int NextPrec = GetTokPrecedence();
    515     if (TokPrec < NextPrec) {
    516       RHS = ParseBinOpRHS(TokPrec+1, RHS);
    517       if (RHS == 0) return 0;
    518     }
    519 
    520     // Merge LHS/RHS.
    521     LHS = new BinaryExprAST(BinOp, LHS, RHS);
    522   }
    523 }
    524 
    525 /// expression
    526 ///   ::= unary binoprhs
    527 ///
    528 static ExprAST *ParseExpression() {
    529   ExprAST *LHS = ParseUnary();
    530   if (!LHS) return 0;
    531 
    532   return ParseBinOpRHS(0, LHS);
    533 }
    534 
    535 /// prototype
    536 ///   ::= id '(' id* ')'
    537 ///   ::= binary LETTER number? (id, id)
    538 ///   ::= unary LETTER (id)
    539 static PrototypeAST *ParsePrototype() {
    540   std::string FnName;
    541 
    542   unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
    543   unsigned BinaryPrecedence = 30;
    544 
    545   switch (CurTok) {
    546   default:
    547     return ErrorP("Expected function name in prototype");
    548   case tok_identifier:
    549     FnName = IdentifierStr;
    550     Kind = 0;
    551     getNextToken();
    552     break;
    553   case tok_unary:
    554     getNextToken();
    555     if (!isascii(CurTok))
    556       return ErrorP("Expected unary operator");
    557     FnName = "unary";
    558     FnName += (char)CurTok;
    559     Kind = 1;
    560     getNextToken();
    561     break;
    562   case tok_binary:
    563     getNextToken();
    564     if (!isascii(CurTok))
    565       return ErrorP("Expected binary operator");
    566     FnName = "binary";
    567     FnName += (char)CurTok;
    568     Kind = 2;
    569     getNextToken();
    570 
    571     // Read the precedence if present.
    572     if (CurTok == tok_number) {
    573       if (NumVal < 1 || NumVal > 100)
    574         return ErrorP("Invalid precedecnce: must be 1..100");
    575       BinaryPrecedence = (unsigned)NumVal;
    576       getNextToken();
    577     }
    578     break;
    579   }
    580 
    581   if (CurTok != '(')
    582     return ErrorP("Expected '(' in prototype");
    583 
    584   std::vector<std::string> ArgNames;
    585   while (getNextToken() == tok_identifier)
    586     ArgNames.push_back(IdentifierStr);
    587   if (CurTok != ')')
    588     return ErrorP("Expected ')' in prototype");
    589 
    590   // success.
    591   getNextToken();  // eat ')'.
    592 
    593   // Verify right number of names for operator.
    594   if (Kind && ArgNames.size() != Kind)
    595     return ErrorP("Invalid number of operands for operator");
    596 
    597   return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
    598 }
    599 
    600 /// definition ::= 'def' prototype expression
    601 static FunctionAST *ParseDefinition() {
    602   getNextToken();  // eat def.
    603   PrototypeAST *Proto = ParsePrototype();
    604   if (Proto == 0) return 0;
    605 
    606   if (ExprAST *E = ParseExpression())
    607     return new FunctionAST(Proto, E);
    608   return 0;
    609 }
    610 
    611 /// toplevelexpr ::= expression
    612 static FunctionAST *ParseTopLevelExpr() {
    613   if (ExprAST *E = ParseExpression()) {
    614     // Make an anonymous proto.
    615     PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
    616     return new FunctionAST(Proto, E);
    617   }
    618   return 0;
    619 }
    620 
    621 /// external ::= 'extern' prototype
    622 static PrototypeAST *ParseExtern() {
    623   getNextToken();  // eat extern.
    624   return ParsePrototype();
    625 }
    626 
    627 //===----------------------------------------------------------------------===//
    628 // Quick and dirty hack
    629 //===----------------------------------------------------------------------===//
    630 
    631 // FIXME: Obviously we can do better than this
    632 std::string GenerateUniqueName(const char *root)
    633 {
    634   static int i = 0;
    635   char s[16];
    636   sprintf(s, "%s%d", root, i++);
    637   std::string S = s;
    638   return S;
    639 }
    640 
    641 std::string MakeLegalFunctionName(std::string Name)
    642 {
    643   std::string NewName;
    644   if (!Name.length())
    645       return GenerateUniqueName("anon_func_");
    646 
    647   // Start with what we have
    648   NewName = Name;
    649 
    650   // Look for a numberic first character
    651   if (NewName.find_first_of("0123456789") == 0) {
    652     NewName.insert(0, 1, 'n');
    653   }
    654 
    655   // Replace illegal characters with their ASCII equivalent
    656   std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    657   size_t pos;
    658   while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
    659     char old_c = NewName.at(pos);
    660     char new_str[16];
    661     sprintf(new_str, "%d", (int)old_c);
    662     NewName = NewName.replace(pos, 1, new_str);
    663   }
    664 
    665   return NewName;
    666 }
    667 
    668 //===----------------------------------------------------------------------===//
    669 // MCJIT object cache class
    670 //===----------------------------------------------------------------------===//
    671 
    672 class MCJITObjectCache : public ObjectCache {
    673 public:
    674   MCJITObjectCache() {
    675     // Set IR cache directory
    676     sys::fs::current_path(CacheDir);
    677     sys::path::append(CacheDir, "toy_object_cache");
    678   }
    679 
    680   virtual ~MCJITObjectCache() {
    681   }
    682 
    683   virtual void notifyObjectCompiled(const Module *M, const MemoryBuffer *Obj) {
    684     // Get the ModuleID
    685     const std::string ModuleID = M->getModuleIdentifier();
    686 
    687     // If we've flagged this as an IR file, cache it
    688     if (0 == ModuleID.compare(0, 3, "IR:")) {
    689       std::string IRFileName = ModuleID.substr(3);
    690       SmallString<128>IRCacheFile = CacheDir;
    691       sys::path::append(IRCacheFile, IRFileName);
    692       if (!sys::fs::exists(CacheDir.str()) && sys::fs::create_directory(CacheDir.str())) {
    693         fprintf(stderr, "Unable to create cache directory\n");
    694         return;
    695       }
    696       std::string ErrStr;
    697       raw_fd_ostream IRObjectFile(IRCacheFile.c_str(), ErrStr, raw_fd_ostream::F_Binary);
    698       IRObjectFile << Obj->getBuffer();
    699     }
    700   }
    701 
    702   // MCJIT will call this function before compiling any module
    703   // MCJIT takes ownership of both the MemoryBuffer object and the memory
    704   // to which it refers.
    705   virtual MemoryBuffer* getObject(const Module* M) {
    706     // Get the ModuleID
    707     const std::string ModuleID = M->getModuleIdentifier();
    708 
    709     // If we've flagged this as an IR file, cache it
    710     if (0 == ModuleID.compare(0, 3, "IR:")) {
    711       std::string IRFileName = ModuleID.substr(3);
    712       SmallString<128> IRCacheFile = CacheDir;
    713       sys::path::append(IRCacheFile, IRFileName);
    714       if (!sys::fs::exists(IRCacheFile.str())) {
    715         // This file isn't in our cache
    716         return NULL;
    717       }
    718       std::unique_ptr<MemoryBuffer> IRObjectBuffer;
    719       MemoryBuffer::getFile(IRCacheFile.c_str(), IRObjectBuffer, -1, false);
    720       // MCJIT will want to write into this buffer, and we don't want that
    721       // because the file has probably just been mmapped.  Instead we make
    722       // a copy.  The filed-based buffer will be released when it goes
    723       // out of scope.
    724       return MemoryBuffer::getMemBufferCopy(IRObjectBuffer->getBuffer());
    725     }
    726 
    727     return NULL;
    728   }
    729 
    730 private:
    731   SmallString<128> CacheDir;
    732 };
    733 
    734 //===----------------------------------------------------------------------===//
    735 // MCJIT helper class
    736 //===----------------------------------------------------------------------===//
    737 
    738 class MCJITHelper
    739 {
    740 public:
    741   MCJITHelper(LLVMContext& C) : Context(C), OpenModule(NULL) {}
    742   ~MCJITHelper();
    743 
    744   Function *getFunction(const std::string FnName);
    745   Module *getModuleForNewFunction();
    746   void *getPointerToFunction(Function* F);
    747   void *getPointerToNamedFunction(const std::string &Name);
    748   ExecutionEngine *compileModule(Module *M);
    749   void closeCurrentModule();
    750   void addModule(Module *M);
    751   void dump();
    752 
    753 private:
    754   typedef std::vector<Module*> ModuleVector;
    755 
    756   LLVMContext  &Context;
    757   Module       *OpenModule;
    758   ModuleVector  Modules;
    759   std::map<Module *, ExecutionEngine *> EngineMap;
    760   MCJITObjectCache OurObjectCache;
    761 };
    762 
    763 class HelpingMemoryManager : public SectionMemoryManager
    764 {
    765   HelpingMemoryManager(const HelpingMemoryManager&) = delete;
    766   void operator=(const HelpingMemoryManager&) = delete;
    767 
    768 public:
    769   HelpingMemoryManager(MCJITHelper *Helper) : MasterHelper(Helper) {}
    770   virtual ~HelpingMemoryManager() {}
    771 
    772   /// This method returns the address of the specified function.
    773   /// Our implementation will attempt to find functions in other
    774   /// modules associated with the MCJITHelper to cross link functions
    775   /// from one generated module to another.
    776   ///
    777   /// If \p AbortOnFailure is false and no function with the given name is
    778   /// found, this function returns a null pointer. Otherwise, it prints a
    779   /// message to stderr and aborts.
    780   virtual void *getPointerToNamedFunction(const std::string &Name,
    781                                           bool AbortOnFailure = true);
    782 private:
    783   MCJITHelper *MasterHelper;
    784 };
    785 
    786 void *HelpingMemoryManager::getPointerToNamedFunction(const std::string &Name,
    787                                         bool AbortOnFailure)
    788 {
    789   // Try the standard symbol resolution first, but ask it not to abort.
    790   void *pfn = SectionMemoryManager::getPointerToNamedFunction(Name, false);
    791   if (pfn)
    792     return pfn;
    793 
    794   pfn = MasterHelper->getPointerToNamedFunction(Name);
    795   if (!pfn && AbortOnFailure)
    796     report_fatal_error("Program used external function '" + Name +
    797                         "' which could not be resolved!");
    798   return pfn;
    799 }
    800 
    801 MCJITHelper::~MCJITHelper()
    802 {
    803   // Walk the vector of modules.
    804   ModuleVector::iterator it, end;
    805   for (it = Modules.begin(), end = Modules.end();
    806        it != end; ++it) {
    807     // See if we have an execution engine for this module.
    808     std::map<Module*, ExecutionEngine*>::iterator mapIt = EngineMap.find(*it);
    809     // If we have an EE, the EE owns the module so just delete the EE.
    810     if (mapIt != EngineMap.end()) {
    811       delete mapIt->second;
    812     } else {
    813       // Otherwise, we still own the module.  Delete it now.
    814       delete *it;
    815     }
    816   }
    817 }
    818 
    819 Function *MCJITHelper::getFunction(const std::string FnName) {
    820   ModuleVector::iterator begin = Modules.begin();
    821   ModuleVector::iterator end = Modules.end();
    822   ModuleVector::iterator it;
    823   for (it = begin; it != end; ++it) {
    824     Function *F = (*it)->getFunction(FnName);
    825     if (F) {
    826       if (*it == OpenModule)
    827           return F;
    828 
    829       assert(OpenModule != NULL);
    830 
    831       // This function is in a module that has already been JITed.
    832       // We need to generate a new prototype for external linkage.
    833       Function *PF = OpenModule->getFunction(FnName);
    834       if (PF && !PF->empty()) {
    835         ErrorF("redefinition of function across modules");
    836         return 0;
    837       }
    838 
    839       // If we don't have a prototype yet, create one.
    840       if (!PF)
    841         PF = Function::Create(F->getFunctionType(),
    842                                       Function::ExternalLinkage,
    843                                       FnName,
    844                                       OpenModule);
    845       return PF;
    846     }
    847   }
    848   return NULL;
    849 }
    850 
    851 Module *MCJITHelper::getModuleForNewFunction() {
    852   // If we have a Module that hasn't been JITed, use that.
    853   if (OpenModule)
    854     return OpenModule;
    855 
    856   // Otherwise create a new Module.
    857   std::string ModName = GenerateUniqueName("mcjit_module_");
    858   Module *M = new Module(ModName, Context);
    859   Modules.push_back(M);
    860   OpenModule = M;
    861   return M;
    862 }
    863 
    864 void *MCJITHelper::getPointerToFunction(Function* F) {
    865   // Look for this function in an existing module
    866   ModuleVector::iterator begin = Modules.begin();
    867   ModuleVector::iterator end = Modules.end();
    868   ModuleVector::iterator it;
    869   std::string FnName = F->getName();
    870   for (it = begin; it != end; ++it) {
    871     Function *MF = (*it)->getFunction(FnName);
    872     if (MF == F) {
    873       std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
    874       if (eeIt != EngineMap.end()) {
    875         void *P = eeIt->second->getPointerToFunction(F);
    876         if (P)
    877           return P;
    878       } else {
    879         ExecutionEngine *EE = compileModule(*it);
    880         void *P = EE->getPointerToFunction(F);
    881         if (P)
    882           return P;
    883       }
    884     }
    885   }
    886   return NULL;
    887 }
    888 
    889 void MCJITHelper::closeCurrentModule() {
    890   OpenModule = NULL;
    891 }
    892 
    893 ExecutionEngine *MCJITHelper::compileModule(Module *M) {
    894   if (M == OpenModule)
    895     closeCurrentModule();
    896 
    897   std::string ErrStr;
    898   ExecutionEngine *NewEngine = EngineBuilder(M)
    899                                             .setErrorStr(&ErrStr)
    900                                             .setMCJITMemoryManager(new HelpingMemoryManager(this))
    901                                             .create();
    902   if (!NewEngine) {
    903     fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
    904     exit(1);
    905   }
    906 
    907   if (UseObjectCache)
    908     NewEngine->setObjectCache(&OurObjectCache);
    909 
    910   // Get the ModuleID so we can identify IR input files
    911   const std::string ModuleID = M->getModuleIdentifier();
    912 
    913   // If we've flagged this as an IR file, it doesn't need function passes run.
    914   if (0 != ModuleID.compare(0, 3, "IR:")) {
    915     // Create a function pass manager for this engine
    916     FunctionPassManager *FPM = new FunctionPassManager(M);
    917 
    918     // Set up the optimizer pipeline.  Start with registering info about how the
    919     // target lays out data structures.
    920     FPM->add(new DataLayout(*NewEngine->getDataLayout()));
    921     // Provide basic AliasAnalysis support for GVN.
    922     FPM->add(createBasicAliasAnalysisPass());
    923     // Promote allocas to registers.
    924     FPM->add(createPromoteMemoryToRegisterPass());
    925     // Do simple "peephole" optimizations and bit-twiddling optzns.
    926     FPM->add(createInstructionCombiningPass());
    927     // Reassociate expressions.
    928     FPM->add(createReassociatePass());
    929     // Eliminate Common SubExpressions.
    930     FPM->add(createGVNPass());
    931     // Simplify the control flow graph (deleting unreachable blocks, etc).
    932     FPM->add(createCFGSimplificationPass());
    933     FPM->doInitialization();
    934 
    935     // For each function in the module
    936     Module::iterator it;
    937     Module::iterator end = M->end();
    938     for (it = M->begin(); it != end; ++it) {
    939       // Run the FPM on this function
    940       FPM->run(*it);
    941     }
    942 
    943     // We don't need this anymore
    944     delete FPM;
    945   }
    946 
    947   // Store this engine
    948   EngineMap[M] = NewEngine;
    949   NewEngine->finalizeObject();
    950 
    951   return NewEngine;
    952 }
    953 
    954 void *MCJITHelper::getPointerToNamedFunction(const std::string &Name)
    955 {
    956   // Look for the functions in our modules, compiling only as necessary
    957   ModuleVector::iterator begin = Modules.begin();
    958   ModuleVector::iterator end = Modules.end();
    959   ModuleVector::iterator it;
    960   for (it = begin; it != end; ++it) {
    961     Function *F = (*it)->getFunction(Name);
    962     if (F && !F->empty()) {
    963       std::map<Module*, ExecutionEngine*>::iterator eeIt = EngineMap.find(*it);
    964       if (eeIt != EngineMap.end()) {
    965         void *P = eeIt->second->getPointerToFunction(F);
    966         if (P)
    967           return P;
    968       } else {
    969         ExecutionEngine *EE = compileModule(*it);
    970         void *P = EE->getPointerToFunction(F);
    971         if (P)
    972           return P;
    973       }
    974     }
    975   }
    976   return NULL;
    977 }
    978 
    979 void MCJITHelper::addModule(Module* M) {
    980   Modules.push_back(M);
    981 }
    982 
    983 void MCJITHelper::dump()
    984 {
    985   ModuleVector::iterator begin = Modules.begin();
    986   ModuleVector::iterator end = Modules.end();
    987   ModuleVector::iterator it;
    988   for (it = begin; it != end; ++it)
    989     (*it)->dump();
    990 }
    991 
    992 //===----------------------------------------------------------------------===//
    993 // Code Generation
    994 //===----------------------------------------------------------------------===//
    995 
    996 static MCJITHelper *TheHelper;
    997 static IRBuilder<> Builder(getGlobalContext());
    998 static std::map<std::string, AllocaInst*> NamedValues;
    999 
   1000 Value *ErrorV(const char *Str) { Error(Str); return 0; }
   1001 
   1002 /// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
   1003 /// the function.  This is used for mutable variables etc.
   1004 static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
   1005                                           const std::string &VarName) {
   1006   IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
   1007                  TheFunction->getEntryBlock().begin());
   1008   return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
   1009                            VarName.c_str());
   1010 }
   1011 
   1012 Value *NumberExprAST::Codegen() {
   1013   return ConstantFP::get(getGlobalContext(), APFloat(Val));
   1014 }
   1015 
   1016 Value *VariableExprAST::Codegen() {
   1017   // Look this variable up in the function.
   1018   Value *V = NamedValues[Name];
   1019   char ErrStr[256];
   1020   sprintf(ErrStr, "Unknown variable name %s", Name.c_str());
   1021   if (V == 0) return ErrorV(ErrStr);
   1022 
   1023   // Load the value.
   1024   return Builder.CreateLoad(V, Name.c_str());
   1025 }
   1026 
   1027 Value *UnaryExprAST::Codegen() {
   1028   Value *OperandV = Operand->Codegen();
   1029   if (OperandV == 0) return 0;
   1030 
   1031   Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("unary")+Opcode));
   1032   if (F == 0)
   1033     return ErrorV("Unknown unary operator");
   1034 
   1035   return Builder.CreateCall(F, OperandV, "unop");
   1036 }
   1037 
   1038 Value *BinaryExprAST::Codegen() {
   1039   // Special case '=' because we don't want to emit the LHS as an expression.
   1040   if (Op == '=') {
   1041     // Assignment requires the LHS to be an identifier.
   1042     VariableExprAST *LHSE = static_cast<VariableExprAST*>(LHS);
   1043     if (!LHSE)
   1044       return ErrorV("destination of '=' must be a variable");
   1045     // Codegen the RHS.
   1046     Value *Val = RHS->Codegen();
   1047     if (Val == 0) return 0;
   1048 
   1049     // Look up the name.
   1050     Value *Variable = NamedValues[LHSE->getName()];
   1051     if (Variable == 0) return ErrorV("Unknown variable name");
   1052 
   1053     Builder.CreateStore(Val, Variable);
   1054     return Val;
   1055   }
   1056 
   1057   Value *L = LHS->Codegen();
   1058   Value *R = RHS->Codegen();
   1059   if (L == 0 || R == 0) return 0;
   1060 
   1061   switch (Op) {
   1062   case '+': return Builder.CreateFAdd(L, R, "addtmp");
   1063   case '-': return Builder.CreateFSub(L, R, "subtmp");
   1064   case '*': return Builder.CreateFMul(L, R, "multmp");
   1065   case '/': return Builder.CreateFDiv(L, R, "divtmp");
   1066   case '<':
   1067     L = Builder.CreateFCmpULT(L, R, "cmptmp");
   1068     // Convert bool 0/1 to double 0.0 or 1.0
   1069     return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
   1070                                 "booltmp");
   1071   default: break;
   1072   }
   1073 
   1074   // If it wasn't a builtin binary operator, it must be a user defined one. Emit
   1075   // a call to it.
   1076   Function *F = TheHelper->getFunction(MakeLegalFunctionName(std::string("binary")+Op));
   1077   assert(F && "binary operator not found!");
   1078 
   1079   Value *Ops[] = { L, R };
   1080   return Builder.CreateCall(F, Ops, "binop");
   1081 }
   1082 
   1083 Value *CallExprAST::Codegen() {
   1084   // Look up the name in the global module table.
   1085   Function *CalleeF = TheHelper->getFunction(Callee);
   1086   if (CalleeF == 0)
   1087     return ErrorV("Unknown function referenced");
   1088 
   1089   // If argument mismatch error.
   1090   if (CalleeF->arg_size() != Args.size())
   1091     return ErrorV("Incorrect # arguments passed");
   1092 
   1093   std::vector<Value*> ArgsV;
   1094   for (unsigned i = 0, e = Args.size(); i != e; ++i) {
   1095     ArgsV.push_back(Args[i]->Codegen());
   1096     if (ArgsV.back() == 0) return 0;
   1097   }
   1098 
   1099   return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
   1100 }
   1101 
   1102 Value *IfExprAST::Codegen() {
   1103   Value *CondV = Cond->Codegen();
   1104   if (CondV == 0) return 0;
   1105 
   1106   // Convert condition to a bool by comparing equal to 0.0.
   1107   CondV = Builder.CreateFCmpONE(CondV,
   1108                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
   1109                                 "ifcond");
   1110 
   1111   Function *TheFunction = Builder.GetInsertBlock()->getParent();
   1112 
   1113   // Create blocks for the then and else cases.  Insert the 'then' block at the
   1114   // end of the function.
   1115   BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
   1116   BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
   1117   BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
   1118 
   1119   Builder.CreateCondBr(CondV, ThenBB, ElseBB);
   1120 
   1121   // Emit then value.
   1122   Builder.SetInsertPoint(ThenBB);
   1123 
   1124   Value *ThenV = Then->Codegen();
   1125   if (ThenV == 0) return 0;
   1126 
   1127   Builder.CreateBr(MergeBB);
   1128   // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
   1129   ThenBB = Builder.GetInsertBlock();
   1130 
   1131   // Emit else block.
   1132   TheFunction->getBasicBlockList().push_back(ElseBB);
   1133   Builder.SetInsertPoint(ElseBB);
   1134 
   1135   Value *ElseV = Else->Codegen();
   1136   if (ElseV == 0) return 0;
   1137 
   1138   Builder.CreateBr(MergeBB);
   1139   // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
   1140   ElseBB = Builder.GetInsertBlock();
   1141 
   1142   // Emit merge block.
   1143   TheFunction->getBasicBlockList().push_back(MergeBB);
   1144   Builder.SetInsertPoint(MergeBB);
   1145   PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
   1146                                   "iftmp");
   1147 
   1148   PN->addIncoming(ThenV, ThenBB);
   1149   PN->addIncoming(ElseV, ElseBB);
   1150   return PN;
   1151 }
   1152 
   1153 Value *ForExprAST::Codegen() {
   1154   // Output this as:
   1155   //   var = alloca double
   1156   //   ...
   1157   //   start = startexpr
   1158   //   store start -> var
   1159   //   goto loop
   1160   // loop:
   1161   //   ...
   1162   //   bodyexpr
   1163   //   ...
   1164   // loopend:
   1165   //   step = stepexpr
   1166   //   endcond = endexpr
   1167   //
   1168   //   curvar = load var
   1169   //   nextvar = curvar + step
   1170   //   store nextvar -> var
   1171   //   br endcond, loop, endloop
   1172   // outloop:
   1173 
   1174   Function *TheFunction = Builder.GetInsertBlock()->getParent();
   1175 
   1176   // Create an alloca for the variable in the entry block.
   1177   AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
   1178 
   1179   // Emit the start code first, without 'variable' in scope.
   1180   Value *StartVal = Start->Codegen();
   1181   if (StartVal == 0) return 0;
   1182 
   1183   // Store the value into the alloca.
   1184   Builder.CreateStore(StartVal, Alloca);
   1185 
   1186   // Make the new basic block for the loop header, inserting after current
   1187   // block.
   1188   BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
   1189 
   1190   // Insert an explicit fall through from the current block to the LoopBB.
   1191   Builder.CreateBr(LoopBB);
   1192 
   1193   // Start insertion in LoopBB.
   1194   Builder.SetInsertPoint(LoopBB);
   1195 
   1196   // Within the loop, the variable is defined equal to the PHI node.  If it
   1197   // shadows an existing variable, we have to restore it, so save it now.
   1198   AllocaInst *OldVal = NamedValues[VarName];
   1199   NamedValues[VarName] = Alloca;
   1200 
   1201   // Emit the body of the loop.  This, like any other expr, can change the
   1202   // current BB.  Note that we ignore the value computed by the body, but don't
   1203   // allow an error.
   1204   if (Body->Codegen() == 0)
   1205     return 0;
   1206 
   1207   // Emit the step value.
   1208   Value *StepVal;
   1209   if (Step) {
   1210     StepVal = Step->Codegen();
   1211     if (StepVal == 0) return 0;
   1212   } else {
   1213     // If not specified, use 1.0.
   1214     StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
   1215   }
   1216 
   1217   // Compute the end condition.
   1218   Value *EndCond = End->Codegen();
   1219   if (EndCond == 0) return EndCond;
   1220 
   1221   // Reload, increment, and restore the alloca.  This handles the case where
   1222   // the body of the loop mutates the variable.
   1223   Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
   1224   Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
   1225   Builder.CreateStore(NextVar, Alloca);
   1226 
   1227   // Convert condition to a bool by comparing equal to 0.0.
   1228   EndCond = Builder.CreateFCmpONE(EndCond,
   1229                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
   1230                                   "loopcond");
   1231 
   1232   // Create the "after loop" block and insert it.
   1233   BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
   1234 
   1235   // Insert the conditional branch into the end of LoopEndBB.
   1236   Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
   1237 
   1238   // Any new code will be inserted in AfterBB.
   1239   Builder.SetInsertPoint(AfterBB);
   1240 
   1241   // Restore the unshadowed variable.
   1242   if (OldVal)
   1243     NamedValues[VarName] = OldVal;
   1244   else
   1245     NamedValues.erase(VarName);
   1246 
   1247 
   1248   // for expr always returns 0.0.
   1249   return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
   1250 }
   1251 
   1252 Value *VarExprAST::Codegen() {
   1253   std::vector<AllocaInst *> OldBindings;
   1254 
   1255   Function *TheFunction = Builder.GetInsertBlock()->getParent();
   1256 
   1257   // Register all variables and emit their initializer.
   1258   for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
   1259     const std::string &VarName = VarNames[i].first;
   1260     ExprAST *Init = VarNames[i].second;
   1261 
   1262     // Emit the initializer before adding the variable to scope, this prevents
   1263     // the initializer from referencing the variable itself, and permits stuff
   1264     // like this:
   1265     //  var a = 1 in
   1266     //    var a = a in ...   # refers to outer 'a'.
   1267     Value *InitVal;
   1268     if (Init) {
   1269       InitVal = Init->Codegen();
   1270       if (InitVal == 0) return 0;
   1271     } else { // If not specified, use 0.0.
   1272       InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
   1273     }
   1274 
   1275     AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
   1276     Builder.CreateStore(InitVal, Alloca);
   1277 
   1278     // Remember the old variable binding so that we can restore the binding when
   1279     // we unrecurse.
   1280     OldBindings.push_back(NamedValues[VarName]);
   1281 
   1282     // Remember this binding.
   1283     NamedValues[VarName] = Alloca;
   1284   }
   1285 
   1286   // Codegen the body, now that all vars are in scope.
   1287   Value *BodyVal = Body->Codegen();
   1288   if (BodyVal == 0) return 0;
   1289 
   1290   // Pop all our variables from scope.
   1291   for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
   1292     NamedValues[VarNames[i].first] = OldBindings[i];
   1293 
   1294   // Return the body computation.
   1295   return BodyVal;
   1296 }
   1297 
   1298 Function *PrototypeAST::Codegen() {
   1299   // Make the function type:  double(double,double) etc.
   1300   std::vector<Type*> Doubles(Args.size(),
   1301                              Type::getDoubleTy(getGlobalContext()));
   1302   FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
   1303                                        Doubles, false);
   1304 
   1305   std::string FnName = MakeLegalFunctionName(Name);
   1306 
   1307   Module* M = TheHelper->getModuleForNewFunction();
   1308 
   1309   Function *F = Function::Create(FT, Function::ExternalLinkage, FnName, M);
   1310 
   1311   // If F conflicted, there was already something named 'FnName'.  If it has a
   1312   // body, don't allow redefinition or reextern.
   1313   if (F->getName() != FnName) {
   1314     // Delete the one we just made and get the existing one.
   1315     F->eraseFromParent();
   1316     F = M->getFunction(Name);
   1317 
   1318     // If F already has a body, reject this.
   1319     if (!F->empty()) {
   1320       ErrorF("redefinition of function");
   1321       return 0;
   1322     }
   1323 
   1324     // If F took a different number of args, reject.
   1325     if (F->arg_size() != Args.size()) {
   1326       ErrorF("redefinition of function with different # args");
   1327       return 0;
   1328     }
   1329   }
   1330 
   1331   // Set names for all arguments.
   1332   unsigned Idx = 0;
   1333   for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
   1334        ++AI, ++Idx)
   1335     AI->setName(Args[Idx]);
   1336 
   1337   return F;
   1338 }
   1339 
   1340 /// CreateArgumentAllocas - Create an alloca for each argument and register the
   1341 /// argument in the symbol table so that references to it will succeed.
   1342 void PrototypeAST::CreateArgumentAllocas(Function *F) {
   1343   Function::arg_iterator AI = F->arg_begin();
   1344   for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
   1345     // Create an alloca for this variable.
   1346     AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
   1347 
   1348     // Store the initial value into the alloca.
   1349     Builder.CreateStore(AI, Alloca);
   1350 
   1351     // Add arguments to variable symbol table.
   1352     NamedValues[Args[Idx]] = Alloca;
   1353   }
   1354 }
   1355 
   1356 Function *FunctionAST::Codegen() {
   1357   NamedValues.clear();
   1358 
   1359   Function *TheFunction = Proto->Codegen();
   1360   if (TheFunction == 0)
   1361     return 0;
   1362 
   1363   // If this is an operator, install it.
   1364   if (Proto->isBinaryOp())
   1365     BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
   1366 
   1367   // Create a new basic block to start insertion into.
   1368   BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
   1369   Builder.SetInsertPoint(BB);
   1370 
   1371   // Add all arguments to the symbol table and create their allocas.
   1372   Proto->CreateArgumentAllocas(TheFunction);
   1373 
   1374   if (Value *RetVal = Body->Codegen()) {
   1375     // Finish off the function.
   1376     Builder.CreateRet(RetVal);
   1377 
   1378     // Validate the generated code, checking for consistency.
   1379     verifyFunction(*TheFunction);
   1380 
   1381     return TheFunction;
   1382   }
   1383 
   1384   // Error reading body, remove function.
   1385   TheFunction->eraseFromParent();
   1386 
   1387   if (Proto->isBinaryOp())
   1388     BinopPrecedence.erase(Proto->getOperatorName());
   1389   return 0;
   1390 }
   1391 
   1392 //===----------------------------------------------------------------------===//
   1393 // Top-Level parsing and JIT Driver
   1394 //===----------------------------------------------------------------------===//
   1395 
   1396 static void HandleDefinition() {
   1397   if (FunctionAST *F = ParseDefinition()) {
   1398     TheHelper->closeCurrentModule();
   1399     if (Function *LF = F->Codegen()) {
   1400 #ifndef MINIMAL_STDERR_OUTPUT
   1401       fprintf(stderr, "Read function definition:");
   1402       LF->dump();
   1403 #endif
   1404     }
   1405   } else {
   1406     // Skip token for error recovery.
   1407     getNextToken();
   1408   }
   1409 }
   1410 
   1411 static void HandleExtern() {
   1412   if (PrototypeAST *P = ParseExtern()) {
   1413     if (Function *F = P->Codegen()) {
   1414 #ifndef MINIMAL_STDERR_OUTPUT
   1415       fprintf(stderr, "Read extern: ");
   1416       F->dump();
   1417 #endif
   1418     }
   1419   } else {
   1420     // Skip token for error recovery.
   1421     getNextToken();
   1422   }
   1423 }
   1424 
   1425 static void HandleTopLevelExpression() {
   1426   // Evaluate a top-level expression into an anonymous function.
   1427   if (FunctionAST *F = ParseTopLevelExpr()) {
   1428     if (Function *LF = F->Codegen()) {
   1429       // JIT the function, returning a function pointer.
   1430       void *FPtr = TheHelper->getPointerToFunction(LF);
   1431 
   1432       // Cast it to the right type (takes no arguments, returns a double) so we
   1433       // can call it as a native function.
   1434       double (*FP)() = (double (*)())(intptr_t)FPtr;
   1435 #ifdef MINIMAL_STDERR_OUTPUT
   1436       FP();
   1437 #else
   1438       fprintf(stderr, "Evaluated to %f\n", FP());
   1439 #endif
   1440     }
   1441   } else {
   1442     // Skip token for error recovery.
   1443     getNextToken();
   1444   }
   1445 }
   1446 
   1447 /// top ::= definition | external | expression | ';'
   1448 static void MainLoop() {
   1449   while (1) {
   1450 #ifndef MINIMAL_STDERR_OUTPUT
   1451     fprintf(stderr, "ready> ");
   1452 #endif
   1453     switch (CurTok) {
   1454     case tok_eof:    return;
   1455     case ';':        getNextToken(); break;  // ignore top-level semicolons.
   1456     case tok_def:    HandleDefinition(); break;
   1457     case tok_extern: HandleExtern(); break;
   1458     default:         HandleTopLevelExpression(); break;
   1459     }
   1460   }
   1461 }
   1462 
   1463 //===----------------------------------------------------------------------===//
   1464 // "Library" functions that can be "extern'd" from user code.
   1465 //===----------------------------------------------------------------------===//
   1466 
   1467 /// putchard - putchar that takes a double and returns 0.
   1468 extern "C"
   1469 double putchard(double X) {
   1470   putchar((char)X);
   1471   return 0;
   1472 }
   1473 
   1474 /// printd - printf that takes a double prints it as "%f\n", returning 0.
   1475 extern "C"
   1476 double printd(double X) {
   1477   printf("%f", X);
   1478   return 0;
   1479 }
   1480 
   1481 extern "C"
   1482 double printlf() {
   1483   printf("\n");
   1484   return 0;
   1485 }
   1486 
   1487 //===----------------------------------------------------------------------===//
   1488 // Command line input file handler
   1489 //===----------------------------------------------------------------------===//
   1490 
   1491 Module* parseInputIR(std::string InputFile) {
   1492   SMDiagnostic Err;
   1493   Module *M = ParseIRFile(InputFile, Err, getGlobalContext());
   1494   if (!M) {
   1495     Err.print("IR parsing failed: ", errs());
   1496     return NULL;
   1497   }
   1498 
   1499   char ModID[256];
   1500   sprintf(ModID, "IR:%s", InputFile.c_str());
   1501   M->setModuleIdentifier(ModID);
   1502 
   1503   TheHelper->addModule(M);
   1504   return M;
   1505 }
   1506 
   1507 //===----------------------------------------------------------------------===//
   1508 // Main driver code.
   1509 //===----------------------------------------------------------------------===//
   1510 
   1511 int main(int argc, char **argv) {
   1512   InitializeNativeTarget();
   1513   InitializeNativeTargetAsmPrinter();
   1514   InitializeNativeTargetAsmParser();
   1515   LLVMContext &Context = getGlobalContext();
   1516 
   1517   cl::ParseCommandLineOptions(argc, argv,
   1518                               "Kaleidoscope example program\n");
   1519 
   1520   // Install standard binary operators.
   1521   // 1 is lowest precedence.
   1522   BinopPrecedence['='] = 2;
   1523   BinopPrecedence['<'] = 10;
   1524   BinopPrecedence['+'] = 20;
   1525   BinopPrecedence['-'] = 20;
   1526   BinopPrecedence['/'] = 40;
   1527   BinopPrecedence['*'] = 40;  // highest.
   1528 
   1529   // Prime the first token.
   1530 #ifndef MINIMAL_STDERR_OUTPUT
   1531   fprintf(stderr, "ready> ");
   1532 #endif
   1533   getNextToken();
   1534 
   1535   // Make the helper, which holds all the code.
   1536   TheHelper = new MCJITHelper(Context);
   1537 
   1538   if (!InputIR.empty()) {
   1539     parseInputIR(InputIR);
   1540   }
   1541 
   1542   // Run the main "interpreter loop" now.
   1543   MainLoop();
   1544 
   1545 #ifndef MINIMAL_STDERR_OUTPUT
   1546   // Print out all of the generated code.
   1547   TheHelper->dump();
   1548 #endif
   1549 
   1550   return 0;
   1551 }
   1552