Home | History | Annotate | Download | only in Chapter7
      1 #include "llvm/Analysis/Passes.h"
      2 #include "llvm/Analysis/Verifier.h"
      3 #include "llvm/ExecutionEngine/ExecutionEngine.h"
      4 #include "llvm/ExecutionEngine/JIT.h"
      5 #include "llvm/IR/DataLayout.h"
      6 #include "llvm/IR/DerivedTypes.h"
      7 #include "llvm/IR/IRBuilder.h"
      8 #include "llvm/IR/LLVMContext.h"
      9 #include "llvm/IR/Module.h"
     10 #include "llvm/PassManager.h"
     11 #include "llvm/Support/TargetSelect.h"
     12 #include "llvm/Transforms/Scalar.h"
     13 #include <cstdio>
     14 #include <map>
     15 #include <string>
     16 #include <vector>
     17 using namespace llvm;
     18 
     19 //===----------------------------------------------------------------------===//
     20 // Lexer
     21 //===----------------------------------------------------------------------===//
     22 
     23 // The lexer returns tokens [0-255] if it is an unknown character, otherwise one
     24 // of these for known things.
     25 enum Token {
     26   tok_eof = -1,
     27 
     28   // commands
     29   tok_def = -2, tok_extern = -3,
     30 
     31   // primary
     32   tok_identifier = -4, tok_number = -5,
     33 
     34   // control
     35   tok_if = -6, tok_then = -7, tok_else = -8,
     36   tok_for = -9, tok_in = -10,
     37 
     38   // operators
     39   tok_binary = -11, tok_unary = -12,
     40 
     41   // var definition
     42   tok_var = -13
     43 };
     44 
     45 static std::string IdentifierStr;  // Filled in if tok_identifier
     46 static double NumVal;              // Filled in if tok_number
     47 
     48 /// gettok - Return the next token from standard input.
     49 static int gettok() {
     50   static int LastChar = ' ';
     51 
     52   // Skip any whitespace.
     53   while (isspace(LastChar))
     54     LastChar = getchar();
     55 
     56   if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
     57     IdentifierStr = LastChar;
     58     while (isalnum((LastChar = getchar())))
     59       IdentifierStr += LastChar;
     60 
     61     if (IdentifierStr == "def") return tok_def;
     62     if (IdentifierStr == "extern") return tok_extern;
     63     if (IdentifierStr == "if") return tok_if;
     64     if (IdentifierStr == "then") return tok_then;
     65     if (IdentifierStr == "else") return tok_else;
     66     if (IdentifierStr == "for") return tok_for;
     67     if (IdentifierStr == "in") return tok_in;
     68     if (IdentifierStr == "binary") return tok_binary;
     69     if (IdentifierStr == "unary") return tok_unary;
     70     if (IdentifierStr == "var") return tok_var;
     71     return tok_identifier;
     72   }
     73 
     74   if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
     75     std::string NumStr;
     76     do {
     77       NumStr += LastChar;
     78       LastChar = getchar();
     79     } while (isdigit(LastChar) || LastChar == '.');
     80 
     81     NumVal = strtod(NumStr.c_str(), 0);
     82     return tok_number;
     83   }
     84 
     85   if (LastChar == '#') {
     86     // Comment until end of line.
     87     do LastChar = getchar();
     88     while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
     89 
     90     if (LastChar != EOF)
     91       return gettok();
     92   }
     93 
     94   // Check for end of file.  Don't eat the EOF.
     95   if (LastChar == EOF)
     96     return tok_eof;
     97 
     98   // Otherwise, just return the character as its ascii value.
     99   int ThisChar = LastChar;
    100   LastChar = getchar();
    101   return ThisChar;
    102 }
    103 
    104 //===----------------------------------------------------------------------===//
    105 // Abstract Syntax Tree (aka Parse Tree)
    106 //===----------------------------------------------------------------------===//
    107 
    108 /// ExprAST - Base class for all expression nodes.
    109 class ExprAST {
    110 public:
    111   virtual ~ExprAST() {}
    112   virtual Value *Codegen() = 0;
    113 };
    114 
    115 /// NumberExprAST - Expression class for numeric literals like "1.0".
    116 class NumberExprAST : public ExprAST {
    117   double Val;
    118 public:
    119   NumberExprAST(double val) : Val(val) {}
    120   virtual Value *Codegen();
    121 };
    122 
    123 /// VariableExprAST - Expression class for referencing a variable, like "a".
    124 class VariableExprAST : public ExprAST {
    125   std::string Name;
    126 public:
    127   VariableExprAST(const std::string &name) : Name(name) {}
    128   const std::string &getName() const { return Name; }
    129   virtual Value *Codegen();
    130 };
    131 
    132 /// UnaryExprAST - Expression class for a unary operator.
    133 class UnaryExprAST : public ExprAST {
    134   char Opcode;
    135   ExprAST *Operand;
    136 public:
    137   UnaryExprAST(char opcode, ExprAST *operand)
    138     : Opcode(opcode), Operand(operand) {}
    139   virtual Value *Codegen();
    140 };
    141 
    142 /// BinaryExprAST - Expression class for a binary operator.
    143 class BinaryExprAST : public ExprAST {
    144   char Op;
    145   ExprAST *LHS, *RHS;
    146 public:
    147   BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
    148     : Op(op), LHS(lhs), RHS(rhs) {}
    149   virtual Value *Codegen();
    150 };
    151 
    152 /// CallExprAST - Expression class for function calls.
    153 class CallExprAST : public ExprAST {
    154   std::string Callee;
    155   std::vector<ExprAST*> Args;
    156 public:
    157   CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
    158     : Callee(callee), Args(args) {}
    159   virtual Value *Codegen();
    160 };
    161 
    162 /// IfExprAST - Expression class for if/then/else.
    163 class IfExprAST : public ExprAST {
    164   ExprAST *Cond, *Then, *Else;
    165 public:
    166   IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
    167   : Cond(cond), Then(then), Else(_else) {}
    168   virtual Value *Codegen();
    169 };
    170 
    171 /// ForExprAST - Expression class for for/in.
    172 class ForExprAST : public ExprAST {
    173   std::string VarName;
    174   ExprAST *Start, *End, *Step, *Body;
    175 public:
    176   ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
    177              ExprAST *step, ExprAST *body)
    178     : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
    179   virtual Value *Codegen();
    180 };
    181 
    182 /// VarExprAST - Expression class for var/in
    183 class VarExprAST : public ExprAST {
    184   std::vector<std::pair<std::string, ExprAST*> > VarNames;
    185   ExprAST *Body;
    186 public:
    187   VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
    188              ExprAST *body)
    189   : VarNames(varnames), Body(body) {}
    190 
    191   virtual Value *Codegen();
    192 };
    193 
    194 /// PrototypeAST - This class represents the "prototype" for a function,
    195 /// which captures its argument names as well as if it is an operator.
    196 class PrototypeAST {
    197   std::string Name;
    198   std::vector<std::string> Args;
    199   bool isOperator;
    200   unsigned Precedence;  // Precedence if a binary op.
    201 public:
    202   PrototypeAST(const std::string &name, const std::vector<std::string> &args,
    203                bool isoperator = false, unsigned prec = 0)
    204   : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
    205 
    206   bool isUnaryOp() const { return isOperator && Args.size() == 1; }
    207   bool isBinaryOp() const { return isOperator && Args.size() == 2; }
    208 
    209   char getOperatorName() const {
    210     assert(isUnaryOp() || isBinaryOp());
    211     return Name[Name.size()-1];
    212   }
    213 
    214   unsigned getBinaryPrecedence() const { return Precedence; }
    215 
    216   Function *Codegen();
    217 
    218   void CreateArgumentAllocas(Function *F);
    219 };
    220 
    221 /// FunctionAST - This class represents a function definition itself.
    222 class FunctionAST {
    223   PrototypeAST *Proto;
    224   ExprAST *Body;
    225 public:
    226   FunctionAST(PrototypeAST *proto, ExprAST *body)
    227     : Proto(proto), Body(body) {}
    228 
    229   Function *Codegen();
    230 };
    231 
    232 //===----------------------------------------------------------------------===//
    233 // Parser
    234 //===----------------------------------------------------------------------===//
    235 
    236 /// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
    237 /// token the parser is looking at.  getNextToken reads another token from the
    238 /// lexer and updates CurTok with its results.
    239 static int CurTok;
    240 static int getNextToken() {
    241   return CurTok = gettok();
    242 }
    243 
    244 /// BinopPrecedence - This holds the precedence for each binary operator that is
    245 /// defined.
    246 static std::map<char, int> BinopPrecedence;
    247 
    248 /// GetTokPrecedence - Get the precedence of the pending binary operator token.
    249 static int GetTokPrecedence() {
    250   if (!isascii(CurTok))
    251     return -1;
    252 
    253   // Make sure it's a declared binop.
    254   int TokPrec = BinopPrecedence[CurTok];
    255   if (TokPrec <= 0) return -1;
    256   return TokPrec;
    257 }
    258 
    259 /// Error* - These are little helper functions for error handling.
    260 ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
    261 PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
    262 FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
    263 
    264 static ExprAST *ParseExpression();
    265 
    266 /// identifierexpr
    267 ///   ::= identifier
    268 ///   ::= identifier '(' expression* ')'
    269 static ExprAST *ParseIdentifierExpr() {
    270   std::string IdName = IdentifierStr;
    271 
    272   getNextToken();  // eat identifier.
    273 
    274   if (CurTok != '(') // Simple variable ref.
    275     return new VariableExprAST(IdName);
    276 
    277   // Call.
    278   getNextToken();  // eat (
    279   std::vector<ExprAST*> Args;
    280   if (CurTok != ')') {
    281     while (1) {
    282       ExprAST *Arg = ParseExpression();
    283       if (!Arg) return 0;
    284       Args.push_back(Arg);
    285 
    286       if (CurTok == ')') break;
    287 
    288       if (CurTok != ',')
    289         return Error("Expected ')' or ',' in argument list");
    290       getNextToken();
    291     }
    292   }
    293 
    294   // Eat the ')'.
    295   getNextToken();
    296 
    297   return new CallExprAST(IdName, Args);
    298 }
    299 
    300 /// numberexpr ::= number
    301 static ExprAST *ParseNumberExpr() {
    302   ExprAST *Result = new NumberExprAST(NumVal);
    303   getNextToken(); // consume the number
    304   return Result;
    305 }
    306 
    307 /// parenexpr ::= '(' expression ')'
    308 static ExprAST *ParseParenExpr() {
    309   getNextToken();  // eat (.
    310   ExprAST *V = ParseExpression();
    311   if (!V) return 0;
    312 
    313   if (CurTok != ')')
    314     return Error("expected ')'");
    315   getNextToken();  // eat ).
    316   return V;
    317 }
    318 
    319 /// ifexpr ::= 'if' expression 'then' expression 'else' expression
    320 static ExprAST *ParseIfExpr() {
    321   getNextToken();  // eat the if.
    322 
    323   // condition.
    324   ExprAST *Cond = ParseExpression();
    325   if (!Cond) return 0;
    326 
    327   if (CurTok != tok_then)
    328     return Error("expected then");
    329   getNextToken();  // eat the then
    330 
    331   ExprAST *Then = ParseExpression();
    332   if (Then == 0) return 0;
    333 
    334   if (CurTok != tok_else)
    335     return Error("expected else");
    336 
    337   getNextToken();
    338 
    339   ExprAST *Else = ParseExpression();
    340   if (!Else) return 0;
    341 
    342   return new IfExprAST(Cond, Then, Else);
    343 }
    344 
    345 /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
    346 static ExprAST *ParseForExpr() {
    347   getNextToken();  // eat the for.
    348 
    349   if (CurTok != tok_identifier)
    350     return Error("expected identifier after for");
    351 
    352   std::string IdName = IdentifierStr;
    353   getNextToken();  // eat identifier.
    354 
    355   if (CurTok != '=')
    356     return Error("expected '=' after for");
    357   getNextToken();  // eat '='.
    358 
    359 
    360   ExprAST *Start = ParseExpression();
    361   if (Start == 0) return 0;
    362   if (CurTok != ',')
    363     return Error("expected ',' after for start value");
    364   getNextToken();
    365 
    366   ExprAST *End = ParseExpression();
    367   if (End == 0) return 0;
    368 
    369   // The step value is optional.
    370   ExprAST *Step = 0;
    371   if (CurTok == ',') {
    372     getNextToken();
    373     Step = ParseExpression();
    374     if (Step == 0) return 0;
    375   }
    376 
    377   if (CurTok != tok_in)
    378     return Error("expected 'in' after for");
    379   getNextToken();  // eat 'in'.
    380 
    381   ExprAST *Body = ParseExpression();
    382   if (Body == 0) return 0;
    383 
    384   return new ForExprAST(IdName, Start, End, Step, Body);
    385 }
    386 
    387 /// varexpr ::= 'var' identifier ('=' expression)?
    388 //                    (',' identifier ('=' expression)?)* 'in' expression
    389 static ExprAST *ParseVarExpr() {
    390   getNextToken();  // eat the var.
    391 
    392   std::vector<std::pair<std::string, ExprAST*> > VarNames;
    393 
    394   // At least one variable name is required.
    395   if (CurTok != tok_identifier)
    396     return Error("expected identifier after var");
    397 
    398   while (1) {
    399     std::string Name = IdentifierStr;
    400     getNextToken();  // eat identifier.
    401 
    402     // Read the optional initializer.
    403     ExprAST *Init = 0;
    404     if (CurTok == '=') {
    405       getNextToken(); // eat the '='.
    406 
    407       Init = ParseExpression();
    408       if (Init == 0) return 0;
    409     }
    410 
    411     VarNames.push_back(std::make_pair(Name, Init));
    412 
    413     // End of var list, exit loop.
    414     if (CurTok != ',') break;
    415     getNextToken(); // eat the ','.
    416 
    417     if (CurTok != tok_identifier)
    418       return Error("expected identifier list after var");
    419   }
    420 
    421   // At this point, we have to have 'in'.
    422   if (CurTok != tok_in)
    423     return Error("expected 'in' keyword after 'var'");
    424   getNextToken();  // eat 'in'.
    425 
    426   ExprAST *Body = ParseExpression();
    427   if (Body == 0) return 0;
    428 
    429   return new VarExprAST(VarNames, Body);
    430 }
    431 
    432 /// primary
    433 ///   ::= identifierexpr
    434 ///   ::= numberexpr
    435 ///   ::= parenexpr
    436 ///   ::= ifexpr
    437 ///   ::= forexpr
    438 ///   ::= varexpr
    439 static ExprAST *ParsePrimary() {
    440   switch (CurTok) {
    441   default: return Error("unknown token when expecting an expression");
    442   case tok_identifier: return ParseIdentifierExpr();
    443   case tok_number:     return ParseNumberExpr();
    444   case '(':            return ParseParenExpr();
    445   case tok_if:         return ParseIfExpr();
    446   case tok_for:        return ParseForExpr();
    447   case tok_var:        return ParseVarExpr();
    448   }
    449 }
    450 
    451 /// unary
    452 ///   ::= primary
    453 ///   ::= '!' unary
    454 static ExprAST *ParseUnary() {
    455   // If the current token is not an operator, it must be a primary expr.
    456   if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
    457     return ParsePrimary();
    458 
    459   // If this is a unary operator, read it.
    460   int Opc = CurTok;
    461   getNextToken();
    462   if (ExprAST *Operand = ParseUnary())
    463     return new UnaryExprAST(Opc, Operand);
    464   return 0;
    465 }
    466 
    467 /// binoprhs
    468 ///   ::= ('+' unary)*
    469 static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
    470   // If this is a binop, find its precedence.
    471   while (1) {
    472     int TokPrec = GetTokPrecedence();
    473 
    474     // If this is a binop that binds at least as tightly as the current binop,
    475     // consume it, otherwise we are done.
    476     if (TokPrec < ExprPrec)
    477       return LHS;
    478 
    479     // Okay, we know this is a binop.
    480     int BinOp = CurTok;
    481     getNextToken();  // eat binop
    482 
    483     // Parse the unary expression after the binary operator.
    484     ExprAST *RHS = ParseUnary();
    485     if (!RHS) return 0;
    486 
    487     // If BinOp binds less tightly with RHS than the operator after RHS, let
    488     // the pending operator take RHS as its LHS.
    489     int NextPrec = GetTokPrecedence();
    490     if (TokPrec < NextPrec) {
    491       RHS = ParseBinOpRHS(TokPrec+1, RHS);
    492       if (RHS == 0) return 0;
    493     }
    494 
    495     // Merge LHS/RHS.
    496     LHS = new BinaryExprAST(BinOp, LHS, RHS);
    497   }
    498 }
    499 
    500 /// expression
    501 ///   ::= unary binoprhs
    502 ///
    503 static ExprAST *ParseExpression() {
    504   ExprAST *LHS = ParseUnary();
    505   if (!LHS) return 0;
    506 
    507   return ParseBinOpRHS(0, LHS);
    508 }
    509 
    510 /// prototype
    511 ///   ::= id '(' id* ')'
    512 ///   ::= binary LETTER number? (id, id)
    513 ///   ::= unary LETTER (id)
    514 static PrototypeAST *ParsePrototype() {
    515   std::string FnName;
    516 
    517   unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
    518   unsigned BinaryPrecedence = 30;
    519 
    520   switch (CurTok) {
    521   default:
    522     return ErrorP("Expected function name in prototype");
    523   case tok_identifier:
    524     FnName = IdentifierStr;
    525     Kind = 0;
    526     getNextToken();
    527     break;
    528   case tok_unary:
    529     getNextToken();
    530     if (!isascii(CurTok))
    531       return ErrorP("Expected unary operator");
    532     FnName = "unary";
    533     FnName += (char)CurTok;
    534     Kind = 1;
    535     getNextToken();
    536     break;
    537   case tok_binary:
    538     getNextToken();
    539     if (!isascii(CurTok))
    540       return ErrorP("Expected binary operator");
    541     FnName = "binary";
    542     FnName += (char)CurTok;
    543     Kind = 2;
    544     getNextToken();
    545 
    546     // Read the precedence if present.
    547     if (CurTok == tok_number) {
    548       if (NumVal < 1 || NumVal > 100)
    549         return ErrorP("Invalid precedecnce: must be 1..100");
    550       BinaryPrecedence = (unsigned)NumVal;
    551       getNextToken();
    552     }
    553     break;
    554   }
    555 
    556   if (CurTok != '(')
    557     return ErrorP("Expected '(' in prototype");
    558 
    559   std::vector<std::string> ArgNames;
    560   while (getNextToken() == tok_identifier)
    561     ArgNames.push_back(IdentifierStr);
    562   if (CurTok != ')')
    563     return ErrorP("Expected ')' in prototype");
    564 
    565   // success.
    566   getNextToken();  // eat ')'.
    567 
    568   // Verify right number of names for operator.
    569   if (Kind && ArgNames.size() != Kind)
    570     return ErrorP("Invalid number of operands for operator");
    571 
    572   return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
    573 }
    574 
    575 /// definition ::= 'def' prototype expression
    576 static FunctionAST *ParseDefinition() {
    577   getNextToken();  // eat def.
    578   PrototypeAST *Proto = ParsePrototype();
    579   if (Proto == 0) return 0;
    580 
    581   if (ExprAST *E = ParseExpression())
    582     return new FunctionAST(Proto, E);
    583   return 0;
    584 }
    585 
    586 /// toplevelexpr ::= expression
    587 static FunctionAST *ParseTopLevelExpr() {
    588   if (ExprAST *E = ParseExpression()) {
    589     // Make an anonymous proto.
    590     PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
    591     return new FunctionAST(Proto, E);
    592   }
    593   return 0;
    594 }
    595 
    596 /// external ::= 'extern' prototype
    597 static PrototypeAST *ParseExtern() {
    598   getNextToken();  // eat extern.
    599   return ParsePrototype();
    600 }
    601 
    602 //===----------------------------------------------------------------------===//
    603 // Code Generation
    604 //===----------------------------------------------------------------------===//
    605 
    606 static Module *TheModule;
    607 static IRBuilder<> Builder(getGlobalContext());
    608 static std::map<std::string, AllocaInst*> NamedValues;
    609 static FunctionPassManager *TheFPM;
    610 
    611 Value *ErrorV(const char *Str) { Error(Str); return 0; }
    612 
    613 /// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
    614 /// the function.  This is used for mutable variables etc.
    615 static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
    616                                           const std::string &VarName) {
    617   IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
    618                  TheFunction->getEntryBlock().begin());
    619   return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
    620                            VarName.c_str());
    621 }
    622 
    623 Value *NumberExprAST::Codegen() {
    624   return ConstantFP::get(getGlobalContext(), APFloat(Val));
    625 }
    626 
    627 Value *VariableExprAST::Codegen() {
    628   // Look this variable up in the function.
    629   Value *V = NamedValues[Name];
    630   if (V == 0) return ErrorV("Unknown variable name");
    631 
    632   // Load the value.
    633   return Builder.CreateLoad(V, Name.c_str());
    634 }
    635 
    636 Value *UnaryExprAST::Codegen() {
    637   Value *OperandV = Operand->Codegen();
    638   if (OperandV == 0) return 0;
    639 
    640   Function *F = TheModule->getFunction(std::string("unary")+Opcode);
    641   if (F == 0)
    642     return ErrorV("Unknown unary operator");
    643 
    644   return Builder.CreateCall(F, OperandV, "unop");
    645 }
    646 
    647 Value *BinaryExprAST::Codegen() {
    648   // Special case '=' because we don't want to emit the LHS as an expression.
    649   if (Op == '=') {
    650     // Assignment requires the LHS to be an identifier.
    651     VariableExprAST *LHSE = dynamic_cast<VariableExprAST*>(LHS);
    652     if (!LHSE)
    653       return ErrorV("destination of '=' must be a variable");
    654     // Codegen the RHS.
    655     Value *Val = RHS->Codegen();
    656     if (Val == 0) return 0;
    657 
    658     // Look up the name.
    659     Value *Variable = NamedValues[LHSE->getName()];
    660     if (Variable == 0) return ErrorV("Unknown variable name");
    661 
    662     Builder.CreateStore(Val, Variable);
    663     return Val;
    664   }
    665 
    666   Value *L = LHS->Codegen();
    667   Value *R = RHS->Codegen();
    668   if (L == 0 || R == 0) return 0;
    669 
    670   switch (Op) {
    671   case '+': return Builder.CreateFAdd(L, R, "addtmp");
    672   case '-': return Builder.CreateFSub(L, R, "subtmp");
    673   case '*': return Builder.CreateFMul(L, R, "multmp");
    674   case '<':
    675     L = Builder.CreateFCmpULT(L, R, "cmptmp");
    676     // Convert bool 0/1 to double 0.0 or 1.0
    677     return Builder.CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
    678                                 "booltmp");
    679   default: break;
    680   }
    681 
    682   // If it wasn't a builtin binary operator, it must be a user defined one. Emit
    683   // a call to it.
    684   Function *F = TheModule->getFunction(std::string("binary")+Op);
    685   assert(F && "binary operator not found!");
    686 
    687   Value *Ops[] = { L, R };
    688   return Builder.CreateCall(F, Ops, "binop");
    689 }
    690 
    691 Value *CallExprAST::Codegen() {
    692   // Look up the name in the global module table.
    693   Function *CalleeF = TheModule->getFunction(Callee);
    694   if (CalleeF == 0)
    695     return ErrorV("Unknown function referenced");
    696 
    697   // If argument mismatch error.
    698   if (CalleeF->arg_size() != Args.size())
    699     return ErrorV("Incorrect # arguments passed");
    700 
    701   std::vector<Value*> ArgsV;
    702   for (unsigned i = 0, e = Args.size(); i != e; ++i) {
    703     ArgsV.push_back(Args[i]->Codegen());
    704     if (ArgsV.back() == 0) return 0;
    705   }
    706 
    707   return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
    708 }
    709 
    710 Value *IfExprAST::Codegen() {
    711   Value *CondV = Cond->Codegen();
    712   if (CondV == 0) return 0;
    713 
    714   // Convert condition to a bool by comparing equal to 0.0.
    715   CondV = Builder.CreateFCmpONE(CondV,
    716                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
    717                                 "ifcond");
    718 
    719   Function *TheFunction = Builder.GetInsertBlock()->getParent();
    720 
    721   // Create blocks for the then and else cases.  Insert the 'then' block at the
    722   // end of the function.
    723   BasicBlock *ThenBB = BasicBlock::Create(getGlobalContext(), "then", TheFunction);
    724   BasicBlock *ElseBB = BasicBlock::Create(getGlobalContext(), "else");
    725   BasicBlock *MergeBB = BasicBlock::Create(getGlobalContext(), "ifcont");
    726 
    727   Builder.CreateCondBr(CondV, ThenBB, ElseBB);
    728 
    729   // Emit then value.
    730   Builder.SetInsertPoint(ThenBB);
    731 
    732   Value *ThenV = Then->Codegen();
    733   if (ThenV == 0) return 0;
    734 
    735   Builder.CreateBr(MergeBB);
    736   // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
    737   ThenBB = Builder.GetInsertBlock();
    738 
    739   // Emit else block.
    740   TheFunction->getBasicBlockList().push_back(ElseBB);
    741   Builder.SetInsertPoint(ElseBB);
    742 
    743   Value *ElseV = Else->Codegen();
    744   if (ElseV == 0) return 0;
    745 
    746   Builder.CreateBr(MergeBB);
    747   // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
    748   ElseBB = Builder.GetInsertBlock();
    749 
    750   // Emit merge block.
    751   TheFunction->getBasicBlockList().push_back(MergeBB);
    752   Builder.SetInsertPoint(MergeBB);
    753   PHINode *PN = Builder.CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
    754                                   "iftmp");
    755 
    756   PN->addIncoming(ThenV, ThenBB);
    757   PN->addIncoming(ElseV, ElseBB);
    758   return PN;
    759 }
    760 
    761 Value *ForExprAST::Codegen() {
    762   // Output this as:
    763   //   var = alloca double
    764   //   ...
    765   //   start = startexpr
    766   //   store start -> var
    767   //   goto loop
    768   // loop:
    769   //   ...
    770   //   bodyexpr
    771   //   ...
    772   // loopend:
    773   //   step = stepexpr
    774   //   endcond = endexpr
    775   //
    776   //   curvar = load var
    777   //   nextvar = curvar + step
    778   //   store nextvar -> var
    779   //   br endcond, loop, endloop
    780   // outloop:
    781 
    782   Function *TheFunction = Builder.GetInsertBlock()->getParent();
    783 
    784   // Create an alloca for the variable in the entry block.
    785   AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
    786 
    787   // Emit the start code first, without 'variable' in scope.
    788   Value *StartVal = Start->Codegen();
    789   if (StartVal == 0) return 0;
    790 
    791   // Store the value into the alloca.
    792   Builder.CreateStore(StartVal, Alloca);
    793 
    794   // Make the new basic block for the loop header, inserting after current
    795   // block.
    796   BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
    797 
    798   // Insert an explicit fall through from the current block to the LoopBB.
    799   Builder.CreateBr(LoopBB);
    800 
    801   // Start insertion in LoopBB.
    802   Builder.SetInsertPoint(LoopBB);
    803 
    804   // Within the loop, the variable is defined equal to the PHI node.  If it
    805   // shadows an existing variable, we have to restore it, so save it now.
    806   AllocaInst *OldVal = NamedValues[VarName];
    807   NamedValues[VarName] = Alloca;
    808 
    809   // Emit the body of the loop.  This, like any other expr, can change the
    810   // current BB.  Note that we ignore the value computed by the body, but don't
    811   // allow an error.
    812   if (Body->Codegen() == 0)
    813     return 0;
    814 
    815   // Emit the step value.
    816   Value *StepVal;
    817   if (Step) {
    818     StepVal = Step->Codegen();
    819     if (StepVal == 0) return 0;
    820   } else {
    821     // If not specified, use 1.0.
    822     StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
    823   }
    824 
    825   // Compute the end condition.
    826   Value *EndCond = End->Codegen();
    827   if (EndCond == 0) return EndCond;
    828 
    829   // Reload, increment, and restore the alloca.  This handles the case where
    830   // the body of the loop mutates the variable.
    831   Value *CurVar = Builder.CreateLoad(Alloca, VarName.c_str());
    832   Value *NextVar = Builder.CreateFAdd(CurVar, StepVal, "nextvar");
    833   Builder.CreateStore(NextVar, Alloca);
    834 
    835   // Convert condition to a bool by comparing equal to 0.0.
    836   EndCond = Builder.CreateFCmpONE(EndCond,
    837                               ConstantFP::get(getGlobalContext(), APFloat(0.0)),
    838                                   "loopcond");
    839 
    840   // Create the "after loop" block and insert it.
    841   BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
    842 
    843   // Insert the conditional branch into the end of LoopEndBB.
    844   Builder.CreateCondBr(EndCond, LoopBB, AfterBB);
    845 
    846   // Any new code will be inserted in AfterBB.
    847   Builder.SetInsertPoint(AfterBB);
    848 
    849   // Restore the unshadowed variable.
    850   if (OldVal)
    851     NamedValues[VarName] = OldVal;
    852   else
    853     NamedValues.erase(VarName);
    854 
    855 
    856   // for expr always returns 0.0.
    857   return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
    858 }
    859 
    860 Value *VarExprAST::Codegen() {
    861   std::vector<AllocaInst *> OldBindings;
    862 
    863   Function *TheFunction = Builder.GetInsertBlock()->getParent();
    864 
    865   // Register all variables and emit their initializer.
    866   for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
    867     const std::string &VarName = VarNames[i].first;
    868     ExprAST *Init = VarNames[i].second;
    869 
    870     // Emit the initializer before adding the variable to scope, this prevents
    871     // the initializer from referencing the variable itself, and permits stuff
    872     // like this:
    873     //  var a = 1 in
    874     //    var a = a in ...   # refers to outer 'a'.
    875     Value *InitVal;
    876     if (Init) {
    877       InitVal = Init->Codegen();
    878       if (InitVal == 0) return 0;
    879     } else { // If not specified, use 0.0.
    880       InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
    881     }
    882 
    883     AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
    884     Builder.CreateStore(InitVal, Alloca);
    885 
    886     // Remember the old variable binding so that we can restore the binding when
    887     // we unrecurse.
    888     OldBindings.push_back(NamedValues[VarName]);
    889 
    890     // Remember this binding.
    891     NamedValues[VarName] = Alloca;
    892   }
    893 
    894   // Codegen the body, now that all vars are in scope.
    895   Value *BodyVal = Body->Codegen();
    896   if (BodyVal == 0) return 0;
    897 
    898   // Pop all our variables from scope.
    899   for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
    900     NamedValues[VarNames[i].first] = OldBindings[i];
    901 
    902   // Return the body computation.
    903   return BodyVal;
    904 }
    905 
    906 Function *PrototypeAST::Codegen() {
    907   // Make the function type:  double(double,double) etc.
    908   std::vector<Type*> Doubles(Args.size(),
    909                              Type::getDoubleTy(getGlobalContext()));
    910   FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
    911                                        Doubles, false);
    912 
    913   Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
    914 
    915   // If F conflicted, there was already something named 'Name'.  If it has a
    916   // body, don't allow redefinition or reextern.
    917   if (F->getName() != Name) {
    918     // Delete the one we just made and get the existing one.
    919     F->eraseFromParent();
    920     F = TheModule->getFunction(Name);
    921 
    922     // If F already has a body, reject this.
    923     if (!F->empty()) {
    924       ErrorF("redefinition of function");
    925       return 0;
    926     }
    927 
    928     // If F took a different number of args, reject.
    929     if (F->arg_size() != Args.size()) {
    930       ErrorF("redefinition of function with different # args");
    931       return 0;
    932     }
    933   }
    934 
    935   // Set names for all arguments.
    936   unsigned Idx = 0;
    937   for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
    938        ++AI, ++Idx)
    939     AI->setName(Args[Idx]);
    940 
    941   return F;
    942 }
    943 
    944 /// CreateArgumentAllocas - Create an alloca for each argument and register the
    945 /// argument in the symbol table so that references to it will succeed.
    946 void PrototypeAST::CreateArgumentAllocas(Function *F) {
    947   Function::arg_iterator AI = F->arg_begin();
    948   for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
    949     // Create an alloca for this variable.
    950     AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
    951 
    952     // Store the initial value into the alloca.
    953     Builder.CreateStore(AI, Alloca);
    954 
    955     // Add arguments to variable symbol table.
    956     NamedValues[Args[Idx]] = Alloca;
    957   }
    958 }
    959 
    960 Function *FunctionAST::Codegen() {
    961   NamedValues.clear();
    962 
    963   Function *TheFunction = Proto->Codegen();
    964   if (TheFunction == 0)
    965     return 0;
    966 
    967   // If this is an operator, install it.
    968   if (Proto->isBinaryOp())
    969     BinopPrecedence[Proto->getOperatorName()] = Proto->getBinaryPrecedence();
    970 
    971   // Create a new basic block to start insertion into.
    972   BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
    973   Builder.SetInsertPoint(BB);
    974 
    975   // Add all arguments to the symbol table and create their allocas.
    976   Proto->CreateArgumentAllocas(TheFunction);
    977 
    978   if (Value *RetVal = Body->Codegen()) {
    979     // Finish off the function.
    980     Builder.CreateRet(RetVal);
    981 
    982     // Validate the generated code, checking for consistency.
    983     verifyFunction(*TheFunction);
    984 
    985     // Optimize the function.
    986     TheFPM->run(*TheFunction);
    987 
    988     return TheFunction;
    989   }
    990 
    991   // Error reading body, remove function.
    992   TheFunction->eraseFromParent();
    993 
    994   if (Proto->isBinaryOp())
    995     BinopPrecedence.erase(Proto->getOperatorName());
    996   return 0;
    997 }
    998 
    999 //===----------------------------------------------------------------------===//
   1000 // Top-Level parsing and JIT Driver
   1001 //===----------------------------------------------------------------------===//
   1002 
   1003 static ExecutionEngine *TheExecutionEngine;
   1004 
   1005 static void HandleDefinition() {
   1006   if (FunctionAST *F = ParseDefinition()) {
   1007     if (Function *LF = F->Codegen()) {
   1008       fprintf(stderr, "Read function definition:");
   1009       LF->dump();
   1010     }
   1011   } else {
   1012     // Skip token for error recovery.
   1013     getNextToken();
   1014   }
   1015 }
   1016 
   1017 static void HandleExtern() {
   1018   if (PrototypeAST *P = ParseExtern()) {
   1019     if (Function *F = P->Codegen()) {
   1020       fprintf(stderr, "Read extern: ");
   1021       F->dump();
   1022     }
   1023   } else {
   1024     // Skip token for error recovery.
   1025     getNextToken();
   1026   }
   1027 }
   1028 
   1029 static void HandleTopLevelExpression() {
   1030   // Evaluate a top-level expression into an anonymous function.
   1031   if (FunctionAST *F = ParseTopLevelExpr()) {
   1032     if (Function *LF = F->Codegen()) {
   1033       // JIT the function, returning a function pointer.
   1034       void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
   1035 
   1036       // Cast it to the right type (takes no arguments, returns a double) so we
   1037       // can call it as a native function.
   1038       double (*FP)() = (double (*)())(intptr_t)FPtr;
   1039       fprintf(stderr, "Evaluated to %f\n", FP());
   1040     }
   1041   } else {
   1042     // Skip token for error recovery.
   1043     getNextToken();
   1044   }
   1045 }
   1046 
   1047 /// top ::= definition | external | expression | ';'
   1048 static void MainLoop() {
   1049   while (1) {
   1050     fprintf(stderr, "ready> ");
   1051     switch (CurTok) {
   1052     case tok_eof:    return;
   1053     case ';':        getNextToken(); break;  // ignore top-level semicolons.
   1054     case tok_def:    HandleDefinition(); break;
   1055     case tok_extern: HandleExtern(); break;
   1056     default:         HandleTopLevelExpression(); break;
   1057     }
   1058   }
   1059 }
   1060 
   1061 //===----------------------------------------------------------------------===//
   1062 // "Library" functions that can be "extern'd" from user code.
   1063 //===----------------------------------------------------------------------===//
   1064 
   1065 /// putchard - putchar that takes a double and returns 0.
   1066 extern "C"
   1067 double putchard(double X) {
   1068   putchar((char)X);
   1069   return 0;
   1070 }
   1071 
   1072 /// printd - printf that takes a double prints it as "%f\n", returning 0.
   1073 extern "C"
   1074 double printd(double X) {
   1075   printf("%f\n", X);
   1076   return 0;
   1077 }
   1078 
   1079 //===----------------------------------------------------------------------===//
   1080 // Main driver code.
   1081 //===----------------------------------------------------------------------===//
   1082 
   1083 int main() {
   1084   InitializeNativeTarget();
   1085   LLVMContext &Context = getGlobalContext();
   1086 
   1087   // Install standard binary operators.
   1088   // 1 is lowest precedence.
   1089   BinopPrecedence['='] = 2;
   1090   BinopPrecedence['<'] = 10;
   1091   BinopPrecedence['+'] = 20;
   1092   BinopPrecedence['-'] = 20;
   1093   BinopPrecedence['*'] = 40;  // highest.
   1094 
   1095   // Prime the first token.
   1096   fprintf(stderr, "ready> ");
   1097   getNextToken();
   1098 
   1099   // Make the module, which holds all the code.
   1100   TheModule = new Module("my cool jit", Context);
   1101 
   1102   // Create the JIT.  This takes ownership of the module.
   1103   std::string ErrStr;
   1104   TheExecutionEngine = EngineBuilder(TheModule).setErrorStr(&ErrStr).create();
   1105   if (!TheExecutionEngine) {
   1106     fprintf(stderr, "Could not create ExecutionEngine: %s\n", ErrStr.c_str());
   1107     exit(1);
   1108   }
   1109 
   1110   FunctionPassManager OurFPM(TheModule);
   1111 
   1112   // Set up the optimizer pipeline.  Start with registering info about how the
   1113   // target lays out data structures.
   1114   OurFPM.add(new DataLayout(*TheExecutionEngine->getDataLayout()));
   1115   // Provide basic AliasAnalysis support for GVN.
   1116   OurFPM.add(createBasicAliasAnalysisPass());
   1117   // Promote allocas to registers.
   1118   OurFPM.add(createPromoteMemoryToRegisterPass());
   1119   // Do simple "peephole" optimizations and bit-twiddling optzns.
   1120   OurFPM.add(createInstructionCombiningPass());
   1121   // Reassociate expressions.
   1122   OurFPM.add(createReassociatePass());
   1123   // Eliminate Common SubExpressions.
   1124   OurFPM.add(createGVNPass());
   1125   // Simplify the control flow graph (deleting unreachable blocks, etc).
   1126   OurFPM.add(createCFGSimplificationPass());
   1127 
   1128   OurFPM.doInitialization();
   1129 
   1130   // Set the global so the code gen can use this.
   1131   TheFPM = &OurFPM;
   1132 
   1133   // Run the main "interpreter loop" now.
   1134   MainLoop();
   1135 
   1136   TheFPM = 0;
   1137 
   1138   // Print out all of the generated code.
   1139   TheModule->dump();
   1140 
   1141   return 0;
   1142 }
   1143