{"id":29,"date":"2020-08-13T12:05:42","date_gmt":"2020-08-13T04:05:42","guid":{"rendered":"http:\/\/47.108.144.50\/?p=29"},"modified":"2020-08-13T20:37:49","modified_gmt":"2020-08-13T12:37:49","slug":"llvm%e5%ae%98%e6%96%b9%e4%b8%87%e8%8a%b1%e7%ad%92%e6%95%99%e7%a8%8b2-%e4%ba%a7%e7%94%9fllvm%e4%b8%ad%e9%97%b4%e4%bb%a3%e7%a0%81","status":"publish","type":"post","link":"http:\/\/pareto.fun\/?p=29","title":{"rendered":"llvm\u524d\u7aef-\u5b98\u65b9\u4e07\u82b1\u7b52\u6559\u7a0b2-\u4ea7\u751fllvm\u4e2d\u95f4\u4ee3\u7801"},"content":{"rendered":"\n

\u82f1\u6587\u770b\u591a\u4e86\u8fd8\u662f\u5934\u75db\uff0c\u8fd8\u662f\u76f4\u63a5\u4e0a\u4ee3\u7801<\/strong><\/p>\n\n\n\n

\u4ee3\u7801\u76f8\u6bd4\u4e8e\u4e0a\u4e00\u7bc7\u4e3a\u6bcf\u4e2a\u8bed\u6cd5\u6811\u65b0\u589e\u4e86\u751f\u6210\u6307\u4ee4\u7684\u51fd\u6570codegen\uff0c\u5e76\u4e14\u65b0\u589e\u4e86\u4e00\u4e9b\u5168\u5c40\u53d8\u91cf\u3002<\/p>\n\n\n\n

static LLVMContext TheContext;
static IRBuilder<> Builder(TheContext);
static std::unique_ptr<Module> TheModule;
static std::map<std::string, Value *> NamedValues;<\/pre>\n\n\n\n
TheContext \u8fd9\u662f\u4e2a\u795e\u5947\u7684\u53d8\u91cf\uff0c\u5f88\u591a\u51fd\u6570\u53c2\u6570\u90fd\u8981\u7528\u5b83\uff0c\u5b98\u65b9\u89e3\u91ca\u8bf4\u8fd9\u4e2a\u5bf9\u8c61\u6709llvm\u7edd\u5927\u591a\u6570\u7684\u6570\u636e\u7ed3\u6784\uff0c\u7c7b\u578b\u548c\u5e38\u91cf\u8868\u3002<\/p>\n\n\n\n
Builder \u4e00\u4e2a\u751f\u6210IR\u6307\u4ee4\u7684\u8f85\u52a9\u7c7b\u3002<\/p>\n\n\n\n
TheModule \u6240\u6709\u751f\u6210\u7684\u6307\u4ee4\u90fd\u4f1a\u653e\u5728\u8fd9\u91cc\u3002<\/p>\n\n\n\n
NameValues \u5c31\u5f53\u4f5c\u4e00\u4e2a\u7b26\u53f7\u8868\uff0c\u53d1\u751f\u51fd\u6570\u8c03\u7528\u65f6\u5176\u4e2d\u7684\u53c2\u6570\u5c31\u4f1a\u4ece\u8fd9\u627e\u3002<\/p>\n\n\n\n
Value *NumberExprAST::codegen() {
  return ConstantFP::get(TheContext, APFloat(Val));
}
\u200b
Value *VariableExprAST::codegen() {
  \/\/ Look this variable up in the function.
  Value *V = NamedValues[Name];
  if (!V)
    LogErrorV(\"Unknown variable name\");
  return V;
}<\/pre>\n\n\n\n
\u5b9e\u9645\u4e0a\uff0cNumberExprAST\u548cVariableExprAST\u7684codegen\u65b9\u6cd5\u90fd\u4e0d\u4ea7\u751fIR\u6307\u4ee4\uff0c\u4ec5\u4e3a\u4e0a\u5c42\u7684\u6307\u4ee4\u63d0\u4f9b\u5bf9\u8c61\uff0c\u60f3\u60f3\u4e5f\u89c9\u5f97\u5408\u7406\uff0c\u6bd5\u7adf\u7eaf\u6570\u5b57\u548c\u6807\u8bc6\u7b26\u6ca1\u6709\u4efb\u4f55\u610f\u4e49\u3002<\/p>\n\n\n\n
Value *BinaryExprAST::codegen() {
  Value *L = LHS->codegen();
  Value *R = RHS->codegen();
  if (!L || !R)
    return nullptr;
\u200b
  switch (Op) {
  case '+':
    return Builder.CreateFAdd(L, R, \"addtmp\");
  case '-':
    return Builder.CreateFSub(L, R, \"subtmp\");
  case '*':
    return Builder.CreateFMul(L, R, \"multmp\");
  case '<':
    L = Builder.CreateFCmpULT(L, R, \"cmptmp\");
    \/\/ Convert bool 0\/1 to double 0.0 or 1.0
    return Builder.CreateUIToFP(L, Type::getDoubleTy(TheContext),
                                \"booltmp\");
  default:
    return LogErrorV(\"invalid binary operator\");
  }
}<\/pre>\n\n\n\n
\u4ee3\u7801\u7b80\u5355\u53d6\u51fa\u4e24\u4e2a\u64cd\u4f5c\u6570\uff0c\u6839\u636e\u5177\u4f53\u7684\u64cd\u4f5c\u7b26\u5229\u7528Builder\u6765\u751f\u6210\u6307\u4ee4\u3002Builder.CreateF(,,)\u7684\u7b2c\u4e09\u4e2a\u53c2\u6570\u662f\u751f\u6210\u6307\u4ee4\u4e2d\u53d8\u91cf\u7684\u540d\u79f0\u3002<\/p>\n\n\n\n
\u7279\u6b8a\u70b9\u7684\u5c31\u662f ‘<‘ , \u6bd4\u8f83\u540e\u7684bool \u503c\u6216\u8005bool vector \u8f6c\u5316\u4e3a double\u3002<\/p>\n\n\n\n
Value *CallExprAST::codegen() {
  \/\/ Look up the name in the global module table.
  Function *CalleeF = TheModule->getFunction(Callee);
  if (!CalleeF)
    return LogErrorV(\"Unknown function referenced\");
\u200b
  \/\/ If argument mismatch error.
  if (CalleeF->arg_size() != Args.size())
    return LogErrorV(\"Incorrect # arguments passed\");
\u200b
  std::vector<Value *> ArgsV;
  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
    ArgsV.push_back(Args[i]->codegen());
    if (!ArgsV.back())
      return nullptr;
  }
\u200b
  return Builder.CreateCall(CalleeF, ArgsV, \"calltmp\");
}<\/pre>\n\n\n\n
\u8fd9\u662f\u4ea7\u751f\u8c03\u7528\u51fd\u6570\u7684IR\uff0c\u5224\u65ad\u662f\u5426\u5df2\u7ecf\u5b9a\u4e49\u4e86\u51fd\u6570\uff0c\u5df2\u5b9a\u4e49\u5219\u5224\u65ad\u53c2\u6570\u4e2a\u6570\u662f\u5426\u76f8\u540c\uff0c\u76f8\u540c\u5219\u751f\u6210\u8c03\u7528\u6307\u4ee4\u3002<\/p>\n\n\n\n
Function *PrototypeAST::codegen() {
  \/\/ Make the function type:  double(double,double) etc.
  std::vector<Type*> Doubles(Args.size(),
                             Type::getDoubleTy(TheContext));
  FunctionType *FT =
    FunctionType::get(Type::getDoubleTy(TheContext), Doubles, false);
\u200b
  Function *F =
    Function::Create(FT, Function::ExternalLinkage, Name, TheModule.get());<\/pre>\n\n\n\n
PrototypeAST \u4e3adef \u548cexternal \u670d\u52a1\uff0c\u662fFunctionAST\u7684\u6210\u5458\u4e4b\u4e00\uff0c\u8fd9\u6bb5\u4ee3\u7801\u662f\u4e3aFunctionAST->codegen\u505a\u94fa\u57ab\u3002\u8fd9\u4e2a\u51fd\u6570\u4e0e\u5176\u4ed6codegen\u51fd\u6570\u4e0d\u540c\u7684\u662f\u8fd4\u56defunction* \u4e0d\u662fvalues*\uff0c\u539f\u56e0\u5982\u4e0a\uff0c\u4e3adef \u548c external\u670d\u52a1\u3002\u7b2c\u4e00\u884c\u521b\u5efa\u4e3aArg.size() \u4e2adouble\u7684vector\u3002\u7b2c\u4e8c\u884c\u521b\u5efa\u4e86\u4f7f\u7528Arg.size()\u4e2adouble\u4f5c\u4e3a\u53c2\u6570\uff0c\u8fd4\u56de\u503c\u4e3adouble\u7684\u51fd\u6570\u7c7b\u578b\uff0c\u6700\u540e\u4e00\u884c\u521b\u5efa\u4e86\u51fd\u6570\u6307\u5b9a\u4e86\u51fd\u6570\u7c7b\u578b\u3001linkage\uff0c\u540d\u79f0\u548c\u63d2\u5165\u4ee3\u7801\u7684\u6a21\u5757\u3002\u8fd9\u91cc\u51fd\u6570\u662f\u6ca1\u6709\u51fd\u6570\u4f53\u7684\uff0c\u5c31\u662fllvm \u6765\u8868\u793a\u51fd\u6570\u5b9a\u4e49\u7684\u65b9\u6cd5\u3002\u5982\u679c\u662f\u4e00\u4e2aexternal\u51fd\u6570\u5230\u8fd9\u91cc\u5c31\u7ed3\u675f\u4e86\u3002\u4f46\u5bf9\u4e8e\u51fd\u6570\u5b9a\u4e49\u6211\u4eec\u9700\u8981\u51fd\u6570\u4f53\u3002<\/p>\n\n\n\n
Function *FunctionAST::codegen() {
  \/\/ First, check for an existing function from a previous 'extern' declaration.
  Function *TheFunction = TheModule->getFunction(Proto->getName());
\u200b
  if (!TheFunction)
    TheFunction = Proto->codegen();
\u200b
  if (!TheFunction)
    return nullptr;
\u200b
  \/\/ Create a new basic block to start insertion into.
  BasicBlock *BB = BasicBlock::Create(TheContext, \"entry\", TheFunction);
  Builder.SetInsertPoint(BB);
\u200b
  \/\/ Record the function arguments in the NamedValues map.
  NamedValues.clear();
  for (auto &Arg : TheFunction->args())
    NamedValues[std::string(Arg.getName())] = &Arg;
\u200b
  if (Value *RetVal = Body->codegen()) {
    \/\/ Finish off the function.
    Builder.CreateRet(RetVal);
\u200b
    \/\/ Validate the generated code, checking for consistency.
    verifyFunction(*TheFunction);
\u200b
    return TheFunction;
  }
\u200b
  \/\/ Error reading body, remove function.
  TheFunction->eraseFromParent();
  return nullptr;
}<\/pre>\n\n\n\n
\u5224\u65ad\u6a21\u5757\u4e2d\u662f\u5426\u5b9a\u4e49\u4e86\u51fd\u6570\uff0c\u672a\u5b9a\u4e49\u5219\u91cd\u65b0\u5b9a\u4e49\uff0cbody->codegen()\u751f\u6210\u51fd\u6570\u4f53\u7684\u8fd0\u7b97\u6267\u884c\uff0c\u5728\u751f\u6210ret\u6307\u4ee4\uff0c\u68c0\u67e5\u6307\u4ee4\u662f\u5426\u6b63\u5e38\uff0c\u8fd4\u56de\u51fd\u6570\u3002<\/p>\n\n\n\n
#include \"llvm\/ADT\/STLExtras.h\"
#include \"llvm\/IR\/BasicBlock.h\"
#include \"llvm\/IR\/Constants.h\"
#include \"llvm\/IR\/DerivedTypes.h\"
#include \"llvm\/IR\/Function.h\"
#include \"llvm\/IR\/IRBuilder.h\"
#include \"llvm\/IR\/LLVMContext.h\"
#include \"llvm\/IR\/Module.h\"
#include \"llvm\/IR\/Type.h\"
#include \"llvm\/IR\/Verifier.h\"
#include <algorithm>
#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <map>
#include <memory>
#include <string>
#include <vector>
\u200b
using namespace llvm;
\u200b
\/\/===----------------------------------------------------------------------===\/\/
\/\/ Lexer
\/\/===----------------------------------------------------------------------===\/\/
\u200b
\/\/ The lexer returns tokens [0-255] if it is an unknown character, otherwise one
\/\/ of these for known things.
enum Token {
  tok_eof = -1,
\u200b
  \/\/ commands
  tok_def = -2,
  tok_extern = -3,
\u200b
  \/\/ primary
  tok_identifier = -4,
  tok_number = -5
};
\u200b
static std::string IdentifierStr; \/\/ Filled in if tok_identifier
static double NumVal;             \/\/ Filled in if tok_number
\u200b
\/\/\/ gettok - Return the next token from standard input.
static int gettok() {
  static int LastChar = ' ';
\u200b
  \/\/ Skip any whitespace.
  while (isspace(LastChar))
    LastChar = getchar();
\u200b
  if (isalpha(LastChar)) { \/\/ identifier: [a-zA-Z][a-zA-Z0-9]*
    IdentifierStr = LastChar;
    while (isalnum((LastChar = getchar())))
      IdentifierStr += LastChar;
\u200b
    if (IdentifierStr == \"def\")
      return tok_def;
    if (IdentifierStr == \"extern\")
      return tok_extern;
    return tok_identifier;
  }
\u200b
  if (isdigit(LastChar) || LastChar == '.') { \/\/ Number: [0-9.]+
    std::string NumStr;
    do {
      NumStr += LastChar;
      LastChar = getchar();
    } while (isdigit(LastChar) || LastChar == '.');
\u200b
    NumVal = strtod(NumStr.c_str(), nullptr);
    return tok_number;
  }
\u200b
  if (LastChar == '#') {
    \/\/ Comment until end of line.
    do
      LastChar = getchar();
    while (LastChar != EOF && LastChar != '\\n' && LastChar != '\\r');
\u200b
    if (LastChar != EOF)
      return gettok();
  }
\u200b
  \/\/ Check for end of file.  Don't eat the EOF.
  if (LastChar == EOF)
    return tok_eof;
\u200b
  \/\/ Otherwise, just return the character as its ascii value.
  int ThisChar = LastChar;
  LastChar = getchar();
  return ThisChar;
}
\u200b
\/\/===----------------------------------------------------------------------===\/\/
\/\/ Abstract Syntax Tree (aka Parse Tree)
\/\/===----------------------------------------------------------------------===\/\/
\u200b
namespace {
\u200b
\/\/\/ ExprAST - Base class for all expression nodes.
class ExprAST {
public:
  virtual ~ExprAST() = default;
\u200b
  virtual Value *codegen() = 0;
};
\u200b
\/\/\/ NumberExprAST - Expression class for numeric literals like \"1.0\".
class NumberExprAST : public ExprAST {
  double Val;
\u200b
public:
  NumberExprAST(double Val) : Val(Val) {}
\u200b
  Value *codegen() override;
};
\u200b
\/\/\/ VariableExprAST - Expression class for referencing a variable, like \"a\".
class VariableExprAST : public ExprAST {
  std::string Name;
\u200b
public:
  VariableExprAST(const std::string &Name) : Name(Name) {}
\u200b
  Value *codegen() override;
};
\u200b
\/\/\/ BinaryExprAST - Expression class for a binary operator.
class BinaryExprAST : public ExprAST {
  char Op;
  std::unique_ptr<ExprAST> LHS, RHS;
\u200b
public:
  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
                std::unique_ptr<ExprAST> RHS)
      : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
\u200b
  Value *codegen() override;
};
\u200b
\/\/\/ CallExprAST - Expression class for function calls.
class CallExprAST : public ExprAST {
  std::string Callee;
  std::vector<std::unique_ptr<ExprAST>> Args;
\u200b
public:
  CallExprAST(const std::string &Callee,
              std::vector<std::unique_ptr<ExprAST>> Args)
      : Callee(Callee), Args(std::move(Args)) {}
\u200b
  Value *codegen() override;
};
\u200b
\/\/\/ PrototypeAST - This class represents the \"prototype\" for a function,
\/\/\/ which captures its name, and its argument names (thus implicitly the number
\/\/\/ of arguments the function takes).
class PrototypeAST {
  std::string Name;
  std::vector<std::string> Args;
\u200b
public:
  PrototypeAST(const std::string &Name, std::vector<std::string> Args)
      : Name(Name), Args(std::move(Args)) {}
\u200b
  Function *codegen();
  const std::string &getName() const { return Name; }
};
\u200b
\/\/\/ FunctionAST - This class represents a function definition itself.
class FunctionAST {
  std::unique_ptr<PrototypeAST> Proto;
  std::unique_ptr<ExprAST> Body;
\u200b
public:
  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
              std::unique_ptr<ExprAST> Body)
      : Proto(std::move(Proto)), Body(std::move(Body)) {}
\u200b
  Function *codegen();
};
\u200b
} \/\/ end anonymous namespace
\u200b
\/\/===----------------------------------------------------------------------===\/\/
\/\/ Parser
\/\/===----------------------------------------------------------------------===\/\/
\u200b
\/\/\/ CurTok\/getNextToken - Provide a simple token buffer.  CurTok is the current
\/\/\/ token the parser is looking at.  getNextToken reads another token from the
\/\/\/ lexer and updates CurTok with its results.
static int CurTok;
static int getNextToken() { return CurTok = gettok(); }
\u200b
\/\/\/ BinopPrecedence - This holds the precedence for each binary operator that is
\/\/\/ defined.
static std::map<char, int> BinopPrecedence;
\u200b
\/\/\/ GetTokPrecedence - Get the precedence of the pending binary operator token.
static int GetTokPrecedence() {
  if (!isascii(CurTok))
    return -1;
\u200b
  \/\/ Make sure it's a declared binop.
  int TokPrec = BinopPrecedence[CurTok];
  if (TokPrec <= 0)
    return -1;
  return TokPrec;
}
\u200b
\/\/\/ LogError* - These are little helper functions for error handling.
std::unique_ptr<ExprAST> LogError(const char *Str) {
  fprintf(stderr, \"Error: %s\\n\", Str);
  return nullptr;
}
\u200b
std::unique_ptr<PrototypeAST> LogErrorP(const char *Str) {
  LogError(Str);
  return nullptr;
}
\u200b
static std::unique_ptr<ExprAST> ParseExpression();
\u200b
\/\/\/ numberexpr ::= number
static std::unique_ptr<ExprAST> ParseNumberExpr() {
  auto Result = std::make_unique<NumberExprAST>(NumVal);
  getNextToken(); \/\/ consume the number
  return std::move(Result);
}
\u200b
\/\/\/ parenexpr ::= '(' expression ')'
static std::unique_ptr<ExprAST> ParseParenExpr() {
  getNextToken(); \/\/ eat (.
  auto V = ParseExpression();
  if (!V)
    return nullptr;
\u200b
  if (CurTok != ')')
    return LogError(\"expected ')'\");
  getNextToken(); \/\/ eat ).
  return V;
}
\u200b
\/\/\/ identifierexpr
\/\/\/   ::= identifier
\/\/\/   ::= identifier '(' expression* ')'
static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
  std::string IdName = IdentifierStr;
\u200b
  getNextToken(); \/\/ eat identifier.
\u200b
  if (CurTok != '(') \/\/ Simple variable ref.
    return std::make_unique<VariableExprAST>(IdName);
\u200b
  \/\/ Call.
  getNextToken(); \/\/ eat (
  std::vector<std::unique_ptr<ExprAST>> Args;
  if (CurTok != ')') {
    while (true) {
      if (auto Arg = ParseExpression())
        Args.push_back(std::move(Arg));
      else
        return nullptr;
\u200b
      if (CurTok == ')')
        break;
\u200b
      if (CurTok != ',')
        return LogError(\"Expected ')' or ',' in argument list\");
      getNextToken();
    }
  }
\u200b
  \/\/ Eat the ')'.
  getNextToken();
\u200b
  return std::make_unique<CallExprAST>(IdName, std::move(Args));
}
\u200b
\/\/\/ primary
\/\/\/   ::= identifierexpr
\/\/\/   ::= numberexpr
\/\/\/   ::= parenexpr
static std::unique_ptr<ExprAST> ParsePrimary() {
  switch (CurTok) {
  default:
    return LogError(\"unknown token when expecting an expression\");
  case tok_identifier:
    return ParseIdentifierExpr();
  case tok_number:
    return ParseNumberExpr();
  case '(':
    return ParseParenExpr();
  }
}
\u200b
\/\/\/ binoprhs
\/\/\/   ::= ('+' primary)*
static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
                                              std::unique_ptr<ExprAST> LHS) {
  \/\/ If this is a binop, find its precedence.
  while (true) {
    int TokPrec = GetTokPrecedence();
\u200b
    \/\/ If this is a binop that binds at least as tightly as the current binop,
    \/\/ consume it, otherwise we are done.
    if (TokPrec < ExprPrec)
      return LHS;
\u200b
    \/\/ Okay, we know this is a binop.
    int BinOp = CurTok;
    getNextToken(); \/\/ eat binop
\u200b
    \/\/ Parse the primary expression after the binary operator.
    auto RHS = ParsePrimary();
    if (!RHS)
      return nullptr;
\u200b
    \/\/ If BinOp binds less tightly with RHS than the operator after RHS, let
    \/\/ the pending operator take RHS as its LHS.
    int NextPrec = GetTokPrecedence();
    if (TokPrec < NextPrec) {
      RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
      if (!RHS)
        return nullptr;
    }
\u200b
    \/\/ Merge LHS\/RHS.
    LHS =
        std::make_unique<BinaryExprAST>(BinOp, std::move(LHS), std::move(RHS));
  }
}
\u200b
\/\/\/ expression
\/\/\/   ::= primary binoprhs
\/\/\/
static std::unique_ptr<ExprAST> ParseExpression() {
  auto LHS = ParsePrimary();
  if (!LHS)
    return nullptr;
\u200b
  return ParseBinOpRHS(0, std::move(LHS));
}
\u200b
\/\/\/ prototype
\/\/\/   ::= id '(' id* ')'
static std::unique_ptr<PrototypeAST> ParsePrototype() {
  if (CurTok != tok_identifier)
    return LogErrorP(\"Expected function name in prototype\");
\u200b
  std::string FnName = IdentifierStr;
  getNextToken();
\u200b
  if (CurTok != '(')
    return LogErrorP(\"Expected '(' in prototype\");
\u200b
  std::vector<std::string> ArgNames;
  while (getNextToken() == tok_identifier)
    ArgNames.push_back(IdentifierStr);
  if (CurTok != ')')
    return LogErrorP(\"Expected ')' in prototype\");
\u200b
  \/\/ success.
  getNextToken(); \/\/ eat ')'.
\u200b
  return std::make_unique<PrototypeAST>(FnName, std::move(ArgNames));
}
\u200b
\/\/\/ definition ::= 'def' prototype expression
static std::unique_ptr<FunctionAST> ParseDefinition() {
  getNextToken(); \/\/ eat def.
  auto Proto = ParsePrototype();
  if (!Proto)
    return nullptr;
\u200b
  if (auto E = ParseExpression())
    return std::make_unique<FunctionAST>(std::move(Proto), std::move(E));
  return nullptr;
}
\u200b
\/\/\/ toplevelexpr ::= expression
static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
  if (auto E = ParseExpression()) {
    \/\/ Make an anonymous proto.
    auto Proto = std::make_unique<PrototypeAST>(\"__anon_expr\",
                                                 std::vector<std::string>());
    return std::make_unique<FunctionAST>(std::move(Proto), std::move(E));
  }
  return nullptr;
}
\u200b
\/\/\/ external ::= 'extern' prototype
static std::unique_ptr<PrototypeAST> ParseExtern() {
  getNextToken(); \/\/ eat extern.
  return ParsePrototype();
}
\u200b
\/\/===----------------------------------------------------------------------===\/\/
\/\/ Code Generation
\/\/===----------------------------------------------------------------------===\/\/
\u200b
static LLVMContext TheContext;
static IRBuilder<> Builder(TheContext);
static std::unique_ptr<Module> TheModule;
static std::map<std::string, Value *> NamedValues;
\u200b
Value *LogErrorV(const char *Str) {
  LogError(Str);
  return nullptr;
}
\u200b
Value *NumberExprAST::codegen() {
  return ConstantFP::get(TheContext, APFloat(Val));
}
\u200b
Value *VariableExprAST::codegen() {
  \/\/ Look this variable up in the function.
  Value *V = NamedValues[Name];
  if (!V)
    return LogErrorV(\"Unknown variable name\");
  return V;
}
\u200b
Value *BinaryExprAST::codegen() {
  Value *L = LHS->codegen();
  Value *R = RHS->codegen();
  if (!L || !R)
    return nullptr;
\u200b
  switch (Op) {
  case '+':
    return Builder.CreateFAdd(L, R, \"addtmp\");
  case '-':
    return Builder.CreateFSub(L, R, \"subtmp\");
  case '*':
    return Builder.CreateFMul(L, R, \"multmp\");
  case '<':
    L = Builder.CreateFCmpULT(L, R, \"cmptmp\");
    \/\/ Convert bool 0\/1 to double 0.0 or 1.0
    return Builder.CreateUIToFP(L, Type::getDoubleTy(TheContext), \"booltmp\");
  default:
    return LogErrorV(\"invalid binary operator\");
  }
}
\u200b
Value *CallExprAST::codegen() {
  \/\/ Look up the name in the global module table.
  Function *CalleeF = TheModule->getFunction(Callee);
  if (!CalleeF)
    return LogErrorV(\"Unknown function referenced\");
\u200b
  \/\/ If argument mismatch error.
  if (CalleeF->arg_size() != Args.size())
    return LogErrorV(\"Incorrect # arguments passed\");
\u200b
  std::vector<Value *> ArgsV;
  for (unsigned i = 0, e = Args.size(); i != e; ++i) {
    ArgsV.push_back(Args[i]->codegen());
    if (!ArgsV.back())
      return nullptr;
  }
\u200b
  return Builder.CreateCall(CalleeF, ArgsV, \"calltmp\");
}
\u200b
Function *PrototypeAST::codegen() {
  \/\/ Make the function type:  double(double,double) etc.
  std::vector<Type *> Doubles(Args.size(), Type::getDoubleTy(TheContext));
  FunctionType *FT =
      FunctionType::get(Type::getDoubleTy(TheContext), Doubles, false);
\u200b
  Function *F =
      Function::Create(FT, Function::ExternalLinkage, Name, TheModule.get());
\u200b
  \/\/ Set names for all arguments.
  unsigned Idx = 0;
  for (auto &Arg : F->args())
    Arg.setName(Args[Idx++]);
\u200b
  return F;
}
\u200b
Function *FunctionAST::codegen() {
  \/\/ First, check for an existing function from a previous 'extern' declaration.
  Function *TheFunction = TheModule->getFunction(Proto->getName());
\u200b
  if (!TheFunction)
    TheFunction = Proto->codegen();
\u200b
  if (!TheFunction)
    return nullptr;
\u200b
  \/\/ Create a new basic block to start insertion into.
  BasicBlock *BB = BasicBlock::Create(TheContext, \"entry\", TheFunction);
  Builder.SetInsertPoint(BB);
\u200b
  \/\/ Record the function arguments in the NamedValues map.
  NamedValues.clear();
  for (auto &Arg : TheFunction->args())
    NamedValues[std::string(Arg.getName())] = &Arg;
\u200b
  if (Value *RetVal = Body->codegen()) {
    \/\/ Finish off the function.
    Builder.CreateRet(RetVal);
\u200b
    \/\/ Validate the generated code, checking for consistency.
    verifyFunction(*TheFunction);
\u200b
    return TheFunction;
  }
\u200b
  \/\/ Error reading body, remove function.
  TheFunction->eraseFromParent();
  return nullptr;
}
\u200b
\/\/===----------------------------------------------------------------------===\/\/
\/\/ Top-Level parsing and JIT Driver
\/\/===----------------------------------------------------------------------===\/\/
\u200b
static void HandleDefinition() {
  if (auto FnAST = ParseDefinition()) {
    if (auto *FnIR = FnAST->codegen()) {
      fprintf(stderr, \"Read function definition:\");
      FnIR->print(errs());
      fprintf(stderr, \"\\n\");
    }
  } else {
    \/\/ Skip token for error recovery.
    getNextToken();
  }
}
\u200b
static void HandleExtern() {
  if (auto ProtoAST = ParseExtern()) {
    if (auto *FnIR = ProtoAST->codegen()) {
      fprintf(stderr, \"Read extern: \");
      FnIR->print(errs());
      fprintf(stderr, \"\\n\");
    }
  } else {
    \/\/ Skip token for error recovery.
    getNextToken();
  }
}
\u200b
static void HandleTopLevelExpression() {
  \/\/ Evaluate a top-level expression into an anonymous function.
  if (auto FnAST = ParseTopLevelExpr()) {
    if (auto *FnIR = FnAST->codegen()) {
      fprintf(stderr, \"Read top-level expression:\");
      FnIR->print(errs());
      fprintf(stderr, \"\\n\");
    }
  } else {
    \/\/ Skip token for error recovery.
    getNextToken();
  }
}
\u200b
\/\/\/ top ::= definition | external | expression | ';'
static void MainLoop() {
  while (true) {
    fprintf(stderr, \"ready> \");
    switch (CurTok) {
    case tok_eof:
      return;
    case ';': \/\/ ignore top-level semicolons.
      getNextToken();
      break;
    case tok_def:
      HandleDefinition();
      break;
    case tok_extern:
      HandleExtern();
      break;
    default:
      HandleTopLevelExpression();
      break;
    }
  }
}
\u200b
\/\/===----------------------------------------------------------------------===\/\/
\/\/ Main driver code.
\/\/===----------------------------------------------------------------------===\/\/
\u200b
int main() {
  \/\/ Install standard binary operators.
  \/\/ 1 is lowest precedence.
  BinopPrecedence['<'] = 10;
  BinopPrecedence['+'] = 20;
  BinopPrecedence['-'] = 20;
  BinopPrecedence['*'] = 40; \/\/ highest.
\u200b
  \/\/ Prime the first token.
  fprintf(stderr, \"ready> \");
  getNextToken();
\u200b
  \/\/ Make the module, which holds all the code.
  TheModule = std::make_unique<Module>(\"my cool jit\", TheContext);
\u200b
  \/\/ Run the main \"interpreter loop\" now.
  MainLoop();
\u200b
  \/\/ Print out all of the generated code.
  TheModule->print(errs(), nullptr);
\u200b
  return 0;
}<\/pre>\n\n\n\n
\u7f16\u8bd1\u547d\u4ee4<\/p>\n\n\n\n
$LLVM_HOME\/bin\/clang++ -g -O3 toy.cpp `$LLVM_HOME\/bin\/llvm-config --cxxflags --ldflags --system-libs --libs core` -o toy -I\/usr\/local\/include<\/pre>\n\n\n\n
\u5148\u4ece\u7b80\u5355\u7684\u5f00\u59cb\u5206\u6790:<\/p>\n\n\n\n
ready> 1;  \nready>Read top-level expression:define double @__anon_expr() {\nentry:\n  ret double 1.000000e+00\n}<\/pre>\n\n\n\n
\u56e0\u4e3a\u65e2\u4e0d\u662fdef \u4e5f\u4e0d\u662f extern \u76f4\u63a5\u8fdb\u53bb\u5230HandleTopLevelExpression\uff0c ParseTopLevelExpr\u521b\u5efa\u4e86FunctionAST\u8bed\u6cd5\u6811\uff0c \u5982\u56fe\uff1a<\/p>\n\n\n\n
\"image-20200812173710923\"<\/figure>\n\n\n\n
PrototypeAST \u7684\u540d\u79f0\u4e3a”__anon_expr” , \u53c2\u6570\u4e3a\u7a7a\uff0cNumberExprAST \u5b58\u4e86\u4e2a”1″\uff0c\u8bed\u6cd5\u6811\u751f\u6210\u7ed3\u675f\u540e\u3002<\/p>\n\n\n\n
\u8c03\u7528FnAST->codegen() \u6765\u751f\u6210\u5bf9\u5e94\u8bed\u6cd5\u6811\u7684IR\u6307\u4ee4\u3002\u5148\u751f\u6210\u51fd\u6570\u5b9a\u4e49\u518d\u751f\u6210\u51fd\u6570\u4f53\u3002\u8fc7\u7a0b\u63cf\u8ff0\u8fc7\u4e86\uff0c\u4e0d\u591a\u8d58\u8ff0\u3002<\/p>\n\n\n\n
https:\/\/llvm.org\/docs\/tutorial\/MyFirstLanguageFrontend\/LangImpl03.html<\/a><\/p>\n\n\n\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
\u82f1\u6587\u770b\u591a\u4e86\u8fd8\u662f\u5934\u75db\uff0c\u8fd8\u662f\u76f4\u63a5\u4e0a\u4ee3\u7801 \u4ee3\u7801\u76f8\u6bd4\u4e8e\u4e0a\u4e00\u7bc7\u4e3a\u6bcf\u4e2a\u8bed\u6cd5\u6811\u65b0\u589e\u4e86\u751f\u6210\u6307\u4ee4\u7684\u51fd\u6570codegen\uff0c […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"_links":{"self":[{"href":"http:\/\/pareto.fun\/index.php?rest_route=\/wp\/v2\/posts\/29"}],"collection":[{"href":"http:\/\/pareto.fun\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/pareto.fun\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/pareto.fun\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/pareto.fun\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=29"}],"version-history":[{"count":2,"href":"http:\/\/pareto.fun\/index.php?rest_route=\/wp\/v2\/posts\/29\/revisions"}],"predecessor-version":[{"id":33,"href":"http:\/\/pareto.fun\/index.php?rest_route=\/wp\/v2\/posts\/29\/revisions\/33"}],"wp:attachment":[{"href":"http:\/\/pareto.fun\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=29"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/pareto.fun\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=29"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/pareto.fun\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=29"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}