llvm入门教程-Kaleidoscope前端-3-代码生成

/// ExprAST - Base class for all expression nodes.
class ExprAST {
public:
  virtual ~ExprAST() {}
  virtual Value *codegen() = 0;
};

/// NumberExprAST - Expression class for numeric literals like "1.0".
class NumberExprAST : public ExprAST {
  double Val;

public:
  NumberExprAST(double Val) : Val(Val) {}
  virtual Value *codegen();
};
...

static LLVMContext TheContext;
static IRBuilder<> Builder(TheContext);
static std::unique_ptr<Module> TheModule;
static std::map<std::string, Value *> NamedValues;

Value *LogErrorV(const char *Str) {
  LogError(Str);
  return nullptr;
}

Value *NumberExprAST::codegen() {
  return ConstantFP::get(TheContext, APFloat(Val));
}

Value *VariableExprAST::codegen() {
  // Look this variable up in the function.
  Value *V = NamedValues[Name];
  if (!V)
    LogErrorV("Unknown variable name");
  return V;
}

Value *BinaryExprAST::codegen() {
  Value *L = LHS->codegen();
  Value *R = RHS->codegen();
  if (!L || !R)
    return nullptr;

  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");
  }
}

Value *CallExprAST::codegen() {
  // Look up the name in the global module table.
  Function *CalleeF = TheModule->getFunction(Callee);
  if (!CalleeF)
    return LogErrorV("Unknown function referenced");

  // If argument mismatch error.
  if (CalleeF->arg_size() != Args.size())
    return LogErrorV("Incorrect # arguments passed");

  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;
  }

  return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
}

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);

  Function *F =
    Function::Create(FT, Function::ExternalLinkage, Name, TheModule.get());

// Set names for all arguments.
unsigned Idx = 0;
for (auto &Arg : F->args())
  Arg.setName(Args[Idx++]);

return F;

Function *FunctionAST::codegen() {
    // First, check for an existing function from a previous 'extern' declaration.
  Function *TheFunction = TheModule->getFunction(Proto->getName());

  if (!TheFunction)
    TheFunction = Proto->codegen();

  if (!TheFunction)
    return nullptr;

  if (!TheFunction->empty())
    return (Function*)LogErrorV("Function cannot be redefined.");

// Create a new basic block to start insertion into.
BasicBlock *BB = BasicBlock::Create(TheContext, "entry", TheFunction);
Builder.SetInsertPoint(BB);

// Record the function arguments in the NamedValues map.
NamedValues.clear();
for (auto &Arg : TheFunction->args())
  NamedValues[Arg.getName()] = &Arg;

if (Value *RetVal = Body->codegen()) {
  // Finish off the function.
  Builder.CreateRet(RetVal);

  // Validate the generated code, checking for consistency.
  verifyFunction(*TheFunction);

  return TheFunction;
}

// Error reading body, remove function.
TheFunction->eraseFromParent();
return nullptr;
}

extern foo(a);     # ok, defines foo.
    def foo(b) b;      # Error: Unknown variable name. (decl using 'a' takes precedence).

ready> 4+5;
    Read top-level expression:
    define double @0() {
    entry:
      ret double 9.000000e+00
    }

ready> def foo(a b) a*a + 2*a*b + b*b;
    Read function definition:
    define double @foo(double %a, double %b) {
    entry:
      %multmp = fmul double %a, %a
      %multmp1 = fmul double 2.000000e+00, %a
      %multmp2 = fmul double %multmp1, %b
      %addtmp = fadd double %multmp, %multmp2
      %multmp3 = fmul double %b, %b
      %addtmp4 = fadd double %addtmp, %multmp3
      ret double %addtmp4
    }

ready> def bar(a) foo(a, 4.0) + bar(31337);
    Read function definition:
    define double @bar(double %a) {
    entry:
      %calltmp = call double @foo(double %a, double 4.000000e+00)
      %calltmp1 = call double @bar(double 3.133700e+04)
      %addtmp = fadd double %calltmp, %calltmp1
      ret double %addtmp
    }

ready> extern cos(x);
    Read extern:
    declare double @cos(double)

    ready> cos(1.234);
    Read top-level expression:
    define double @1() {
    entry:
      %calltmp = call double @cos(double 1.234000e+00)
      ret double %calltmp
    }

ready> ^D
    ; ModuleID = 'my cool jit'

    define double @0() {
    entry:
      %addtmp = fadd double 4.000000e+00, 5.000000e+00
      ret double %addtmp
    }

    define double @foo(double %a, double %b) {
    entry:
      %multmp = fmul double %a, %a
      %multmp1 = fmul double 2.000000e+00, %a
      %multmp2 = fmul double %multmp1, %b
      %addtmp = fadd double %multmp, %multmp2
      %multmp3 = fmul double %b, %b
      %addtmp4 = fadd double %addtmp, %multmp3
      ret double %addtmp4
    }

    define double @bar(double %a) {
    entry:
      %calltmp = call double @foo(double %a, double 4.000000e+00)
      %calltmp1 = call double @bar(double 3.133700e+04)
      %addtmp = fadd double %calltmp, %calltmp1
      ret double %addtmp
    }

    declare double @cos(double)

    define double @1() {
    entry:
      %calltmp = call double @cos(double 1.234000e+00)
      ret double %calltmp
    }

# Compile
clang++ -g -O3 toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core` -o toy
# Run
./toy