Kaleidoscope - C++11 modernization.

Justin Bogner via llvm-commits llvm-commits at lists.llvm.org
Mon Aug 17 22:03:36 PDT 2015


Lang Hames via llvm-commits <llvm-commits at lists.llvm.org> writes:
> Hi All,
>
> Attached is a patch to partially C++11'ify the Kaleidoscope tutorials. There
> are a few LLVM coding convention fixes and range-based for loops in here, but
> the bulk of the patch is concerned with switching raw pointers to unique_ptr.
>
> This is a significant change from the original Kaleidoscope tutorials which
> deliberately avoided any memory management so as not to overcomplicate the
> examples. I thought it was time to revisit this idea, since C++11 has removed
> a lot of the complication of C++ memory management, and there's a benefit to
> having the tutorial code more closely resemble the rest of the LLVM codebase. 
>
> Any thoughts/feedback on this direction?

This is great - it isn't really harder to understand and it's that much
closer to what the code you'll actually want to write after reading the
tutorial. LGTM.

It does look like this adds a long line or two though - do you mind
clang-format'ing the patch? Actually, a lot of this code predates our
formatting rules and you're touching half of the lines anyway, so it's
probably reasonable to just clang-format the whole thing in a prep patch
before this one if you feel like it.

> I see this as a first step towards fully modernizing the Kaleidoscope
> tutorials. My next step will be to update Chapter 4 onwards to bring them up
> to speed with the recent JIT API changes - I've already started work on a
> follow-up patch for this. If anybody else is interested in helping me bring
> these tutorials up to speed let me know - assistance will very welcome.
>
> - Lang.
>
> Index: docs/tutorial/LangImpl1.rst
> ===================================================================
> --- docs/tutorial/LangImpl1.rst	(revision 245236)
> +++ docs/tutorial/LangImpl1.rst	(working copy)
> @@ -25,7 +25,7 @@
>  about teaching compiler techniques and LLVM specifically, *not* about
>  teaching modern and sane software engineering principles. In practice,
>  this means that we'll take a number of shortcuts to simplify the
> -exposition. For example, the code leaks memory, uses global variables
> +exposition. For example, the code uses global variables
>  all over the place, doesn't use nice design patterns like
>  `visitors <http://en.wikipedia.org/wiki/Visitor_pattern>`_, etc... but
>  it is very simple. If you dig in and use the code as a basis for future
> Index: docs/tutorial/LangImpl2.rst
> ===================================================================
> --- docs/tutorial/LangImpl2.rst	(revision 245236)
> +++ docs/tutorial/LangImpl2.rst	(working copy)
> @@ -45,7 +45,7 @@
>      class NumberExprAST : public ExprAST {
>        double Val;
>      public:
> -      NumberExprAST(double val) : Val(val) {}
> +      NumberExprAST(double Val) : Val(Val) {}
>      };
>  
>  The code above shows the definition of the base ExprAST class and one
> @@ -66,16 +66,17 @@
>      class VariableExprAST : public ExprAST {
>        std::string Name;
>      public:
> -      VariableExprAST(const std::string &name) : Name(name) {}
> +      VariableExprAST(const std::string &Name) : Name(Name) {}
>      };
>  
>      /// BinaryExprAST - Expression class for a binary operator.
>      class BinaryExprAST : public ExprAST {
>        char Op;
> -      ExprAST *LHS, *RHS;
> +      std::unique_ptr<ExprAST> LHS, RHS;
>      public:
> -      BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
> -        : Op(op), LHS(lhs), RHS(rhs) {}
> +      BinaryExprAST(char op, std::unique_ptr<ExprAST> LHS,
> +                    std::unique_ptr<ExprAST> RHS)
> +        : Op(op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
>      };
>  
>      /// CallExprAST - Expression class for function calls.
> @@ -83,8 +84,9 @@
>        std::string Callee;
>        std::vector<ExprAST*> Args;
>      public:
> -      CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
> -        : Callee(callee), Args(args) {}
> +      CallExprAST(const std::string &Callee,
> +                  std::vector<std::unique_ptr<ExprAST>> Args)
> +        : Callee(Callee), Args(std::move(Args)) {}
>      };
>  
>  This is all (intentionally) rather straight-forward: variables capture
> @@ -110,17 +112,18 @@
>        std::string Name;
>        std::vector<std::string> Args;
>      public:
> -      PrototypeAST(const std::string &name, const std::vector<std::string> &args)
> -        : Name(name), Args(args) {}
> +      PrototypeAST(const std::string &name, std::vector<std::string> Args)
> +        : Name(name), Args(std::move(Args)) {}
>      };
>  
>      /// FunctionAST - This class represents a function definition itself.
>      class FunctionAST {
> -      PrototypeAST *Proto;
> -      ExprAST *Body;
> +      std::unique_ptr<PrototypeAST> Proto;
> +      std::unique_ptr<ExprAST> Body;
>      public:
> -      FunctionAST(PrototypeAST *proto, ExprAST *body)
> -        : Proto(proto), Body(body) {}
> +      FunctionAST(std::unique_ptr<PrototypeAST> Proto,
> +                  std::unique_ptr<ExprAST> Body)
> +        : Proto(std::move(Proto)), Body(std::move(Body)) {}
>      };
>  
>  In Kaleidoscope, functions are typed with just a count of their
> @@ -142,9 +145,10 @@
>  
>  .. code-block:: c++
>  
> -      ExprAST *X = new VariableExprAST("x");
> -      ExprAST *Y = new VariableExprAST("y");
> -      ExprAST *Result = new BinaryExprAST('+', X, Y);
> +      auto LHS = llvm::make_unique<VariableExprAST>("x");
> +      auto RHS = llvm::make_unique<VariableExprAST>("y");
> +      auto Result = std::make_unique<BinaryExprAST>('+', std::move(LHS),
> +                                                    std::move(RHS));
>  
>  In order to do this, we'll start by defining some basic helper routines:
>  
> @@ -190,10 +194,10 @@
>  .. code-block:: c++
>  
>      /// numberexpr ::= number
> -    static ExprAST *ParseNumberExpr() {
> -      ExprAST *Result = new NumberExprAST(NumVal);
> +    static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +      auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>        getNextToken(); // consume the number
> -      return Result;
> +      return std::move(Result);
>      }
>  
>  This routine is very simple: it expects to be called when the current
> @@ -211,10 +215,10 @@
>  .. code-block:: c++
>  
>      /// parenexpr ::= '(' expression ')'
> -    static ExprAST *ParseParenExpr() {
> +    static std::unique_ptr<ExprAST> ParseParenExpr() {
>        getNextToken();  // eat (.
> -      ExprAST *V = ParseExpression();
> -      if (!V) return 0;
> +      auto V = ParseExpression();
> +      if (!V) return nullptr;
>  
>        if (CurTok != ')')
>          return Error("expected ')'");
> @@ -250,22 +254,22 @@
>      /// identifierexpr
>      ///   ::= identifier
>      ///   ::= identifier '(' expression* ')'
> -    static ExprAST *ParseIdentifierExpr() {
> +    static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>        std::string IdName = IdentifierStr;
>  
>        getNextToken();  // eat identifier.
>  
>        if (CurTok != '(') // Simple variable ref.
> -        return new VariableExprAST(IdName);
> +        return llvm::make_unique<VariableExprAST>(IdName);
>  
>        // Call.
>        getNextToken();  // eat (
> -      std::vector<ExprAST*> Args;
> +      std::vector<std::unique_ptr<ExprAST>> Args;
>        if (CurTok != ')') {
>          while (1) {
> -          ExprAST *Arg = ParseExpression();
> -          if (!Arg) return 0;
> -          Args.push_back(Arg);
> +          auto Arg = ParseExpression();
> +          if (!Arg) return nullptr;
> +          Args.push_back(std::move(Arg));
>  
>            if (CurTok == ')') break;
>  
> @@ -278,7 +282,7 @@
>        // Eat the ')'.
>        getNextToken();
>  
> -      return new CallExprAST(IdName, Args);
> +      return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
>      }
>  
>  This routine follows the same style as the other routines. (It expects
> @@ -303,7 +307,7 @@
>      ///   ::= identifierexpr
>      ///   ::= numberexpr
>      ///   ::= parenexpr
> -    static ExprAST *ParsePrimary() {
> +    static std::unique_ptr<ExprAST> ParsePrimary() {
>        switch (CurTok) {
>        default: return Error("unknown token when expecting an expression");
>        case tok_identifier: return ParseIdentifierExpr();
> @@ -390,11 +394,11 @@
>      /// expression
>      ///   ::= primary binoprhs
>      ///
> -    static ExprAST *ParseExpression() {
> -      ExprAST *LHS = ParsePrimary();
> -      if (!LHS) return 0;
> +    static std::unique_ptr<ExprAST> ParseExpression() {
> +      auto LHS = ParsePrimary();
> +      if (!LHS) return nullptr;
>  
> -      return ParseBinOpRHS(0, LHS);
> +      return ParseBinOpRHS(0, std::move(LHS));
>      }
>  
>  ``ParseBinOpRHS`` is the function that parses the sequence of pairs for
> @@ -416,7 +420,8 @@
>  
>      /// binoprhs
>      ///   ::= ('+' primary)*
> -    static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +    static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
> +                                                  std::unique_ptr<ExprAST> LHS) {
>        // If this is a binop, find its precedence.
>        while (1) {
>          int TokPrec = GetTokPrecedence();
> @@ -440,8 +445,8 @@
>          getNextToken();  // eat binop
>  
>          // Parse the primary expression after the binary operator.
> -        ExprAST *RHS = ParsePrimary();
> -        if (!RHS) return 0;
> +        auto RHS = ParsePrimary();
> +        if (!RHS) return nullptr;
>  
>  As such, this code eats (and remembers) the binary operator and then
>  parses the primary expression that follows. This builds up the whole
> @@ -474,7 +479,8 @@
>          }
>  
>          // Merge LHS/RHS.
> -        LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +        LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS),
> +                                               std::move(RHS));
>        }  // loop around to the top of the while loop.
>      }
>  
> @@ -498,11 +504,12 @@
>          // the pending operator take RHS as its LHS.
>          int NextPrec = GetTokPrecedence();
>          if (TokPrec < NextPrec) {
> -          RHS = ParseBinOpRHS(TokPrec+1, RHS);
> +          RHS = ParseBinOpRHS(TokPrec+1, std::move(RHS));
>            if (RHS == 0) return 0;
>          }
>          // Merge LHS/RHS.
> -        LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +        LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS),
> +                                               std::move(RHS));
>        }  // loop around to the top of the while loop.
>      }
>  
> @@ -541,7 +548,7 @@
>  
>      /// prototype
>      ///   ::= id '(' id* ')'
> -    static PrototypeAST *ParsePrototype() {
> +    static std::unique_ptr<PrototypeAST> ParsePrototype() {
>        if (CurTok != tok_identifier)
>          return ErrorP("Expected function name in prototype");
>  
> @@ -561,7 +568,7 @@
>        // success.
>        getNextToken();  // eat ')'.
>  
> -      return new PrototypeAST(FnName, ArgNames);
> +      return llvm::make_unique<PrototypeAST>(FnName, std::move(ArgNames));
>      }
>  
>  Given this, a function definition is very simple, just a prototype plus
> @@ -570,14 +577,14 @@
>  .. code-block:: c++
>  
>      /// definition ::= 'def' prototype expression
> -    static FunctionAST *ParseDefinition() {
> +    static std::unique_ptr<FunctionAST> ParseDefinition() {
>        getNextToken();  // eat def.
> -      PrototypeAST *Proto = ParsePrototype();
> -      if (Proto == 0) return 0;
> +      auto Proto = ParsePrototype();
> +      if (!Proto) return nullptr;
>  
> -      if (ExprAST *E = ParseExpression())
> -        return new FunctionAST(Proto, E);
> -      return 0;
> +      if (auto E = ParseExpression())
> +        return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +      return nullptr;
>      }
>  
>  In addition, we support 'extern' to declare functions like 'sin' and
> @@ -587,7 +594,7 @@
>  .. code-block:: c++
>  
>      /// external ::= 'extern' prototype
> -    static PrototypeAST *ParseExtern() {
> +    static std::unique_ptr<PrototypeAST> ParseExtern() {
>        getNextToken();  // eat extern.
>        return ParsePrototype();
>      }
> @@ -599,13 +606,13 @@
>  .. code-block:: c++
>  
>      /// toplevelexpr ::= expression
> -    static FunctionAST *ParseTopLevelExpr() {
> -      if (ExprAST *E = ParseExpression()) {
> +    static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
> +      if (auto E = ParseExpression()) {
>          // Make an anonymous proto.
> -        PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -        return new FunctionAST(Proto, E);
> +        auto Proto = llvm::make_unique<PrototypeAST>("", std::vector<std::string>());
> +        return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>        }
> -      return 0;
> +      return nullptr;
>      }
>  
>  Now that we have all the pieces, let's build a little driver that will
> Index: docs/tutorial/LangImpl3.rst
> ===================================================================
> --- docs/tutorial/LangImpl3.rst	(revision 245236)
> +++ docs/tutorial/LangImpl3.rst	(working copy)
> @@ -42,7 +42,7 @@
>      class NumberExprAST : public ExprAST {
>        double Val;
>      public:
> -      NumberExprAST(double val) : Val(val) {}
> +      NumberExprAST(double Val) : Val(Val) {}
>        virtual Value *Codegen();
>      };
>      ...
> Index: docs/tutorial/LangImpl4.rst
> ===================================================================
> --- docs/tutorial/LangImpl4.rst	(revision 245236)
> +++ docs/tutorial/LangImpl4.rst	(working copy)
> @@ -260,12 +260,12 @@
>  
>      static void HandleTopLevelExpression() {
>        // Evaluate a top-level expression into an anonymous function.
> -      if (FunctionAST *F = ParseTopLevelExpr()) {
> -        if (Function *LF = F->Codegen()) {
> -          LF->dump();  // Dump the function for exposition purposes.
> +      if (auto FnAST = ParseTopLevelExpr()) {
> +        if (auto *FnIR = FnAST->Codegen()) {
> +          FnIR->dump();  // Dump the function for exposition purposes.
>  
>            // JIT the function, returning a function pointer.
> -          void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
> +          void *FPtr = TheExecutionEngine->getPointerToFunction(FnIR);
>  
>            // Cast it to the right type (takes no arguments, returns a double) so we
>            // can call it as a native function.
> Index: docs/tutorial/LangImpl5.rst
> ===================================================================
> --- docs/tutorial/LangImpl5.rst	(revision 245236)
> +++ docs/tutorial/LangImpl5.rst	(working copy)
> @@ -90,10 +90,11 @@
>  
>      /// IfExprAST - Expression class for if/then/else.
>      class IfExprAST : public ExprAST {
> -      ExprAST *Cond, *Then, *Else;
> +      std::unique<ExprAST> Cond, Then, Else;
>      public:
> -      IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
> -        : Cond(cond), Then(then), Else(_else) {}
> +      IfExprAST(std::unique_ptr<ExprAST> Cond, std::unique_ptr<ExprAST> Then,
> +                std::unique_ptr<ExprAST> Else)
> +        : Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}
>        virtual Value *Codegen();
>      };
>  
> @@ -109,36 +110,37 @@
>  .. code-block:: c++
>  
>      /// ifexpr ::= 'if' expression 'then' expression 'else' expression
> -    static ExprAST *ParseIfExpr() {
> +    static std::unique_ptr<ExprAST> ParseIfExpr() {
>        getNextToken();  // eat the if.
>  
>        // condition.
> -      ExprAST *Cond = ParseExpression();
> -      if (!Cond) return 0;
> +      auto Cond = ParseExpression();
> +      if (!Cond) return nullptr;
>  
>        if (CurTok != tok_then)
>          return Error("expected then");
>        getNextToken();  // eat the then
>  
> -      ExprAST *Then = ParseExpression();
> -      if (Then == 0) return 0;
> +      auto Then = ParseExpression();
> +      if (Then) return nullptr;
>  
>        if (CurTok != tok_else)
>          return Error("expected else");
>  
>        getNextToken();
>  
> -      ExprAST *Else = ParseExpression();
> -      if (!Else) return 0;
> +      auto Else = ParseExpression();
> +      if (!Else) return nullptr;
>  
> -      return new IfExprAST(Cond, Then, Else);
> +      return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
> +                                          std::move(Else));
>      }
>  
>  Next we hook it up as a primary expression:
>  
>  .. code-block:: c++
>  
> -    static ExprAST *ParsePrimary() {
> +    static std::unique_ptr<ExprAST> ParsePrimary() {
>        switch (CurTok) {
>        default: return Error("unknown token when expecting an expression");
>        case tok_identifier: return ParseIdentifierExpr();
> @@ -269,7 +271,7 @@
>  
>      Value *IfExprAST::Codegen() {
>        Value *CondV = Cond->Codegen();
> -      if (CondV == 0) return 0;
> +      if (!CondV) return nullptr;
>  
>        // Convert condition to a bool by comparing equal to 0.0.
>        CondV = Builder.CreateFCmpONE(CondV,
> @@ -464,11 +466,13 @@
>      /// ForExprAST - Expression class for for/in.
>      class ForExprAST : public ExprAST {
>        std::string VarName;
> -      ExprAST *Start, *End, *Step, *Body;
> +      std::unique_ptr<ExprAST> Start, End, Step, Body;
>      public:
> -      ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
> -                 ExprAST *step, ExprAST *body)
> -        : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
> +      ForExprAST(const std::string &VarName, std::unique_ptr<ExprAST> Start,
> +                 std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
> +                 std::unique_ptr<ExprAST> Body)
> +        : VarName(VarName), Start(std::move(Start)), End(std::move(End)),
> +          Step(std::move(Step)), Body(std::move(Body)) {}
>        virtual Value *Codegen();
>      };
>  
> @@ -483,7 +487,7 @@
>  .. code-block:: c++
>  
>      /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
> -    static ExprAST *ParseForExpr() {
> +    static std::unique_ptr<ExprAST> ParseForExpr() {
>        getNextToken();  // eat the for.
>  
>        if (CurTok != tok_identifier)
> @@ -497,31 +501,33 @@
>        getNextToken();  // eat '='.
>  
>  
> -      ExprAST *Start = ParseExpression();
> -      if (Start == 0) return 0;
> +      auto Start = ParseExpression();
> +      if (!Start) return nullptr;
>        if (CurTok != ',')
>          return Error("expected ',' after for start value");
>        getNextToken();
>  
> -      ExprAST *End = ParseExpression();
> -      if (End == 0) return 0;
> +      auto End = ParseExpression();
> +      if (!End) return nullptr;
>  
>        // The step value is optional.
> -      ExprAST *Step = 0;
> +      std::unique_ptr<ExprAST> Step;
>        if (CurTok == ',') {
>          getNextToken();
>          Step = ParseExpression();
> -        if (Step == 0) return 0;
> +        if (!Step) return nullptr;
>        }
>  
>        if (CurTok != tok_in)
>          return Error("expected 'in' after for");
>        getNextToken();  // eat 'in'.
>  
> -      ExprAST *Body = ParseExpression();
> -      if (Body == 0) return 0;
> +      auto Body = ParseExpression();
> +      if (!Body) return nullptr;
>  
> -      return new ForExprAST(IdName, Start, End, Step, Body);
> +      return llvm::make_unique<ForExprAST>(IdName, std::move(Start),
> +                                           std::move(End), std::move(Step),
> +                                           std::move(Body));
>      }
>  
>  LLVM IR for the 'for' Loop
> Index: docs/tutorial/LangImpl6.rst
> ===================================================================
> --- docs/tutorial/LangImpl6.rst	(revision 245236)
> +++ docs/tutorial/LangImpl6.rst	(working copy)
> @@ -129,15 +129,16 @@
>      class PrototypeAST {
>        std::string Name;
>        std::vector<std::string> Args;
> -      bool isOperator;
> +      bool IsOperator;
>        unsigned Precedence;  // Precedence if a binary op.
>      public:
> -      PrototypeAST(const std::string &name, const std::vector<std::string> &args,
> -                   bool isoperator = false, unsigned prec = 0)
> -      : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
> +      PrototypeAST(const std::string &name, std::vector<std::string> Args,
> +                   bool IsOperator = false, unsigned Prec = 0)
> +      : Name(name), Args(std::move(Args)), IsOperator(IsOperator),
> +        Precedence(Prec) {}
>  
> -      bool isUnaryOp() const { return isOperator && Args.size() == 1; }
> -      bool isBinaryOp() const { return isOperator && Args.size() == 2; }
> +      bool isUnaryOp() const { return IsOperator && Args.size() == 1; }
> +      bool isBinaryOp() const { return IsOperator && Args.size() == 2; }
>  
>        char getOperatorName() const {
>          assert(isUnaryOp() || isBinaryOp());
> @@ -161,7 +162,7 @@
>      /// prototype
>      ///   ::= id '(' id* ')'
>      ///   ::= binary LETTER number? (id, id)
> -    static PrototypeAST *ParsePrototype() {
> +    static std::unique_ptr<PrototypeAST> ParsePrototype() {
>        std::string FnName;
>  
>        unsigned Kind = 0;  // 0 = identifier, 1 = unary, 2 = binary.
> @@ -210,7 +211,8 @@
>        if (Kind && ArgNames.size() != Kind)
>          return ErrorP("Invalid number of operands for operator");
>  
> -      return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
> +      return llvm::make_unique<PrototypeAST>(FnName, std::move(ArgNames),
> +                                             Kind != 0, BinaryPrecedence);
>      }
>  
>  This is all fairly straightforward parsing code, and we have already
> @@ -305,10 +307,10 @@
>      /// UnaryExprAST - Expression class for a unary operator.
>      class UnaryExprAST : public ExprAST {
>        char Opcode;
> -      ExprAST *Operand;
> +      std::unique_ptr<ExprAST> Operand;
>      public:
> -      UnaryExprAST(char opcode, ExprAST *operand)
> -        : Opcode(opcode), Operand(operand) {}
> +      UnaryExprAST(char Opcode, std::unique_ptr<ExprAST> Operand)
> +        : Opcode(Opcode), Operand(std::move(Operand)) {}
>        virtual Value *Codegen();
>      };
>  
> @@ -322,7 +324,7 @@
>      /// unary
>      ///   ::= primary
>      ///   ::= '!' unary
> -    static ExprAST *ParseUnary() {
> +    static std::unique_ptr<ExprAST> ParseUnary() {
>        // If the current token is not an operator, it must be a primary expr.
>        if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
>          return ParsePrimary();
> @@ -330,9 +332,9 @@
>        // If this is a unary operator, read it.
>        int Opc = CurTok;
>        getNextToken();
> -      if (ExprAST *Operand = ParseUnary())
> -        return new UnaryExprAST(Opc, Operand);
> -      return 0;
> +      if (auto Operand = ParseUnary())
> +        return llvm::unique_ptr<UnaryExprAST>(Opc, std::move(Operand));
> +      return nullptr;
>      }
>  
>  The grammar we add is pretty straightforward here. If we see a unary
> @@ -350,21 +352,22 @@
>  
>      /// binoprhs
>      ///   ::= ('+' unary)*
> -    static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +    static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
> +                                                  std::unique_ptr<ExprAST> LHS) {
>        ...
>          // Parse the unary expression after the binary operator.
> -        ExprAST *RHS = ParseUnary();
> -        if (!RHS) return 0;
> +        auto RHS = ParseUnary();
> +        if (!RHS) return nullptr;
>        ...
>      }
>      /// expression
>      ///   ::= unary binoprhs
>      ///
> -    static ExprAST *ParseExpression() {
> -      ExprAST *LHS = ParseUnary();
> -      if (!LHS) return 0;
> +    static std::unique_ptr<ExprAST> ParseExpression() {
> +      auto LHS = ParseUnary();
> +      if (!LHS) return nullptr;
>  
> -      return ParseBinOpRHS(0, LHS);
> +      return ParseBinOpRHS(0, std::move(LHS));
>      }
>  
>  With these two simple changes, we are now able to parse unary operators
> @@ -378,7 +381,7 @@
>      ///   ::= id '(' id* ')'
>      ///   ::= binary LETTER number? (id, id)
>      ///   ::= unary LETTER (id)
> -    static PrototypeAST *ParsePrototype() {
> +    static std::unique_ptr<PrototypeAST> ParsePrototype() {
>        std::string FnName;
>  
>        unsigned Kind = 0;  // 0 = identifier, 1 = unary, 2 = binary.
> Index: docs/tutorial/LangImpl7.rst
> ===================================================================
> --- docs/tutorial/LangImpl7.rst	(revision 245236)
> +++ docs/tutorial/LangImpl7.rst	(working copy)
> @@ -573,7 +573,7 @@
>        // Special case '=' because we don't want to emit the LHS as an expression.
>        if (Op == '=') {
>          // Assignment requires the LHS to be an identifier.
> -        VariableExprAST *LHSE = dynamic_cast<VariableExprAST*>(LHS);
> +        VariableExprAST *LHSE = dynamic_cast<VariableExprAST*>(LHS.get());
>          if (!LHSE)
>            return ErrorV("destination of '=' must be a variable");
>  
> @@ -663,12 +663,12 @@
>  
>      /// VarExprAST - Expression class for var/in
>      class VarExprAST : public ExprAST {
> -      std::vector<std::pair<std::string, ExprAST*> > VarNames;
> -      ExprAST *Body;
> +      std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames;
> +      std::unique_ptr<ExprAST> Body;
>      public:
> -      VarExprAST(const std::vector<std::pair<std::string, ExprAST*> > &varnames,
> -                 ExprAST *body)
> -      : VarNames(varnames), Body(body) {}
> +      VarExprAST(std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames,
> +                 std::unique_ptr<ExprAST> body)
> +      : VarNames(std::move(VarNames)), Body(std::move(Body)) {}
>  
>        virtual Value *Codegen();
>      };
> @@ -690,7 +690,7 @@
>      ///   ::= ifexpr
>      ///   ::= forexpr
>      ///   ::= varexpr
> -    static ExprAST *ParsePrimary() {
> +    static std::unique_ptr<ExprAST> ParsePrimary() {
>        switch (CurTok) {
>        default: return Error("unknown token when expecting an expression");
>        case tok_identifier: return ParseIdentifierExpr();
> @@ -708,10 +708,10 @@
>  
>      /// varexpr ::= 'var' identifier ('=' expression)?
>      //                    (',' identifier ('=' expression)?)* 'in' expression
> -    static ExprAST *ParseVarExpr() {
> +    static std::unique_ptr<ExprAST> ParseVarExpr() {
>        getNextToken();  // eat the var.
>  
> -      std::vector<std::pair<std::string, ExprAST*> > VarNames;
> +      std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames;
>  
>        // At least one variable name is required.
>        if (CurTok != tok_identifier)
> @@ -727,15 +727,15 @@
>          getNextToken();  // eat identifier.
>  
>          // Read the optional initializer.
> -        ExprAST *Init = 0;
> +        std::unique_ptr<ExprAST> Init;
>          if (CurTok == '=') {
>            getNextToken(); // eat the '='.
>  
>            Init = ParseExpression();
> -          if (Init == 0) return 0;
> +          if (!Init) return nullptr;
>          }
>  
> -        VarNames.push_back(std::make_pair(Name, Init));
> +        VarNames.push_back(std::make_pair(Name, std::move(Init)));
>  
>          // End of var list, exit loop.
>          if (CurTok != ',') break;
> @@ -755,10 +755,11 @@
>          return Error("expected 'in' keyword after 'var'");
>        getNextToken();  // eat 'in'.
>  
> -      ExprAST *Body = ParseExpression();
> -      if (Body == 0) return 0;
> +      auto Body = ParseExpression();
> +      if (!Body) return nullptr;
>  
> -      return new VarExprAST(VarNames, Body);
> +      return llvm::make_unique<VarExprAST>(std::move(VarNames),
> +                                           std::move(Body));
>      }
>  
>  Now that we can parse and represent the code, we need to support
> @@ -774,7 +775,7 @@
>        // Register all variables and emit their initializer.
>        for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
>          const std::string &VarName = VarNames[i].first;
> -        ExprAST *Init = VarNames[i].second;
> +        ExprAST *Init = VarNames[i].second.get();
>  
>  Basically it loops over all the variables, installing them one at a
>  time. For each variable we put into the symbol table, we remember the
> Index: docs/tutorial/LangImpl8.rst
> ===================================================================
> --- docs/tutorial/LangImpl8.rst	(revision 245236)
> +++ docs/tutorial/LangImpl8.rst	(working copy)
> @@ -75,8 +75,8 @@
>  
>  .. code-block:: udiff
>  
> -  -    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -  +    PrototypeAST *Proto = new PrototypeAST("main", std::vector<std::string>());
> +  -    auto Proto = llvm::make_unique<PrototypeAST>("", std::vector<std::string>());
> +  +    auto Proto = llvm::make_unique<PrototypeAST>("main", std::vector<std::string>());
>  
>  just with the simple change of giving it a name.
>  
> @@ -108,12 +108,12 @@
>    @@ -1108,17 +1108,8 @@ static void HandleExtern() {
>     static void HandleTopLevelExpression() {
>       // Evaluate a top-level expression into an anonymous function.
> -     if (FunctionAST *F = ParseTopLevelExpr()) {
> -  -    if (Function *LF = F->Codegen()) {
> +     if (auto FnAST = ParseTopLevelExpr()) {
> +  -    if (auto *FnIR = FnAST->Codegen()) {
>    -      // We're just doing this to make sure it executes.
>    -      TheExecutionEngine->finalizeObject();
>    -      // JIT the function, returning a function pointer.
> -  -      void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
> +  -      void *FPtr = TheExecutionEngine->getPointerToFunction(FnIR);
>    -
>    -      // Cast it to the right type (takes no arguments, returns a double) so we
>    -      // can call it as a native function.
> @@ -318,7 +318,8 @@
>  
>  .. code-block:: c++
>  
> -   LHS = new BinaryExprAST(BinLoc, BinOp, LHS, RHS);
> +   LHS = llvm::make_unique<BinaryExprAST>(BinLoc, BinOp, std::move(LHS),
> +                                          std::move(RHS));
>  
>  giving us locations for each of our expressions and variables.
>  
> Index: examples/Kaleidoscope/Chapter2/toy.cpp
> ===================================================================
> --- examples/Kaleidoscope/Chapter2/toy.cpp	(revision 245236)
> +++ examples/Kaleidoscope/Chapter2/toy.cpp	(working copy)
> @@ -1,6 +1,6 @@
> +#include "llvm/ADT/STLExtras.h"
>  #include <cctype>
>  #include <cstdio>
> -#include <cstdlib>
>  #include <map>
>  #include <string>
>  #include <vector>
> @@ -85,29 +85,31 @@
>  /// NumberExprAST - Expression class for numeric literals like "1.0".
>  class NumberExprAST : public ExprAST {
>  public:
> -  NumberExprAST(double val) {}
> +  NumberExprAST(double Val) {}
>  };
>  
>  /// VariableExprAST - Expression class for referencing a variable, like "a".
>  class VariableExprAST : public ExprAST {
>    std::string Name;
>  public:
> -  VariableExprAST(const std::string &name) : Name(name) {}
> +  VariableExprAST(const std::string &Name) : Name(Name) {}
>  };
>  
>  /// BinaryExprAST - Expression class for a binary operator.
>  class BinaryExprAST : public ExprAST {
>  public:
> -  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) {}
> +  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
> +                std::unique_ptr<ExprAST> RHS) {}
>  };
>  
>  /// CallExprAST - Expression class for function calls.
>  class CallExprAST : public ExprAST {
>    std::string Callee;
> -  std::vector<ExprAST*> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>  public:
> -  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
> -    : Callee(callee), Args(args) {}
> +  CallExprAST(const std::string &Callee,
> +              std::vector<std::unique_ptr<ExprAST>> Args)
> +    : Callee(Callee), Args(std::move(Args)) {}
>  };
>  
>  /// PrototypeAST - This class represents the "prototype" for a function,
> @@ -117,15 +119,16 @@
>    std::string Name;
>    std::vector<std::string> Args;
>  public:
> -  PrototypeAST(const std::string &name, const std::vector<std::string> &args)
> -    : Name(name), Args(args) {}
> +  PrototypeAST(const std::string &Name, std::vector<std::string> Args)
> +    : Name(Name), Args(std::move(Args)) {}
>    
>  };
>  
>  /// FunctionAST - This class represents a function definition itself.
>  class FunctionAST {
>  public:
> -  FunctionAST(PrototypeAST *proto, ExprAST *body) {}
> +  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
> +              std::unique_ptr<ExprAST> Body) {}
>  };
>  } // end anonymous namespace
>  
> @@ -157,30 +160,37 @@
>  }
>  
>  /// Error* - These are little helper functions for error handling.
> -ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
> -PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
> +std::unique_ptr<ExprAST> Error(const char *Str) {
> +  fprintf(stderr, "Error: %s\n", Str);
> +  return nullptr;
> +}
> +std::unique_ptr<PrototypeAST> ErrorP(const char *Str) {
> +  Error(Str);
> +  return nullptr;
> +}
>  
> -static ExprAST *ParseExpression();
> +static std::unique_ptr<ExprAST> ParseExpression();
>  
>  /// identifierexpr
>  ///   ::= identifier
>  ///   ::= identifier '(' expression* ')'
> -static ExprAST *ParseIdentifierExpr() {
> +static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>    std::string IdName = IdentifierStr;
>    
>    getNextToken();  // eat identifier.
>    
>    if (CurTok != '(') // Simple variable ref.
> -    return new VariableExprAST(IdName);
> +    return llvm::make_unique<VariableExprAST>(IdName);
>    
>    // Call.
>    getNextToken();  // eat (
> -  std::vector<ExprAST*> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>    if (CurTok != ')') {
>      while (1) {
> -      ExprAST *Arg = ParseExpression();
> -      if (!Arg) return 0;
> -      Args.push_back(Arg);
> +      if (auto Arg = ParseExpression())
> +        Args.push_back(std::move(Arg));
> +      else
> +        return nullptr;
>  
>        if (CurTok == ')') break;
>  
> @@ -193,21 +203,22 @@
>    // Eat the ')'.
>    getNextToken();
>    
> -  return new CallExprAST(IdName, Args);
> +  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
>  }
>  
>  /// numberexpr ::= number
> -static ExprAST *ParseNumberExpr() {
> -  ExprAST *Result = new NumberExprAST(NumVal);
> +static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>    getNextToken(); // consume the number
> -  return Result;
> +  return std::move(Result);
>  }
>  
>  /// parenexpr ::= '(' expression ')'
> -static ExprAST *ParseParenExpr() {
> +static std::unique_ptr<ExprAST> ParseParenExpr() {
>    getNextToken();  // eat (.
> -  ExprAST *V = ParseExpression();
> -  if (!V) return 0;
> +  auto V = ParseExpression();
> +  if (!V)
> +    return nullptr;
>    
>    if (CurTok != ')')
>      return Error("expected ')'");
> @@ -219,7 +230,7 @@
>  ///   ::= identifierexpr
>  ///   ::= numberexpr
>  ///   ::= parenexpr
> -static ExprAST *ParsePrimary() {
> +static std::unique_ptr<ExprAST> ParsePrimary() {
>    switch (CurTok) {
>    default: return Error("unknown token when expecting an expression");
>    case tok_identifier: return ParseIdentifierExpr();
> @@ -230,7 +241,8 @@
>  
>  /// binoprhs
>  ///   ::= ('+' primary)*
> -static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
> +                                              std::unique_ptr<ExprAST> LHS) {
>    // If this is a binop, find its precedence.
>    while (1) {
>      int TokPrec = GetTokPrecedence();
> @@ -245,35 +257,36 @@
>      getNextToken();  // eat binop
>      
>      // Parse the primary expression after the binary operator.
> -    ExprAST *RHS = ParsePrimary();
> -    if (!RHS) return 0;
> +    auto RHS = ParsePrimary();
> +    if (!RHS) return nullptr;
>      
>      // 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, RHS);
> -      if (RHS == 0) return 0;
> +      RHS = ParseBinOpRHS(TokPrec+1, std::move(RHS));
> +      if (!RHS) return nullptr;
>      }
>      
>      // Merge LHS/RHS.
> -    LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS),
> +                                           std::move(RHS));
>    }
>  }
>  
>  /// expression
>  ///   ::= primary binoprhs
>  ///
> -static ExprAST *ParseExpression() {
> -  ExprAST *LHS = ParsePrimary();
> -  if (!LHS) return 0;
> +static std::unique_ptr<ExprAST> ParseExpression() {
> +  auto LHS = ParsePrimary();
> +  if (!LHS) return nullptr;
>    
> -  return ParseBinOpRHS(0, LHS);
> +  return ParseBinOpRHS(0, std::move(LHS));
>  }
>  
>  /// prototype
>  ///   ::= id '(' id* ')'
> -static PrototypeAST *ParsePrototype() {
> +static std::unique_ptr<PrototypeAST> ParsePrototype() {
>    if (CurTok != tok_identifier)
>      return ErrorP("Expected function name in prototype");
>  
> @@ -292,32 +305,34 @@
>    // success.
>    getNextToken();  // eat ')'.
>    
> -  return new PrototypeAST(FnName, ArgNames);
> +  return llvm::make_unique<PrototypeAST>(std::move(FnName),
> +                                         std::move(ArgNames));
>  }
>  
>  /// definition ::= 'def' prototype expression
> -static FunctionAST *ParseDefinition() {
> +static std::unique_ptr<FunctionAST> ParseDefinition() {
>    getNextToken();  // eat def.
> -  PrototypeAST *Proto = ParsePrototype();
> -  if (Proto == 0) return 0;
> +  auto Proto = ParsePrototype();
> +  if (!Proto) return nullptr;
>  
> -  if (ExprAST *E = ParseExpression())
> -    return new FunctionAST(Proto, E);
> -  return 0;
> +  if (auto E = ParseExpression())
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +  return nullptr;
>  }
>  
>  /// toplevelexpr ::= expression
> -static FunctionAST *ParseTopLevelExpr() {
> -  if (ExprAST *E = ParseExpression()) {
> +static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
> +  if (auto E = ParseExpression()) {
>      // Make an anonymous proto.
> -    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -    return new FunctionAST(Proto, E);
> +    auto Proto = llvm::make_unique<PrototypeAST>("",
> +                                                 std::vector<std::string>());
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>    }
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// external ::= 'extern' prototype
> -static PrototypeAST *ParseExtern() {
> +static std::unique_ptr<PrototypeAST> ParseExtern() {
>    getNextToken();  // eat extern.
>    return ParsePrototype();
>  }
> Index: examples/Kaleidoscope/Chapter3/toy.cpp
> ===================================================================
> --- examples/Kaleidoscope/Chapter3/toy.cpp	(revision 245236)
> +++ examples/Kaleidoscope/Chapter3/toy.cpp	(working copy)
> @@ -1,3 +1,4 @@
> +#include "llvm/ADT/STLExtras.h"
>  #include "llvm/IR/Verifier.h"
>  #include "llvm/IR/DerivedTypes.h"
>  #include "llvm/IR/IRBuilder.h"
> @@ -92,7 +93,7 @@
>  class NumberExprAST : public ExprAST {
>    double Val;
>  public:
> -  NumberExprAST(double val) : Val(val) {}
> +  NumberExprAST(double Val) : Val(Val) {}
>    Value *Codegen() override;
>  };
>  
> @@ -100,27 +101,29 @@
>  class VariableExprAST : public ExprAST {
>    std::string Name;
>  public:
> -  VariableExprAST(const std::string &name) : Name(name) {}
> +  VariableExprAST(const std::string &Name) : Name(Name) {}
>    Value *Codegen() override;
>  };
>  
>  /// BinaryExprAST - Expression class for a binary operator.
>  class BinaryExprAST : public ExprAST {
>    char Op;
> -  ExprAST *LHS, *RHS;
> +  std::unique_ptr<ExprAST> LHS, RHS;
>  public:
> -  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs) 
> -    : Op(op), LHS(lhs), RHS(rhs) {}
> +  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
> +                std::unique_ptr<ExprAST> RHS)
> +    : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
>    Value *Codegen() override;
>  };
>  
>  /// CallExprAST - Expression class for function calls.
>  class CallExprAST : public ExprAST {
>    std::string Callee;
> -  std::vector<ExprAST*> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>  public:
> -  CallExprAST(const std::string &callee, std::vector<ExprAST*> &args)
> -    : Callee(callee), Args(args) {}
> +  CallExprAST(const std::string &Callee,
> +              std::vector<std::unique_ptr<ExprAST>> Args)
> +    : Callee(Callee), Args(std::move(Args)) {}
>    Value *Codegen() override;
>  };
>  
> @@ -131,19 +134,20 @@
>    std::string Name;
>    std::vector<std::string> Args;
>  public:
> -  PrototypeAST(const std::string &name, const std::vector<std::string> &args)
> -    : Name(name), Args(args) {}
> +  PrototypeAST(const std::string &Name, std::vector<std::string> Args)
> +    : Name(Name), Args(std::move(Args)) {}
>    
>    Function *Codegen();
>  };
>  
>  /// FunctionAST - This class represents a function definition itself.
>  class FunctionAST {
> -  PrototypeAST *Proto;
> -  ExprAST *Body;
> +  std::unique_ptr<PrototypeAST> Proto;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  FunctionAST(PrototypeAST *proto, ExprAST *body)
> -    : Proto(proto), Body(body) {}
> +  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
> +              std::unique_ptr<ExprAST> Body)
> +    : Proto(std::move(Proto)), Body(std::move(Body)) {}
>    
>    Function *Codegen();
>  };
> @@ -177,31 +181,41 @@
>  }
>  
>  /// Error* - These are little helper functions for error handling.
> -ExprAST *Error(const char *Str) { fprintf(stderr, "Error: %s\n", Str);return 0;}
> -PrototypeAST *ErrorP(const char *Str) { Error(Str); return 0; }
> -FunctionAST *ErrorF(const char *Str) { Error(Str); return 0; }
> +std::unique_ptr<ExprAST> Error(const char *Str) {
> +  fprintf(stderr, "Error: %s\n", Str);
> +  return nullptr;
> +}
> +std::unique_ptr<PrototypeAST> ErrorP(const char *Str) {
> +  Error(Str);
> +  return nullptr;
> +}
> +std::unique_ptr<FunctionAST> ErrorF(const char *Str) {
> +  Error(Str);
> +  return nullptr;
> +}
>  
> -static ExprAST *ParseExpression();
> +static std::unique_ptr<ExprAST> ParseExpression();
>  
>  /// identifierexpr
>  ///   ::= identifier
>  ///   ::= identifier '(' expression* ')'
> -static ExprAST *ParseIdentifierExpr() {
> +static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>    std::string IdName = IdentifierStr;
>    
>    getNextToken();  // eat identifier.
>    
>    if (CurTok != '(') // Simple variable ref.
> -    return new VariableExprAST(IdName);
> +    return llvm::make_unique<VariableExprAST>(IdName);
>    
>    // Call.
>    getNextToken();  // eat (
> -  std::vector<ExprAST*> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>    if (CurTok != ')') {
>      while (1) {
> -      ExprAST *Arg = ParseExpression();
> -      if (!Arg) return 0;
> -      Args.push_back(Arg);
> +      if (auto Arg = ParseExpression())
> +        Args.push_back(std::move(Arg));
> +      else
> +        return nullptr;
>  
>        if (CurTok == ')') break;
>  
> @@ -214,21 +228,22 @@
>    // Eat the ')'.
>    getNextToken();
>    
> -  return new CallExprAST(IdName, Args);
> +  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
>  }
>  
>  /// numberexpr ::= number
> -static ExprAST *ParseNumberExpr() {
> -  ExprAST *Result = new NumberExprAST(NumVal);
> +static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>    getNextToken(); // consume the number
> -  return Result;
> +  return std::move(Result);
>  }
>  
>  /// parenexpr ::= '(' expression ')'
> -static ExprAST *ParseParenExpr() {
> +static std::unique_ptr<ExprAST> ParseParenExpr() {
>    getNextToken();  // eat (.
> -  ExprAST *V = ParseExpression();
> -  if (!V) return 0;
> +  auto V = ParseExpression();
> +  if (!V)
> +    return nullptr;
>    
>    if (CurTok != ')')
>      return Error("expected ')'");
> @@ -240,7 +255,7 @@
>  ///   ::= identifierexpr
>  ///   ::= numberexpr
>  ///   ::= parenexpr
> -static ExprAST *ParsePrimary() {
> +static std::unique_ptr<ExprAST> ParsePrimary() {
>    switch (CurTok) {
>    default: return Error("unknown token when expecting an expression");
>    case tok_identifier: return ParseIdentifierExpr();
> @@ -251,7 +266,8 @@
>  
>  /// binoprhs
>  ///   ::= ('+' primary)*
> -static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
> +                                              std::unique_ptr<ExprAST> LHS) {
>    // If this is a binop, find its precedence.
>    while (1) {
>      int TokPrec = GetTokPrecedence();
> @@ -266,35 +282,36 @@
>      getNextToken();  // eat binop
>      
>      // Parse the primary expression after the binary operator.
> -    ExprAST *RHS = ParsePrimary();
> -    if (!RHS) return 0;
> +    auto RHS = ParsePrimary();
> +    if (!RHS) return nullptr;
>      
>      // 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, RHS);
> -      if (RHS == 0) return 0;
> +      RHS = ParseBinOpRHS(TokPrec+1, std::move(RHS));
> +      if (!RHS) return nullptr;
>      }
>      
>      // Merge LHS/RHS.
> -    LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS),
> +                                           std::move(RHS));
>    }
>  }
>  
>  /// expression
>  ///   ::= primary binoprhs
>  ///
> -static ExprAST *ParseExpression() {
> -  ExprAST *LHS = ParsePrimary();
> -  if (!LHS) return 0;
> +static std::unique_ptr<ExprAST> ParseExpression() {
> +  auto LHS = ParsePrimary();
> +  if (!LHS) return nullptr;
>    
> -  return ParseBinOpRHS(0, LHS);
> +  return ParseBinOpRHS(0, std::move(LHS));
>  }
>  
>  /// prototype
>  ///   ::= id '(' id* ')'
> -static PrototypeAST *ParsePrototype() {
> +static std::unique_ptr<PrototypeAST> ParsePrototype() {
>    if (CurTok != tok_identifier)
>      return ErrorP("Expected function name in prototype");
>  
> @@ -313,32 +330,34 @@
>    // success.
>    getNextToken();  // eat ')'.
>    
> -  return new PrototypeAST(FnName, ArgNames);
> +  return llvm::make_unique<PrototypeAST>(std::move(FnName),
> +                                         std::move(ArgNames));
>  }
>  
>  /// definition ::= 'def' prototype expression
> -static FunctionAST *ParseDefinition() {
> +static std::unique_ptr<FunctionAST> ParseDefinition() {
>    getNextToken();  // eat def.
> -  PrototypeAST *Proto = ParsePrototype();
> -  if (Proto == 0) return 0;
> +  auto Proto = ParsePrototype();
> +  if (!Proto) return nullptr;
>  
> -  if (ExprAST *E = ParseExpression())
> -    return new FunctionAST(Proto, E);
> -  return 0;
> +  if (auto E = ParseExpression())
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +  return nullptr;
>  }
>  
>  /// toplevelexpr ::= expression
> -static FunctionAST *ParseTopLevelExpr() {
> -  if (ExprAST *E = ParseExpression()) {
> +static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
> +  if (auto E = ParseExpression()) {
>      // Make an anonymous proto.
> -    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -    return new FunctionAST(Proto, E);
> +    auto Proto = llvm::make_unique<PrototypeAST>("",
> +                                                 std::vector<std::string>());
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>    }
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// external ::= 'extern' prototype
> -static PrototypeAST *ParseExtern() {
> +static std::unique_ptr<PrototypeAST> ParseExtern() {
>    getNextToken();  // eat extern.
>    return ParsePrototype();
>  }
> @@ -351,7 +370,7 @@
>  static IRBuilder<> Builder(getGlobalContext());
>  static std::map<std::string, Value*> NamedValues;
>  
> -Value *ErrorV(const char *Str) { Error(Str); return 0; }
> +Value *ErrorV(const char *Str) { Error(Str); return nullptr; }
>  
>  Value *NumberExprAST::Codegen() {
>    return ConstantFP::get(getGlobalContext(), APFloat(Val));
> @@ -366,7 +385,7 @@
>  Value *BinaryExprAST::Codegen() {
>    Value *L = LHS->Codegen();
>    Value *R = RHS->Codegen();
> -  if (L == 0 || R == 0) return 0;
> +  if (!L || !R) return nullptr;
>    
>    switch (Op) {
>    case '+': return Builder.CreateFAdd(L, R, "addtmp");
> @@ -384,7 +403,7 @@
>  Value *CallExprAST::Codegen() {
>    // Look up the name in the global module table.
>    Function *CalleeF = TheModule->getFunction(Callee);
> -  if (CalleeF == 0)
> +  if (!CalleeF)
>      return ErrorV("Unknown function referenced");
>    
>    // If argument mismatch error.
> @@ -394,7 +413,7 @@
>    std::vector<Value*> ArgsV;
>    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
>      ArgsV.push_back(Args[i]->Codegen());
> -    if (ArgsV.back() == 0) return 0;
> +    if (!ArgsV.back()) return nullptr;
>    }
>    
>    return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
> @@ -407,7 +426,8 @@
>    FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
>                                         Doubles, false);
>    
> -  Function *F = Function::Create(FT, Function::ExternalLinkage, Name, TheModule);
> +  Function *F = Function::Create(FT, Function::ExternalLinkage, Name,
> +                                 TheModule);
>    
>    // If F conflicted, there was already something named 'Name'.  If it has a
>    // body, don't allow redefinition or reextern.
> @@ -419,13 +439,13 @@
>      // If F already has a body, reject this.
>      if (!F->empty()) {
>        ErrorF("redefinition of function");
> -      return 0;
> +      return nullptr;
>      }
>      
>      // If F took a different number of args, reject.
>      if (F->arg_size() != Args.size()) {
>        ErrorF("redefinition of function with different # args");
> -      return 0;
> +      return nullptr;
>      }
>    }
>    
> @@ -446,8 +466,8 @@
>    NamedValues.clear();
>    
>    Function *TheFunction = Proto->Codegen();
> -  if (TheFunction == 0)
> -    return 0;
> +  if (!TheFunction)
> +    return nullptr;
>    
>    // Create a new basic block to start insertion into.
>    BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
> @@ -465,7 +485,7 @@
>    
>    // Error reading body, remove function.
>    TheFunction->eraseFromParent();
> -  return 0;
> +  return nullptr;
>  }
>  
>  //===----------------------------------------------------------------------===//
> @@ -473,10 +493,10 @@
>  //===----------------------------------------------------------------------===//
>  
>  static void HandleDefinition() {
> -  if (FunctionAST *F = ParseDefinition()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseDefinition()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        fprintf(stderr, "Read function definition:");
> -      LF->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -485,10 +505,10 @@
>  }
>  
>  static void HandleExtern() {
> -  if (PrototypeAST *P = ParseExtern()) {
> -    if (Function *F = P->Codegen()) {
> +  if (auto ProtoAST = ParseExtern()) {
> +    if (auto *FnIR = ProtoAST->Codegen()) {
>        fprintf(stderr, "Read extern: ");
> -      F->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -498,10 +518,10 @@
>  
>  static void HandleTopLevelExpression() {
>    // Evaluate a top-level expression into an anonymous function.
> -  if (FunctionAST *F = ParseTopLevelExpr()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseTopLevelExpr()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        fprintf(stderr, "Read top-level expression:");
> -      LF->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -553,7 +573,8 @@
>    getNextToken();
>  
>    // Make the module, which holds all the code.
> -  TheModule = new Module("my cool jit", Context);
> +  std::unique_ptr<Module> Owner = llvm::make_unique<Module>("my cool jit", Context);
> +  TheModule = Owner.get();
>  
>    // Run the main "interpreter loop" now.
>    MainLoop();
> Index: examples/Kaleidoscope/Chapter4/toy.cpp
> ===================================================================
> --- examples/Kaleidoscope/Chapter4/toy.cpp	(revision 245236)
> +++ examples/Kaleidoscope/Chapter4/toy.cpp	(working copy)
> @@ -1,3 +1,4 @@
> +#include "llvm/ADT/STLExtras.h"
>  #include "llvm/Analysis/BasicAliasAnalysis.h"
>  #include "llvm/Analysis/Passes.h"
>  #include "llvm/ExecutionEngine/ExecutionEngine.h"
> @@ -105,40 +106,38 @@
>  /// NumberExprAST - Expression class for numeric literals like "1.0".
>  class NumberExprAST : public ExprAST {
>    double Val;
> -
>  public:
> -  NumberExprAST(double val) : Val(val) {}
> +  NumberExprAST(double Val) : Val(Val) {}
>    Value *Codegen() override;
>  };
>  
>  /// VariableExprAST - Expression class for referencing a variable, like "a".
>  class VariableExprAST : public ExprAST {
>    std::string Name;
> -
>  public:
> -  VariableExprAST(const std::string &name) : Name(name) {}
> +  VariableExprAST(const std::string &Name) : Name(Name) {}
>    Value *Codegen() override;
>  };
>  
>  /// BinaryExprAST - Expression class for a binary operator.
>  class BinaryExprAST : public ExprAST {
>    char Op;
> -  ExprAST *LHS, *RHS;
> -
> +  std::unique_ptr<ExprAST> LHS, RHS;
>  public:
> -  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
> -      : Op(op), LHS(lhs), RHS(rhs) {}
> +  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
> +                std::unique_ptr<ExprAST> RHS)
> +      : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
>    Value *Codegen() override;
>  };
>  
>  /// CallExprAST - Expression class for function calls.
>  class CallExprAST : public ExprAST {
>    std::string Callee;
> -  std::vector<ExprAST *> Args;
> -
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>  public:
> -  CallExprAST(const std::string &callee, std::vector<ExprAST *> &args)
> -      : Callee(callee), Args(args) {}
> +  CallExprAST(const std::string &Callee,
> +              std::vector<std::unique_ptr<ExprAST>> Args)
> +      : Callee(Callee), Args(std::move(Args)) {}
>    Value *Codegen() override;
>  };
>  
> @@ -148,22 +147,20 @@
>  class PrototypeAST {
>    std::string Name;
>    std::vector<std::string> Args;
> -
>  public:
> -  PrototypeAST(const std::string &name, const std::vector<std::string> &args)
> -      : Name(name), Args(args) {}
> -
> +  PrototypeAST(const std::string &name, std::vector<std::string> Args)
> +      : Name(name), Args(std::move(Args)) {}
>    Function *Codegen();
>  };
>  
>  /// FunctionAST - This class represents a function definition itself.
>  class FunctionAST {
> -  PrototypeAST *Proto;
> -  ExprAST *Body;
> -
> +  std::unique_ptr<PrototypeAST> Proto;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  FunctionAST(PrototypeAST *proto, ExprAST *body) : Proto(proto), Body(body) {}
> -
> +  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
> +              std::unique_ptr<ExprAST> Body)
> +    : Proto(std::move(Proto)), Body(std::move(Body)) {}
>    Function *Codegen();
>  };
>  } // end anonymous namespace
> @@ -195,41 +192,41 @@
>  }
>  
>  /// Error* - These are little helper functions for error handling.
> -ExprAST *Error(const char *Str) {
> +std::unique_ptr<ExprAST> Error(const char *Str) {
>    fprintf(stderr, "Error: %s\n", Str);
> -  return 0;
> +  return nullptr;
>  }
> -PrototypeAST *ErrorP(const char *Str) {
> +std::unique_ptr<PrototypeAST> ErrorP(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
> -FunctionAST *ErrorF(const char *Str) {
> +std::unique_ptr<FunctionAST> ErrorF(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
> -static ExprAST *ParseExpression();
> +static std::unique_ptr<ExprAST> ParseExpression();
>  
>  /// identifierexpr
>  ///   ::= identifier
>  ///   ::= identifier '(' expression* ')'
> -static ExprAST *ParseIdentifierExpr() {
> +static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>    std::string IdName = IdentifierStr;
>  
>    getNextToken(); // eat identifier.
>  
>    if (CurTok != '(') // Simple variable ref.
> -    return new VariableExprAST(IdName);
> +    return llvm::make_unique<VariableExprAST>(IdName);
>  
>    // Call.
>    getNextToken(); // eat (
> -  std::vector<ExprAST *> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>    if (CurTok != ')') {
>      while (1) {
> -      ExprAST *Arg = ParseExpression();
> -      if (!Arg)
> -        return 0;
> -      Args.push_back(Arg);
> +      if (auto Arg = ParseExpression())
> +        Args.push_back(std::move(Arg));
> +      else
> +        return nullptr;
>  
>        if (CurTok == ')')
>          break;
> @@ -243,22 +240,22 @@
>    // Eat the ')'.
>    getNextToken();
>  
> -  return new CallExprAST(IdName, Args);
> +  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
>  }
>  
>  /// numberexpr ::= number
> -static ExprAST *ParseNumberExpr() {
> -  ExprAST *Result = new NumberExprAST(NumVal);
> +static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>    getNextToken(); // consume the number
> -  return Result;
> +  return std::move(Result);
>  }
>  
>  /// parenexpr ::= '(' expression ')'
> -static ExprAST *ParseParenExpr() {
> +static std::unique_ptr<ExprAST> ParseParenExpr() {
>    getNextToken(); // eat (.
> -  ExprAST *V = ParseExpression();
> +  auto V = ParseExpression();
>    if (!V)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != ')')
>      return Error("expected ')'");
> @@ -270,7 +267,7 @@
>  ///   ::= identifierexpr
>  ///   ::= numberexpr
>  ///   ::= parenexpr
> -static ExprAST *ParsePrimary() {
> +static std::unique_ptr<ExprAST> ParsePrimary() {
>    switch (CurTok) {
>    default:
>      return Error("unknown token when expecting an expression");
> @@ -285,7 +282,8 @@
>  
>  /// binoprhs
>  ///   ::= ('+' primary)*
> -static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
> +                                              std::unique_ptr<ExprAST> LHS) {
>    // If this is a binop, find its precedence.
>    while (1) {
>      int TokPrec = GetTokPrecedence();
> @@ -300,38 +298,39 @@
>      getNextToken(); // eat binop
>  
>      // Parse the primary expression after the binary operator.
> -    ExprAST *RHS = ParsePrimary();
> +    auto RHS = ParsePrimary();
>      if (!RHS)
> -      return 0;
> +      return nullptr;
>  
>      // 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, RHS);
> -      if (RHS == 0)
> -        return 0;
> +      RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
> +      if (!RHS)
> +        return nullptr;
>      }
>  
>      // Merge LHS/RHS.
> -    LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS),
> +                                           std::move(RHS));
>    }
>  }
>  
>  /// expression
>  ///   ::= primary binoprhs
>  ///
> -static ExprAST *ParseExpression() {
> -  ExprAST *LHS = ParsePrimary();
> +static std::unique_ptr<ExprAST> ParseExpression() {
> +  auto LHS = ParsePrimary();
>    if (!LHS)
> -    return 0;
> +    return nullptr;
>  
> -  return ParseBinOpRHS(0, LHS);
> +  return ParseBinOpRHS(0, std::move(LHS));
>  }
>  
>  /// prototype
>  ///   ::= id '(' id* ')'
> -static PrototypeAST *ParsePrototype() {
> +static std::unique_ptr<PrototypeAST> ParsePrototype() {
>    if (CurTok != tok_identifier)
>      return ErrorP("Expected function name in prototype");
>  
> @@ -350,33 +349,34 @@
>    // success.
>    getNextToken(); // eat ')'.
>  
> -  return new PrototypeAST(FnName, ArgNames);
> +  return llvm::make_unique<PrototypeAST>(FnName, std::move(ArgNames));
>  }
>  
>  /// definition ::= 'def' prototype expression
> -static FunctionAST *ParseDefinition() {
> +static std::unique_ptr<FunctionAST> ParseDefinition() {
>    getNextToken(); // eat def.
> -  PrototypeAST *Proto = ParsePrototype();
> -  if (Proto == 0)
> -    return 0;
> +  auto Proto = ParsePrototype();
> +  if (!Proto)
> +    return nullptr;
>  
> -  if (ExprAST *E = ParseExpression())
> -    return new FunctionAST(Proto, E);
> -  return 0;
> +  if (auto E = ParseExpression())
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +  return nullptr;
>  }
>  
>  /// toplevelexpr ::= expression
> -static FunctionAST *ParseTopLevelExpr() {
> -  if (ExprAST *E = ParseExpression()) {
> +static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
> +  if (auto E = ParseExpression()) {
>      // Make an anonymous proto.
> -    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -    return new FunctionAST(Proto, E);
> +    auto Proto = llvm::make_unique<PrototypeAST>("",
> +                                                 std::vector<std::string>());
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>    }
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// external ::= 'extern' prototype
> -static PrototypeAST *ParseExtern() {
> +static std::unique_ptr<PrototypeAST> ParseExtern() {
>    getNextToken(); // eat extern.
>    return ParsePrototype();
>  }
> @@ -505,7 +505,7 @@
>        Function *PF = OpenModule->getFunction(FnName);
>        if (PF && !PF->empty()) {
>          ErrorF("redefinition of function across modules");
> -        return 0;
> +        return nullptr;
>        }
>  
>        // If we don't have a prototype yet, create one.
> @@ -626,7 +626,7 @@
>  
>  Value *ErrorV(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
>  Value *NumberExprAST::Codegen() {
> @@ -642,8 +642,8 @@
>  Value *BinaryExprAST::Codegen() {
>    Value *L = LHS->Codegen();
>    Value *R = RHS->Codegen();
> -  if (L == 0 || R == 0)
> -    return 0;
> +  if (!L || !R)
> +    return nullptr;
>  
>    switch (Op) {
>    case '+':
> @@ -665,7 +665,7 @@
>  Value *CallExprAST::Codegen() {
>    // Look up the name in the global module table.
>    Function *CalleeF = JITHelper->getFunction(Callee);
> -  if (CalleeF == 0)
> +  if (!CalleeF)
>      return ErrorV("Unknown function referenced");
>  
>    // If argument mismatch error.
> @@ -675,8 +675,8 @@
>    std::vector<Value *> ArgsV;
>    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
>      ArgsV.push_back(Args[i]->Codegen());
> -    if (ArgsV.back() == 0)
> -      return 0;
> +    if (!ArgsV.back())
> +      return nullptr;
>    }
>  
>    return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
> @@ -704,13 +704,13 @@
>      // If F already has a body, reject this.
>      if (!F->empty()) {
>        ErrorF("redefinition of function");
> -      return 0;
> +      return nullptr;
>      }
>  
>      // If F took a different number of args, reject.
>      if (F->arg_size() != Args.size()) {
>        ErrorF("redefinition of function with different # args");
> -      return 0;
> +      return nullptr;
>      }
>    }
>  
> @@ -731,8 +731,8 @@
>    NamedValues.clear();
>  
>    Function *TheFunction = Proto->Codegen();
> -  if (TheFunction == 0)
> -    return 0;
> +  if (!TheFunction)
> +    return nullptr;
>  
>    // Create a new basic block to start insertion into.
>    BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
> @@ -750,7 +750,7 @@
>  
>    // Error reading body, remove function.
>    TheFunction->eraseFromParent();
> -  return 0;
> +  return nullptr;
>  }
>  
>  //===----------------------------------------------------------------------===//
> @@ -758,10 +758,10 @@
>  //===----------------------------------------------------------------------===//
>  
>  static void HandleDefinition() {
> -  if (FunctionAST *F = ParseDefinition()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseDefinition()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        fprintf(stderr, "Read function definition:");
> -      LF->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -770,10 +770,10 @@
>  }
>  
>  static void HandleExtern() {
> -  if (PrototypeAST *P = ParseExtern()) {
> -    if (Function *F = P->Codegen()) {
> +  if (auto ProtoAST = ParseExtern()) {
> +    if (auto *FnIR = ProtoAST->Codegen()) {
>        fprintf(stderr, "Read extern: ");
> -      F->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -783,10 +783,10 @@
>  
>  static void HandleTopLevelExpression() {
>    // Evaluate a top-level expression into an anonymous function.
> -  if (FunctionAST *F = ParseTopLevelExpr()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseTopLevelExpr()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        // JIT the function, returning a function pointer.
> -      void *FPtr = JITHelper->getPointerToFunction(LF);
> +      void *FPtr = JITHelper->getPointerToFunction(FnIR);
>  
>        // Cast it to the right type (takes no arguments, returns a double) so we
>        // can call it as a native function.
> Index: examples/Kaleidoscope/Chapter5/toy.cpp
> ===================================================================
> --- examples/Kaleidoscope/Chapter5/toy.cpp	(revision 245236)
> +++ examples/Kaleidoscope/Chapter5/toy.cpp	(working copy)
> @@ -123,62 +123,61 @@
>  /// NumberExprAST - Expression class for numeric literals like "1.0".
>  class NumberExprAST : public ExprAST {
>    double Val;
> -
>  public:
> -  NumberExprAST(double val) : Val(val) {}
> +  NumberExprAST(double Val) : Val(Val) {}
>    Value *Codegen() override;
>  };
>  
>  /// VariableExprAST - Expression class for referencing a variable, like "a".
>  class VariableExprAST : public ExprAST {
>    std::string Name;
> -
>  public:
> -  VariableExprAST(const std::string &name) : Name(name) {}
> +  VariableExprAST(const std::string &Name) : Name(Name) {}
>    Value *Codegen() override;
>  };
>  
>  /// BinaryExprAST - Expression class for a binary operator.
>  class BinaryExprAST : public ExprAST {
>    char Op;
> -  ExprAST *LHS, *RHS;
> -
> +  std::unique_ptr<ExprAST> LHS, RHS;
>  public:
> -  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
> -      : Op(op), LHS(lhs), RHS(rhs) {}
> +  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
> +                std::unique_ptr<ExprAST> RHS)
> +      : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
>    Value *Codegen() override;
>  };
>  
>  /// CallExprAST - Expression class for function calls.
>  class CallExprAST : public ExprAST {
>    std::string Callee;
> -  std::vector<ExprAST *> Args;
> -
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>  public:
> -  CallExprAST(const std::string &callee, std::vector<ExprAST *> &args)
> -      : Callee(callee), Args(args) {}
> +  CallExprAST(const std::string &Callee,
> +              std::vector<std::unique_ptr<ExprAST>> Args)
> +      : Callee(Callee), Args(std::move(Args)) {}
>    Value *Codegen() override;
>  };
>  
>  /// IfExprAST - Expression class for if/then/else.
>  class IfExprAST : public ExprAST {
> -  ExprAST *Cond, *Then, *Else;
> -
> +  std::unique_ptr<ExprAST> Cond, Then, Else;
>  public:
> -  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
> -      : Cond(cond), Then(then), Else(_else) {}
> +  IfExprAST(std::unique_ptr<ExprAST> Cond, std::unique_ptr<ExprAST> Then,
> +            std::unique_ptr<ExprAST> Else)
> +      : Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}
>    Value *Codegen() override;
>  };
>  
>  /// ForExprAST - Expression class for for/in.
>  class ForExprAST : public ExprAST {
>    std::string VarName;
> -  ExprAST *Start, *End, *Step, *Body;
> -
> +  std::unique_ptr<ExprAST> Start, End, Step, Body;
>  public:
> -  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
> -             ExprAST *step, ExprAST *body)
> -      : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
> +  ForExprAST(const std::string &VarName, std::unique_ptr<ExprAST> Start,
> +             std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
> +             std::unique_ptr<ExprAST> Body)
> +      : VarName(VarName), Start(std::move(Start)), End(std::move(End)),
> +        Step(std::move(Step)), Body(std::move(Body)) {}
>    Value *Codegen() override;
>  };
>  
> @@ -188,22 +187,20 @@
>  class PrototypeAST {
>    std::string Name;
>    std::vector<std::string> Args;
> -
>  public:
> -  PrototypeAST(const std::string &name, const std::vector<std::string> &args)
> -      : Name(name), Args(args) {}
> -
> +  PrototypeAST(const std::string &name, std::vector<std::string> Args)
> +      : Name(name), Args(std::move(Args)) {}
>    Function *Codegen();
>  };
>  
>  /// FunctionAST - This class represents a function definition itself.
>  class FunctionAST {
> -  PrototypeAST *Proto;
> -  ExprAST *Body;
> -
> +  std::unique_ptr<PrototypeAST> Proto;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  FunctionAST(PrototypeAST *proto, ExprAST *body) : Proto(proto), Body(body) {}
> -
> +  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
> +              std::unique_ptr<ExprAST> Body)
> +    : Proto(std::move(Proto)), Body(std::move(Body)) {}
>    Function *Codegen();
>  };
>  } // end anonymous namespace
> @@ -235,41 +232,41 @@
>  }
>  
>  /// Error* - These are little helper functions for error handling.
> -ExprAST *Error(const char *Str) {
> +std::unique_ptr<ExprAST> Error(const char *Str) {
>    fprintf(stderr, "Error: %s\n", Str);
> -  return 0;
> +  return nullptr;
>  }
> -PrototypeAST *ErrorP(const char *Str) {
> +std::unique_ptr<PrototypeAST> ErrorP(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
> -FunctionAST *ErrorF(const char *Str) {
> +std::unique_ptr<FunctionAST> ErrorF(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
> -static ExprAST *ParseExpression();
> +static std::unique_ptr<ExprAST> ParseExpression();
>  
>  /// identifierexpr
>  ///   ::= identifier
>  ///   ::= identifier '(' expression* ')'
> -static ExprAST *ParseIdentifierExpr() {
> +static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>    std::string IdName = IdentifierStr;
>  
>    getNextToken(); // eat identifier.
>  
>    if (CurTok != '(') // Simple variable ref.
> -    return new VariableExprAST(IdName);
> +    return llvm::make_unique<VariableExprAST>(IdName);
>  
>    // Call.
>    getNextToken(); // eat (
> -  std::vector<ExprAST *> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>    if (CurTok != ')') {
>      while (1) {
> -      ExprAST *Arg = ParseExpression();
> -      if (!Arg)
> -        return 0;
> -      Args.push_back(Arg);
> +      if (auto Arg = ParseExpression())
> +        Args.push_back(std::move(Arg));
> +      else
> +        return nullptr;
>  
>        if (CurTok == ')')
>          break;
> @@ -283,22 +280,22 @@
>    // Eat the ')'.
>    getNextToken();
>  
> -  return new CallExprAST(IdName, Args);
> +  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
>  }
>  
>  /// numberexpr ::= number
> -static ExprAST *ParseNumberExpr() {
> -  ExprAST *Result = new NumberExprAST(NumVal);
> +static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>    getNextToken(); // consume the number
> -  return Result;
> +  return std::move(Result);
>  }
>  
>  /// parenexpr ::= '(' expression ')'
> -static ExprAST *ParseParenExpr() {
> +static std::unique_ptr<ExprAST> ParseParenExpr() {
>    getNextToken(); // eat (.
> -  ExprAST *V = ParseExpression();
> +  auto V = ParseExpression();
>    if (!V)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != ')')
>      return Error("expected ')'");
> @@ -307,36 +304,37 @@
>  }
>  
>  /// ifexpr ::= 'if' expression 'then' expression 'else' expression
> -static ExprAST *ParseIfExpr() {
> +static std::unique_ptr<ExprAST> ParseIfExpr() {
>    getNextToken(); // eat the if.
>  
>    // condition.
> -  ExprAST *Cond = ParseExpression();
> +  auto Cond = ParseExpression();
>    if (!Cond)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != tok_then)
>      return Error("expected then");
>    getNextToken(); // eat the then
>  
> -  ExprAST *Then = ParseExpression();
> -  if (Then == 0)
> -    return 0;
> +  auto Then = ParseExpression();
> +  if (!Then)
> +    return nullptr;
>  
>    if (CurTok != tok_else)
>      return Error("expected else");
>  
>    getNextToken();
>  
> -  ExprAST *Else = ParseExpression();
> +  auto Else = ParseExpression();
>    if (!Else)
> -    return 0;
> +    return nullptr;
>  
> -  return new IfExprAST(Cond, Then, Else);
> +  return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
> +                                      std::move(Else));
>  }
>  
>  /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
> -static ExprAST *ParseForExpr() {
> +static std::unique_ptr<ExprAST> ParseForExpr() {
>    getNextToken(); // eat the for.
>  
>    if (CurTok != tok_identifier)
> @@ -349,35 +347,36 @@
>      return Error("expected '=' after for");
>    getNextToken(); // eat '='.
>  
> -  ExprAST *Start = ParseExpression();
> -  if (Start == 0)
> -    return 0;
> +  auto Start = ParseExpression();
> +  if (!Start)
> +    return nullptr;
>    if (CurTok != ',')
>      return Error("expected ',' after for start value");
>    getNextToken();
>  
> -  ExprAST *End = ParseExpression();
> -  if (End == 0)
> -    return 0;
> +  auto End = ParseExpression();
> +  if (!End)
> +    return nullptr;
>  
>    // The step value is optional.
> -  ExprAST *Step = 0;
> +  std::unique_ptr<ExprAST> Step;
>    if (CurTok == ',') {
>      getNextToken();
>      Step = ParseExpression();
> -    if (Step == 0)
> -      return 0;
> +    if (!Step)
> +      return nullptr;
>    }
>  
>    if (CurTok != tok_in)
>      return Error("expected 'in' after for");
>    getNextToken(); // eat 'in'.
>  
> -  ExprAST *Body = ParseExpression();
> -  if (Body == 0)
> -    return 0;
> +  auto Body = ParseExpression();
> +  if (!Body)
> +    return nullptr;
>  
> -  return new ForExprAST(IdName, Start, End, Step, Body);
> +  return llvm::make_unique<ForExprAST>(IdName, std::move(Start), std::move(End),
> +                                       std::move(Step), std::move(Body));
>  }
>  
>  /// primary
> @@ -386,7 +385,7 @@
>  ///   ::= parenexpr
>  ///   ::= ifexpr
>  ///   ::= forexpr
> -static ExprAST *ParsePrimary() {
> +static std::unique_ptr<ExprAST> ParsePrimary() {
>    switch (CurTok) {
>    default:
>      return Error("unknown token when expecting an expression");
> @@ -405,7 +404,8 @@
>  
>  /// binoprhs
>  ///   ::= ('+' primary)*
> -static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec,
> +                                              std::unique_ptr<ExprAST> LHS) {
>    // If this is a binop, find its precedence.
>    while (1) {
>      int TokPrec = GetTokPrecedence();
> @@ -420,38 +420,39 @@
>      getNextToken(); // eat binop
>  
>      // Parse the primary expression after the binary operator.
> -    ExprAST *RHS = ParsePrimary();
> +    auto RHS = ParsePrimary();
>      if (!RHS)
> -      return 0;
> +      return nullptr;
>  
>      // 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, RHS);
> -      if (RHS == 0)
> -        return 0;
> +      RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
> +      if (!RHS)
> +        return nullptr;
>      }
>  
>      // Merge LHS/RHS.
> -    LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS),
> +                                           std::move(RHS));
>    }
>  }
>  
>  /// expression
>  ///   ::= primary binoprhs
>  ///
> -static ExprAST *ParseExpression() {
> -  ExprAST *LHS = ParsePrimary();
> +static std::unique_ptr<ExprAST> ParseExpression() {
> +  auto LHS = ParsePrimary();
>    if (!LHS)
> -    return 0;
> +    return nullptr;
>  
> -  return ParseBinOpRHS(0, LHS);
> +  return ParseBinOpRHS(0, std::move(LHS));
>  }
>  
>  /// prototype
>  ///   ::= id '(' id* ')'
> -static PrototypeAST *ParsePrototype() {
> +static std::unique_ptr<PrototypeAST> ParsePrototype() {
>    if (CurTok != tok_identifier)
>      return ErrorP("Expected function name in prototype");
>  
> @@ -470,33 +471,34 @@
>    // success.
>    getNextToken(); // eat ')'.
>  
> -  return new PrototypeAST(FnName, ArgNames);
> +  return llvm::make_unique<PrototypeAST>(FnName, std::move(ArgNames));
>  }
>  
>  /// definition ::= 'def' prototype expression
> -static FunctionAST *ParseDefinition() {
> +static std::unique_ptr<FunctionAST> ParseDefinition() {
>    getNextToken(); // eat def.
> -  PrototypeAST *Proto = ParsePrototype();
> -  if (Proto == 0)
> -    return 0;
> +  auto Proto = ParsePrototype();
> +  if (!Proto)
> +    return nullptr;
>  
> -  if (ExprAST *E = ParseExpression())
> -    return new FunctionAST(Proto, E);
> -  return 0;
> +  if (auto E = ParseExpression())
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +  return nullptr;
>  }
>  
>  /// toplevelexpr ::= expression
> -static FunctionAST *ParseTopLevelExpr() {
> -  if (ExprAST *E = ParseExpression()) {
> +static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
> +  if (auto E = ParseExpression()) {
>      // Make an anonymous proto.
> -    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -    return new FunctionAST(Proto, E);
> +    auto Proto = llvm::make_unique<PrototypeAST>("",
> +                                                 std::vector<std::string>());
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>    }
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// external ::= 'extern' prototype
> -static PrototypeAST *ParseExtern() {
> +static std::unique_ptr<PrototypeAST> ParseExtern() {
>    getNextToken(); // eat extern.
>    return ParsePrototype();
>  }
> @@ -512,7 +514,7 @@
>  
>  Value *ErrorV(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
>  Value *NumberExprAST::Codegen() {
> @@ -528,8 +530,8 @@
>  Value *BinaryExprAST::Codegen() {
>    Value *L = LHS->Codegen();
>    Value *R = RHS->Codegen();
> -  if (L == 0 || R == 0)
> -    return 0;
> +  if (!L || !R)
> +    return nullptr;
>  
>    switch (Op) {
>    case '+':
> @@ -551,7 +553,7 @@
>  Value *CallExprAST::Codegen() {
>    // Look up the name in the global module table.
>    Function *CalleeF = TheModule->getFunction(Callee);
> -  if (CalleeF == 0)
> +  if (!CalleeF)
>      return ErrorV("Unknown function referenced");
>  
>    // If argument mismatch error.
> @@ -561,8 +563,8 @@
>    std::vector<Value *> ArgsV;
>    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
>      ArgsV.push_back(Args[i]->Codegen());
> -    if (ArgsV.back() == 0)
> -      return 0;
> +    if (!ArgsV.back())
> +      return nullptr;
>    }
>  
>    return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
> @@ -570,8 +572,8 @@
>  
>  Value *IfExprAST::Codegen() {
>    Value *CondV = Cond->Codegen();
> -  if (CondV == 0)
> -    return 0;
> +  if (!CondV)
> +    return nullptr;
>  
>    // Convert condition to a bool by comparing equal to 0.0.
>    CondV = Builder.CreateFCmpONE(
> @@ -592,8 +594,8 @@
>    Builder.SetInsertPoint(ThenBB);
>  
>    Value *ThenV = Then->Codegen();
> -  if (ThenV == 0)
> -    return 0;
> +  if (!ThenV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
> @@ -604,8 +606,8 @@
>    Builder.SetInsertPoint(ElseBB);
>  
>    Value *ElseV = Else->Codegen();
> -  if (ElseV == 0)
> -    return 0;
> +  if (!ElseV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
> @@ -641,8 +643,8 @@
>  
>    // Emit the start code first, without 'variable' in scope.
>    Value *StartVal = Start->Codegen();
> -  if (StartVal == 0)
> -    return 0;
> +  if (!StartVal)
> +    return nullptr;
>  
>    // Make the new basic block for the loop header, inserting after current
>    // block.
> @@ -670,15 +672,15 @@
>    // Emit the body of the loop.  This, like any other expr, can change the
>    // current BB.  Note that we ignore the value computed by the body, but don't
>    // allow an error.
> -  if (Body->Codegen() == 0)
> -    return 0;
> +  if (!Body->Codegen())
> +    return nullptr;
>  
>    // Emit the step value.
>    Value *StepVal;
>    if (Step) {
>      StepVal = Step->Codegen();
> -    if (StepVal == 0)
> -      return 0;
> +    if (!StepVal)
> +      return nullptr;
>    } else {
>      // If not specified, use 1.0.
>      StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
> @@ -688,7 +690,7 @@
>  
>    // Compute the end condition.
>    Value *EndCond = End->Codegen();
> -  if (EndCond == 0)
> +  if (!EndCond)
>      return EndCond;
>  
>    // Convert condition to a bool by comparing equal to 0.0.
> @@ -739,13 +741,13 @@
>      // If F already has a body, reject this.
>      if (!F->empty()) {
>        ErrorF("redefinition of function");
> -      return 0;
> +      return nullptr;
>      }
>  
>      // If F took a different number of args, reject.
>      if (F->arg_size() != Args.size()) {
>        ErrorF("redefinition of function with different # args");
> -      return 0;
> +      return nullptr;
>      }
>    }
>  
> @@ -766,8 +768,8 @@
>    NamedValues.clear();
>  
>    Function *TheFunction = Proto->Codegen();
> -  if (TheFunction == 0)
> -    return 0;
> +  if (!TheFunction)
> +    return nullptr;
>  
>    // Create a new basic block to start insertion into.
>    BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
> @@ -788,7 +790,7 @@
>  
>    // Error reading body, remove function.
>    TheFunction->eraseFromParent();
> -  return 0;
> +  return nullptr;
>  }
>  
>  //===----------------------------------------------------------------------===//
> @@ -798,10 +800,10 @@
>  static ExecutionEngine *TheExecutionEngine;
>  
>  static void HandleDefinition() {
> -  if (FunctionAST *F = ParseDefinition()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseDefinition()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        fprintf(stderr, "Read function definition:");
> -      LF->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -810,10 +812,10 @@
>  }
>  
>  static void HandleExtern() {
> -  if (PrototypeAST *P = ParseExtern()) {
> -    if (Function *F = P->Codegen()) {
> +  if (auto ProtoAST = ParseExtern()) {
> +    if (auto *FnIR = ProtoAST->Codegen()) {
>        fprintf(stderr, "Read extern: ");
> -      F->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -823,11 +825,11 @@
>  
>  static void HandleTopLevelExpression() {
>    // Evaluate a top-level expression into an anonymous function.
> -  if (FunctionAST *F = ParseTopLevelExpr()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseTopLevelExpr()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        TheExecutionEngine->finalizeObject();
>        // JIT the function, returning a function pointer.
> -      void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
> +      void *FPtr = TheExecutionEngine->getPointerToFunction(FnIR);
>  
>        // Cast it to the right type (takes no arguments, returns a double) so we
>        // can call it as a native function.
> Index: examples/Kaleidoscope/Chapter6/toy.cpp
> ===================================================================
> --- examples/Kaleidoscope/Chapter6/toy.cpp	(revision 245236)
> +++ examples/Kaleidoscope/Chapter6/toy.cpp	(working copy)
> @@ -131,73 +131,72 @@
>  /// NumberExprAST - Expression class for numeric literals like "1.0".
>  class NumberExprAST : public ExprAST {
>    double Val;
> -
>  public:
> -  NumberExprAST(double val) : Val(val) {}
> +  NumberExprAST(double Val) : Val(Val) {}
>    Value *Codegen() override;
>  };
>  
>  /// VariableExprAST - Expression class for referencing a variable, like "a".
>  class VariableExprAST : public ExprAST {
>    std::string Name;
> -
>  public:
> -  VariableExprAST(const std::string &name) : Name(name) {}
> +  VariableExprAST(const std::string &Name) : Name(Name) {}
>    Value *Codegen() override;
>  };
>  
>  /// UnaryExprAST - Expression class for a unary operator.
>  class UnaryExprAST : public ExprAST {
>    char Opcode;
> -  ExprAST *Operand;
> +  std::unique_ptr<ExprAST> Operand;
>  
>  public:
> -  UnaryExprAST(char opcode, ExprAST *operand)
> -      : Opcode(opcode), Operand(operand) {}
> +  UnaryExprAST(char Opcode, std::unique_ptr<ExprAST> Operand)
> +      : Opcode(Opcode), Operand(std::move(Operand)) {}
>    Value *Codegen() override;
>  };
>  
>  /// BinaryExprAST - Expression class for a binary operator.
>  class BinaryExprAST : public ExprAST {
>    char Op;
> -  ExprAST *LHS, *RHS;
> -
> +  std::unique_ptr<ExprAST> LHS, RHS;
>  public:
> -  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
> -      : Op(op), LHS(lhs), RHS(rhs) {}
> +  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
> +                std::unique_ptr<ExprAST> RHS)
> +      : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
>    Value *Codegen() override;
>  };
>  
>  /// CallExprAST - Expression class for function calls.
>  class CallExprAST : public ExprAST {
>    std::string Callee;
> -  std::vector<ExprAST *> Args;
> -
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>  public:
> -  CallExprAST(const std::string &callee, std::vector<ExprAST *> &args)
> -      : Callee(callee), Args(args) {}
> +  CallExprAST(const std::string &Callee,
> +              std::vector<std::unique_ptr<ExprAST>> Args)
> +      : Callee(Callee), Args(std::move(Args)) {}
>    Value *Codegen() override;
>  };
>  
>  /// IfExprAST - Expression class for if/then/else.
>  class IfExprAST : public ExprAST {
> -  ExprAST *Cond, *Then, *Else;
> -
> +  std::unique_ptr<ExprAST> Cond, Then, Else;
>  public:
> -  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
> -      : Cond(cond), Then(then), Else(_else) {}
> +  IfExprAST(std::unique_ptr<ExprAST> Cond, std::unique_ptr<ExprAST> Then,
> +            std::unique_ptr<ExprAST> Else)
> +      : Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}
>    Value *Codegen() override;
>  };
>  
>  /// ForExprAST - Expression class for for/in.
>  class ForExprAST : public ExprAST {
>    std::string VarName;
> -  ExprAST *Start, *End, *Step, *Body;
> -
> +  std::unique_ptr<ExprAST> Start, End, Step, Body;
>  public:
> -  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
> -             ExprAST *step, ExprAST *body)
> -      : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
> +  ForExprAST(const std::string &VarName, std::unique_ptr<ExprAST> Start,
> +             std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
> +             std::unique_ptr<ExprAST> Body)
> +    : VarName(VarName), Start(std::move(Start)), End(std::move(End)),
> +      Step(std::move(Step)), Body(std::move(Body)) {}
>    Value *Codegen() override;
>  };
>  
> @@ -207,15 +206,16 @@
>  class PrototypeAST {
>    std::string Name;
>    std::vector<std::string> Args;
> -  bool isOperator;
> +  bool IsOperator;
>    unsigned Precedence; // Precedence if a binary op.
>  public:
> -  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
> -               bool isoperator = false, unsigned prec = 0)
> -      : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
> +  PrototypeAST(const std::string &Name, std::vector<std::string> Args,
> +               bool IsOperator = false, unsigned Prec = 0)
> +    : Name(Name), Args(std::move(Args)), IsOperator(IsOperator),
> +      Precedence(Prec) {}
>  
> -  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
> -  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
> +  bool isUnaryOp() const { return IsOperator && Args.size() == 1; }
> +  bool isBinaryOp() const { return IsOperator && Args.size() == 2; }
>  
>    char getOperatorName() const {
>      assert(isUnaryOp() || isBinaryOp());
> @@ -229,12 +229,11 @@
>  
>  /// FunctionAST - This class represents a function definition itself.
>  class FunctionAST {
> -  PrototypeAST *Proto;
> -  ExprAST *Body;
> -
> +  std::unique_ptr<PrototypeAST> Proto;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  FunctionAST(PrototypeAST *proto, ExprAST *body) : Proto(proto), Body(body) {}
> -
> +  FunctionAST(std::unique_ptr<PrototypeAST> Proto, std::unique_ptr<ExprAST> Body)
> +      : Proto(std::move(Proto)), Body(std::move(Body)) {}
>    Function *Codegen();
>  };
>  } // end anonymous namespace
> @@ -266,41 +265,41 @@
>  }
>  
>  /// Error* - These are little helper functions for error handling.
> -ExprAST *Error(const char *Str) {
> +std::unique_ptr<ExprAST> Error(const char *Str) {
>    fprintf(stderr, "Error: %s\n", Str);
> -  return 0;
> +  return nullptr;
>  }
> -PrototypeAST *ErrorP(const char *Str) {
> +std::unique_ptr<PrototypeAST> ErrorP(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
> -FunctionAST *ErrorF(const char *Str) {
> +std::unique_ptr<FunctionAST> ErrorF(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
> -static ExprAST *ParseExpression();
> +static std::unique_ptr<ExprAST> ParseExpression();
>  
>  /// identifierexpr
>  ///   ::= identifier
>  ///   ::= identifier '(' expression* ')'
> -static ExprAST *ParseIdentifierExpr() {
> +static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>    std::string IdName = IdentifierStr;
>  
>    getNextToken(); // eat identifier.
>  
>    if (CurTok != '(') // Simple variable ref.
> -    return new VariableExprAST(IdName);
> +    return llvm::make_unique<VariableExprAST>(IdName);
>  
>    // Call.
>    getNextToken(); // eat (
> -  std::vector<ExprAST *> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>    if (CurTok != ')') {
>      while (1) {
> -      ExprAST *Arg = ParseExpression();
> -      if (!Arg)
> -        return 0;
> -      Args.push_back(Arg);
> +      if (auto Arg = ParseExpression())
> +        Args.push_back(std::move(Arg));
> +      else
> +        return nullptr;
>  
>        if (CurTok == ')')
>          break;
> @@ -314,22 +313,22 @@
>    // Eat the ')'.
>    getNextToken();
>  
> -  return new CallExprAST(IdName, Args);
> +  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
>  }
>  
>  /// numberexpr ::= number
> -static ExprAST *ParseNumberExpr() {
> -  ExprAST *Result = new NumberExprAST(NumVal);
> +static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>    getNextToken(); // consume the number
> -  return Result;
> +  return std::move(Result);
>  }
>  
>  /// parenexpr ::= '(' expression ')'
> -static ExprAST *ParseParenExpr() {
> +static std::unique_ptr<ExprAST> ParseParenExpr() {
>    getNextToken(); // eat (.
> -  ExprAST *V = ParseExpression();
> +  auto V = ParseExpression();
>    if (!V)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != ')')
>      return Error("expected ')'");
> @@ -338,36 +337,37 @@
>  }
>  
>  /// ifexpr ::= 'if' expression 'then' expression 'else' expression
> -static ExprAST *ParseIfExpr() {
> +static std::unique_ptr<ExprAST> ParseIfExpr() {
>    getNextToken(); // eat the if.
>  
>    // condition.
> -  ExprAST *Cond = ParseExpression();
> +  auto Cond = ParseExpression();
>    if (!Cond)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != tok_then)
>      return Error("expected then");
>    getNextToken(); // eat the then
>  
> -  ExprAST *Then = ParseExpression();
> -  if (Then == 0)
> -    return 0;
> +  auto Then = ParseExpression();
> +  if (!Then)
> +    return nullptr;
>  
>    if (CurTok != tok_else)
>      return Error("expected else");
>  
>    getNextToken();
>  
> -  ExprAST *Else = ParseExpression();
> +  auto Else = ParseExpression();
>    if (!Else)
> -    return 0;
> +    return nullptr;
>  
> -  return new IfExprAST(Cond, Then, Else);
> +  return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
> +                                      std::move(Else));
>  }
>  
>  /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
> -static ExprAST *ParseForExpr() {
> +static std::unique_ptr<ExprAST> ParseForExpr() {
>    getNextToken(); // eat the for.
>  
>    if (CurTok != tok_identifier)
> @@ -380,35 +380,36 @@
>      return Error("expected '=' after for");
>    getNextToken(); // eat '='.
>  
> -  ExprAST *Start = ParseExpression();
> -  if (Start == 0)
> -    return 0;
> +  auto Start = ParseExpression();
> +  if (!Start)
> +    return nullptr;
>    if (CurTok != ',')
>      return Error("expected ',' after for start value");
>    getNextToken();
>  
> -  ExprAST *End = ParseExpression();
> -  if (End == 0)
> -    return 0;
> +  auto End = ParseExpression();
> +  if (!End)
> +    return nullptr;
>  
>    // The step value is optional.
> -  ExprAST *Step = 0;
> +  std::unique_ptr<ExprAST> Step;
>    if (CurTok == ',') {
>      getNextToken();
>      Step = ParseExpression();
> -    if (Step == 0)
> -      return 0;
> +    if (!Step)
> +      return nullptr;
>    }
>  
>    if (CurTok != tok_in)
>      return Error("expected 'in' after for");
>    getNextToken(); // eat 'in'.
>  
> -  ExprAST *Body = ParseExpression();
> -  if (Body == 0)
> -    return 0;
> +  auto Body = ParseExpression();
> +  if (!Body)
> +    return nullptr;
>  
> -  return new ForExprAST(IdName, Start, End, Step, Body);
> +  return llvm::make_unique<ForExprAST>(IdName, std::move(Start), std::move(End),
> +                                       std::move(Step), std::move(Body));
>  }
>  
>  /// primary
> @@ -417,7 +418,7 @@
>  ///   ::= parenexpr
>  ///   ::= ifexpr
>  ///   ::= forexpr
> -static ExprAST *ParsePrimary() {
> +static std::unique_ptr<ExprAST> ParsePrimary() {
>    switch (CurTok) {
>    default:
>      return Error("unknown token when expecting an expression");
> @@ -437,7 +438,7 @@
>  /// unary
>  ///   ::= primary
>  ///   ::= '!' unary
> -static ExprAST *ParseUnary() {
> +static std::unique_ptr<ExprAST> ParseUnary() {
>    // If the current token is not an operator, it must be a primary expr.
>    if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
>      return ParsePrimary();
> @@ -445,14 +446,14 @@
>    // If this is a unary operator, read it.
>    int Opc = CurTok;
>    getNextToken();
> -  if (ExprAST *Operand = ParseUnary())
> -    return new UnaryExprAST(Opc, Operand);
> -  return 0;
> +  if (auto Operand = ParseUnary())
> +    return llvm::make_unique<UnaryExprAST>(Opc, std::move(Operand));
> +  return nullptr;
>  }
>  
>  /// binoprhs
>  ///   ::= ('+' unary)*
> -static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +  static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec, std::unique_ptr<ExprAST> LHS) {
>    // If this is a binop, find its precedence.
>    while (1) {
>      int TokPrec = GetTokPrecedence();
> @@ -467,40 +468,40 @@
>      getNextToken(); // eat binop
>  
>      // Parse the unary expression after the binary operator.
> -    ExprAST *RHS = ParseUnary();
> +    auto RHS = ParseUnary();
>      if (!RHS)
> -      return 0;
> +      return nullptr;
>  
>      // 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, RHS);
> -      if (RHS == 0)
> -        return 0;
> +      RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
> +      if (!RHS)
> +        return nullptr;
>      }
>  
>      // Merge LHS/RHS.
> -    LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS), std::move(RHS));
>    }
>  }
>  
>  /// expression
>  ///   ::= unary binoprhs
>  ///
> -static ExprAST *ParseExpression() {
> -  ExprAST *LHS = ParseUnary();
> +static std::unique_ptr<ExprAST> ParseExpression() {
> +  auto LHS = ParseUnary();
>    if (!LHS)
> -    return 0;
> +    return nullptr;
>  
> -  return ParseBinOpRHS(0, LHS);
> +  return ParseBinOpRHS(0, std::move(LHS));
>  }
>  
>  /// prototype
>  ///   ::= id '(' id* ')'
>  ///   ::= binary LETTER number? (id, id)
>  ///   ::= unary LETTER (id)
> -static PrototypeAST *ParsePrototype() {
> +static std::unique_ptr<PrototypeAST> ParsePrototype() {
>    std::string FnName;
>  
>    unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
> @@ -558,33 +559,34 @@
>    if (Kind && ArgNames.size() != Kind)
>      return ErrorP("Invalid number of operands for operator");
>  
> -  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
> +  return llvm::make_unique<PrototypeAST>(FnName, ArgNames, Kind != 0,
> +                                         BinaryPrecedence);
>  }
>  
>  /// definition ::= 'def' prototype expression
> -static FunctionAST *ParseDefinition() {
> +static std::unique_ptr<FunctionAST> ParseDefinition() {
>    getNextToken(); // eat def.
> -  PrototypeAST *Proto = ParsePrototype();
> -  if (Proto == 0)
> -    return 0;
> +  auto Proto = ParsePrototype();
> +  if (!Proto)
> +    return nullptr;
>  
> -  if (ExprAST *E = ParseExpression())
> -    return new FunctionAST(Proto, E);
> -  return 0;
> +  if (auto E = ParseExpression())
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +  return nullptr;
>  }
>  
>  /// toplevelexpr ::= expression
> -static FunctionAST *ParseTopLevelExpr() {
> -  if (ExprAST *E = ParseExpression()) {
> +static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
> +  if (auto E = ParseExpression()) {
>      // Make an anonymous proto.
> -    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -    return new FunctionAST(Proto, E);
> +    auto Proto = llvm::make_unique<PrototypeAST>("", std::vector<std::string>());
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>    }
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// external ::= 'extern' prototype
> -static PrototypeAST *ParseExtern() {
> +static std::unique_ptr<PrototypeAST> ParseExtern() {
>    getNextToken(); // eat extern.
>    return ParsePrototype();
>  }
> @@ -600,7 +602,7 @@
>  
>  Value *ErrorV(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
>  Value *NumberExprAST::Codegen() {
> @@ -615,11 +617,11 @@
>  
>  Value *UnaryExprAST::Codegen() {
>    Value *OperandV = Operand->Codegen();
> -  if (OperandV == 0)
> -    return 0;
> +  if (!OperandV)
> +    return nullptr;
>  
>    Function *F = TheModule->getFunction(std::string("unary") + Opcode);
> -  if (F == 0)
> +  if (!F)
>      return ErrorV("Unknown unary operator");
>  
>    return Builder.CreateCall(F, OperandV, "unop");
> @@ -628,8 +630,8 @@
>  Value *BinaryExprAST::Codegen() {
>    Value *L = LHS->Codegen();
>    Value *R = RHS->Codegen();
> -  if (L == 0 || R == 0)
> -    return 0;
> +  if (!L || !R)
> +    return nullptr;
>  
>    switch (Op) {
>    case '+':
> @@ -659,7 +661,7 @@
>  Value *CallExprAST::Codegen() {
>    // Look up the name in the global module table.
>    Function *CalleeF = TheModule->getFunction(Callee);
> -  if (CalleeF == 0)
> +  if (!CalleeF)
>      return ErrorV("Unknown function referenced");
>  
>    // If argument mismatch error.
> @@ -669,8 +671,8 @@
>    std::vector<Value *> ArgsV;
>    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
>      ArgsV.push_back(Args[i]->Codegen());
> -    if (ArgsV.back() == 0)
> -      return 0;
> +    if (!ArgsV.back())
> +      return nullptr;
>    }
>  
>    return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
> @@ -678,8 +680,8 @@
>  
>  Value *IfExprAST::Codegen() {
>    Value *CondV = Cond->Codegen();
> -  if (CondV == 0)
> -    return 0;
> +  if (!CondV)
> +    return nullptr;
>  
>    // Convert condition to a bool by comparing equal to 0.0.
>    CondV = Builder.CreateFCmpONE(
> @@ -700,8 +702,8 @@
>    Builder.SetInsertPoint(ThenBB);
>  
>    Value *ThenV = Then->Codegen();
> -  if (ThenV == 0)
> -    return 0;
> +  if (!ThenV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
> @@ -712,8 +714,8 @@
>    Builder.SetInsertPoint(ElseBB);
>  
>    Value *ElseV = Else->Codegen();
> -  if (ElseV == 0)
> -    return 0;
> +  if (!ElseV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
> @@ -749,8 +751,8 @@
>  
>    // Emit the start code first, without 'variable' in scope.
>    Value *StartVal = Start->Codegen();
> -  if (StartVal == 0)
> -    return 0;
> +  if (!StartVal)
> +    return nullptr;
>  
>    // Make the new basic block for the loop header, inserting after current
>    // block.
> @@ -778,15 +780,15 @@
>    // Emit the body of the loop.  This, like any other expr, can change the
>    // current BB.  Note that we ignore the value computed by the body, but don't
>    // allow an error.
> -  if (Body->Codegen() == 0)
> -    return 0;
> +  if (!Body->Codegen())
> +    return nullptr;
>  
>    // Emit the step value.
>    Value *StepVal;
>    if (Step) {
>      StepVal = Step->Codegen();
> -    if (StepVal == 0)
> -      return 0;
> +    if (!StepVal)
> +      return nullptr;
>    } else {
>      // If not specified, use 1.0.
>      StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
> @@ -796,7 +798,7 @@
>  
>    // Compute the end condition.
>    Value *EndCond = End->Codegen();
> -  if (EndCond == 0)
> +  if (!EndCond)
>      return EndCond;
>  
>    // Convert condition to a bool by comparing equal to 0.0.
> @@ -847,13 +849,13 @@
>      // If F already has a body, reject this.
>      if (!F->empty()) {
>        ErrorF("redefinition of function");
> -      return 0;
> +      return nullptr;
>      }
>  
>      // If F took a different number of args, reject.
>      if (F->arg_size() != Args.size()) {
>        ErrorF("redefinition of function with different # args");
> -      return 0;
> +      return nullptr;
>      }
>    }
>  
> @@ -874,8 +876,8 @@
>    NamedValues.clear();
>  
>    Function *TheFunction = Proto->Codegen();
> -  if (TheFunction == 0)
> -    return 0;
> +  if (!TheFunction)
> +    return nullptr;
>  
>    // If this is an operator, install it.
>    if (Proto->isBinaryOp())
> @@ -903,7 +905,7 @@
>  
>    if (Proto->isBinaryOp())
>      BinopPrecedence.erase(Proto->getOperatorName());
> -  return 0;
> +  return nullptr;
>  }
>  
>  //===----------------------------------------------------------------------===//
> @@ -913,10 +915,10 @@
>  static ExecutionEngine *TheExecutionEngine;
>  
>  static void HandleDefinition() {
> -  if (FunctionAST *F = ParseDefinition()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseDefinition()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        fprintf(stderr, "Read function definition:");
> -      LF->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -925,10 +927,10 @@
>  }
>  
>  static void HandleExtern() {
> -  if (PrototypeAST *P = ParseExtern()) {
> -    if (Function *F = P->Codegen()) {
> +  if (auto ProtoAST = ParseExtern()) {
> +    if (auto *FnIR = ProtoAST->Codegen()) {
>        fprintf(stderr, "Read extern: ");
> -      F->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -938,11 +940,11 @@
>  
>  static void HandleTopLevelExpression() {
>    // Evaluate a top-level expression into an anonymous function.
> -  if (FunctionAST *F = ParseTopLevelExpr()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseTopLevelExpr()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        TheExecutionEngine->finalizeObject();
>        // JIT the function, returning a function pointer.
> -      void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
> +      void *FPtr = TheExecutionEngine->getPointerToFunction(FnIR);
>  
>        // Cast it to the right type (takes no arguments, returns a double) so we
>        // can call it as a native function.
> Index: examples/Kaleidoscope/Chapter7/toy.cpp
> ===================================================================
> --- examples/Kaleidoscope/Chapter7/toy.cpp	(revision 245236)
> +++ examples/Kaleidoscope/Chapter7/toy.cpp	(working copy)
> @@ -136,18 +136,16 @@
>  /// NumberExprAST - Expression class for numeric literals like "1.0".
>  class NumberExprAST : public ExprAST {
>    double Val;
> -
>  public:
> -  NumberExprAST(double val) : Val(val) {}
> +  NumberExprAST(double Val) : Val(Val) {}
>    Value *Codegen() override;
>  };
>  
>  /// VariableExprAST - Expression class for referencing a variable, like "a".
>  class VariableExprAST : public ExprAST {
>    std::string Name;
> -
>  public:
> -  VariableExprAST(const std::string &name) : Name(name) {}
> +  VariableExprAST(const std::string &Name) : Name(Name) {}
>    const std::string &getName() const { return Name; }
>    Value *Codegen() override;
>  };
> @@ -155,68 +153,66 @@
>  /// UnaryExprAST - Expression class for a unary operator.
>  class UnaryExprAST : public ExprAST {
>    char Opcode;
> -  ExprAST *Operand;
> -
> +  std::unique_ptr<ExprAST> Operand;
>  public:
> -  UnaryExprAST(char opcode, ExprAST *operand)
> -      : Opcode(opcode), Operand(operand) {}
> +  UnaryExprAST(char Opcode, std::unique_ptr<ExprAST> Operand)
> +      : Opcode(Opcode), Operand(std::move(Operand)) {}
>    Value *Codegen() override;
>  };
>  
>  /// BinaryExprAST - Expression class for a binary operator.
>  class BinaryExprAST : public ExprAST {
>    char Op;
> -  ExprAST *LHS, *RHS;
> -
> +  std::unique_ptr<ExprAST> LHS, RHS;
>  public:
> -  BinaryExprAST(char op, ExprAST *lhs, ExprAST *rhs)
> -      : Op(op), LHS(lhs), RHS(rhs) {}
> +  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
> +                std::unique_ptr<ExprAST> RHS)
> +      : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
>    Value *Codegen() override;
>  };
>  
>  /// CallExprAST - Expression class for function calls.
>  class CallExprAST : public ExprAST {
>    std::string Callee;
> -  std::vector<ExprAST *> Args;
> -
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>  public:
> -  CallExprAST(const std::string &callee, std::vector<ExprAST *> &args)
> -      : Callee(callee), Args(args) {}
> +  CallExprAST(const std::string &Callee,
> +              std::vector<std::unique_ptr<ExprAST>> Args)
> +      : Callee(Callee), Args(std::move(Args)) {}
>    Value *Codegen() override;
>  };
>  
>  /// IfExprAST - Expression class for if/then/else.
>  class IfExprAST : public ExprAST {
> -  ExprAST *Cond, *Then, *Else;
> -
> +  std::unique_ptr<ExprAST> Cond, Then, Else;
>  public:
> -  IfExprAST(ExprAST *cond, ExprAST *then, ExprAST *_else)
> -      : Cond(cond), Then(then), Else(_else) {}
> +  IfExprAST(std::unique_ptr<ExprAST> Cond, std::unique_ptr<ExprAST> Then,
> +            std::unique_ptr<ExprAST> Else)
> +      : Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}
>    Value *Codegen() override;
>  };
>  
>  /// ForExprAST - Expression class for for/in.
>  class ForExprAST : public ExprAST {
>    std::string VarName;
> -  ExprAST *Start, *End, *Step, *Body;
> -
> +  std::unique_ptr<ExprAST> Start, End, Step, Body;
>  public:
> -  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
> -             ExprAST *step, ExprAST *body)
> -      : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
> +  ForExprAST(const std::string &VarName, std::unique_ptr<ExprAST> Start,
> +             std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
> +             std::unique_ptr<ExprAST> Body)
> +      : VarName(VarName), Start(std::move(Start)), End(std::move(End)),
> +        Step(std::move(Step)), Body(std::move(Body)) {}
>    Value *Codegen() override;
>  };
>  
>  /// VarExprAST - Expression class for var/in
>  class VarExprAST : public ExprAST {
> -  std::vector<std::pair<std::string, ExprAST *> > VarNames;
> -  ExprAST *Body;
> -
> +  std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  VarExprAST(const std::vector<std::pair<std::string, ExprAST *> > &varnames,
> -             ExprAST *body)
> -      : VarNames(varnames), Body(body) {}
> -
> +  VarExprAST(std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames,
> +             std::unique_ptr<ExprAST> Body)
> +    : VarNames(std::move(VarNames)), Body(std::move(Body)) {}
>    Value *Codegen() override;
>  };
>  
> @@ -225,15 +221,16 @@
>  class PrototypeAST {
>    std::string Name;
>    std::vector<std::string> Args;
> -  bool isOperator;
> +  bool IsOperator;
>    unsigned Precedence; // Precedence if a binary op.
>  public:
> -  PrototypeAST(const std::string &name, const std::vector<std::string> &args,
> -               bool isoperator = false, unsigned prec = 0)
> -      : Name(name), Args(args), isOperator(isoperator), Precedence(prec) {}
> +  PrototypeAST(const std::string &Name, std::vector<std::string> Args,
> +               bool IsOperator = false, unsigned Prec = 0)
> +    : Name(Name), Args(std::move(Args)), IsOperator(IsOperator),
> +      Precedence(Prec) {}
>  
> -  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
> -  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
> +  bool isUnaryOp() const { return IsOperator && Args.size() == 1; }
> +  bool isBinaryOp() const { return IsOperator && Args.size() == 2; }
>  
>    char getOperatorName() const {
>      assert(isUnaryOp() || isBinaryOp());
> @@ -249,12 +246,11 @@
>  
>  /// FunctionAST - This class represents a function definition itself.
>  class FunctionAST {
> -  PrototypeAST *Proto;
> -  ExprAST *Body;
> -
> +  std::unique_ptr<PrototypeAST> Proto;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  FunctionAST(PrototypeAST *proto, ExprAST *body) : Proto(proto), Body(body) {}
> -
> +  FunctionAST(std::unique_ptr<PrototypeAST> Proto, std::unique_ptr<ExprAST> Body)
> +      : Proto(std::move(Proto)), Body(std::move(Body)) {}
>    Function *Codegen();
>  };
>  } // end anonymous namespace
> @@ -286,41 +282,41 @@
>  }
>  
>  /// Error* - These are little helper functions for error handling.
> -ExprAST *Error(const char *Str) {
> +std::unique_ptr<ExprAST> Error(const char *Str) {
>    fprintf(stderr, "Error: %s\n", Str);
> -  return 0;
> +  return nullptr;
>  }
> -PrototypeAST *ErrorP(const char *Str) {
> +std::unique_ptr<PrototypeAST> ErrorP(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
> -FunctionAST *ErrorF(const char *Str) {
> +std::unique_ptr<FunctionAST> ErrorF(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
> -static ExprAST *ParseExpression();
> +static std::unique_ptr<ExprAST> ParseExpression();
>  
>  /// identifierexpr
>  ///   ::= identifier
>  ///   ::= identifier '(' expression* ')'
> -static ExprAST *ParseIdentifierExpr() {
> +static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>    std::string IdName = IdentifierStr;
>  
>    getNextToken(); // eat identifier.
>  
>    if (CurTok != '(') // Simple variable ref.
> -    return new VariableExprAST(IdName);
> +    return llvm::make_unique<VariableExprAST>(IdName);
>  
>    // Call.
>    getNextToken(); // eat (
> -  std::vector<ExprAST *> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>    if (CurTok != ')') {
>      while (1) {
> -      ExprAST *Arg = ParseExpression();
> -      if (!Arg)
> -        return 0;
> -      Args.push_back(Arg);
> +      if (auto Arg = ParseExpression())
> +        Args.push_back(std::move(Arg));
> +      else
> +        return nullptr;
>  
>        if (CurTok == ')')
>          break;
> @@ -334,22 +330,22 @@
>    // Eat the ')'.
>    getNextToken();
>  
> -  return new CallExprAST(IdName, Args);
> +  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
>  }
>  
>  /// numberexpr ::= number
> -static ExprAST *ParseNumberExpr() {
> -  ExprAST *Result = new NumberExprAST(NumVal);
> +static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>    getNextToken(); // consume the number
> -  return Result;
> +  return std::move(Result);
>  }
>  
>  /// parenexpr ::= '(' expression ')'
> -static ExprAST *ParseParenExpr() {
> +static std::unique_ptr<ExprAST> ParseParenExpr() {
>    getNextToken(); // eat (.
> -  ExprAST *V = ParseExpression();
> +  auto V = ParseExpression();
>    if (!V)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != ')')
>      return Error("expected ')'");
> @@ -358,36 +354,37 @@
>  }
>  
>  /// ifexpr ::= 'if' expression 'then' expression 'else' expression
> -static ExprAST *ParseIfExpr() {
> +static std::unique_ptr<ExprAST> ParseIfExpr() {
>    getNextToken(); // eat the if.
>  
>    // condition.
> -  ExprAST *Cond = ParseExpression();
> +  auto Cond = ParseExpression();
>    if (!Cond)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != tok_then)
>      return Error("expected then");
>    getNextToken(); // eat the then
>  
> -  ExprAST *Then = ParseExpression();
> -  if (Then == 0)
> -    return 0;
> +  auto Then = ParseExpression();
> +  if (!Then)
> +    return nullptr;
>  
>    if (CurTok != tok_else)
>      return Error("expected else");
>  
>    getNextToken();
>  
> -  ExprAST *Else = ParseExpression();
> +  auto Else = ParseExpression();
>    if (!Else)
> -    return 0;
> +    return nullptr;
>  
> -  return new IfExprAST(Cond, Then, Else);
> +  return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
> +                                      std::move(Else));
>  }
>  
>  /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
> -static ExprAST *ParseForExpr() {
> +static std::unique_ptr<ExprAST> ParseForExpr() {
>    getNextToken(); // eat the for.
>  
>    if (CurTok != tok_identifier)
> @@ -400,43 +397,44 @@
>      return Error("expected '=' after for");
>    getNextToken(); // eat '='.
>  
> -  ExprAST *Start = ParseExpression();
> -  if (Start == 0)
> -    return 0;
> +  auto Start = ParseExpression();
> +  if (!Start)
> +    return nullptr;
>    if (CurTok != ',')
>      return Error("expected ',' after for start value");
>    getNextToken();
>  
> -  ExprAST *End = ParseExpression();
> -  if (End == 0)
> -    return 0;
> +  auto End = ParseExpression();
> +  if (!End)
> +    return nullptr;
>  
>    // The step value is optional.
> -  ExprAST *Step = 0;
> +  std::unique_ptr<ExprAST> Step;
>    if (CurTok == ',') {
>      getNextToken();
>      Step = ParseExpression();
> -    if (Step == 0)
> -      return 0;
> +    if (!Step)
> +      return nullptr;
>    }
>  
>    if (CurTok != tok_in)
>      return Error("expected 'in' after for");
>    getNextToken(); // eat 'in'.
>  
> -  ExprAST *Body = ParseExpression();
> -  if (Body == 0)
> -    return 0;
> +  auto Body = ParseExpression();
> +  if (!Body)
> +    return nullptr;
>  
> -  return new ForExprAST(IdName, Start, End, Step, Body);
> +  return llvm::make_unique<ForExprAST>(IdName, std::move(Start), std::move(End),
> +                                       std::move(Step), std::move(Body));
>  }
>  
>  /// varexpr ::= 'var' identifier ('=' expression)?
>  //                    (',' identifier ('=' expression)?)* 'in' expression
> -static ExprAST *ParseVarExpr() {
> +static std::unique_ptr<ExprAST> ParseVarExpr() {
>    getNextToken(); // eat the var.
>  
> -  std::vector<std::pair<std::string, ExprAST *> > VarNames;
> +  std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames;
>  
>    // At least one variable name is required.
>    if (CurTok != tok_identifier)
> @@ -447,16 +445,16 @@
>      getNextToken(); // eat identifier.
>  
>      // Read the optional initializer.
> -    ExprAST *Init = 0;
> +    std::unique_ptr<ExprAST> Init = nullptr;
>      if (CurTok == '=') {
>        getNextToken(); // eat the '='.
>  
>        Init = ParseExpression();
> -      if (Init == 0)
> -        return 0;
> +      if (!Init)
> +        return nullptr;
>      }
>  
> -    VarNames.push_back(std::make_pair(Name, Init));
> +    VarNames.push_back(std::make_pair(Name, std::move(Init)));
>  
>      // End of var list, exit loop.
>      if (CurTok != ',')
> @@ -472,11 +470,11 @@
>      return Error("expected 'in' keyword after 'var'");
>    getNextToken(); // eat 'in'.
>  
> -  ExprAST *Body = ParseExpression();
> -  if (Body == 0)
> -    return 0;
> +  auto Body = ParseExpression();
> +  if (!Body)
> +    return nullptr;
>  
> -  return new VarExprAST(VarNames, Body);
> +  return llvm::make_unique<VarExprAST>(std::move(VarNames), std::move(Body));
>  }
>  
>  /// primary
> @@ -486,7 +484,7 @@
>  ///   ::= ifexpr
>  ///   ::= forexpr
>  ///   ::= varexpr
> -static ExprAST *ParsePrimary() {
> +static std::unique_ptr<ExprAST> ParsePrimary() {
>    switch (CurTok) {
>    default:
>      return Error("unknown token when expecting an expression");
> @@ -508,7 +506,7 @@
>  /// unary
>  ///   ::= primary
>  ///   ::= '!' unary
> -static ExprAST *ParseUnary() {
> +static std::unique_ptr<ExprAST> ParseUnary() {
>    // If the current token is not an operator, it must be a primary expr.
>    if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
>      return ParsePrimary();
> @@ -516,14 +514,14 @@
>    // If this is a unary operator, read it.
>    int Opc = CurTok;
>    getNextToken();
> -  if (ExprAST *Operand = ParseUnary())
> -    return new UnaryExprAST(Opc, Operand);
> -  return 0;
> +  if (auto Operand = ParseUnary())
> +    return llvm::make_unique<UnaryExprAST>(Opc, std::move(Operand));
> +  return nullptr;
>  }
>  
>  /// binoprhs
>  ///   ::= ('+' unary)*
> -static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +  static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec, std::unique_ptr<ExprAST> LHS) {
>    // If this is a binop, find its precedence.
>    while (1) {
>      int TokPrec = GetTokPrecedence();
> @@ -538,40 +536,40 @@
>      getNextToken(); // eat binop
>  
>      // Parse the unary expression after the binary operator.
> -    ExprAST *RHS = ParseUnary();
> +    auto RHS = ParseUnary();
>      if (!RHS)
> -      return 0;
> +      return nullptr;
>  
>      // 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, RHS);
> -      if (RHS == 0)
> -        return 0;
> +      RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
> +      if (!RHS)
> +        return nullptr;
>      }
>  
>      // Merge LHS/RHS.
> -    LHS = new BinaryExprAST(BinOp, LHS, RHS);
> +    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS), std::move(RHS));
>    }
>  }
>  
>  /// expression
>  ///   ::= unary binoprhs
>  ///
> -static ExprAST *ParseExpression() {
> -  ExprAST *LHS = ParseUnary();
> +static std::unique_ptr<ExprAST> ParseExpression() {
> +  auto LHS = ParseUnary();
>    if (!LHS)
> -    return 0;
> +    return nullptr;
>  
> -  return ParseBinOpRHS(0, LHS);
> +  return ParseBinOpRHS(0, std::move(LHS));
>  }
>  
>  /// prototype
>  ///   ::= id '(' id* ')'
>  ///   ::= binary LETTER number? (id, id)
>  ///   ::= unary LETTER (id)
> -static PrototypeAST *ParsePrototype() {
> +static std::unique_ptr<PrototypeAST> ParsePrototype() {
>    std::string FnName;
>  
>    unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
> @@ -629,33 +627,34 @@
>    if (Kind && ArgNames.size() != Kind)
>      return ErrorP("Invalid number of operands for operator");
>  
> -  return new PrototypeAST(FnName, ArgNames, Kind != 0, BinaryPrecedence);
> +  return llvm::make_unique<PrototypeAST>(FnName, ArgNames, Kind != 0,
> +                                         BinaryPrecedence);
>  }
>  
>  /// definition ::= 'def' prototype expression
> -static FunctionAST *ParseDefinition() {
> +static std::unique_ptr<FunctionAST> ParseDefinition() {
>    getNextToken(); // eat def.
> -  PrototypeAST *Proto = ParsePrototype();
> -  if (Proto == 0)
> -    return 0;
> +  auto Proto = ParsePrototype();
> +  if (!Proto)
> +    return nullptr;
>  
> -  if (ExprAST *E = ParseExpression())
> -    return new FunctionAST(Proto, E);
> -  return 0;
> +  if (auto E = ParseExpression())
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +  return nullptr;
>  }
>  
>  /// toplevelexpr ::= expression
> -static FunctionAST *ParseTopLevelExpr() {
> -  if (ExprAST *E = ParseExpression()) {
> +static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
> +  if (auto E = ParseExpression()) {
>      // Make an anonymous proto.
> -    PrototypeAST *Proto = new PrototypeAST("", std::vector<std::string>());
> -    return new FunctionAST(Proto, E);
> +    auto Proto = llvm::make_unique<PrototypeAST>("", std::vector<std::string>());
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>    }
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// external ::= 'extern' prototype
> -static PrototypeAST *ParseExtern() {
> +static std::unique_ptr<PrototypeAST> ParseExtern() {
>    getNextToken(); // eat extern.
>    return ParsePrototype();
>  }
> @@ -671,7 +670,7 @@
>  
>  Value *ErrorV(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
> @@ -691,7 +690,7 @@
>  Value *VariableExprAST::Codegen() {
>    // Look this variable up in the function.
>    Value *V = NamedValues[Name];
> -  if (V == 0)
> +  if (!V)
>      return ErrorV("Unknown variable name");
>  
>    // Load the value.
> @@ -700,11 +699,11 @@
>  
>  Value *UnaryExprAST::Codegen() {
>    Value *OperandV = Operand->Codegen();
> -  if (OperandV == 0)
> -    return 0;
> +  if (!OperandV)
> +    return nullptr;
>  
>    Function *F = TheModule->getFunction(std::string("unary") + Opcode);
> -  if (F == 0)
> +  if (!F)
>      return ErrorV("Unknown unary operator");
>  
>    return Builder.CreateCall(F, OperandV, "unop");
> @@ -717,17 +716,17 @@
>      // This assume we're building without RTTI because LLVM builds that way by
>      // default.  If you build LLVM with RTTI this can be changed to a
>      // dynamic_cast for automatic error checking.
> -    VariableExprAST *LHSE = static_cast<VariableExprAST *>(LHS);
> +    VariableExprAST *LHSE = static_cast<VariableExprAST*>(LHS.get());
>      if (!LHSE)
>        return ErrorV("destination of '=' must be a variable");
>      // Codegen the RHS.
>      Value *Val = RHS->Codegen();
> -    if (Val == 0)
> -      return 0;
> +    if (!Val)
> +      return nullptr;
>  
>      // Look up the name.
>      Value *Variable = NamedValues[LHSE->getName()];
> -    if (Variable == 0)
> +    if (!Variable)
>        return ErrorV("Unknown variable name");
>  
>      Builder.CreateStore(Val, Variable);
> @@ -736,8 +735,8 @@
>  
>    Value *L = LHS->Codegen();
>    Value *R = RHS->Codegen();
> -  if (L == 0 || R == 0)
> -    return 0;
> +  if (!L || !R)
> +    return nullptr;
>  
>    switch (Op) {
>    case '+':
> @@ -767,7 +766,7 @@
>  Value *CallExprAST::Codegen() {
>    // Look up the name in the global module table.
>    Function *CalleeF = TheModule->getFunction(Callee);
> -  if (CalleeF == 0)
> +  if (!CalleeF)
>      return ErrorV("Unknown function referenced");
>  
>    // If argument mismatch error.
> @@ -777,8 +776,8 @@
>    std::vector<Value *> ArgsV;
>    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
>      ArgsV.push_back(Args[i]->Codegen());
> -    if (ArgsV.back() == 0)
> -      return 0;
> +    if (!ArgsV.back())
> +      return nullptr;
>    }
>  
>    return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
> @@ -786,8 +785,8 @@
>  
>  Value *IfExprAST::Codegen() {
>    Value *CondV = Cond->Codegen();
> -  if (CondV == 0)
> -    return 0;
> +  if (!CondV)
> +    return nullptr;
>  
>    // Convert condition to a bool by comparing equal to 0.0.
>    CondV = Builder.CreateFCmpONE(
> @@ -808,8 +807,8 @@
>    Builder.SetInsertPoint(ThenBB);
>  
>    Value *ThenV = Then->Codegen();
> -  if (ThenV == 0)
> -    return 0;
> +  if (!ThenV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
> @@ -820,8 +819,8 @@
>    Builder.SetInsertPoint(ElseBB);
>  
>    Value *ElseV = Else->Codegen();
> -  if (ElseV == 0)
> -    return 0;
> +  if (!ElseV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
> @@ -866,8 +865,8 @@
>  
>    // Emit the start code first, without 'variable' in scope.
>    Value *StartVal = Start->Codegen();
> -  if (StartVal == 0)
> -    return 0;
> +  if (!StartVal)
> +    return nullptr;
>  
>    // Store the value into the alloca.
>    Builder.CreateStore(StartVal, Alloca);
> @@ -891,15 +890,15 @@
>    // Emit the body of the loop.  This, like any other expr, can change the
>    // current BB.  Note that we ignore the value computed by the body, but don't
>    // allow an error.
> -  if (Body->Codegen() == 0)
> -    return 0;
> +  if (!Body->Codegen())
> +    return nullptr;
>  
>    // Emit the step value.
>    Value *StepVal;
>    if (Step) {
>      StepVal = Step->Codegen();
> -    if (StepVal == 0)
> -      return 0;
> +    if (!StepVal)
> +      return nullptr;
>    } else {
>      // If not specified, use 1.0.
>      StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
> @@ -907,7 +906,7 @@
>  
>    // Compute the end condition.
>    Value *EndCond = End->Codegen();
> -  if (EndCond == 0)
> +  if (!EndCond)
>      return EndCond;
>  
>    // Reload, increment, and restore the alloca.  This handles the case where
> @@ -948,7 +947,7 @@
>    // Register all variables and emit their initializer.
>    for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
>      const std::string &VarName = VarNames[i].first;
> -    ExprAST *Init = VarNames[i].second;
> +    ExprAST *Init = VarNames[i].second.get();
>  
>      // Emit the initializer before adding the variable to scope, this prevents
>      // the initializer from referencing the variable itself, and permits stuff
> @@ -958,8 +957,8 @@
>      Value *InitVal;
>      if (Init) {
>        InitVal = Init->Codegen();
> -      if (InitVal == 0)
> -        return 0;
> +      if (!InitVal)
> +        return nullptr;
>      } else { // If not specified, use 0.0.
>        InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
>      }
> @@ -977,8 +976,8 @@
>  
>    // Codegen the body, now that all vars are in scope.
>    Value *BodyVal = Body->Codegen();
> -  if (BodyVal == 0)
> -    return 0;
> +  if (!BodyVal)
> +    return nullptr;
>  
>    // Pop all our variables from scope.
>    for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
> @@ -1008,13 +1007,13 @@
>      // If F already has a body, reject this.
>      if (!F->empty()) {
>        ErrorF("redefinition of function");
> -      return 0;
> +      return nullptr;
>      }
>  
>      // If F took a different number of args, reject.
>      if (F->arg_size() != Args.size()) {
>        ErrorF("redefinition of function with different # args");
> -      return 0;
> +      return nullptr;
>      }
>    }
>  
> @@ -1047,8 +1046,8 @@
>    NamedValues.clear();
>  
>    Function *TheFunction = Proto->Codegen();
> -  if (TheFunction == 0)
> -    return 0;
> +  if (!TheFunction)
> +    return nullptr;
>  
>    // If this is an operator, install it.
>    if (Proto->isBinaryOp())
> @@ -1079,7 +1078,7 @@
>  
>    if (Proto->isBinaryOp())
>      BinopPrecedence.erase(Proto->getOperatorName());
> -  return 0;
> +  return nullptr;
>  }
>  
>  //===----------------------------------------------------------------------===//
> @@ -1089,10 +1088,10 @@
>  static ExecutionEngine *TheExecutionEngine;
>  
>  static void HandleDefinition() {
> -  if (FunctionAST *F = ParseDefinition()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseDefinition()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        fprintf(stderr, "Read function definition:");
> -      LF->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -1101,10 +1100,10 @@
>  }
>  
>  static void HandleExtern() {
> -  if (PrototypeAST *P = ParseExtern()) {
> -    if (Function *F = P->Codegen()) {
> +  if (auto ProtoAST = ParseExtern()) {
> +    if (auto *FnIR = ProtoAST->Codegen()) {
>        fprintf(stderr, "Read extern: ");
> -      F->dump();
> +      FnIR->dump();
>      }
>    } else {
>      // Skip token for error recovery.
> @@ -1114,11 +1113,11 @@
>  
>  static void HandleTopLevelExpression() {
>    // Evaluate a top-level expression into an anonymous function.
> -  if (FunctionAST *F = ParseTopLevelExpr()) {
> -    if (Function *LF = F->Codegen()) {
> +  if (auto FnAST = ParseTopLevelExpr()) {
> +    if (auto *FnIR = FnAST->Codegen()) {
>        TheExecutionEngine->finalizeObject();
>        // JIT the function, returning a function pointer.
> -      void *FPtr = TheExecutionEngine->getPointerToFunction(LF);
> +      void *FPtr = TheExecutionEngine->getPointerToFunction(FnIR);
>  
>        // Cast it to the right type (takes no arguments, returns a double) so we
>        // can call it as a native function.
> Index: examples/Kaleidoscope/Chapter8/toy.cpp
> ===================================================================
> --- examples/Kaleidoscope/Chapter8/toy.cpp	(revision 245236)
> +++ examples/Kaleidoscope/Chapter8/toy.cpp	(working copy)
> @@ -203,7 +203,6 @@
>  /// ExprAST - Base class for all expression nodes.
>  class ExprAST {
>    SourceLocation Loc;
> -
>  public:
>    int getLine() const { return Loc.Line; }
>    int getCol() const { return Loc.Col; }
> @@ -218,9 +217,8 @@
>  /// NumberExprAST - Expression class for numeric literals like "1.0".
>  class NumberExprAST : public ExprAST {
>    double Val;
> -
>  public:
> -  NumberExprAST(double val) : Val(val) {}
> +  NumberExprAST(double Val) : Val(Val) {}
>    std::ostream &dump(std::ostream &out, int ind) override {
>      return ExprAST::dump(out << Val, ind);
>    }
> @@ -230,10 +228,9 @@
>  /// VariableExprAST - Expression class for referencing a variable, like "a".
>  class VariableExprAST : public ExprAST {
>    std::string Name;
> -
>  public:
> -  VariableExprAST(SourceLocation Loc, const std::string &name)
> -      : ExprAST(Loc), Name(name) {}
> +  VariableExprAST(SourceLocation Loc, const std::string &Name)
> +      : ExprAST(Loc), Name(Name) {}
>    const std::string &getName() const { return Name; }
>    std::ostream &dump(std::ostream &out, int ind) override {
>      return ExprAST::dump(out << Name, ind);
> @@ -244,11 +241,10 @@
>  /// UnaryExprAST - Expression class for a unary operator.
>  class UnaryExprAST : public ExprAST {
>    char Opcode;
> -  ExprAST *Operand;
> -
> +  std::unique_ptr<ExprAST> Operand;
>  public:
> -  UnaryExprAST(char opcode, ExprAST *operand)
> -      : Opcode(opcode), Operand(operand) {}
> +  UnaryExprAST(char Opcode, std::unique_ptr<ExprAST> Operand)
> +      : Opcode(Opcode), Operand(std::move(Operand)) {}
>    std::ostream &dump(std::ostream &out, int ind) override {
>      ExprAST::dump(out << "unary" << Opcode, ind);
>      Operand->dump(out, ind + 1);
> @@ -260,11 +256,11 @@
>  /// BinaryExprAST - Expression class for a binary operator.
>  class BinaryExprAST : public ExprAST {
>    char Op;
> -  ExprAST *LHS, *RHS;
> -
> +  std::unique_ptr<ExprAST> LHS, RHS;
>  public:
> -  BinaryExprAST(SourceLocation Loc, char op, ExprAST *lhs, ExprAST *rhs)
> -      : ExprAST(Loc), Op(op), LHS(lhs), RHS(rhs) {}
> +  BinaryExprAST(SourceLocation Loc, char Op, std::unique_ptr<ExprAST> LHS,
> +                std::unique_ptr<ExprAST> RHS)
> +      : ExprAST(Loc), Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
>    std::ostream &dump(std::ostream &out, int ind) override {
>      ExprAST::dump(out << "binary" << Op, ind);
>      LHS->dump(indent(out, ind) << "LHS:", ind + 1);
> @@ -277,15 +273,14 @@
>  /// CallExprAST - Expression class for function calls.
>  class CallExprAST : public ExprAST {
>    std::string Callee;
> -  std::vector<ExprAST *> Args;
> -
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>  public:
> -  CallExprAST(SourceLocation Loc, const std::string &callee,
> -              std::vector<ExprAST *> &args)
> -      : ExprAST(Loc), Callee(callee), Args(args) {}
> +  CallExprAST(SourceLocation Loc, const std::string &Callee,
> +              std::vector<std::unique_ptr<ExprAST>> Args)
> +      : ExprAST(Loc), Callee(Callee), Args(std::move(Args)) {}
>    std::ostream &dump(std::ostream &out, int ind) override {
>      ExprAST::dump(out << "call " << Callee, ind);
> -    for (ExprAST *Arg : Args)
> +    for (const auto &Arg : Args)
>        Arg->dump(indent(out, ind + 1), ind + 1);
>      return out;
>    }
> @@ -294,11 +289,11 @@
>  
>  /// IfExprAST - Expression class for if/then/else.
>  class IfExprAST : public ExprAST {
> -  ExprAST *Cond, *Then, *Else;
> -
> +  std::unique_ptr<ExprAST> Cond, Then, Else;
>  public:
> -  IfExprAST(SourceLocation Loc, ExprAST *cond, ExprAST *then, ExprAST *_else)
> -      : ExprAST(Loc), Cond(cond), Then(then), Else(_else) {}
> +  IfExprAST(SourceLocation Loc, std::unique_ptr<ExprAST> Cond,
> +            std::unique_ptr<ExprAST> Then, std::unique_ptr<ExprAST> Else)
> +    : ExprAST(Loc), Cond(std::move(Cond)), Then(std::move(Then)), Else(std::move(Else)) {}
>    std::ostream &dump(std::ostream &out, int ind) override {
>      ExprAST::dump(out << "if", ind);
>      Cond->dump(indent(out, ind) << "Cond:", ind + 1);
> @@ -312,12 +307,13 @@
>  /// ForExprAST - Expression class for for/in.
>  class ForExprAST : public ExprAST {
>    std::string VarName;
> -  ExprAST *Start, *End, *Step, *Body;
> -
> +  std::unique_ptr<ExprAST> Start, End, Step, Body;
>  public:
> -  ForExprAST(const std::string &varname, ExprAST *start, ExprAST *end,
> -             ExprAST *step, ExprAST *body)
> -      : VarName(varname), Start(start), End(end), Step(step), Body(body) {}
> +  ForExprAST(const std::string &VarName, std::unique_ptr<ExprAST> Start,
> +             std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
> +             std::unique_ptr<ExprAST> Body)
> +      : VarName(VarName), Start(std::move(Start)), End(std::move(End)),
> +        Step(std::move(Step)), Body(std::move(Body)) {}
>    std::ostream &dump(std::ostream &out, int ind) override {
>      ExprAST::dump(out << "for", ind);
>      Start->dump(indent(out, ind) << "Cond:", ind + 1);
> @@ -331,14 +327,12 @@
>  
>  /// VarExprAST - Expression class for var/in
>  class VarExprAST : public ExprAST {
> -  std::vector<std::pair<std::string, ExprAST *> > VarNames;
> -  ExprAST *Body;
> -
> +  std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  VarExprAST(const std::vector<std::pair<std::string, ExprAST *> > &varnames,
> -             ExprAST *body)
> -      : VarNames(varnames), Body(body) {}
> -
> +  VarExprAST(std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames,
> +             std::unique_ptr<ExprAST> Body)
> +      : VarNames(std::move(VarNames)), Body(std::move(Body)) {}
>    std::ostream &dump(std::ostream &out, int ind) override {
>      ExprAST::dump(out << "var", ind);
>      for (const auto &NamedVar : VarNames)
> @@ -354,19 +348,18 @@
>  class PrototypeAST {
>    std::string Name;
>    std::vector<std::string> Args;
> -  bool isOperator;
> +  bool IsOperator;
>    unsigned Precedence; // Precedence if a binary op.
>    int Line;
> -
>  public:
> -  PrototypeAST(SourceLocation Loc, const std::string &name,
> -               const std::vector<std::string> &args, bool isoperator = false,
> -               unsigned prec = 0)
> -      : Name(name), Args(args), isOperator(isoperator), Precedence(prec),
> -        Line(Loc.Line) {}
> +  PrototypeAST(SourceLocation Loc, const std::string &Name,
> +               std::vector<std::string> Args, bool IsOperator = false,
> +               unsigned Prec = 0)
> +    : Name(Name), Args(std::move(Args)), IsOperator(IsOperator),
> +      Precedence(Prec), Line(Loc.Line) {}
>  
> -  bool isUnaryOp() const { return isOperator && Args.size() == 1; }
> -  bool isBinaryOp() const { return isOperator && Args.size() == 2; }
> +  bool isUnaryOp() const { return IsOperator && Args.size() == 1; }
> +  bool isBinaryOp() const { return IsOperator && Args.size() == 2; }
>  
>    char getOperatorName() const {
>      assert(isUnaryOp() || isBinaryOp());
> @@ -383,11 +376,12 @@
>  
>  /// FunctionAST - This class represents a function definition itself.
>  class FunctionAST {
> -  PrototypeAST *Proto;
> -  ExprAST *Body;
> -
> +  std::unique_ptr<PrototypeAST> Proto;
> +  std::unique_ptr<ExprAST> Body;
>  public:
> -  FunctionAST(PrototypeAST *proto, ExprAST *body) : Proto(proto), Body(body) {}
> +  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
> +              std::unique_ptr<ExprAST> Body)
> +      : Proto(std::move(Proto)), Body(std::move(Body)) {}
>  
>    std::ostream &dump(std::ostream &out, int ind) {
>      indent(out, ind) << "FunctionAST\n";
> @@ -427,25 +421,25 @@
>  }
>  
>  /// Error* - These are little helper functions for error handling.
> -ExprAST *Error(const char *Str) {
> +std::unique_ptr<ExprAST> Error(const char *Str) {
>    fprintf(stderr, "Error: %s\n", Str);
> -  return 0;
> +  return nullptr;
>  }
> -PrototypeAST *ErrorP(const char *Str) {
> +std::unique_ptr<PrototypeAST> ErrorP(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
> -FunctionAST *ErrorF(const char *Str) {
> +std::unique_ptr<FunctionAST> ErrorF(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
> -static ExprAST *ParseExpression();
> +static std::unique_ptr<ExprAST> ParseExpression();
>  
>  /// identifierexpr
>  ///   ::= identifier
>  ///   ::= identifier '(' expression* ')'
> -static ExprAST *ParseIdentifierExpr() {
> +  static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
>    std::string IdName = IdentifierStr;
>  
>    SourceLocation LitLoc = CurLoc;
> @@ -453,17 +447,17 @@
>    getNextToken(); // eat identifier.
>  
>    if (CurTok != '(') // Simple variable ref.
> -    return new VariableExprAST(LitLoc, IdName);
> +    return llvm::make_unique<VariableExprAST>(LitLoc, IdName);
>  
>    // Call.
>    getNextToken(); // eat (
> -  std::vector<ExprAST *> Args;
> +  std::vector<std::unique_ptr<ExprAST>> Args;
>    if (CurTok != ')') {
>      while (1) {
> -      ExprAST *Arg = ParseExpression();
> +      auto Arg = ParseExpression();
>        if (!Arg)
> -        return 0;
> -      Args.push_back(Arg);
> +        return nullptr;
> +      Args.push_back(std::move(Arg));
>  
>        if (CurTok == ')')
>          break;
> @@ -477,22 +471,22 @@
>    // Eat the ')'.
>    getNextToken();
>  
> -  return new CallExprAST(LitLoc, IdName, Args);
> +  return llvm::make_unique<CallExprAST>(LitLoc, IdName, std::move(Args));
>  }
>  
>  /// numberexpr ::= number
> -static ExprAST *ParseNumberExpr() {
> -  ExprAST *Result = new NumberExprAST(NumVal);
> +static std::unique_ptr<ExprAST> ParseNumberExpr() {
> +  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
>    getNextToken(); // consume the number
> -  return Result;
> +  return std::move(Result);
>  }
>  
>  /// parenexpr ::= '(' expression ')'
> -static ExprAST *ParseParenExpr() {
> +static std::unique_ptr<ExprAST> ParseParenExpr() {
>    getNextToken(); // eat (.
> -  ExprAST *V = ParseExpression();
> +  auto V = ParseExpression();
>    if (!V)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != ')')
>      return Error("expected ')'");
> @@ -501,38 +495,39 @@
>  }
>  
>  /// ifexpr ::= 'if' expression 'then' expression 'else' expression
> -static ExprAST *ParseIfExpr() {
> +static std::unique_ptr<ExprAST> ParseIfExpr() {
>    SourceLocation IfLoc = CurLoc;
>  
>    getNextToken(); // eat the if.
>  
>    // condition.
> -  ExprAST *Cond = ParseExpression();
> +  auto Cond = ParseExpression();
>    if (!Cond)
> -    return 0;
> +    return nullptr;
>  
>    if (CurTok != tok_then)
>      return Error("expected then");
>    getNextToken(); // eat the then
>  
> -  ExprAST *Then = ParseExpression();
> -  if (Then == 0)
> -    return 0;
> +  auto Then = ParseExpression();
> +  if (!Then)
> +    return nullptr;
>  
>    if (CurTok != tok_else)
>      return Error("expected else");
>  
>    getNextToken();
>  
> -  ExprAST *Else = ParseExpression();
> +  auto Else = ParseExpression();
>    if (!Else)
> -    return 0;
> +    return nullptr;
>  
> -  return new IfExprAST(IfLoc, Cond, Then, Else);
> +  return llvm::make_unique<IfExprAST>(IfLoc, std::move(Cond), std::move(Then),
> +                                      std::move(Else));
>  }
>  
>  /// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
> -static ExprAST *ParseForExpr() {
> +static std::unique_ptr<ExprAST> ParseForExpr() {
>    getNextToken(); // eat the for.
>  
>    if (CurTok != tok_identifier)
> @@ -545,43 +540,44 @@
>      return Error("expected '=' after for");
>    getNextToken(); // eat '='.
>  
> -  ExprAST *Start = ParseExpression();
> -  if (Start == 0)
> -    return 0;
> +  auto Start = ParseExpression();
> +  if (!Start)
> +    return nullptr;
>    if (CurTok != ',')
>      return Error("expected ',' after for start value");
>    getNextToken();
>  
> -  ExprAST *End = ParseExpression();
> -  if (End == 0)
> -    return 0;
> +  auto End = ParseExpression();
> +  if (!End)
> +    return nullptr;
>  
>    // The step value is optional.
> -  ExprAST *Step = 0;
> +  std::unique_ptr<ExprAST> Step;
>    if (CurTok == ',') {
>      getNextToken();
>      Step = ParseExpression();
> -    if (Step == 0)
> -      return 0;
> +    if (!Step)
> +      return nullptr;
>    }
>  
>    if (CurTok != tok_in)
>      return Error("expected 'in' after for");
>    getNextToken(); // eat 'in'.
>  
> -  ExprAST *Body = ParseExpression();
> -  if (Body == 0)
> -    return 0;
> +  auto Body = ParseExpression();
> +  if (!Body)
> +    return nullptr;
>  
> -  return new ForExprAST(IdName, Start, End, Step, Body);
> +  return llvm::make_unique<ForExprAST>(IdName, std::move(Start), std::move(End),
> +                                       std::move(Step), std::move(Body));
>  }
>  
>  /// varexpr ::= 'var' identifier ('=' expression)?
>  //                    (',' identifier ('=' expression)?)* 'in' expression
> -static ExprAST *ParseVarExpr() {
> +static std::unique_ptr<ExprAST> ParseVarExpr() {
>    getNextToken(); // eat the var.
>  
> -  std::vector<std::pair<std::string, ExprAST *> > VarNames;
> +  std::vector<std::pair<std::string, std::unique_ptr<ExprAST>>> VarNames;
>  
>    // At least one variable name is required.
>    if (CurTok != tok_identifier)
> @@ -592,16 +588,16 @@
>      getNextToken(); // eat identifier.
>  
>      // Read the optional initializer.
> -    ExprAST *Init = 0;
> +    std::unique_ptr<ExprAST> Init = nullptr;
>      if (CurTok == '=') {
>        getNextToken(); // eat the '='.
>  
>        Init = ParseExpression();
> -      if (Init == 0)
> -        return 0;
> +      if (!Init)
> +        return nullptr;
>      }
>  
> -    VarNames.push_back(std::make_pair(Name, Init));
> +    VarNames.push_back(std::make_pair(Name, std::move(Init)));
>  
>      // End of var list, exit loop.
>      if (CurTok != ',')
> @@ -617,11 +613,11 @@
>      return Error("expected 'in' keyword after 'var'");
>    getNextToken(); // eat 'in'.
>  
> -  ExprAST *Body = ParseExpression();
> -  if (Body == 0)
> -    return 0;
> +  auto Body = ParseExpression();
> +  if (!Body)
> +    return nullptr;
>  
> -  return new VarExprAST(VarNames, Body);
> +  return llvm::make_unique<VarExprAST>(std::move(VarNames), std::move(Body));
>  }
>  
>  /// primary
> @@ -631,7 +627,7 @@
>  ///   ::= ifexpr
>  ///   ::= forexpr
>  ///   ::= varexpr
> -static ExprAST *ParsePrimary() {
> +static std::unique_ptr<ExprAST> ParsePrimary() {
>    switch (CurTok) {
>    default:
>      return Error("unknown token when expecting an expression");
> @@ -653,7 +649,7 @@
>  /// unary
>  ///   ::= primary
>  ///   ::= '!' unary
> -static ExprAST *ParseUnary() {
> +static std::unique_ptr<ExprAST> ParseUnary() {
>    // If the current token is not an operator, it must be a primary expr.
>    if (!isascii(CurTok) || CurTok == '(' || CurTok == ',')
>      return ParsePrimary();
> @@ -661,14 +657,14 @@
>    // If this is a unary operator, read it.
>    int Opc = CurTok;
>    getNextToken();
> -  if (ExprAST *Operand = ParseUnary())
> -    return new UnaryExprAST(Opc, Operand);
> -  return 0;
> +  if (auto Operand = ParseUnary())
> +    return llvm::make_unique<UnaryExprAST>(Opc, std::move(Operand));
> +  return nullptr;
>  }
>  
>  /// binoprhs
>  ///   ::= ('+' unary)*
> -static ExprAST *ParseBinOpRHS(int ExprPrec, ExprAST *LHS) {
> +static std::unique_ptr<ExprAST> ParseBinOpRHS(int ExprPrec, std::unique_ptr<ExprAST> LHS) {
>    // If this is a binop, find its precedence.
>    while (1) {
>      int TokPrec = GetTokPrecedence();
> @@ -684,40 +680,41 @@
>      getNextToken(); // eat binop
>  
>      // Parse the unary expression after the binary operator.
> -    ExprAST *RHS = ParseUnary();
> +    auto RHS = ParseUnary();
>      if (!RHS)
> -      return 0;
> +      return nullptr;
>  
>      // 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, RHS);
> -      if (RHS == 0)
> -        return 0;
> +      RHS = ParseBinOpRHS(TokPrec + 1, std::move(RHS));
> +      if (!RHS)
> +        return nullptr;
>      }
>  
>      // Merge LHS/RHS.
> -    LHS = new BinaryExprAST(BinLoc, BinOp, LHS, RHS);
> +    LHS = llvm::make_unique<BinaryExprAST>(BinLoc, BinOp, std::move(LHS),
> +                                           std::move(RHS));
>    }
>  }
>  
>  /// expression
>  ///   ::= unary binoprhs
>  ///
> -static ExprAST *ParseExpression() {
> -  ExprAST *LHS = ParseUnary();
> +static std::unique_ptr<ExprAST> ParseExpression() {
> +  auto LHS = ParseUnary();
>    if (!LHS)
> -    return 0;
> +    return nullptr;
>  
> -  return ParseBinOpRHS(0, LHS);
> +  return ParseBinOpRHS(0, std::move(LHS));
>  }
>  
>  /// prototype
>  ///   ::= id '(' id* ')'
>  ///   ::= binary LETTER number? (id, id)
>  ///   ::= unary LETTER (id)
> -static PrototypeAST *ParsePrototype() {
> +static std::unique_ptr<PrototypeAST> ParsePrototype() {
>    std::string FnName;
>  
>    SourceLocation FnLoc = CurLoc;
> @@ -777,35 +774,36 @@
>    if (Kind && ArgNames.size() != Kind)
>      return ErrorP("Invalid number of operands for operator");
>  
> -  return new PrototypeAST(FnLoc, FnName, ArgNames, Kind != 0, BinaryPrecedence);
> +  return llvm::make_unique<PrototypeAST>(FnLoc, FnName, ArgNames, Kind != 0,
> +                                         BinaryPrecedence);
>  }
>  
>  /// definition ::= 'def' prototype expression
> -static FunctionAST *ParseDefinition() {
> +static std::unique_ptr<FunctionAST> ParseDefinition() {
>    getNextToken(); // eat def.
> -  PrototypeAST *Proto = ParsePrototype();
> -  if (Proto == 0)
> -    return 0;
> +  auto Proto = ParsePrototype();
> +  if (!Proto)
> +    return nullptr;
>  
> -  if (ExprAST *E = ParseExpression())
> -    return new FunctionAST(Proto, E);
> -  return 0;
> +  if (auto E = ParseExpression())
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
> +  return nullptr;
>  }
>  
>  /// toplevelexpr ::= expression
> -static FunctionAST *ParseTopLevelExpr() {
> +static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
>    SourceLocation FnLoc = CurLoc;
> -  if (ExprAST *E = ParseExpression()) {
> +  if (auto E = ParseExpression()) {
>      // Make an anonymous proto.
> -    PrototypeAST *Proto =
> -        new PrototypeAST(FnLoc, "main", std::vector<std::string>());
> -    return new FunctionAST(Proto, E);
> +    auto Proto =
> +      llvm::make_unique<PrototypeAST>(FnLoc, "main", std::vector<std::string>());
> +    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
>    }
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// external ::= 'extern' prototype
> -static PrototypeAST *ParseExtern() {
> +static std::unique_ptr<PrototypeAST> ParseExtern() {
>    getNextToken(); // eat extern.
>    return ParsePrototype();
>  }
> @@ -860,7 +858,7 @@
>  
>  Value *ErrorV(const char *Str) {
>    Error(Str);
> -  return 0;
> +  return nullptr;
>  }
>  
>  /// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
> @@ -881,7 +879,7 @@
>  Value *VariableExprAST::Codegen() {
>    // Look this variable up in the function.
>    Value *V = NamedValues[Name];
> -  if (V == 0)
> +  if (!V)
>      return ErrorV("Unknown variable name");
>  
>    KSDbgInfo.emitLocation(this);
> @@ -891,11 +889,11 @@
>  
>  Value *UnaryExprAST::Codegen() {
>    Value *OperandV = Operand->Codegen();
> -  if (OperandV == 0)
> -    return 0;
> +  if (!OperandV)
> +    return nullptr;
>  
>    Function *F = TheModule->getFunction(std::string("unary") + Opcode);
> -  if (F == 0)
> +  if (!F)
>      return ErrorV("Unknown unary operator");
>  
>    KSDbgInfo.emitLocation(this);
> @@ -911,17 +909,17 @@
>      // This assume we're building without RTTI because LLVM builds that way by
>      // default.  If you build LLVM with RTTI this can be changed to a
>      // dynamic_cast for automatic error checking.
> -    VariableExprAST *LHSE = static_cast<VariableExprAST *>(LHS);
> +    VariableExprAST *LHSE = static_cast<VariableExprAST*>(LHS.get());
>      if (!LHSE)
>        return ErrorV("destination of '=' must be a variable");
>      // Codegen the RHS.
>      Value *Val = RHS->Codegen();
> -    if (Val == 0)
> -      return 0;
> +    if (!Val)
> +      return nullptr;
>  
>      // Look up the name.
>      Value *Variable = NamedValues[LHSE->getName()];
> -    if (Variable == 0)
> +    if (!Variable)
>        return ErrorV("Unknown variable name");
>  
>      Builder.CreateStore(Val, Variable);
> @@ -930,8 +928,8 @@
>  
>    Value *L = LHS->Codegen();
>    Value *R = RHS->Codegen();
> -  if (L == 0 || R == 0)
> -    return 0;
> +  if (!L || !R)
> +    return nullptr;
>  
>    switch (Op) {
>    case '+':
> @@ -963,7 +961,7 @@
>  
>    // Look up the name in the global module table.
>    Function *CalleeF = TheModule->getFunction(Callee);
> -  if (CalleeF == 0)
> +  if (!CalleeF)
>      return ErrorV("Unknown function referenced");
>  
>    // If argument mismatch error.
> @@ -973,8 +971,8 @@
>    std::vector<Value *> ArgsV;
>    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
>      ArgsV.push_back(Args[i]->Codegen());
> -    if (ArgsV.back() == 0)
> -      return 0;
> +    if (!ArgsV.back())
> +      return nullptr;
>    }
>  
>    return Builder.CreateCall(CalleeF, ArgsV, "calltmp");
> @@ -984,8 +982,8 @@
>    KSDbgInfo.emitLocation(this);
>  
>    Value *CondV = Cond->Codegen();
> -  if (CondV == 0)
> -    return 0;
> +  if (!CondV)
> +    return nullptr;
>  
>    // Convert condition to a bool by comparing equal to 0.0.
>    CondV = Builder.CreateFCmpONE(
> @@ -1006,8 +1004,8 @@
>    Builder.SetInsertPoint(ThenBB);
>  
>    Value *ThenV = Then->Codegen();
> -  if (ThenV == 0)
> -    return 0;
> +  if (!ThenV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
> @@ -1018,8 +1016,8 @@
>    Builder.SetInsertPoint(ElseBB);
>  
>    Value *ElseV = Else->Codegen();
> -  if (ElseV == 0)
> -    return 0;
> +  if (!ElseV)
> +    return nullptr;
>  
>    Builder.CreateBr(MergeBB);
>    // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
> @@ -1066,8 +1064,8 @@
>  
>    // Emit the start code first, without 'variable' in scope.
>    Value *StartVal = Start->Codegen();
> -  if (StartVal == 0)
> -    return 0;
> +  if (!StartVal)
> +    return nullptr;
>  
>    // Store the value into the alloca.
>    Builder.CreateStore(StartVal, Alloca);
> @@ -1091,15 +1089,15 @@
>    // Emit the body of the loop.  This, like any other expr, can change the
>    // current BB.  Note that we ignore the value computed by the body, but don't
>    // allow an error.
> -  if (Body->Codegen() == 0)
> -    return 0;
> +  if (!Body->Codegen())
> +    return nullptr;
>  
>    // Emit the step value.
>    Value *StepVal;
>    if (Step) {
>      StepVal = Step->Codegen();
> -    if (StepVal == 0)
> -      return 0;
> +    if (!StepVal)
> +      return nullptr;
>    } else {
>      // If not specified, use 1.0.
>      StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
> @@ -1107,7 +1105,7 @@
>  
>    // Compute the end condition.
>    Value *EndCond = End->Codegen();
> -  if (EndCond == 0)
> +  if (!EndCond)
>      return EndCond;
>  
>    // Reload, increment, and restore the alloca.  This handles the case where
> @@ -1148,7 +1146,7 @@
>    // Register all variables and emit their initializer.
>    for (unsigned i = 0, e = VarNames.size(); i != e; ++i) {
>      const std::string &VarName = VarNames[i].first;
> -    ExprAST *Init = VarNames[i].second;
> +    ExprAST *Init = VarNames[i].second.get();
>  
>      // Emit the initializer before adding the variable to scope, this prevents
>      // the initializer from referencing the variable itself, and permits stuff
> @@ -1158,8 +1156,8 @@
>      Value *InitVal;
>      if (Init) {
>        InitVal = Init->Codegen();
> -      if (InitVal == 0)
> -        return 0;
> +      if (!InitVal)
> +        return nullptr;
>      } else { // If not specified, use 0.0.
>        InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
>      }
> @@ -1179,8 +1177,8 @@
>  
>    // Codegen the body, now that all vars are in scope.
>    Value *BodyVal = Body->Codegen();
> -  if (BodyVal == 0)
> -    return 0;
> +  if (!BodyVal)
> +    return nullptr;
>  
>    // Pop all our variables from scope.
>    for (unsigned i = 0, e = VarNames.size(); i != e; ++i)
> @@ -1210,13 +1208,13 @@
>      // If F already has a body, reject this.
>      if (!F->empty()) {
>        ErrorF("redefinition of function");
> -      return 0;
> +      return nullptr;
>      }
>  
>      // If F took a different number of args, reject.
>      if (F->arg_size() != Args.size()) {
>        ErrorF("redefinition of function with different # args");
> -      return 0;
> +      return nullptr;
>      }
>    }
>  
> @@ -1272,11 +1270,11 @@
>    NamedValues.clear();
>  
>    Function *TheFunction = Proto->Codegen();
> -  if (TheFunction == 0)
> -    return 0;
> +  if (!TheFunction)
> +    return nullptr;
>  
>    // Push the current scope.
> -  KSDbgInfo.LexicalBlocks.push_back(KSDbgInfo.FnScopeMap[Proto]);
> +  KSDbgInfo.LexicalBlocks.push_back(KSDbgInfo.FnScopeMap[Proto.get()]);
>  
>    // Unset the location for the prologue emission (leading instructions with no
>    // location in a function are considered part of the prologue and the debugger
> @@ -1294,7 +1292,7 @@
>    // Add all arguments to the symbol table and create their allocas.
>    Proto->CreateArgumentAllocas(TheFunction);
>  
> -  KSDbgInfo.emitLocation(Body);
> +  KSDbgInfo.emitLocation(Body.get());
>  
>    if (Value *RetVal = Body->Codegen()) {
>      // Finish off the function.
> @@ -1322,7 +1320,7 @@
>    // unconditionally.
>    KSDbgInfo.LexicalBlocks.pop_back();
>  
> -  return 0;
> +  return nullptr;
>  }
>  
>  //===----------------------------------------------------------------------===//
> @@ -1332,8 +1330,8 @@
>  static ExecutionEngine *TheExecutionEngine;
>  
>  static void HandleDefinition() {
> -  if (FunctionAST *F = ParseDefinition()) {
> -    if (!F->Codegen()) {
> +  if (auto FnAST = ParseDefinition()) {
> +    if (!FnAST->Codegen()) {
>        fprintf(stderr, "Error reading function definition:");
>      }
>    } else {
> @@ -1343,8 +1341,8 @@
>  }
>  
>  static void HandleExtern() {
> -  if (PrototypeAST *P = ParseExtern()) {
> -    if (!P->Codegen()) {
> +  if (auto ProtoAST = ParseExtern()) {
> +    if (!ProtoAST->Codegen()) {
>        fprintf(stderr, "Error reading extern");
>      }
>    } else {
> @@ -1355,8 +1353,8 @@
>  
>  static void HandleTopLevelExpression() {
>    // Evaluate a top-level expression into an anonymous function.
> -  if (FunctionAST *F = ParseTopLevelExpr()) {
> -    if (!F->Codegen()) {
> +  if (auto FnAST = ParseTopLevelExpr()) {
> +    if (!FnAST->Codegen()) {
>        fprintf(stderr, "Error generating code for top level expr");
>      }
>    } else {
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