From: Lang Hames <lhames@gmail.com>
Date: Tue, 17 Feb 2015 05:40:42 +0000 (+0000)
Subject: [Orc][Kaleidoscope] Add an example of extreme-laziness in Orc.
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=commitdiff_plain;h=a2fe1f3137831ca4d7708139d38fc074d8052c90;ds=sidebyside

[Orc][Kaleidoscope] Add an example of extreme-laziness in Orc.

The version of the tutorial uses the new compile callbacks API to inject stubs
that trigger IRGen & Codegen of their respective function bodies when they are
first called.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@229466 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/examples/Kaleidoscope/Orc/fully_lazy/CMakeLists.txt b/examples/Kaleidoscope/Orc/fully_lazy/CMakeLists.txt
new file mode 100644
index 00000000000..44886818e0f
--- /dev/null
+++ b/examples/Kaleidoscope/Orc/fully_lazy/CMakeLists.txt
@@ -0,0 +1,12 @@
+set(LLVM_LINK_COMPONENTS
+  Core
+  ExecutionEngine
+  Object
+  RuntimeDyld
+  Support
+  native
+  )
+
+add_kaleidoscope_chapter(Kaleidoscope-Orc-lazy_irgen
+  toy.cpp
+  )
diff --git a/examples/Kaleidoscope/Orc/fully_lazy/Makefile b/examples/Kaleidoscope/Orc/fully_lazy/Makefile
new file mode 100644
index 00000000000..df0fcb35066
--- /dev/null
+++ b/examples/Kaleidoscope/Orc/fully_lazy/Makefile
@@ -0,0 +1,9 @@
+.PHONY: all
+all: toy
+
+toy: toy.cpp
+	clang++ -Wall -std=c++11 toy.cpp -g -O0 -rdynamic -fno-rtti `llvm-config --cppflags --ldflags --system-libs --libs core orcjit native` -o toy
+
+.PHONY: clean
+clean:
+	rm -f toy
diff --git a/examples/Kaleidoscope/Orc/fully_lazy/README.txt b/examples/Kaleidoscope/Orc/fully_lazy/README.txt
new file mode 100644
index 00000000000..c0189319f2c
--- /dev/null
+++ b/examples/Kaleidoscope/Orc/fully_lazy/README.txt
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===/
+//                 Kaleidoscope with Orc - Lazy IRGen Version
+//===----------------------------------------------------------------------===//
+
+This version of Kaleidoscope with Orc demonstrates fully lazy IR-generation.
+Building on the lazy-irgen version of the tutorial, this version injects JIT
+callbacks to defer the bulk of IR-generation and code-generation of functions until
+they are first called.
+
+When a function definition is entered, a JIT callback is created and a stub
+function is built that will call the body of the function indirectly. The body of
+the function is *not* IRGen'd at this point. Instead, the function pointer for
+the indirect call is initialized to point at the JIT callback, and the compile
+action for the callback is initialized with a lambda that IRGens the body of the
+function and adds it to the JIT. The function pointer is updated by the JIT
+callback's update action to point at the newly emitted function body, so future
+calls to the stub will go straight to the body, not through the JIT.
+
+This directory contains a Makefile that allows the code to be built in a
+standalone manner, independent of the larger LLVM build infrastructure. To build
+the program you will need to have 'clang++' and 'llvm-config' in your path.
diff --git a/examples/Kaleidoscope/Orc/fully_lazy/toy.cpp b/examples/Kaleidoscope/Orc/fully_lazy/toy.cpp
new file mode 100644
index 00000000000..10113c6666d
--- /dev/null
+++ b/examples/Kaleidoscope/Orc/fully_lazy/toy.cpp
@@ -0,0 +1,1412 @@
+#include "llvm/Analysis/Passes.h"
+#include "llvm/ExecutionEngine/Orc/CompileUtils.h"
+#include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
+#include "llvm/ExecutionEngine/Orc/LazyEmittingLayer.h"
+#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
+#include "llvm/ExecutionEngine/Orc/OrcTargetSupport.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/LegacyPassManager.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Verifier.h"
+#include "llvm/Support/TargetSelect.h"
+#include "llvm/Transforms/Scalar.h"
+#include <cctype>
+#include <iomanip>
+#include <iostream>
+#include <map>
+#include <sstream>
+#include <string>
+#include <vector>
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// Lexer
+//===----------------------------------------------------------------------===//
+
+// The lexer returns tokens [0-255] if it is an unknown character, otherwise one
+// of these for known things.
+enum Token {
+  tok_eof = -1,
+
+  // commands
+  tok_def = -2, tok_extern = -3,
+
+  // primary
+  tok_identifier = -4, tok_number = -5,
+  
+  // control
+  tok_if = -6, tok_then = -7, tok_else = -8,
+  tok_for = -9, tok_in = -10,
+  
+  // operators
+  tok_binary = -11, tok_unary = -12,
+  
+  // var definition
+  tok_var = -13
+};
+
+static std::string IdentifierStr;  // Filled in if tok_identifier
+static double NumVal;              // Filled in if tok_number
+
+/// gettok - Return the next token from standard input.
+static int gettok() {
+  static int LastChar = ' ';
+
+  // Skip any whitespace.
+  while (isspace(LastChar))
+    LastChar = getchar();
+
+  if (isalpha(LastChar)) { // identifier: [a-zA-Z][a-zA-Z0-9]*
+    IdentifierStr = LastChar;
+    while (isalnum((LastChar = getchar())))
+      IdentifierStr += LastChar;
+
+    if (IdentifierStr == "def") return tok_def;
+    if (IdentifierStr == "extern") return tok_extern;
+    if (IdentifierStr == "if") return tok_if;
+    if (IdentifierStr == "then") return tok_then;
+    if (IdentifierStr == "else") return tok_else;
+    if (IdentifierStr == "for") return tok_for;
+    if (IdentifierStr == "in") return tok_in;
+    if (IdentifierStr == "binary") return tok_binary;
+    if (IdentifierStr == "unary") return tok_unary;
+    if (IdentifierStr == "var") return tok_var;
+    return tok_identifier;
+  }
+
+  if (isdigit(LastChar) || LastChar == '.') {   // Number: [0-9.]+
+    std::string NumStr;
+    do {
+      NumStr += LastChar;
+      LastChar = getchar();
+    } while (isdigit(LastChar) || LastChar == '.');
+
+    NumVal = strtod(NumStr.c_str(), 0);
+    return tok_number;
+  }
+
+  if (LastChar == '#') {
+    // Comment until end of line.
+    do LastChar = getchar();
+    while (LastChar != EOF && LastChar != '\n' && LastChar != '\r');
+    
+    if (LastChar != EOF)
+      return gettok();
+  }
+  
+  // Check for end of file.  Don't eat the EOF.
+  if (LastChar == EOF)
+    return tok_eof;
+
+  // Otherwise, just return the character as its ascii value.
+  int ThisChar = LastChar;
+  LastChar = getchar();
+  return ThisChar;
+}
+
+//===----------------------------------------------------------------------===//
+// Abstract Syntax Tree (aka Parse Tree)
+//===----------------------------------------------------------------------===//
+
+class IRGenContext;
+
+/// ExprAST - Base class for all expression nodes.
+struct ExprAST {
+  virtual ~ExprAST() {}
+  virtual Value *IRGen(IRGenContext &C) const = 0;
+};
+
+/// NumberExprAST - Expression class for numeric literals like "1.0".
+struct NumberExprAST : public ExprAST {
+  NumberExprAST(double Val) : Val(Val) {}
+  Value *IRGen(IRGenContext &C) const override;
+
+  double Val;
+};
+
+/// VariableExprAST - Expression class for referencing a variable, like "a".
+struct VariableExprAST : public ExprAST {
+  VariableExprAST(std::string Name) : Name(std::move(Name)) {}
+  Value *IRGen(IRGenContext &C) const override;
+
+  std::string Name;
+};
+
+/// UnaryExprAST - Expression class for a unary operator.
+struct UnaryExprAST : public ExprAST {
+  UnaryExprAST(char Opcode, std::unique_ptr<ExprAST> Operand) 
+    : Opcode(std::move(Opcode)), Operand(std::move(Operand)) {}
+
+  Value *IRGen(IRGenContext &C) const override;
+
+  char Opcode;
+  std::unique_ptr<ExprAST> Operand;
+};
+
+/// BinaryExprAST - Expression class for a binary operator.
+struct BinaryExprAST : public ExprAST {
+  BinaryExprAST(char Op, std::unique_ptr<ExprAST> LHS,
+                std::unique_ptr<ExprAST> RHS) 
+    : Op(Op), LHS(std::move(LHS)), RHS(std::move(RHS)) {}
+
+  Value *IRGen(IRGenContext &C) const override;
+
+  char Op;
+  std::unique_ptr<ExprAST> LHS, RHS;
+};
+
+/// CallExprAST - Expression class for function calls.
+struct CallExprAST : public ExprAST {
+  CallExprAST(std::string CalleeName,
+              std::vector<std::unique_ptr<ExprAST>> Args)
+    : CalleeName(std::move(CalleeName)), Args(std::move(Args)) {}
+
+  Value *IRGen(IRGenContext &C) const override;
+
+  std::string CalleeName;
+  std::vector<std::unique_ptr<ExprAST>> Args;
+};
+
+/// IfExprAST - Expression class for if/then/else.
+struct IfExprAST : public ExprAST {
+  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 *IRGen(IRGenContext &C) const override;
+
+  std::unique_ptr<ExprAST> Cond, Then, Else;
+};
+
+/// ForExprAST - Expression class for for/in.
+struct ForExprAST : public ExprAST {
+  ForExprAST(std::string VarName, std::unique_ptr<ExprAST> Start,
+             std::unique_ptr<ExprAST> End, std::unique_ptr<ExprAST> Step,
+             std::unique_ptr<ExprAST> Body)
+    : VarName(std::move(VarName)), Start(std::move(Start)), End(std::move(End)),
+      Step(std::move(Step)), Body(std::move(Body)) {}
+
+  Value *IRGen(IRGenContext &C) const override;
+
+  std::string VarName;
+  std::unique_ptr<ExprAST> Start, End, Step, Body;
+};
+
+/// VarExprAST - Expression class for var/in
+struct VarExprAST : public ExprAST {
+  typedef std::pair<std::string, std::unique_ptr<ExprAST>> Binding;
+  typedef std::vector<Binding> BindingList;
+
+  VarExprAST(BindingList VarBindings, std::unique_ptr<ExprAST> Body)
+    : VarBindings(std::move(VarBindings)), Body(std::move(Body)) {}
+
+  Value *IRGen(IRGenContext &C) const override;
+
+  BindingList VarBindings;
+  std::unique_ptr<ExprAST> Body;
+};
+
+/// PrototypeAST - This class represents the "prototype" for a function,
+/// which captures its argument names as well as if it is an operator.
+struct PrototypeAST {
+  PrototypeAST(std::string Name, std::vector<std::string> Args,
+               bool IsOperator = false, unsigned Precedence = 0)
+    : Name(std::move(Name)), Args(std::move(Args)), IsOperator(IsOperator),
+      Precedence(Precedence) {}
+
+  Function *IRGen(IRGenContext &C) const;
+  void CreateArgumentAllocas(Function *F, IRGenContext &C);
+
+  bool isUnaryOp() const { return IsOperator && Args.size() == 1; }
+  bool isBinaryOp() const { return IsOperator && Args.size() == 2; }
+  
+  char getOperatorName() const {
+    assert(isUnaryOp() || isBinaryOp());
+    return Name[Name.size()-1];
+  }
+
+  std::string Name;
+  std::vector<std::string> Args;
+  bool IsOperator;
+  unsigned Precedence;  // Precedence if a binary op.
+};
+
+/// FunctionAST - This class represents a function definition itself.
+struct FunctionAST {
+  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
+              std::unique_ptr<ExprAST> Body)
+    : Proto(std::move(Proto)), Body(std::move(Body)) {}
+
+  Function *IRGen(IRGenContext &C) const;
+
+  std::unique_ptr<PrototypeAST> Proto;
+  std::unique_ptr<ExprAST> Body;
+};
+
+//===----------------------------------------------------------------------===//
+// Parser
+//===----------------------------------------------------------------------===//
+
+/// CurTok/getNextToken - Provide a simple token buffer.  CurTok is the current
+/// token the parser is looking at.  getNextToken reads another token from the
+/// lexer and updates CurTok with its results.
+static int CurTok;
+static int getNextToken() {
+  return CurTok = gettok();
+}
+
+/// BinopPrecedence - This holds the precedence for each binary operator that is
+/// defined.
+static std::map<char, int> BinopPrecedence;
+
+/// GetTokPrecedence - Get the precedence of the pending binary operator token.
+static int GetTokPrecedence() {
+  if (!isascii(CurTok))
+    return -1;
+  
+  // Make sure it's a declared binop.
+  int TokPrec = BinopPrecedence[CurTok];
+  if (TokPrec <= 0) return -1;
+  return TokPrec;
+}
+
+template <typename T>
+std::unique_ptr<T> ErrorU(const std::string &Str) {
+  std::cerr << "Error: " << Str << "\n";
+  return nullptr;
+}
+
+template <typename T>
+T* ErrorP(const std::string &Str) {
+  std::cerr << "Error: " << Str << "\n";
+  return nullptr;
+}
+
+static std::unique_ptr<ExprAST> ParseExpression();
+
+/// identifierexpr
+///   ::= identifier
+///   ::= identifier '(' expression* ')'
+static std::unique_ptr<ExprAST> ParseIdentifierExpr() {
+  std::string IdName = IdentifierStr;
+  
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '(') // Simple variable ref.
+    return llvm::make_unique<VariableExprAST>(IdName);
+  
+  // Call.
+  getNextToken();  // eat (
+  std::vector<std::unique_ptr<ExprAST>> Args;
+  if (CurTok != ')') {
+    while (1) {
+      auto Arg = ParseExpression();
+      if (!Arg) return nullptr;
+      Args.push_back(std::move(Arg));
+
+      if (CurTok == ')') break;
+
+      if (CurTok != ',')
+        return ErrorU<CallExprAST>("Expected ')' or ',' in argument list");
+      getNextToken();
+    }
+  }
+
+  // Eat the ')'.
+  getNextToken();
+  
+  return llvm::make_unique<CallExprAST>(IdName, std::move(Args));
+}
+
+/// numberexpr ::= number
+static std::unique_ptr<NumberExprAST> ParseNumberExpr() {
+  auto Result = llvm::make_unique<NumberExprAST>(NumVal);
+  getNextToken(); // consume the number
+  return Result;
+}
+
+/// parenexpr ::= '(' expression ')'
+static std::unique_ptr<ExprAST> ParseParenExpr() {
+  getNextToken();  // eat (.
+  auto V = ParseExpression();
+  if (!V)
+    return nullptr;
+  
+  if (CurTok != ')')
+    return ErrorU<ExprAST>("expected ')'");
+  getNextToken();  // eat ).
+  return V;
+}
+
+/// ifexpr ::= 'if' expression 'then' expression 'else' expression
+static std::unique_ptr<ExprAST> ParseIfExpr() {
+  getNextToken();  // eat the if.
+  
+  // condition.
+  auto Cond = ParseExpression();
+  if (!Cond)
+    return nullptr;
+  
+  if (CurTok != tok_then)
+    return ErrorU<ExprAST>("expected then");
+  getNextToken();  // eat the then
+  
+  auto Then = ParseExpression();
+  if (!Then)
+    return nullptr;
+  
+  if (CurTok != tok_else)
+    return ErrorU<ExprAST>("expected else");
+  
+  getNextToken();
+  
+  auto Else = ParseExpression();
+  if (!Else)
+    return nullptr;
+  
+  return llvm::make_unique<IfExprAST>(std::move(Cond), std::move(Then),
+                                      std::move(Else));
+}
+
+/// forexpr ::= 'for' identifier '=' expr ',' expr (',' expr)? 'in' expression
+static std::unique_ptr<ForExprAST> ParseForExpr() {
+  getNextToken();  // eat the for.
+
+  if (CurTok != tok_identifier)
+    return ErrorU<ForExprAST>("expected identifier after for");
+  
+  std::string IdName = IdentifierStr;
+  getNextToken();  // eat identifier.
+  
+  if (CurTok != '=')
+    return ErrorU<ForExprAST>("expected '=' after for");
+  getNextToken();  // eat '='.
+  
+  
+  auto Start = ParseExpression();
+  if (!Start)
+    return nullptr;
+  if (CurTok != ',')
+    return ErrorU<ForExprAST>("expected ',' after for start value");
+  getNextToken();
+  
+  auto End = ParseExpression();
+  if (!End)
+    return nullptr;
+  
+  // The step value is optional.
+  std::unique_ptr<ExprAST> Step;
+  if (CurTok == ',') {
+    getNextToken();
+    Step = ParseExpression();
+    if (!Step)
+      return nullptr;
+  }
+  
+  if (CurTok != tok_in)
+    return ErrorU<ForExprAST>("expected 'in' after for");
+  getNextToken();  // eat 'in'.
+  
+  auto Body = ParseExpression();
+  if (Body)
+    return nullptr;
+
+  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 std::unique_ptr<VarExprAST> ParseVarExpr() {
+  getNextToken();  // eat the var.
+
+  VarExprAST::BindingList VarBindings;
+
+  // At least one variable name is required.
+  if (CurTok != tok_identifier)
+    return ErrorU<VarExprAST>("expected identifier after var");
+  
+  while (1) {
+    std::string Name = IdentifierStr;
+    getNextToken();  // eat identifier.
+
+    // Read the optional initializer.
+    std::unique_ptr<ExprAST> Init;
+    if (CurTok == '=') {
+      getNextToken(); // eat the '='.
+      
+      Init = ParseExpression();
+      if (!Init)
+        return nullptr;
+    }
+    
+    VarBindings.push_back(VarExprAST::Binding(Name, std::move(Init)));
+    
+    // End of var list, exit loop.
+    if (CurTok != ',') break;
+    getNextToken(); // eat the ','.
+    
+    if (CurTok != tok_identifier)
+      return ErrorU<VarExprAST>("expected identifier list after var");
+  }
+  
+  // At this point, we have to have 'in'.
+  if (CurTok != tok_in)
+    return ErrorU<VarExprAST>("expected 'in' keyword after 'var'");
+  getNextToken();  // eat 'in'.
+  
+  auto Body = ParseExpression();
+  if (!Body)
+    return nullptr;
+  
+  return llvm::make_unique<VarExprAST>(std::move(VarBindings), std::move(Body));
+}
+
+/// primary
+///   ::= identifierexpr
+///   ::= numberexpr
+///   ::= parenexpr
+///   ::= ifexpr
+///   ::= forexpr
+///   ::= varexpr
+static std::unique_ptr<ExprAST> ParsePrimary() {
+  switch (CurTok) {
+  default: return ErrorU<ExprAST>("unknown token when expecting an expression");
+  case tok_identifier: return ParseIdentifierExpr();
+  case tok_number:     return ParseNumberExpr();
+  case '(':            return ParseParenExpr();
+  case tok_if:         return ParseIfExpr();
+  case tok_for:        return ParseForExpr();
+  case tok_var:        return ParseVarExpr();
+  }
+}
+
+/// unary
+///   ::= primary
+///   ::= '!' unary
+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();
+  
+  // If this is a unary operator, read it.
+  int Opc = CurTok;
+  getNextToken();
+  if (auto Operand = ParseUnary())
+    return llvm::make_unique<UnaryExprAST>(Opc, std::move(Operand));
+  return nullptr;
+}
+
+/// binoprhs
+///   ::= ('+' unary)*
+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();
+    
+    // If this is a binop that binds at least as tightly as the current binop,
+    // consume it, otherwise we are done.
+    if (TokPrec < ExprPrec)
+      return LHS;
+    
+    // Okay, we know this is a binop.
+    int BinOp = CurTok;
+    getNextToken();  // eat binop
+    
+    // Parse the unary expression after the binary operator.
+    auto RHS = ParseUnary();
+    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, std::move(RHS));
+      if (!RHS)
+        return nullptr;
+    }
+    
+    // Merge LHS/RHS.
+    LHS = llvm::make_unique<BinaryExprAST>(BinOp, std::move(LHS), std::move(RHS));
+  }
+}
+
+/// expression
+///   ::= unary binoprhs
+///
+static std::unique_ptr<ExprAST> ParseExpression() {
+  auto LHS = ParseUnary();
+  if (!LHS)
+    return nullptr;
+  
+  return ParseBinOpRHS(0, std::move(LHS));
+}
+
+/// prototype
+///   ::= id '(' id* ')'
+///   ::= binary LETTER number? (id, id)
+///   ::= unary LETTER (id)
+static std::unique_ptr<PrototypeAST> ParsePrototype() {
+  std::string FnName;
+  
+  unsigned Kind = 0; // 0 = identifier, 1 = unary, 2 = binary.
+  unsigned BinaryPrecedence = 30;
+  
+  switch (CurTok) {
+  default:
+    return ErrorU<PrototypeAST>("Expected function name in prototype");
+  case tok_identifier:
+    FnName = IdentifierStr;
+    Kind = 0;
+    getNextToken();
+    break;
+  case tok_unary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorU<PrototypeAST>("Expected unary operator");
+    FnName = "unary";
+    FnName += (char)CurTok;
+    Kind = 1;
+    getNextToken();
+    break;
+  case tok_binary:
+    getNextToken();
+    if (!isascii(CurTok))
+      return ErrorU<PrototypeAST>("Expected binary operator");
+    FnName = "binary";
+    FnName += (char)CurTok;
+    Kind = 2;
+    getNextToken();
+    
+    // Read the precedence if present.
+    if (CurTok == tok_number) {
+      if (NumVal < 1 || NumVal > 100)
+        return ErrorU<PrototypeAST>("Invalid precedecnce: must be 1..100");
+      BinaryPrecedence = (unsigned)NumVal;
+      getNextToken();
+    }
+    break;
+  }
+  
+  if (CurTok != '(')
+    return ErrorU<PrototypeAST>("Expected '(' in prototype");
+  
+  std::vector<std::string> ArgNames;
+  while (getNextToken() == tok_identifier)
+    ArgNames.push_back(IdentifierStr);
+  if (CurTok != ')')
+    return ErrorU<PrototypeAST>("Expected ')' in prototype");
+  
+  // success.
+  getNextToken();  // eat ')'.
+  
+  // Verify right number of names for operator.
+  if (Kind && ArgNames.size() != Kind)
+    return ErrorU<PrototypeAST>("Invalid number of operands for operator");
+  
+  return llvm::make_unique<PrototypeAST>(FnName, std::move(ArgNames), Kind != 0,
+                                         BinaryPrecedence);
+}
+
+/// definition ::= 'def' prototype expression
+static std::unique_ptr<FunctionAST> ParseDefinition() {
+  getNextToken();  // eat def.
+  auto Proto = ParsePrototype();
+  if (!Proto)
+    return nullptr;
+
+  if (auto Body = ParseExpression())
+    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(Body));
+  return nullptr;
+}
+
+/// toplevelexpr ::= expression
+static std::unique_ptr<FunctionAST> ParseTopLevelExpr() {
+  if (auto E = ParseExpression()) {
+    // Make an anonymous proto.
+    auto Proto =
+      llvm::make_unique<PrototypeAST>("__anon_expr", std::vector<std::string>());
+    return llvm::make_unique<FunctionAST>(std::move(Proto), std::move(E));
+  }
+  return nullptr;
+}
+
+/// external ::= 'extern' prototype
+static std::unique_ptr<PrototypeAST> ParseExtern() {
+  getNextToken();  // eat extern.
+  return ParsePrototype();
+}
+
+//===----------------------------------------------------------------------===//
+// Code Generation
+//===----------------------------------------------------------------------===//
+
+// FIXME: Obviously we can do better than this
+std::string GenerateUniqueName(const std::string &Root) {
+  static int i = 0;
+  std::ostringstream NameStream;
+  NameStream << Root << ++i;
+  return NameStream.str();
+}
+
+std::string MakeLegalFunctionName(std::string Name)
+{
+  std::string NewName;
+  assert(!Name.empty() && "Base name must not be empty");
+
+  // Start with what we have
+  NewName = Name;
+
+  // Look for a numberic first character
+  if (NewName.find_first_of("0123456789") == 0) {
+    NewName.insert(0, 1, 'n');
+  }
+
+  // Replace illegal characters with their ASCII equivalent
+  std::string legal_elements = "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+  size_t pos;
+  while ((pos = NewName.find_first_not_of(legal_elements)) != std::string::npos) {
+    std::ostringstream NumStream;
+    NumStream << (int)NewName.at(pos);
+    NewName = NewName.replace(pos, 1, NumStream.str());
+  }
+
+  return NewName;
+}
+
+class SessionContext {
+public:
+  SessionContext(LLVMContext &C) : Context(C) {}
+  LLVMContext& getLLVMContext() const { return Context; }
+  void addPrototypeAST(std::unique_ptr<PrototypeAST> P);
+  PrototypeAST* getPrototypeAST(const std::string &Name);
+  std::map<std::string, std::unique_ptr<FunctionAST>> FunctionDefs; 
+private:
+  typedef std::map<std::string, std::unique_ptr<PrototypeAST>> PrototypeMap;
+  LLVMContext &Context;
+  PrototypeMap Prototypes;
+};
+
+void SessionContext::addPrototypeAST(std::unique_ptr<PrototypeAST> P) {
+  Prototypes[P->Name] = std::move(P);
+}
+
+PrototypeAST* SessionContext::getPrototypeAST(const std::string &Name) {
+  PrototypeMap::iterator I = Prototypes.find(Name);
+  if (I != Prototypes.end())
+    return I->second.get();
+  return nullptr;
+}
+
+class IRGenContext {
+public:
+
+  IRGenContext(SessionContext &S)
+    : Session(S),
+      M(new Module(GenerateUniqueName("jit_module_"),
+                   Session.getLLVMContext())),
+      Builder(Session.getLLVMContext()) {}
+
+  SessionContext& getSession() { return Session; }
+  Module& getM() const { return *M; }
+  std::unique_ptr<Module> takeM() { return std::move(M); }
+  IRBuilder<>& getBuilder() { return Builder; }
+  LLVMContext& getLLVMContext() { return Session.getLLVMContext(); }
+  Function* getPrototype(const std::string &Name);
+
+  std::map<std::string, AllocaInst*> NamedValues;
+private:
+  SessionContext &Session;
+  std::unique_ptr<Module> M;
+  IRBuilder<> Builder;
+};
+
+Function* IRGenContext::getPrototype(const std::string &Name) {
+  if (Function *ExistingProto = M->getFunction(Name))
+    return ExistingProto;
+  if (PrototypeAST *ProtoAST = Session.getPrototypeAST(Name))
+    return ProtoAST->IRGen(*this);
+  return nullptr;
+}
+
+/// CreateEntryBlockAlloca - Create an alloca instruction in the entry block of
+/// the function.  This is used for mutable variables etc.
+static AllocaInst *CreateEntryBlockAlloca(Function *TheFunction,
+                                          const std::string &VarName) {
+  IRBuilder<> TmpB(&TheFunction->getEntryBlock(),
+                 TheFunction->getEntryBlock().begin());
+  return TmpB.CreateAlloca(Type::getDoubleTy(getGlobalContext()), 0,
+                           VarName.c_str());
+}
+
+Value *NumberExprAST::IRGen(IRGenContext &C) const {
+  return ConstantFP::get(C.getLLVMContext(), APFloat(Val));
+}
+
+Value *VariableExprAST::IRGen(IRGenContext &C) const {
+  // Look this variable up in the function.
+  Value *V = C.NamedValues[Name];
+
+  if (V == 0)
+    return ErrorP<Value>("Unknown variable name '" + Name + "'");
+
+  // Load the value.
+  return C.getBuilder().CreateLoad(V, Name.c_str());
+}
+
+Value *UnaryExprAST::IRGen(IRGenContext &C) const {
+  if (Value *OperandV = Operand->IRGen(C)) {
+    std::string FnName = MakeLegalFunctionName(std::string("unary")+Opcode);
+    if (Function *F = C.getPrototype(FnName))
+      return C.getBuilder().CreateCall(F, OperandV, "unop");
+    return ErrorP<Value>("Unknown unary operator");
+  }
+
+  // Could not codegen operand - return null.
+  return nullptr;
+}
+
+Value *BinaryExprAST::IRGen(IRGenContext &C) const {
+  // Special case '=' because we don't want to emit the LHS as an expression.
+  if (Op == '=') {
+    // Assignment requires the LHS to be an identifier.
+    auto LHSVar = static_cast<VariableExprAST&>(*LHS);
+    // Codegen the RHS.
+    Value *Val = RHS->IRGen(C);
+    if (!Val) return nullptr;
+
+    // Look up the name.
+    if (auto Variable = C.NamedValues[LHSVar.Name]) {
+      C.getBuilder().CreateStore(Val, Variable);
+      return Val;
+    }
+    return ErrorP<Value>("Unknown variable name");
+  }
+  
+  Value *L = LHS->IRGen(C);
+  Value *R = RHS->IRGen(C);
+  if (!L || !R) return nullptr;
+  
+  switch (Op) {
+  case '+': return C.getBuilder().CreateFAdd(L, R, "addtmp");
+  case '-': return C.getBuilder().CreateFSub(L, R, "subtmp");
+  case '*': return C.getBuilder().CreateFMul(L, R, "multmp");
+  case '/': return C.getBuilder().CreateFDiv(L, R, "divtmp");
+  case '<':
+    L = C.getBuilder().CreateFCmpULT(L, R, "cmptmp");
+    // Convert bool 0/1 to double 0.0 or 1.0
+    return C.getBuilder().CreateUIToFP(L, Type::getDoubleTy(getGlobalContext()),
+                                "booltmp");
+  default: break;
+  }
+  
+  // If it wasn't a builtin binary operator, it must be a user defined one. Emit
+  // a call to it.
+  std::string FnName = MakeLegalFunctionName(std::string("binary")+Op);
+  if (Function *F = C.getPrototype(FnName)) {
+    Value *Ops[] = { L, R };
+    return C.getBuilder().CreateCall(F, Ops, "binop");
+  }
+   
+  return ErrorP<Value>("Unknown binary operator");
+}
+
+Value *CallExprAST::IRGen(IRGenContext &C) const {
+  // Look up the name in the global module table.
+  if (auto CalleeF = C.getPrototype(CalleeName)) {
+    // If argument mismatch error.
+    if (CalleeF->arg_size() != Args.size())
+      return ErrorP<Value>("Incorrect # arguments passed");
+
+    std::vector<Value*> ArgsV;
+    for (unsigned i = 0, e = Args.size(); i != e; ++i) {
+      ArgsV.push_back(Args[i]->IRGen(C));
+      if (!ArgsV.back()) return nullptr;
+    }
+    
+    return C.getBuilder().CreateCall(CalleeF, ArgsV, "calltmp");
+  }
+
+  return ErrorP<Value>("Unknown function referenced");
+}
+
+Value *IfExprAST::IRGen(IRGenContext &C) const {
+  Value *CondV = Cond->IRGen(C);
+  if (!CondV) return nullptr;
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  ConstantFP *FPZero = 
+    ConstantFP::get(C.getLLVMContext(), APFloat(0.0));
+  CondV = C.getBuilder().CreateFCmpONE(CondV, FPZero, "ifcond");
+  
+  Function *TheFunction = C.getBuilder().GetInsertBlock()->getParent();
+  
+  // Create blocks for the then and else cases.  Insert the 'then' block at the
+  // end of the function.
+  BasicBlock *ThenBB = BasicBlock::Create(C.getLLVMContext(), "then", TheFunction);
+  BasicBlock *ElseBB = BasicBlock::Create(C.getLLVMContext(), "else");
+  BasicBlock *MergeBB = BasicBlock::Create(C.getLLVMContext(), "ifcont");
+  
+  C.getBuilder().CreateCondBr(CondV, ThenBB, ElseBB);
+  
+  // Emit then value.
+  C.getBuilder().SetInsertPoint(ThenBB);
+  
+  Value *ThenV = Then->IRGen(C);
+  if (!ThenV) return nullptr;
+  
+  C.getBuilder().CreateBr(MergeBB);
+  // Codegen of 'Then' can change the current block, update ThenBB for the PHI.
+  ThenBB = C.getBuilder().GetInsertBlock();
+  
+  // Emit else block.
+  TheFunction->getBasicBlockList().push_back(ElseBB);
+  C.getBuilder().SetInsertPoint(ElseBB);
+  
+  Value *ElseV = Else->IRGen(C);
+  if (!ElseV) return nullptr;
+  
+  C.getBuilder().CreateBr(MergeBB);
+  // Codegen of 'Else' can change the current block, update ElseBB for the PHI.
+  ElseBB = C.getBuilder().GetInsertBlock();
+  
+  // Emit merge block.
+  TheFunction->getBasicBlockList().push_back(MergeBB);
+  C.getBuilder().SetInsertPoint(MergeBB);
+  PHINode *PN = C.getBuilder().CreatePHI(Type::getDoubleTy(getGlobalContext()), 2,
+                                  "iftmp");
+  
+  PN->addIncoming(ThenV, ThenBB);
+  PN->addIncoming(ElseV, ElseBB);
+  return PN;
+}
+
+Value *ForExprAST::IRGen(IRGenContext &C) const {
+  // Output this as:
+  //   var = alloca double
+  //   ...
+  //   start = startexpr
+  //   store start -> var
+  //   goto loop
+  // loop: 
+  //   ...
+  //   bodyexpr
+  //   ...
+  // loopend:
+  //   step = stepexpr
+  //   endcond = endexpr
+  //
+  //   curvar = load var
+  //   nextvar = curvar + step
+  //   store nextvar -> var
+  //   br endcond, loop, endloop
+  // outloop:
+  
+  Function *TheFunction = C.getBuilder().GetInsertBlock()->getParent();
+
+  // Create an alloca for the variable in the entry block.
+  AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+  
+  // Emit the start code first, without 'variable' in scope.
+  Value *StartVal = Start->IRGen(C);
+  if (!StartVal) return nullptr;
+  
+  // Store the value into the alloca.
+  C.getBuilder().CreateStore(StartVal, Alloca);
+  
+  // Make the new basic block for the loop header, inserting after current
+  // block.
+  BasicBlock *LoopBB = BasicBlock::Create(getGlobalContext(), "loop", TheFunction);
+  
+  // Insert an explicit fall through from the current block to the LoopBB.
+  C.getBuilder().CreateBr(LoopBB);
+
+  // Start insertion in LoopBB.
+  C.getBuilder().SetInsertPoint(LoopBB);
+  
+  // Within the loop, the variable is defined equal to the PHI node.  If it
+  // shadows an existing variable, we have to restore it, so save it now.
+  AllocaInst *OldVal = C.NamedValues[VarName];
+  C.NamedValues[VarName] = Alloca;
+  
+  // 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->IRGen(C))
+    return nullptr;
+  
+  // Emit the step value.
+  Value *StepVal;
+  if (Step) {
+    StepVal = Step->IRGen(C);
+    if (!StepVal) return nullptr;
+  } else {
+    // If not specified, use 1.0.
+    StepVal = ConstantFP::get(getGlobalContext(), APFloat(1.0));
+  }
+  
+  // Compute the end condition.
+  Value *EndCond = End->IRGen(C);
+  if (EndCond == 0) return EndCond;
+  
+  // Reload, increment, and restore the alloca.  This handles the case where
+  // the body of the loop mutates the variable.
+  Value *CurVar = C.getBuilder().CreateLoad(Alloca, VarName.c_str());
+  Value *NextVar = C.getBuilder().CreateFAdd(CurVar, StepVal, "nextvar");
+  C.getBuilder().CreateStore(NextVar, Alloca);
+  
+  // Convert condition to a bool by comparing equal to 0.0.
+  EndCond = C.getBuilder().CreateFCmpONE(EndCond, 
+                              ConstantFP::get(getGlobalContext(), APFloat(0.0)),
+                                  "loopcond");
+  
+  // Create the "after loop" block and insert it.
+  BasicBlock *AfterBB = BasicBlock::Create(getGlobalContext(), "afterloop", TheFunction);
+  
+  // Insert the conditional branch into the end of LoopEndBB.
+  C.getBuilder().CreateCondBr(EndCond, LoopBB, AfterBB);
+  
+  // Any new code will be inserted in AfterBB.
+  C.getBuilder().SetInsertPoint(AfterBB);
+  
+  // Restore the unshadowed variable.
+  if (OldVal)
+    C.NamedValues[VarName] = OldVal;
+  else
+    C.NamedValues.erase(VarName);
+
+  
+  // for expr always returns 0.0.
+  return Constant::getNullValue(Type::getDoubleTy(getGlobalContext()));
+}
+
+Value *VarExprAST::IRGen(IRGenContext &C) const {
+  std::vector<AllocaInst *> OldBindings;
+  
+  Function *TheFunction = C.getBuilder().GetInsertBlock()->getParent();
+
+  // Register all variables and emit their initializer.
+  for (unsigned i = 0, e = VarBindings.size(); i != e; ++i) {
+    auto &VarName = VarBindings[i].first;
+    auto &Init = VarBindings[i].second;
+    
+    // Emit the initializer before adding the variable to scope, this prevents
+    // the initializer from referencing the variable itself, and permits stuff
+    // like this:
+    //  var a = 1 in
+    //    var a = a in ...   # refers to outer 'a'.
+    Value *InitVal;
+    if (Init) {
+      InitVal = Init->IRGen(C);
+      if (!InitVal) return nullptr;
+    } else // If not specified, use 0.0.
+      InitVal = ConstantFP::get(getGlobalContext(), APFloat(0.0));
+    
+    AllocaInst *Alloca = CreateEntryBlockAlloca(TheFunction, VarName);
+    C.getBuilder().CreateStore(InitVal, Alloca);
+
+    // Remember the old variable binding so that we can restore the binding when
+    // we unrecurse.
+    OldBindings.push_back(C.NamedValues[VarName]);
+    
+    // Remember this binding.
+    C.NamedValues[VarName] = Alloca;
+  }
+  
+  // Codegen the body, now that all vars are in scope.
+  Value *BodyVal = Body->IRGen(C);
+  if (!BodyVal) return nullptr;
+  
+  // Pop all our variables from scope.
+  for (unsigned i = 0, e = VarBindings.size(); i != e; ++i)
+    C.NamedValues[VarBindings[i].first] = OldBindings[i];
+
+  // Return the body computation.
+  return BodyVal;
+}
+
+Function *PrototypeAST::IRGen(IRGenContext &C) const {
+  std::string FnName = MakeLegalFunctionName(Name);
+
+  // Make the function type:  double(double,double) etc.
+  std::vector<Type*> Doubles(Args.size(), 
+                             Type::getDoubleTy(getGlobalContext()));
+  FunctionType *FT = FunctionType::get(Type::getDoubleTy(getGlobalContext()),
+                                       Doubles, false);
+  Function *F = Function::Create(FT, Function::ExternalLinkage, FnName,
+                                 &C.getM());
+
+  // If F conflicted, there was already something named 'FnName'.  If it has a
+  // body, don't allow redefinition or reextern.
+  if (F->getName() != FnName) {
+    // Delete the one we just made and get the existing one.
+    F->eraseFromParent();
+    F = C.getM().getFunction(Name);
+    
+    // If F already has a body, reject this.
+    if (!F->empty()) {
+      ErrorP<Function>("redefinition of function");
+      return nullptr;
+    }
+    
+    // If F took a different number of args, reject.
+    if (F->arg_size() != Args.size()) {
+      ErrorP<Function>("redefinition of function with different # args");
+      return nullptr;
+    }
+  }
+  
+  // Set names for all arguments.
+  unsigned Idx = 0;
+  for (Function::arg_iterator AI = F->arg_begin(); Idx != Args.size();
+       ++AI, ++Idx)
+    AI->setName(Args[Idx]);
+    
+  return F;
+}
+
+/// CreateArgumentAllocas - Create an alloca for each argument and register the
+/// argument in the symbol table so that references to it will succeed.
+void PrototypeAST::CreateArgumentAllocas(Function *F, IRGenContext &C) {
+  Function::arg_iterator AI = F->arg_begin();
+  for (unsigned Idx = 0, e = Args.size(); Idx != e; ++Idx, ++AI) {
+    // Create an alloca for this variable.
+    AllocaInst *Alloca = CreateEntryBlockAlloca(F, Args[Idx]);
+
+    // Store the initial value into the alloca.
+    C.getBuilder().CreateStore(AI, Alloca);
+
+    // Add arguments to variable symbol table.
+    C.NamedValues[Args[Idx]] = Alloca;
+  }
+}
+
+Function *FunctionAST::IRGen(IRGenContext &C) const {
+  C.NamedValues.clear();
+  
+  Function *TheFunction = Proto->IRGen(C);
+  if (!TheFunction)
+    return nullptr;
+  
+  // If this is an operator, install it.
+  if (Proto->isBinaryOp())
+    BinopPrecedence[Proto->getOperatorName()] = Proto->Precedence;
+  
+  // Create a new basic block to start insertion into.
+  BasicBlock *BB = BasicBlock::Create(getGlobalContext(), "entry", TheFunction);
+  C.getBuilder().SetInsertPoint(BB);
+  
+  // Add all arguments to the symbol table and create their allocas.
+  Proto->CreateArgumentAllocas(TheFunction, C);
+
+  if (Value *RetVal = Body->IRGen(C)) {
+    // Finish off the function.
+    C.getBuilder().CreateRet(RetVal);
+
+    // Validate the generated code, checking for consistency.
+    verifyFunction(*TheFunction);
+
+    return TheFunction;
+  }
+  
+  // Error reading body, remove function.
+  TheFunction->eraseFromParent();
+
+  if (Proto->isBinaryOp())
+    BinopPrecedence.erase(Proto->getOperatorName());
+  return nullptr;
+}
+
+//===----------------------------------------------------------------------===//
+// Top-Level parsing and JIT Driver
+//===----------------------------------------------------------------------===//
+
+static std::unique_ptr<llvm::Module> IRGen(SessionContext &S,
+                                           const FunctionAST &F) {
+  IRGenContext C(S);
+  auto LF = F.IRGen(C);
+  if (!LF)
+    return nullptr;
+#ifndef MINIMAL_STDERR_OUTPUT
+  fprintf(stderr, "Read function definition:");
+  LF->dump();
+#endif
+  return C.takeM();
+}
+
+
+static void EarthShatteringKaboom() {
+  fprintf(stderr, "Earth shattering kaboom.");
+  exit(1);
+}
+
+class KaleidoscopeJIT {
+public:
+  typedef ObjectLinkingLayer<> ObjLayerT;
+  typedef IRCompileLayer<ObjLayerT> CompileLayerT;
+  typedef LazyEmittingLayer<CompileLayerT> LazyEmitLayerT;
+
+  typedef LazyEmitLayerT::ModuleSetHandleT ModuleHandleT;
+
+  std::string Mangle(const std::string &Name) {
+    std::string MangledName;
+    {
+      raw_string_ostream MangledNameStream(MangledName);
+      Mang.getNameWithPrefix(MangledNameStream, Name);
+    }
+    return MangledName;
+  }
+
+  KaleidoscopeJIT(SessionContext &Session)
+    : TM(EngineBuilder().selectTarget()),
+      Mang(TM->getDataLayout()), Session(Session),
+      ObjectLayer(
+        [](){ return llvm::make_unique<SectionMemoryManager>(); }),
+      CompileLayer(ObjectLayer, SimpleCompiler(*TM)),
+      LazyEmitLayer(CompileLayer),
+      CompileCallbacks(LazyEmitLayer, Session.getLLVMContext(),
+                       reinterpret_cast<uintptr_t>(EarthShatteringKaboom),
+                       64) {}
+
+  ModuleHandleT addModule(std::unique_ptr<Module> M) {
+    if (!M->getDataLayout())
+      M->setDataLayout(TM->getDataLayout());
+
+    // The LazyEmitLayer takes lists of modules, rather than single modules, so
+    // we'll just build a single-element list.
+    std::vector<std::unique_ptr<Module>> S;
+    S.push_back(std::move(M));
+
+    // We need a memory manager to allocate memory and resolve symbols for this
+    // new module. Create one that resolves symbols by looking back into the JIT.
+    auto MM = createLookasideRTDyldMM<SectionMemoryManager>(
+                [&](const std::string &Name) -> uint64_t {
+                  // First try to find 'Name' within the JIT.
+                  if (auto Symbol = findMangledSymbol(Name))
+                    return Symbol.getAddress();
+
+                  // If we don't find 'Name' in the JIT, see if we have some AST
+                  // for it.
+                  auto DefI = Session.FunctionDefs.find(Name);
+                  if (DefI == Session.FunctionDefs.end())
+                    return 0;
+
+                  // We have AST for 'Name'. IRGen it, add it to the JIT, and
+                  // return the address for it.
+                  // FIXME: What happens if IRGen fails?
+                  addModule(IRGen(Session, *DefI->second));
+
+                  // Remove the function definition's AST now that we've
+                  // finished with it.
+                  Session.FunctionDefs.erase(DefI);
+
+                  return findMangledSymbol(Name).getAddress();
+                },
+                [](const std::string &S) { return 0; } );
+
+    return LazyEmitLayer.addModuleSet(std::move(S), std::move(MM));
+  }
+
+  void removeModule(ModuleHandleT H) { LazyEmitLayer.removeModuleSet(H); }
+
+  JITSymbol findMangledSymbol(const std::string &Name) {
+    return LazyEmitLayer.findSymbol(Name, true);
+  }
+
+  JITSymbol findSymbol(const std::string &Name) {
+    return findMangledSymbol(Mangle(Name));
+  }
+
+  JITSymbol findMangledSymbolIn(LazyEmitLayerT::ModuleSetHandleT H,
+                                const std::string &Name) {
+    return LazyEmitLayer.findSymbolIn(H, Name, true); 
+  }
+
+  JITSymbol findSymbolIn(LazyEmitLayerT::ModuleSetHandleT H,
+                         const std::string &Name) {
+    return findMangledSymbolIn(H, Mangle(Name));
+  }
+
+  void addFunctionDefinition(std::unique_ptr<FunctionAST> FnAST) {
+    // Step 1) IRGen a prototype for this function:
+    IRGenContext C(Session);
+    Function *F = FnAST->Proto->IRGen(C);
+    C.getM().setDataLayout(TM->getDataLayout());
+
+    // Step 2) Create a compile callback that will be used to compile this
+    //         function when it is first called.
+    auto CallbackInfo =
+      CompileCallbacks.getCompileCallback(*F->getFunctionType());
+
+    // Step 3) Create a stub that will indirectly call the body of this
+    //         function. Initialize the function pointer for the indirection to
+    //         point at the compile callback.
+    std::string BodyPtrName = (F->getName() + "$address").str();
+    GlobalVariable *FunctionBodyPointer =
+      createImplPointer(*F, BodyPtrName, CallbackInfo.getAddress());
+    makeStub(*F, *FunctionBodyPointer);
+
+    // Step 3) Add the module to the JIT.
+    auto H = addModule(C.takeM());
+
+    // Step 4) Set the compile and update actions for the callback. The compile
+    //         action will IRGen and Codegen the function. The update action
+    //         will update FunctionBodyPointer to point at the newly compiled
+    //         function pointer.
+    //
+    // FIXME: Use generalized capture for FnAST when we get C++14 support.
+    FunctionAST *FnASTPtr = FnAST.release();
+    CallbackInfo.setCompileAction([this,FnASTPtr](){
+      std::unique_ptr<FunctionAST> Fn(FnASTPtr);
+      auto H = addModule(IRGen(Session, *Fn));
+      return findSymbolIn(H, Fn->Proto->Name).getAddress();
+    });
+    CallbackInfo.setUpdateAction(
+      CompileCallbacks.getLocalFPUpdater(H, BodyPtrName));
+  }
+
+private:
+
+  std::unique_ptr<TargetMachine> TM;
+  Mangler Mang;
+  SessionContext &Session;
+
+  ObjLayerT ObjectLayer;
+  CompileLayerT CompileLayer;
+  LazyEmitLayerT LazyEmitLayer;
+
+  JITCompileCallbackManager<LazyEmitLayerT, OrcX86_64> CompileCallbacks;
+};
+
+static void HandleDefinition(SessionContext &S, KaleidoscopeJIT &J) {
+  if (auto F = ParseDefinition()) {
+    S.addPrototypeAST(llvm::make_unique<PrototypeAST>(*F->Proto));
+    J.addFunctionDefinition(std::move(F));
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleExtern(SessionContext &S) {
+  if (auto P = ParseExtern())
+    S.addPrototypeAST(std::move(P));
+  else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+static void HandleTopLevelExpression(SessionContext &S, KaleidoscopeJIT &J) {
+  // Evaluate a top-level expression into an anonymous function.
+  if (auto F = ParseTopLevelExpr()) {
+    IRGenContext C(S);
+    if (auto ExprFunc = F->IRGen(C)) {
+#ifndef MINIMAL_STDERR_OUTPUT
+      std::cerr << "Expression function:\n";
+      ExprFunc->dump();
+#endif
+      // Add the CodeGen'd module to the JIT. Keep a handle to it: We can remove
+      // this module as soon as we've executed Function ExprFunc.
+      auto H = J.addModule(C.takeM());
+
+      // Get the address of the JIT'd function in memory.
+      auto ExprSymbol = J.findSymbol("__anon_expr");
+      
+      // Cast it to the right type (takes no arguments, returns a double) so we
+      // can call it as a native function.
+      double (*FP)() = (double (*)())(intptr_t)ExprSymbol.getAddress();
+#ifdef MINIMAL_STDERR_OUTPUT
+      FP();
+#else
+      std::cerr << "Evaluated to " << FP() << "\n";
+#endif
+
+      // Remove the function.
+      J.removeModule(H);
+    }
+  } else {
+    // Skip token for error recovery.
+    getNextToken();
+  }
+}
+
+/// top ::= definition | external | expression | ';'
+static void MainLoop() {
+  SessionContext S(getGlobalContext());
+  KaleidoscopeJIT J(S);
+
+  while (1) {
+    switch (CurTok) {
+    case tok_eof:    return;
+    case ';':        getNextToken(); continue;  // ignore top-level semicolons.
+    case tok_def:    HandleDefinition(S, J); break;
+    case tok_extern: HandleExtern(S); break;
+    default:         HandleTopLevelExpression(S, J); break;
+    }
+#ifndef MINIMAL_STDERR_OUTPUT
+    std::cerr << "ready> ";
+#endif
+  }
+}
+
+//===----------------------------------------------------------------------===//
+// "Library" functions that can be "extern'd" from user code.
+//===----------------------------------------------------------------------===//
+
+/// putchard - putchar that takes a double and returns 0.
+extern "C" 
+double putchard(double X) {
+  putchar((char)X);
+  return 0;
+}
+
+/// printd - printf that takes a double prints it as "%f\n", returning 0.
+extern "C" 
+double printd(double X) {
+  printf("%f", X);
+  return 0;
+}
+
+extern "C" 
+double printlf() {
+  printf("\n");
+  return 0;
+}
+
+//===----------------------------------------------------------------------===//
+// Main driver code.
+//===----------------------------------------------------------------------===//
+
+int main() {
+  InitializeNativeTarget();
+  InitializeNativeTargetAsmPrinter();
+  InitializeNativeTargetAsmParser();
+
+  // Install standard binary operators.
+  // 1 is lowest precedence.
+  BinopPrecedence['='] = 2;
+  BinopPrecedence['<'] = 10;
+  BinopPrecedence['+'] = 20;
+  BinopPrecedence['-'] = 20;
+  BinopPrecedence['/'] = 40;
+  BinopPrecedence['*'] = 40;  // highest.
+
+  // Prime the first token.
+#ifndef MINIMAL_STDERR_OUTPUT
+  std::cerr << "ready> ";
+#endif
+  getNextToken();
+
+  std::cerr << std::fixed;
+
+  // Run the main "interpreter loop" now.
+  MainLoop();
+
+  return 0;
+}
+