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+//===----- KaleidoscopeJIT.h - A simple JIT for Kaleidoscope ----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Contains a simple JIT definition for use in the kaleidoscope tutorials.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_EXECUTIONENGINE_ORC_KALEIDOSCOPEJIT_H
+#define LLVM_EXECUTIONENGINE_ORC_KALEIDOSCOPEJIT_H
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/RuntimeDyld.h"
+#include "llvm/ExecutionEngine/SectionMemoryManager.h"
+#include "llvm/ExecutionEngine/Orc/CompileOnDemandLayer.h"
+#include "llvm/ExecutionEngine/Orc/CompileUtils.h"
+#include "llvm/ExecutionEngine/Orc/JITSymbol.h"
+#include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
+#include "llvm/ExecutionEngine/Orc/IRTransformLayer.h"
+#include "llvm/ExecutionEngine/Orc/LambdaResolver.h"
+#include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/Mangler.h"
+#include "llvm/Support/DynamicLibrary.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetMachine.h"
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <vector>
+
+class PrototypeAST;
+class ExprAST;
+
+/// FunctionAST - This class represents a function definition itself.
+class FunctionAST {
+  std::unique_ptr<PrototypeAST> Proto;
+  std::unique_ptr<ExprAST> Body;
+
+public:
+  FunctionAST(std::unique_ptr<PrototypeAST> Proto,
+              std::unique_ptr<ExprAST> Body)
+      : Proto(std::move(Proto)), Body(std::move(Body)) {}
+  const PrototypeAST& getProto() const;
+  const std::string& getName() const;
+  llvm::Function *codegen();
+};
+
+/// This will compile FnAST to IR, rename the function to add the given
+/// suffix (needed to prevent a name-clash with the function's stub),
+/// and then take ownership of the module that the function was compiled
+/// into.
+std::unique_ptr<llvm::Module>
+irgenAndTakeOwnership(FunctionAST &FnAST, const std::string &Suffix);
+
+namespace llvm {
+namespace orc {
+
+class KaleidoscopeJIT {
+private:
+  std::unique_ptr<TargetMachine> TM;
+  const DataLayout DL;
+  ObjectLinkingLayer<> ObjectLayer;
+  IRCompileLayer<decltype(ObjectLayer)> CompileLayer;
+
+  typedef std::function<std::unique_ptr<Module>(std::unique_ptr<Module>)>
+    OptimizeFunction;
+
+  IRTransformLayer<decltype(CompileLayer), OptimizeFunction> OptimizeLayer;
+
+  std::unique_ptr<JITCompileCallbackManager> CompileCallbackMgr;
+  std::unique_ptr<IndirectStubsManager> IndirectStubsMgr;
+
+public:
+  typedef decltype(OptimizeLayer)::ModuleSetHandleT ModuleHandle;
+
+  KaleidoscopeJIT()
+      : TM(EngineBuilder().selectTarget()),
+        DL(TM->createDataLayout()),
+        CompileLayer(ObjectLayer, SimpleCompiler(*TM)),
+        OptimizeLayer(CompileLayer,
+                      [this](std::unique_ptr<Module> M) {
+                        return optimizeModule(std::move(M));
+                      }),
+        CompileCallbackMgr(
+            orc::createLocalCompileCallbackManager(TM->getTargetTriple(), 0)) {
+    auto IndirectStubsMgrBuilder =
+      orc::createLocalIndirectStubsManagerBuilder(TM->getTargetTriple());
+    IndirectStubsMgr = IndirectStubsMgrBuilder();
+    llvm::sys::DynamicLibrary::LoadLibraryPermanently(nullptr);
+  }
+
+  TargetMachine &getTargetMachine() { return *TM; }
+
+  ModuleHandle addModule(std::unique_ptr<Module> M) {
+
+    // Build our symbol resolver:
+    // Lambda 1: Look back into the JIT itself to find symbols that are part of
+    //           the same "logical dylib".
+    // Lambda 2: Search for external symbols in the host process.
+    auto Resolver = createLambdaResolver(
+        [&](const std::string &Name) {
+          if (auto Sym = IndirectStubsMgr->findStub(Name, false))
+            return Sym.toRuntimeDyldSymbol();
+          if (auto Sym = OptimizeLayer.findSymbol(Name, false))
+            return Sym.toRuntimeDyldSymbol();
+          return RuntimeDyld::SymbolInfo(nullptr);
+        },
+        [](const std::string &Name) {
+          if (auto SymAddr =
+                RTDyldMemoryManager::getSymbolAddressInProcess(Name))
+            return RuntimeDyld::SymbolInfo(SymAddr, JITSymbolFlags::Exported);
+          return RuntimeDyld::SymbolInfo(nullptr);
+        });
+
+    // Build a singlton module set to hold our module.
+    std::vector<std::unique_ptr<Module>> Ms;
+    Ms.push_back(std::move(M));
+
+    // Add the set to the JIT with the resolver we created above and a newly
+    // created SectionMemoryManager.
+    return OptimizeLayer.addModuleSet(std::move(Ms),
+                                      make_unique<SectionMemoryManager>(),
+                                      std::move(Resolver));
+  }
+
+  Error addFunctionAST(std::unique_ptr<FunctionAST> FnAST) {
+    // Create a CompileCallback - this is the re-entry point into the compiler
+    // for functions that haven't been compiled yet.
+    auto CCInfo = CompileCallbackMgr->getCompileCallback();
+
+    // Create an indirect stub. This serves as the functions "canonical
+    // definition" - an unchanging (constant address) entry point to the
+    // function implementation.
+    // Initially we point the stub's function-pointer at the compile callback
+    // that we just created. In the compile action for the callback (see below)
+    // we will update the stub's function pointer to point at the function
+    // implementation that we just implemented.
+    if (auto Err = IndirectStubsMgr->createStub(mangle(FnAST->getName()),
+                                                CCInfo.getAddress(),
+                                                JITSymbolFlags::Exported))
+      return Err;
+
+    // Move ownership of FnAST to a shared pointer - C++11 lambdas don't support
+    // capture-by-move, which is be required for unique_ptr.
+    auto SharedFnAST = std::shared_ptr<FunctionAST>(std::move(FnAST));
+
+    // Set the action to compile our AST. This lambda will be run if/when
+    // execution hits the compile callback (via the stub).
+    //
+    // The steps to compile are:
+    // (1) IRGen the function.
+    // (2) Add the IR module to the JIT to make it executable like any other
+    //     module.
+    // (3) Use findSymbol to get the address of the compiled function.
+    // (4) Update the stub pointer to point at the implementation so that
+    ///    subsequent calls go directly to it and bypass the compiler.
+    // (5) Return the address of the implementation: this lambda will actually
+    //     be run inside an attempted call to the function, and we need to
+    //     continue on to the implementation to complete the attempted call.
+    //     The JIT runtime (the resolver block) will use the return address of
+    //     this function as the address to continue at once it has reset the
+    //     CPU state to what it was immediately before the call.
+    CCInfo.setCompileAction(
+      [this, SharedFnAST]() {
+        auto M = irgenAndTakeOwnership(*SharedFnAST, "$impl");
+        addModule(std::move(M));
+        auto Sym = findSymbol(SharedFnAST->getName() + "$impl");
+        assert(Sym && "Couldn't find compiled function?");
+        TargetAddress SymAddr = Sym.getAddress();
+        if (auto Err =
+              IndirectStubsMgr->updatePointer(mangle(SharedFnAST->getName()),
+                                              SymAddr)) {
+          logAllUnhandledErrors(std::move(Err), errs(),
+                                "Error updating function pointer: ");
+          exit(1);
+        }
+
+        return SymAddr;
+      });
+
+    return Error::success();
+  }
+
+  JITSymbol findSymbol(const std::string Name) {
+    return OptimizeLayer.findSymbol(mangle(Name), true);
+  }
+
+  void removeModule(ModuleHandle H) {
+    OptimizeLayer.removeModuleSet(H);
+  }
+
+private:
+
+  std::string mangle(const std::string &Name) {
+    std::string MangledName;
+    raw_string_ostream MangledNameStream(MangledName);
+    Mangler::getNameWithPrefix(MangledNameStream, Name, DL);
+    return MangledNameStream.str();
+  }
+
+  std::unique_ptr<Module> optimizeModule(std::unique_ptr<Module> M) {
+    // Create a function pass manager.
+    auto FPM = llvm::make_unique<legacy::FunctionPassManager>(M.get());
+
+    // Add some optimizations.
+    FPM->add(createInstructionCombiningPass());
+    FPM->add(createReassociatePass());
+    FPM->add(createGVNPass());
+    FPM->add(createCFGSimplificationPass());
+    FPM->doInitialization();
+
+    // Run the optimizations over all functions in the module being added to
+    // the JIT.
+    for (auto &F : *M)
+      FPM->run(F);
+
+    return M;
+  }
+
+};
+
+} // end namespace orc
+} // end namespace llvm
+
+#endif // LLVM_EXECUTIONENGINE_ORC_KALEIDOSCOPEJIT_H