//===-- examples/clang-interpreter/main.cpp - Clang C Interpreter Example -===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "clang/Basic/DiagnosticOptions.h"
#include "clang/CodeGen/CodeGenAction.h"
#include "clang/Driver/Compilation.h"
#include "clang/Driver/Driver.h"
#include "clang/Driver/Tool.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Frontend/CompilerInvocation.h"
#include "clang/Frontend/FrontendDiagnostic.h"
#include "clang/Frontend/TextDiagnosticPrinter.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/ExecutionEngine/Orc/CompileUtils.h"
#include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
#include "llvm/ExecutionEngine/Orc/IRCompileLayer.h"
#include "llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h"
#include "llvm/ExecutionEngine/SectionMemoryManager.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"

using namespace clang;
using namespace clang::driver;

// This function isn't referenced outside its translation unit, but it
// can't use the "static" keyword because its address is used for
// GetMainExecutable (since some platforms don't support taking the
// address of main, and some platforms can't implement GetMainExecutable
// without being given the address of a function in the main executable).
std::string GetExecutablePath(const char *Argv0, void *MainAddr) {
  return llvm::sys::fs::getMainExecutable(Argv0, MainAddr);
}

namespace llvm {
namespace orc {

class SimpleJIT {
private:
  ExecutionSession ES;
  std::unique_ptr<TargetMachine> TM;
  const DataLayout DL;
  MangleAndInterner Mangle{ES, DL};
  JITDylib &MainJD{ES.createJITDylib("<main>")};
  RTDyldObjectLinkingLayer ObjectLayer{ES, createMemMgr};
  IRCompileLayer CompileLayer{ES, ObjectLayer, SimpleCompiler(*TM)};

  static std::unique_ptr<SectionMemoryManager> createMemMgr() {
    return std::make_unique<SectionMemoryManager>();
  }

  SimpleJIT(
      std::unique_ptr<TargetMachine> TM, DataLayout DL,
      std::unique_ptr<DynamicLibrarySearchGenerator> ProcessSymbolsGenerator)
      : TM(std::move(TM)), DL(std::move(DL)) {
    llvm::sys::DynamicLibrary::LoadLibraryPermanently(nullptr);
    MainJD.addGenerator(std::move(ProcessSymbolsGenerator));
  }

public:
  static Expected<std::unique_ptr<SimpleJIT>> Create() {
    auto JTMB = JITTargetMachineBuilder::detectHost();
    if (!JTMB)
      return JTMB.takeError();

    auto TM = JTMB->createTargetMachine();
    if (!TM)
      return TM.takeError();

    auto DL = (*TM)->createDataLayout();

    auto ProcessSymbolsGenerator =
        DynamicLibrarySearchGenerator::GetForCurrentProcess(
            DL.getGlobalPrefix());

    if (!ProcessSymbolsGenerator)
      return ProcessSymbolsGenerator.takeError();

    return std::unique_ptr<SimpleJIT>(new SimpleJIT(
        std::move(*TM), std::move(DL), std::move(*ProcessSymbolsGenerator)));
  }

  const TargetMachine &getTargetMachine() const { return *TM; }

  Error addModule(ThreadSafeModule M) {
    return CompileLayer.add(MainJD, std::move(M));
  }

  Expected<JITEvaluatedSymbol> findSymbol(const StringRef &Name) {
    return ES.lookup({&MainJD}, Mangle(Name));
  }

  Expected<JITTargetAddress> getSymbolAddress(const StringRef &Name) {
    auto Sym = findSymbol(Name);
    if (!Sym)
      return Sym.takeError();
    return Sym->getAddress();
  }
};

} // end namespace orc
} // end namespace llvm

llvm::ExitOnError ExitOnErr;

int main(int argc, const char **argv) {
  // This just needs to be some symbol in the binary; C++ doesn't
  // allow taking the address of ::main however.
  void *MainAddr = (void*) (intptr_t) GetExecutablePath;
  std::string Path = GetExecutablePath(argv[0], MainAddr);
  IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts = new DiagnosticOptions();
  TextDiagnosticPrinter *DiagClient =
    new TextDiagnosticPrinter(llvm::errs(), &*DiagOpts);

  IntrusiveRefCntPtr<DiagnosticIDs> DiagID(new DiagnosticIDs());
  DiagnosticsEngine Diags(DiagID, &*DiagOpts, DiagClient);

  const std::string TripleStr = llvm::sys::getProcessTriple();
  llvm::Triple T(TripleStr);

  // Use ELF on Windows-32 and MingW for now.
#ifndef CLANG_INTERPRETER_COFF_FORMAT
  if (T.isOSBinFormatCOFF())
    T.setObjectFormat(llvm::Triple::ELF);
#endif

  ExitOnErr.setBanner("clang interpreter");

  Driver TheDriver(Path, T.str(), Diags);
  TheDriver.setTitle("clang interpreter");
  TheDriver.setCheckInputsExist(false);

  // FIXME: This is a hack to try to force the driver to do something we can
  // recognize. We need to extend the driver library to support this use model
  // (basically, exactly one input, and the operation mode is hard wired).
  SmallVector<const char *, 16> Args(argv, argv + argc);
  Args.push_back("-fsyntax-only");
  std::unique_ptr<Compilation> C(TheDriver.BuildCompilation(Args));
  if (!C)
    return 0;

  // FIXME: This is copied from ASTUnit.cpp; simplify and eliminate.

  // We expect to get back exactly one command job, if we didn't something
  // failed. Extract that job from the compilation.
  const driver::JobList &Jobs = C->getJobs();
  if (Jobs.size() != 1 || !isa<driver::Command>(*Jobs.begin())) {
    SmallString<256> Msg;
    llvm::raw_svector_ostream OS(Msg);
    Jobs.Print(OS, "; ", true);
    Diags.Report(diag::err_fe_expected_compiler_job) << OS.str();
    return 1;
  }

  const driver::Command &Cmd = cast<driver::Command>(*Jobs.begin());
  if (llvm::StringRef(Cmd.getCreator().getName()) != "clang") {
    Diags.Report(diag::err_fe_expected_clang_command);
    return 1;
  }

  // Initialize a compiler invocation object from the clang (-cc1) arguments.
  const llvm::opt::ArgStringList &CCArgs = Cmd.getArguments();
  std::unique_ptr<CompilerInvocation> CI(new CompilerInvocation);
  CompilerInvocation::CreateFromArgs(*CI, CCArgs, Diags);

  // Show the invocation, with -v.
  if (CI->getHeaderSearchOpts().Verbose) {
    llvm::errs() << "clang invocation:\n";
    Jobs.Print(llvm::errs(), "\n", true);
    llvm::errs() << "\n";
  }

  // FIXME: This is copied from cc1_main.cpp; simplify and eliminate.

  // Create a compiler instance to handle the actual work.
  CompilerInstance Clang;
  Clang.setInvocation(std::move(CI));

  // Create the compilers actual diagnostics engine.
  Clang.createDiagnostics();
  if (!Clang.hasDiagnostics())
    return 1;

  // Infer the builtin include path if unspecified.
  if (Clang.getHeaderSearchOpts().UseBuiltinIncludes &&
      Clang.getHeaderSearchOpts().ResourceDir.empty())
    Clang.getHeaderSearchOpts().ResourceDir =
      CompilerInvocation::GetResourcesPath(argv[0], MainAddr);

  // Create and execute the frontend to generate an LLVM bitcode module.
  std::unique_ptr<CodeGenAction> Act(new EmitLLVMOnlyAction());
  if (!Clang.ExecuteAction(*Act))
    return 1;

  llvm::InitializeNativeTarget();
  llvm::InitializeNativeTargetAsmPrinter();

  int Res = 255;
  std::unique_ptr<llvm::LLVMContext> Ctx(Act->takeLLVMContext());
  std::unique_ptr<llvm::Module> Module = Act->takeModule();

  if (Module) {
    auto J = ExitOnErr(llvm::orc::SimpleJIT::Create());

    ExitOnErr(J->addModule(
        llvm::orc::ThreadSafeModule(std::move(Module), std::move(Ctx))));
    auto Main = (int (*)(...))ExitOnErr(J->getSymbolAddress("main"));
    Res = Main();
  }

  // Shutdown.
  llvm::llvm_shutdown();

  return Res;
}