text: //===- OptimizerDriver.cpp - Allow BugPoint to run passes safely ----------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines an interface that allows bugpoint to run various passes
  // without the threat of a buggy pass corrupting bugpoint (of course, bugpoint
  // may have its own bugs, but that's another story...).  It achieves this by
  // forking a copy of itself and having the child process do the optimizations.
  // If this client dies, we can always fork a new one.  :)
  //
  //===----------------------------------------------------------------------===//
  
  #include "BugDriver.h"
  #include "llvm/Bitcode/ReaderWriter.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/Verifier.h"
  #include "llvm/PassManager.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/FileUtilities.h"
  #include "llvm/Support/Path.h"
  #include "llvm/Support/Program.h"
  #include "llvm/Support/SystemUtils.h"
  #include "llvm/Support/ToolOutputFile.h"
  
  #define DONT_GET_PLUGIN_LOADER_OPTION
  #include "llvm/Support/PluginLoader.h"
  
  #include <fstream>
  
  using namespace llvm;
  
  #define DEBUG_TYPE "bugpoint"
  
  namespace llvm {
    extern cl::opt<std::string> OutputPrefix;
  }
  
  namespace {
    // ChildOutput - This option captures the name of the child output file that
    // is set up by the parent bugpoint process
    cl::opt<std::string> ChildOutput("child-output", cl::ReallyHidden);
    cl::opt<std::string> OptCmd("opt-command", cl::init(""),
                                cl::desc("Path to opt. (default: search path "
                                         "for 'opt'.)"));
  }
  
  /// writeProgramToFile - This writes the current "Program" to the named bitcode
  /// file.  If an error occurs, true is returned.
  ///
  static bool writeProgramToFileAux(tool_output_file &Out, const Module *M) {
    WriteBitcodeToFile(M, Out.os());
    Out.os().close();
    if (!Out.os().has_error()) {
      Out.keep();
      return false;
    }
    return true;
  }
  
  bool BugDriver::writeProgramToFile(const std::string &Filename, int FD,
                                     const Module *M) const {
    tool_output_file Out(Filename.c_str(), FD);
    return writeProgramToFileAux(Out, M);
  }
  
  bool BugDriver::writeProgramToFile(const std::string &Filename,
                                     const Module *M) const {
    std::string ErrInfo;
    tool_output_file Out(Filename.c_str(), ErrInfo, sys::fs::F_None);
    if (ErrInfo.empty())
      return writeProgramToFileAux(Out, M);
    return true;
  }
  
  
  /// EmitProgressBitcode - This function is used to output the current Program
  /// to a file named "bugpoint-ID.bc".
  ///
  void BugDriver::EmitProgressBitcode(const Module *M,
                                      const std::string &ID,
                                      bool NoFlyer)  const {
    // Output the input to the current pass to a bitcode file, emit a message
    // telling the user how to reproduce it: opt -foo blah.bc
    //
    std::string Filename = OutputPrefix + "-" + ID + ".bc";
    if (writeProgramToFile(Filename, M)) {
      errs() <<  "Error opening file '" << Filename << "' for writing!\n";
      return;
    }
  
    outs() << "Emitted bitcode to '" << Filename << "'\n";
    if (NoFlyer || PassesToRun.empty()) return;
    outs() << "\n*** You can reproduce the problem with: ";
    if (UseValgrind) outs() << "valgrind ";
    outs() << "opt " << Filename;
    for (unsigned i = 0, e = PluginLoader::getNumPlugins(); i != e; ++i) {
      outs() << " -load " << PluginLoader::getPlugin(i);
    }
    outs() << " " << getPassesString(PassesToRun) << "\n";
  }
  
  cl::opt<bool> SilencePasses("silence-passes",
          cl::desc("Suppress output of running passes (both stdout and stderr)"));
  
  static cl::list<std::string> OptArgs("opt-args", cl::Positional,
                                       cl::desc("<opt arguments>..."),
                                       cl::ZeroOrMore, cl::PositionalEatsArgs);
  
  /// runPasses - Run the specified passes on Program, outputting a bitcode file
  /// and writing the filename into OutputFile if successful.  If the
  /// optimizations fail for some reason (optimizer crashes), return true,
  /// otherwise return false.  If DeleteOutput is set to true, the bitcode is
  /// deleted on success, and the filename string is undefined.  This prints to
  /// outs() a single line message indicating whether compilation was successful
  /// or failed.
  ///
  bool BugDriver::runPasses(Module *Program,
                            const std::vector<std::string> &Passes,
                            std::string &OutputFilename, bool DeleteOutput,
                            bool Quiet, unsigned NumExtraArgs,
                            const char * const *ExtraArgs) const {
    // setup the output file name
    outs().flush();
    SmallString<128> UniqueFilename;
    std::error_code EC = sys::fs::createUniqueFile(
        OutputPrefix + "-output-%%%%%%%.bc", UniqueFilename);
    if (EC) {
      errs() << getToolName() << ": Error making unique filename: "
             << EC.message() << "\n";
      return 1;
    }
    OutputFilename = UniqueFilename.str();
  
    // set up the input file name
    SmallString<128> InputFilename;
    int InputFD;
    EC = sys::fs::createUniqueFile(OutputPrefix + "-input-%%%%%%%.bc", InputFD,
                                   InputFilename);
    if (EC) {
      errs() << getToolName() << ": Error making unique filename: "
             << EC.message() << "\n";
      return 1;
    }
  
    tool_output_file InFile(InputFilename.c_str(), InputFD);
  
    WriteBitcodeToFile(Program, InFile.os());
    InFile.os().close();
    if (InFile.os().has_error()) {
      errs() << "Error writing bitcode file: " << InputFilename << "\n";
      InFile.os().clear_error();
      return 1;
    }
  
    std::string tool = OptCmd.empty()? sys::FindProgramByName("opt") : OptCmd;
    if (tool.empty()) {
      errs() << "Cannot find `opt' in PATH!\n";
      return 1;
    }
  
    // Ok, everything that could go wrong before running opt is done.
    InFile.keep();
  
    // setup the child process' arguments
    SmallVector<const char*, 8> Args;
    if (UseValgrind) {
      Args.push_back("valgrind");
      Args.push_back("--error-exitcode=1");
      Args.push_back("-q");
      Args.push_back(tool.c_str());
    } else
      Args.push_back(tool.c_str());
  
    Args.push_back("-o");
    Args.push_back(OutputFilename.c_str());
    for (unsigned i = 0, e = OptArgs.size(); i != e; ++i)
      Args.push_back(OptArgs[i].c_str());
    std::vector<std::string> pass_args;
    for (unsigned i = 0, e = PluginLoader::getNumPlugins(); i != e; ++i) {
      pass_args.push_back( std::string("-load"));
      pass_args.push_back( PluginLoader::getPlugin(i));
    }
    for (std::vector<std::string>::const_iterator I = Passes.begin(),
         E = Passes.end(); I != E; ++I )
      pass_args.push_back( std::string("-") + (*I) );
    for (std::vector<std::string>::const_iterator I = pass_args.begin(),
         E = pass_args.end(); I != E; ++I )
      Args.push_back(I->c_str());
    Args.push_back(InputFilename.c_str());
    for (unsigned i = 0; i < NumExtraArgs; ++i)
      Args.push_back(*ExtraArgs);
    Args.push_back(nullptr);
  
    DEBUG(errs() << "\nAbout to run:\t";
          for (unsigned i = 0, e = Args.size()-1; i != e; ++i)
            errs() << " " << Args[i];
          errs() << "\n";
          );
  
    std::string Prog;
    if (UseValgrind)
      Prog = sys::FindProgramByName("valgrind");
    else
      Prog = tool;
  
    // Redirect stdout and stderr to nowhere if SilencePasses is given
    StringRef Nowhere;
    const StringRef *Redirects[3] = {nullptr, &Nowhere, &Nowhere};
  
    std::string ErrMsg;
    int result = sys::ExecuteAndWait(Prog, Args.data(), nullptr,
                                     (SilencePasses ? Redirects : nullptr),
                                     Timeout, MemoryLimit, &ErrMsg);
  
    // If we are supposed to delete the bitcode file or if the passes crashed,
    // remove it now.  This may fail if the file was never created, but that's ok.
    if (DeleteOutput || result != 0)
      sys::fs::remove(OutputFilename);
  
    // Remove the temporary input file as well
    sys::fs::remove(InputFilename.c_str());
  
    if (!Quiet) {
      if (result == 0)
        outs() << "Success!\n";
      else if (result > 0)
        outs() << "Exited with error code '" << result << "'\n";
      else if (result < 0) {
        if (result == -1)
          outs() << "Execute failed: " << ErrMsg << "\n";
        else
          outs() << "Crashed: " << ErrMsg << "\n";
      }
      if (result & 0x01000000)
        outs() << "Dumped core\n";
    }
  
    // Was the child successful?
    return result != 0;
  }
  
  
  /// runPassesOn - Carefully run the specified set of pass on the specified
  /// module, returning the transformed module on success, or a null pointer on
  /// failure.
  Module *BugDriver::runPassesOn(Module *M,
                                 const std::vector<std::string> &Passes,
                                 bool AutoDebugCrashes, unsigned NumExtraArgs,
                                 const char * const *ExtraArgs) {
    std::string BitcodeResult;
    if (runPasses(M, Passes, BitcodeResult, false/*delete*/, true/*quiet*/,
                  NumExtraArgs, ExtraArgs)) {
      if (AutoDebugCrashes) {
        errs() << " Error running this sequence of passes"
               << " on the input program!\n";
        delete swapProgramIn(M);
        EmitProgressBitcode(M, "pass-error",  false);
        exit(debugOptimizerCrash());
      }
      return nullptr;
    }
  
    Module *Ret = ParseInputFile(BitcodeResult, Context);
    if (!Ret) {
      errs() << getToolName() << ": Error reading bitcode file '"
             << BitcodeResult << "'!\n";
      exit(1);
    }
    sys::fs::remove(BitcodeResult);
    return Ret;
  }
  