llvm/tools/gccld/gccld.cpp

//===- gccld.cpp - LLVM 'ld' compatible linker ----------------------------===//
//
// This utility is intended to be compatible with GCC, and follows standard
// system 'ld' conventions.  As such, the default output file is ./a.out.
// Additionally, this program outputs a shell script that is used to invoke LLI
// to execute the program.  In this manner, the generated executable (a.out for
// example), is directly executable, whereas the bytecode file actually lives in
// the a.out.bc file generated by this program.  Also, Force is on by default.
//
// Note that if someone (or a script) deletes the executable program generated,
// the .bc file will be left around.  Considering that this is a temporary hack,
// I'm not too worried about this.
//
//===----------------------------------------------------------------------===//

#include "llvm/Transforms/Utils/Linker.h"
#include "llvm/Module.h"
#include "llvm/PassManager.h"
#include "llvm/Bytecode/Reader.h"
#include "llvm/Bytecode/WriteBytecodePass.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Scalar.h"
#include "Support/FileUtilities.h"
#include "Support/SystemUtils.h"
#include "Support/CommandLine.h"
#include "Support/Signals.h"
#include "Config/unistd.h"
#include "util.h"

#include <fstream>
#include <memory>
#include <set>
#include <algorithm>

//
// External function prototypes
//
extern int
GenerateBytecode (Module * M,
                  bool Strip,
                  bool Internalize,
                  std::ofstream * Out);

extern int
generate_assembly (std::string OutputFilename,
                   std::string InputFilename,
                   std::string llc,
                   char ** const envp);
extern int
generate_native (std::string OutputFilename,
                 std::string InputFilename,
                 std::vector<std::string> Libraries,
                 std::string gcc,
                 char ** const envp);

namespace {
  cl::list<std::string> 
  InputFilenames(cl::Positional, cl::desc("<input bytecode files>"),
                 cl::OneOrMore);

  cl::opt<std::string> 
  OutputFilename("o", cl::desc("Override output filename"), cl::init("a.out"),
                 cl::value_desc("filename"));

  cl::opt<bool>    
  Verbose("v", cl::desc("Print information about actions taken"));
  
  cl::list<std::string> 
  LibPaths("L", cl::desc("Specify a library search path"), cl::Prefix,
           cl::value_desc("directory"));

  cl::list<std::string> 
  Libraries("l", cl::desc("Specify libraries to link to"), cl::Prefix,
            cl::value_desc("library prefix"));

  cl::opt<bool>
  Strip("s", cl::desc("Strip symbol info from executable"));

  cl::opt<bool>
  NoInternalize("disable-internalize",
                cl::desc("Do not mark all symbols as internal"));
  static cl::alias
  ExportDynamic("export-dynamic", cl::desc("Alias for -disable-internalize"),
                cl::aliasopt(NoInternalize));

  cl::opt<bool>
  LinkAsLibrary("link-as-library", cl::desc("Link the .bc files together as a"
                                            " library, not an executable"));

  cl::opt<bool>    
  Native("native", cl::desc("Generate a native binary instead of a shell script"));
  
  // Compatibility options that are ignored but supported by LD
  cl::opt<std::string>
  CO3("soname", cl::Hidden, cl::desc("Compatibility option: ignored"));
  cl::opt<std::string>
  CO4("version-script", cl::Hidden, cl::desc("Compatibility option: ignored"));
  cl::opt<bool>
  CO5("eh-frame-hdr", cl::Hidden, cl::desc("Compatibility option: ignored"));
  cl::opt<bool>
  CO6("r", cl::Hidden, cl::desc("Compatibility option: ignored"));
}

// FileExists - Return true if the specified string is an openable file...
static inline bool FileExists(const std::string &FN) {
  return access(FN.c_str(), F_OK) != -1;
}


// LoadObject - Read the specified "object file", which should not search the
// library path to find it.
static inline std::auto_ptr<Module> LoadObject(std::string FN,
                                               std::string &OutErrorMessage) {
  if (Verbose) std::cerr << "Loading '" << FN << "'\n";
  if (!FileExists(FN)) {
    // Attempt to load from the LLVM_LIB_SEARCH_PATH directory... if we would
    // otherwise fail.  This is used to locate objects like crtend.o.
    //
    char *SearchPath = getenv("LLVM_LIB_SEARCH_PATH");
    if (SearchPath && FileExists(std::string(SearchPath)+"/"+FN))
      FN = std::string(SearchPath)+"/"+FN;
    else {
      OutErrorMessage = "could not find input file '" + FN + "'!";
      return std::auto_ptr<Module>();
    }
  }

  std::string ErrorMessage;
  Module *Result = ParseBytecodeFile(FN, &ErrorMessage);
  if (Result) return std::auto_ptr<Module>(Result);

  OutErrorMessage = "Bytecode file '" + FN + "' corrupt!";
  if (ErrorMessage.size()) OutErrorMessage += ": " + ErrorMessage;
  return std::auto_ptr<Module>();
}


static Module *LoadSingleLibraryObject(const std::string &Filename) {
  std::string ErrorMessage;
  std::auto_ptr<Module> M = LoadObject(Filename, ErrorMessage);
  if (M.get() == 0 && Verbose) {
    std::cerr << "Error loading '" + Filename + "'";
    if (!ErrorMessage.empty()) std::cerr << ": " << ErrorMessage;
    std::cerr << "\n";
  }
  
  return M.release();
}

// LoadLibraryExactName - This looks for a file with a known name and tries to
// load it, similarly to LoadLibraryFromDirectory(). 
static inline bool LoadLibraryExactName(const std::string &FileName,
    std::vector<Module*> &Objects, bool &isArchive) {
  if (Verbose) std::cerr << "  Considering '" << FileName << "'\n";
  if (FileExists(FileName)) {
	if (IsArchive(FileName)) {
      std::string ErrorMessage;
      if (Verbose) std::cerr << "  Loading '" << FileName << "'\n";
      if (!ReadArchiveFile(FileName, Objects, &ErrorMessage)) {
        isArchive = true;
        return false;           // Success!
      }
      if (Verbose) {
        std::cerr << "  Error loading archive '" + FileName + "'";
        if (!ErrorMessage.empty()) std::cerr << ": " << ErrorMessage;
        std::cerr << "\n";
      }
    } else {
      if (Module *M = LoadSingleLibraryObject(FileName)) {
        isArchive = false;
        Objects.push_back(M);
        return false;
      }
    }
  }
  return true;
}

// LoadLibrary - Try to load a library named LIBNAME that contains
// LLVM bytecode. If SEARCH is true, then search for a file named
// libLIBNAME.{a,so,bc} in the current library search path.  Otherwise,
// assume LIBNAME is the real name of the library file.  This method puts
// the loaded modules into the Objects list, and sets isArchive to true if
// a .a file was loaded. It returns true if no library is found or if an
// error occurs; otherwise it returns false.
//
static inline bool LoadLibrary(const std::string &LibName,
                               std::vector<Module*> &Objects, bool &isArchive,
                               bool search, std::string &ErrorMessage) {
  if (search) {
    // First, try the current directory. Then, iterate over the
    // directories in LibPaths, looking for a suitable match for LibName
    // in each one.
    for (unsigned NextLibPathIdx = 0; NextLibPathIdx != LibPaths.size();
         ++NextLibPathIdx) {
      std::string Directory = LibPaths[NextLibPathIdx] + "/";
      if (!LoadLibraryExactName(Directory + "lib" + LibName + ".a",
        Objects, isArchive))
          return false;
      if (!LoadLibraryExactName(Directory + "lib" + LibName + ".so",
        Objects, isArchive))
          return false;
      if (!LoadLibraryExactName(Directory + "lib" + LibName + ".bc",
        Objects, isArchive))
          return false;
    }
  } else {
    // If they said no searching, then assume LibName is the real name.
    if (!LoadLibraryExactName(LibName, Objects, isArchive))
      return false;
  }
  ErrorMessage = "error linking library '-l" + LibName+ "': library not found!";
  return true;
}


static bool LinkLibrary(Module *M, const std::string &LibName,
                        bool search, std::string &ErrorMessage) {
  std::set<std::string> UndefinedSymbols;
  GetAllUndefinedSymbols(M, UndefinedSymbols);
  if (UndefinedSymbols.empty()) {
    if (Verbose) std::cerr << "  No symbols undefined, don't link library!\n";
    return false;  // No need to link anything in!
  }

  std::vector<Module*> Objects;
  bool isArchive;
  if (LoadLibrary(LibName, Objects, isArchive, search, ErrorMessage))
    return true;

  // Figure out which symbols are defined by all of the modules in the .a file
  std::vector<std::set<std::string> > DefinedSymbols;
  DefinedSymbols.resize(Objects.size());
  for (unsigned i = 0; i != Objects.size(); ++i)
    GetAllDefinedSymbols(Objects[i], DefinedSymbols[i]);

  bool Linked = true;
  while (Linked) {     // While we are linking in object files, loop.
    Linked = false;

    for (unsigned i = 0; i != Objects.size(); ++i) {
      // Consider whether we need to link in this module...  we only need to
      // link it in if it defines some symbol which is so far undefined.
      //
      const std::set<std::string> &DefSymbols = DefinedSymbols[i];

      bool ObjectRequired = false;
      for (std::set<std::string>::iterator I = UndefinedSymbols.begin(),
             E = UndefinedSymbols.end(); I != E; ++I)
        if (DefSymbols.count(*I)) {
          if (Verbose)
            std::cerr << "  Found object providing symbol '" << *I << "'...\n";
          ObjectRequired = true;
          break;
        }
      
      // We DO need to link this object into the program...
      if (ObjectRequired) {
        if (LinkModules(M, Objects[i], &ErrorMessage))
          return true;   // Couldn't link in the right object file...        
        
        // Since we have linked in this object, delete it from the list of
        // objects to consider in this archive file.
        std::swap(Objects[i], Objects.back());
        std::swap(DefinedSymbols[i], DefinedSymbols.back());
        Objects.pop_back();
        DefinedSymbols.pop_back();
        --i;   // Do not skip an entry
        
        // The undefined symbols set should have shrunk.
        GetAllUndefinedSymbols(M, UndefinedSymbols);
        Linked = true;  // We have linked something in!
      }
    }
  }
  
  return false;
}


int
main(int argc, char **argv, char ** envp)
{
  cl::ParseCommandLineOptions(argc, argv, " llvm linker for GCC\n");

  std::string ErrorMessage;
  std::auto_ptr<Module> Composite(LoadObject(InputFilenames[0], ErrorMessage));
  if (Composite.get() == 0)
    return PrintAndReturn(argv[0], ErrorMessage);

  // We always look first in the current directory when searching for libraries.
  LibPaths.insert(LibPaths.begin(), ".");

  // If the user specied an extra search path in their environment, respect it.
  if (char *SearchPath = getenv("LLVM_LIB_SEARCH_PATH"))
    LibPaths.push_back(SearchPath);

  for (unsigned i = 1; i < InputFilenames.size(); ++i) {
    // A user may specify an ar archive without -l, perhaps because it
    // is not installed as a library. Detect that and link the library.
    if (IsArchive(InputFilenames[i])) {
      if (Verbose) std::cerr << "Linking archive '" << InputFilenames[i]
                             << "'\n";
      if (LinkLibrary(Composite.get(), InputFilenames[i], false, ErrorMessage))
        return PrintAndReturn(argv[0], ErrorMessage,
                              ": error linking in '" + InputFilenames[i] + "'");
      continue;
    }

    std::auto_ptr<Module> M(LoadObject(InputFilenames[i], ErrorMessage));
    if (M.get() == 0)
      return PrintAndReturn(argv[0], ErrorMessage);

    if (Verbose) std::cerr << "Linking in '" << InputFilenames[i] << "'\n";

    if (LinkModules(Composite.get(), M.get(), &ErrorMessage))
      return PrintAndReturn(argv[0], ErrorMessage,
                            ": error linking in '" + InputFilenames[i] + "'");
  }

  // Remove any consecutive duplicates of the same library...
  Libraries.erase(std::unique(Libraries.begin(), Libraries.end()),
                  Libraries.end());

  // Link in all of the libraries next...
  for (unsigned i = 0; i != Libraries.size(); ++i) {
    if (Verbose) std::cerr << "Linking in library: -l" << Libraries[i] << "\n";
    if (LinkLibrary(Composite.get(), Libraries[i], true, ErrorMessage))
      if (!Native)
        return PrintAndReturn(argv[0], ErrorMessage);
  }

  //
  // Create the output file.
  //
  std::string RealBytecodeOutput = OutputFilename;
  if (!LinkAsLibrary) RealBytecodeOutput += ".bc";
  std::ofstream Out(RealBytecodeOutput.c_str());
  if (!Out.good())
    return PrintAndReturn(argv[0], "error opening '" + RealBytecodeOutput +
                                   "' for writing!");

  //
  // Ensure that the bytecode file gets removed from the disk if we get a
  // SIGINT signal.
  //
  RemoveFileOnSignal(RealBytecodeOutput);

  //
  // Generate the bytecode file.
  //
  if (GenerateBytecode (Composite.get(), Strip, !NoInternalize, &Out))
  {
    Out.close();
    return PrintAndReturn(argv[0], "error generating bytcode");
  }

  //
  // Close the bytecode file.
  //
  Out.close();

  //
  // If we are not linking a library, generate either a native executable
  // or a JIT shell script, depending upon what the user wants.
  //
  if (!LinkAsLibrary) {
    //
    // If the user wants to generate a native executable, compile it from the
    // bytecode file.
    //
    // Otherwise, create a script that will run the bytecode through the JIT.
    //
    if (Native)
    {
      // Name of the Assembly Language output file
      std::string AssemblyFile = OutputFilename + ".s";

      //
      // Mark the output files for removal if we get an interrupt.
      //
      RemoveFileOnSignal (AssemblyFile);
      RemoveFileOnSignal (OutputFilename);

      //
      // Determine the locations of the llc and gcc programs.
      //
      std::string llc=FindExecutable ("llc", argv[0]);
      std::string gcc=FindExecutable ("gcc", argv[0]);
      if (llc.empty())
      {
        return PrintAndReturn (argv[0], "Failed to find llc");
      }

      if (gcc.empty())
      {
        return PrintAndReturn (argv[0], "Failed to find gcc");
      }

      //
      // Generate an assembly language file for the bytecode.
      //
      generate_assembly (AssemblyFile, RealBytecodeOutput, llc, envp);
      generate_native   (OutputFilename, AssemblyFile, Libraries, gcc, envp);

      //
      // Remove the assembly language file.
      //
      removeFile (AssemblyFile);
    }
    else
    {
      // Output the script to start the program...
      std::ofstream Out2(OutputFilename.c_str());
      if (!Out2.good())
        return PrintAndReturn(argv[0], "error opening '" + OutputFilename +
                                       "' for writing!");
      Out2 << "#!/bin/sh\nlli -q $0.bc $*\n";
      Out2.close();
    }
  
    // Make the script executable...
    MakeFileExecutable (OutputFilename);

    // Make the bytecode file readable and directly executable in LLEE as well
    MakeFileExecutable (RealBytecodeOutput);
    MakeFileReadable   (RealBytecodeOutput);
  }

  return 0;
}