Linkloader improvement: mclinker.

Change-Id: I8805e39ccbc2ee204234fb3e71c70c906f3990bb
diff --git a/tools/llvm-mcld/llvm-mcld.cpp b/tools/llvm-mcld/llvm-mcld.cpp
new file mode 100644
index 0000000..835bb59
--- /dev/null
+++ b/tools/llvm-mcld/llvm-mcld.cpp
@@ -0,0 +1,908 @@
+//===- llvm-mcld.cpp ------------------------------------------------------===//
+//
+//                     The MCLinker Project
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include <mcld/Target/TargetMachine.h>
+#include <mcld/Support/TargetSelect.h>
+#include <mcld/Support/TargetRegistry.h>
+#include <mcld/Support/CommandLine.h>
+#include <mcld/Support/DerivedPositionDependentOptions.h>
+#include <mcld/Support/RealPath.h>
+#include <mcld/CodeGen/SectLinkerOption.h>
+
+#include <llvm/Module.h>
+#include <llvm/PassManager.h>
+#include <llvm/Pass.h>
+#include <llvm/ADT/Triple.h>
+#include <llvm/LLVMContext.h>
+#include <llvm/MC/SubtargetFeature.h>
+#include <llvm/Support/CommandLine.h>
+#include <llvm/Support/Debug.h>
+#include <llvm/Support/FormattedStream.h>
+#include <llvm/Support/Host.h>
+#include <llvm/Support/IRReader.h>
+#include <llvm/Support/ManagedStatic.h>
+#include <llvm/Support/TargetRegistry.h>
+#include <llvm/Support/TargetSelect.h>
+#include <llvm/Support/ToolOutputFile.h>
+#include <llvm/Target/TargetData.h>
+#include <llvm/Target/TargetMachine.h>
+
+using namespace llvm;
+
+#ifdef ENABLE_UNITTEST
+#include <gtest.h>
+
+static cl::opt<bool>
+UnitTest("unittest",  cl::desc("do unit test") );
+
+int unit_test( int argc, char* argv[] )
+{
+  testing::InitGoogleTest( &argc, argv );
+  return RUN_ALL_TESTS();
+}
+
+#endif
+
+
+// General options for llc.  Other pass-specific options are specified
+// within the corresponding llc passes, and target-specific options
+// and back-end code generation options are specified with the target machine.
+//
+static cl::opt<std::string>
+InputFilename("dB",
+              cl::desc("set default bitcode"),
+              cl::value_desc("bitcode"));
+
+static cl::opt<std::string>
+OutputFilename("o",
+               cl::desc("Output filename"),
+               cl::value_desc("filename"));
+
+// Determine optimization level.
+static cl::opt<char>
+OptLevel("O",
+         cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
+                  "(default = '-O2')"),
+         cl::Prefix,
+         cl::ZeroOrMore,
+         cl::init(' '));
+
+static cl::opt<std::string>
+TargetTriple("mtriple", cl::desc("Override target triple for module"));
+
+static cl::opt<std::string>
+MArch("march", cl::desc("Architecture to generate code for (see --version)"));
+
+static cl::opt<std::string>
+MCPU("mcpu",
+  cl::desc("Target a specific cpu type (-mcpu=help for details)"),
+  cl::value_desc("cpu-name"),
+  cl::init(""));
+
+static cl::list<std::string>
+MAttrs("mattr",
+  cl::CommaSeparated,
+  cl::desc("Target specific attributes (-mattr=help for details)"),
+  cl::value_desc("a1,+a2,-a3,..."));
+
+static cl::opt<Reloc::Model>
+RelocModel("relocation-model",
+             cl::desc("Choose relocation model"),
+             cl::init(Reloc::Default),
+             cl::values(
+            clEnumValN(Reloc::Default, "default",
+                       "Target default relocation model"),
+            clEnumValN(Reloc::Static, "static",
+                       "Non-relocatable code"),
+            clEnumValN(Reloc::PIC_, "pic",
+                       "Fully relocatable, position independent code"),
+            clEnumValN(Reloc::DynamicNoPIC, "dynamic-no-pic",
+                       "Relocatable external references, non-relocatable code"),
+            clEnumValEnd));
+
+static cl::opt<llvm::CodeModel::Model>
+CMModel("code-model",
+        cl::desc("Choose code model"),
+        cl::init(CodeModel::Default),
+        cl::values(clEnumValN(CodeModel::Default, "default",
+                              "Target default code model"),
+                   clEnumValN(CodeModel::Small, "small",
+                              "Small code model"),
+                   clEnumValN(CodeModel::Kernel, "kernel",
+                              "Kernel code model"),
+                   clEnumValN(CodeModel::Medium, "medium",
+                              "Medium code model"),
+                   clEnumValN(CodeModel::Large, "large",
+                              "Large code model"),
+                   clEnumValEnd));
+
+cl::opt<mcld::CodeGenFileType>
+FileType("filetype", cl::init(mcld::CGFT_EXEFile),
+  cl::desc("Choose a file type (not all types are supported by all targets):"),
+  cl::values(
+       clEnumValN(mcld::CGFT_ASMFile, "asm",
+                  "Emit an assembly ('.s') file"),
+       clEnumValN(mcld::CGFT_OBJFile, "obj",
+                  "Emit a relocatable object ('.o') file"),
+       clEnumValN(mcld::CGFT_ARCFile, "arc",
+                  "Emit an archive ('.a') file"),
+       clEnumValN(mcld::CGFT_DSOFile, "dso",
+                  "Emit an dynamic shared object ('.so') file"),
+       clEnumValN(mcld::CGFT_EXEFile, "exe",
+                  "Emit a executable ('.exe') file"),
+       clEnumValN(mcld::CGFT_NULLFile, "null",
+                  "Emit nothing, for performance testing"),
+       clEnumValEnd));
+
+cl::opt<bool> NoVerify("disable-verify", cl::Hidden,
+                       cl::desc("Do not verify input module"));
+
+static cl::opt<bool>
+EnableFPMAD("enable-fp-mad",
+  cl::desc("Enable less precise MAD instructions to be generated"),
+  cl::init(false));
+
+static cl::opt<bool>
+PrintCode("print-machineinstrs",
+  cl::desc("Print generated machine code"),
+  cl::init(false));
+
+static cl::opt<bool>
+DisableFPElim("disable-fp-elim",
+  cl::desc("Disable frame pointer elimination optimization"),
+  cl::init(false));
+
+static cl::opt<bool>
+DisableFPElimNonLeaf("disable-non-leaf-fp-elim",
+  cl::desc("Disable frame pointer elimination optimization for non-leaf funcs"),
+  cl::init(false));
+
+static cl::opt<bool>
+DisableExcessPrecision("disable-excess-fp-precision",
+  cl::desc("Disable optimizations that may increase FP precision"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableUnsafeFPMath("enable-unsafe-fp-math",
+  cl::desc("Enable optimizations that may decrease FP precision"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableNoInfsFPMath("enable-no-infs-fp-math",
+  cl::desc("Enable FP math optimizations that assume no +-Infs"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableNoNaNsFPMath("enable-no-nans-fp-math",
+  cl::desc("Enable FP math optimizations that assume no NaNs"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableHonorSignDependentRoundingFPMath("enable-sign-dependent-rounding-fp-math",
+  cl::Hidden,
+  cl::desc("Force codegen to assume rounding mode can change dynamically"),
+  cl::init(false));
+
+static cl::opt<bool>
+GenerateSoftFloatCalls("soft-float",
+  cl::desc("Generate software floating point library calls"),
+  cl::init(false));
+
+static cl::opt<llvm::FloatABI::ABIType>
+FloatABIForCalls("float-abi",
+  cl::desc("Choose float ABI type"),
+  cl::init(FloatABI::Default),
+  cl::values(
+    clEnumValN(FloatABI::Default, "default",
+               "Target default float ABI type"),
+    clEnumValN(FloatABI::Soft, "soft",
+               "Soft float ABI (implied by -soft-float)"),
+    clEnumValN(FloatABI::Hard, "hard",
+               "Hard float ABI (uses FP registers)"),
+    clEnumValEnd));
+
+static cl::opt<bool>
+DontPlaceZerosInBSS("nozero-initialized-in-bss",
+  cl::desc("Don't place zero-initialized symbols into bss section"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableJITExceptionHandling("jit-enable-eh",
+  cl::desc("Emit exception handling information"),
+  cl::init(false));
+
+// In debug builds, make this default to true.
+#ifdef NDEBUG
+#define EMIT_DEBUG false
+#else
+#define EMIT_DEBUG true
+#endif
+static cl::opt<bool>
+EmitJitDebugInfo("jit-emit-debug",
+  cl::desc("Emit debug information to debugger"),
+  cl::init(EMIT_DEBUG));
+#undef EMIT_DEBUG
+
+static cl::opt<bool>
+EmitJitDebugInfoToDisk("jit-emit-debug-to-disk",
+  cl::Hidden,
+  cl::desc("Emit debug info objfiles to disk"),
+  cl::init(false));
+
+static cl::opt<bool>
+EnableGuaranteedTailCallOpt("tailcallopt",
+  cl::desc("Turn fastcc calls into tail calls by (potentially) changing ABI."),
+  cl::init(false));
+
+static cl::opt<unsigned>
+OverrideStackAlignment("stack-alignment",
+  cl::desc("Override default stack alignment"),
+  cl::init(0));
+
+static cl::opt<bool>
+EnableRealignStack("realign-stack",
+  cl::desc("Realign stack if needed"),
+  cl::init(true));
+
+static cl::opt<bool>
+DisableSwitchTables(cl::Hidden, "disable-jump-tables",
+  cl::desc("Do not generate jump tables."),
+  cl::init(false));
+
+static cl::opt<std::string>
+TrapFuncName("trap-func", cl::Hidden,
+  cl::desc("Emit a call to trap function rather than a trap instruction"),
+  cl::init(""));
+
+static cl::opt<bool>
+SegmentedStacks("segmented-stacks",
+  cl::desc("Use segmented stacks if possible."),
+  cl::init(false));
+
+//===----------------------------------------------------------------------===//
+// Command Line Options
+// There are four kinds of command line options:
+//   1. input, (may be a file, such as -m and /tmp/XXXX.o.)
+//   2. attribute of inputs, (describing the attributes of inputs, such as
+//      --as-needed and --whole-archive. usually be positional.)
+//   3. scripting options, (represent a subset of link scripting language, such
+//      as --defsym.)
+//   4. and general options. (the rest of options)
+//===----------------------------------------------------------------------===//
+// General Options
+static cl::opt<mcld::sys::fs::Path, false, llvm::cl::parser<mcld::sys::fs::Path> >
+ArgSysRoot("sysroot",
+           cl::desc("Use directory as the location of the sysroot, overriding the configure-time default."),
+           cl::value_desc("directory"),
+           cl::ValueRequired);
+
+static cl::list<mcld::MCLDDirectory, bool, llvm::cl::parser<mcld::MCLDDirectory> >
+ArgSearchDirList("L",
+                 cl::ZeroOrMore,
+                 cl::desc("Add path searchdir to the list of paths that ld will search for archive libraries and ld control scripts."),
+                 cl::value_desc("searchdir"),
+                 cl::Prefix);
+
+static cl::alias
+ArgSearchDirListAlias("library-path",
+                      cl::desc("alias for -L"),
+                      cl::aliasopt(ArgSearchDirList));
+
+static cl::opt<bool>
+ArgTrace("t",
+         cl::desc("Print the names of the input files as ld processes them."));
+
+static cl::alias
+ArgTraceAlias("trace",
+              cl::desc("alias for -t"),
+              cl::aliasopt(ArgTrace));
+
+static cl::opt<bool>
+ArgVerbose("V",
+          cl::desc("Display the version number for ld and list the linker emulations supported."));
+
+static cl::alias
+ArgVerboseAlias("verbose",
+                cl::desc("alias for -V"),
+                cl::aliasopt(ArgVerbose));
+
+static cl::opt<std::string>
+ArgEntry("e",
+         cl::desc("Use entry as the explicit symbol for beginning execution of your program."),
+         cl::value_desc("entry"),
+         cl::ValueRequired);
+
+static cl::alias
+ArgEntryAlias("entry",
+              cl::desc("alias for -e"),
+              cl::aliasopt(ArgEntry));
+
+static cl::opt<bool>
+ArgBsymbolic("Bsymbolic",
+             cl::desc("Bind references within the shared library."),
+             cl::init(false));
+
+static cl::opt<std::string>
+ArgSOName("soname",
+          cl::desc("Set internal name of shared library"),
+          cl::value_desc("name"));
+
+//===----------------------------------------------------------------------===//
+// Inputs
+static cl::list<mcld::sys::fs::Path>
+ArgInputObjectFiles(cl::Positional,
+                    cl::desc("[input object files]"),
+                    cl::ZeroOrMore);
+
+static cl::list<std::string>
+ArgNameSpecList("l",
+            cl::ZeroOrMore,
+            cl::desc("Add the archive or object file specified by namespec to the list of files to link."),
+            cl::value_desc("namespec"),
+            cl::Prefix);
+
+static cl::alias
+ArgNameSpecListAlias("library",
+                 cl::desc("alias for -l"),
+                 cl::aliasopt(ArgNameSpecList));
+
+static cl::list<bool>
+ArgStartGroupList("start-group",
+                  cl::ValueDisallowed,
+                  cl::desc("start to record a group of archives"));
+
+static cl::alias
+ArgStartGroupListAlias("(",
+                       cl::desc("alias for --start-group"),
+                       cl::aliasopt(ArgStartGroupList));
+
+static cl::list<bool>
+ArgEndGroupList("end-group",
+                cl::ValueDisallowed,
+                cl::desc("stop recording a group of archives"));
+
+static cl::alias
+ArgEndGroupListAlias(")",
+                     cl::desc("alias for --end-group"),
+                     cl::aliasopt(ArgEndGroupList));
+
+//===----------------------------------------------------------------------===//
+// Attributes of Inputs
+static cl::list<bool>
+ArgWholeArchiveList("whole-archive",
+                    cl::ValueDisallowed,
+                    cl::desc("For each archive mentioned on the command line after the --whole-archive option, include all object files in the archive."));
+
+static cl::list<bool>
+ArgNoWholeArchiveList("no-whole-archive",
+                    cl::ValueDisallowed,
+                    cl::desc("Turn off the effect of the --whole-archive option for subsequent archive files."));
+
+static cl::list<bool>
+ArgAsNeededList("as-needed",
+                cl::ValueDisallowed,
+                cl::desc("This option affects ELF DT_NEEDED tags for dynamic libraries mentioned on the command line after the --as-needed option."));
+
+static cl::list<bool>
+ArgNoAsNeededList("no-as-needed",
+                cl::ValueDisallowed,
+                cl::desc("Turn off the effect of the --as-needed option for subsequent dynamic libraries"));
+
+static cl::list<bool>
+ArgAddNeededList("add-needed",
+                cl::ValueDisallowed,
+                cl::desc("--add-needed causes DT_NEEDED tags are always emitted for those libraries from DT_NEEDED tags. This is the default behavior."));
+
+static cl::list<bool>
+ArgNoAddNeededList("no-add-needed",
+                cl::ValueDisallowed,
+                cl::desc("--no-add-needed causes DT_NEEDED tags will never be emitted for those libraries from DT_NEEDED tags"));
+
+static cl::list<bool>
+ArgBDynamicList("Bdynamic",
+                cl::ValueDisallowed,
+                cl::desc("Link against dynamic library"));
+
+static cl::alias
+ArgBDynamicListAlias1("dy",
+                     cl::desc("alias for --Bdynamic"),
+                     cl::aliasopt(ArgBDynamicList));
+
+static cl::alias
+ArgBDynamicListAlias2("call_shared",
+                     cl::desc("alias for --Bdynamic"),
+                     cl::aliasopt(ArgBDynamicList));
+
+static cl::list<bool>
+ArgBStaticList("Bstatic",
+                cl::ValueDisallowed,
+                cl::desc("Link against static library"));
+
+static cl::alias
+ArgBStaticListAlias1("dn",
+                     cl::desc("alias for --Bstatic"),
+                     cl::aliasopt(ArgBStaticList));
+
+static cl::alias
+ArgBStaticListAlias2("static",
+                     cl::desc("alias for --Bstatic"),
+                     cl::aliasopt(ArgBStaticList));
+
+static cl::alias
+ArgBStaticListAlias3("non_shared",
+                     cl::desc("alias for --Bstatic"),
+                     cl::aliasopt(ArgBStaticList));
+
+//===----------------------------------------------------------------------===//
+// Scripting Options
+
+
+//===----------------------------------------------------------------------===//
+/// non-member functions
+
+// GetFileNameRoot - Helper function to get the basename of a filename.
+static inline void
+GetFileNameRoot(const std::string &pInputFilename, std::string& pFileNameRoot)
+{
+  std::string outputFilename;
+  /* *** */
+  const std::string& IFN = pInputFilename;
+  int Len = IFN.length();
+  if ((Len > 2) &&
+      IFN[Len-3] == '.' &&
+      ((IFN[Len-2] == 'b' && IFN[Len-1] == 'c') ||
+       (IFN[Len-2] == 'l' && IFN[Len-1] == 'l')))
+    pFileNameRoot = std::string(IFN.begin(), IFN.end()-3); // s/.bc/.s/
+  else
+    pFileNameRoot = std::string(IFN);
+}
+
+static tool_output_file *GetOutputStream(const char* pTargetName,
+                          Triple::OSType pOSType,
+                          mcld::CodeGenFileType pFileType,
+                          const std::string& pInputFilename,
+                          std::string& pOutputFilename)
+{
+  // If we don't yet have an output filename, make one.
+  if (pOutputFilename.empty()) {
+    if (pInputFilename == "-")
+      pOutputFilename = "-";
+    else {
+      GetFileNameRoot(pInputFilename, pOutputFilename);
+
+      switch (pFileType) {
+      case mcld::CGFT_ASMFile:
+        if (pTargetName[0] == 'c') {
+          if (pTargetName[1] == 0)
+            pOutputFilename += ".cbe.c";
+          else if (pTargetName[1] == 'p' && pTargetName[2] == 'p')
+            pOutputFilename += ".cpp";
+          else
+            pOutputFilename += ".s";
+        }
+        else
+          pOutputFilename += ".s";
+        break;
+      case mcld::CGFT_OBJFile:
+        if (pOSType == Triple::Win32)
+          pOutputFilename += ".obj";
+        else
+          pOutputFilename += ".o";
+        break;
+      case mcld::CGFT_DSOFile:
+        if (pOSType == Triple::Win32)
+         pOutputFilename += ".dll";
+        else
+         pOutputFilename += ".so";
+        break;
+      case mcld::CGFT_ARCFile:
+         pOutputFilename += ".a";
+        break;
+      case mcld::CGFT_EXEFile:
+      case mcld::CGFT_NULLFile:
+        // do nothing
+        break;
+      default:
+        assert(0 && "Unknown file type");
+      }
+    }
+  }
+
+  // Decide if we need "binary" output.
+  bool Binary = false;
+  switch (pFileType) {
+  default: assert(0 && "Unknown file type");
+  case mcld::CGFT_ASMFile:
+    break;
+  case mcld::CGFT_ARCFile:
+  case mcld::CGFT_OBJFile:
+  case mcld::CGFT_DSOFile:
+  case mcld::CGFT_EXEFile:
+  case mcld::CGFT_NULLFile:
+    Binary = true;
+    break;
+  }
+
+  // Open the file.
+  std::string error;
+  unsigned OpenFlags = 0;
+  if (Binary) OpenFlags |= raw_fd_ostream::F_Binary;
+  tool_output_file *FDOut = new tool_output_file(pOutputFilename.c_str(), error,
+                                                 OpenFlags);
+  if (!error.empty()) {
+    errs() << error << '\n';
+    delete FDOut;
+    return 0;
+  }
+
+  return FDOut;
+}
+
+static bool ProcessLinkerInputsFromCommand(mcld::SectLinkerOption &pOption) {
+  // -----  Set up General Options  ----- //
+  // set up soname
+  pOption.info().output().setSOName(ArgSOName);
+
+  // set up sysroot
+  if (!ArgSysRoot.empty()) {
+    if (exists(ArgSysRoot) && is_directory(ArgSysRoot))
+      pOption.info().options().setSysroot(ArgSysRoot);
+  }
+
+  // add all search directories
+  cl::list<mcld::MCLDDirectory>::iterator sd;
+  cl::list<mcld::MCLDDirectory>::iterator sdEnd = ArgSearchDirList.end();
+  for (sd=ArgSearchDirList.begin(); sd!=sdEnd; ++sd) {
+    if (sd->isInSysroot())
+      sd->setSysroot(pOption.info().options().sysroot());
+    if (exists(sd->path()) && is_directory(sd->path())) {
+      pOption.info().options().directories().add(*sd);
+    }
+    else {
+      // FIXME: need a warning function
+      errs() << "WARNING: can not open search directory `-L"
+             << sd->name()
+             << "'.\n";
+    }
+  }
+
+  pOption.info().options().setTrace(ArgTrace);
+  pOption.info().options().setVerbose(ArgVerbose);
+  pOption.info().options().setEntry(ArgEntry);
+  pOption.info().options().setBsymbolic(ArgBsymbolic);
+
+  // -----  Set up Inputs  ----- //
+  // add all start-group
+  cl::list<bool>::iterator sg;
+  cl::list<bool>::iterator sgEnd = ArgStartGroupList.end();
+  for (sg=ArgStartGroupList.begin(); sg!=sgEnd; ++sg) {
+    // calculate position
+    pOption.appendOption(new mcld::StartGroupOption(
+                                    ArgStartGroupList.getPosition(sg-ArgStartGroupList.begin())));
+  }
+
+  // add all end-group
+  cl::list<bool>::iterator eg;
+  cl::list<bool>::iterator egEnd = ArgEndGroupList.end();
+  for (eg=ArgEndGroupList.begin(); eg!=egEnd; ++eg) {
+    // calculate position
+    pOption.appendOption(new mcld::EndGroupOption(
+                                    ArgEndGroupList.getPosition(eg-ArgEndGroupList.begin())));
+  }
+
+  // add all namespecs
+  cl::list<std::string>::iterator ns;
+  cl::list<std::string>::iterator nsEnd = ArgNameSpecList.end();
+  for (ns=ArgNameSpecList.begin(); ns!=nsEnd; ++ns) {
+    // calculate position
+    pOption.appendOption(new mcld::NamespecOption(
+                                    ArgNameSpecList.getPosition(ns-ArgNameSpecList.begin()),
+                                    *ns));
+  }
+
+  // add all object files
+  cl::list<mcld::sys::fs::Path>::iterator obj;
+  cl::list<mcld::sys::fs::Path>::iterator objEnd = ArgInputObjectFiles.end();
+  for (obj=ArgInputObjectFiles.begin(); obj!=objEnd; ++obj) {
+    // calculate position
+    pOption.appendOption(new mcld::InputFileOption(
+                                    ArgInputObjectFiles.getPosition(obj-ArgInputObjectFiles.begin()),
+                                    *obj));
+  }
+
+  // -----  Set up Attributes of Inputs  ----- //
+  // --whole-archive
+  cl::list<bool>::iterator attr = ArgWholeArchiveList.begin();
+  cl::list<bool>::iterator attrEnd = ArgWholeArchiveList.end();
+  for (; attr!=attrEnd; ++attr) {
+    pOption.appendOption(new mcld::WholeArchiveOption(
+                                    ArgWholeArchiveList.getPosition(attr-ArgWholeArchiveList.begin())));
+  }
+
+  // --no-whole-archive
+  attr = ArgNoWholeArchiveList.begin();
+  attrEnd = ArgNoWholeArchiveList.end();
+  for (; attr!=attrEnd; ++attr) {
+    pOption.appendOption(new mcld::NoWholeArchiveOption(
+                                    ArgNoWholeArchiveList.getPosition(attr-ArgNoWholeArchiveList.begin())));
+  }
+
+  // --as-needed
+  attr = ArgAsNeededList.begin();
+  attrEnd = ArgAsNeededList.end();
+  while(attr != attrEnd) {
+    pOption.appendOption(new mcld::AsNeededOption(
+                                    ArgAsNeededList.getPosition(attr-ArgAsNeededList.begin())));
+    ++attr;
+  }
+
+  // --no-as-needed
+  attr = ArgNoAsNeededList.begin();
+  attrEnd = ArgNoAsNeededList.end();
+  while(attr != attrEnd) {
+    pOption.appendOption(new mcld::NoAsNeededOption(
+                                    ArgNoAsNeededList.getPosition(attr-ArgNoAsNeededList.begin())));
+    ++attr;
+  }
+
+  // --add-needed
+  attr = ArgAddNeededList.begin();
+  attrEnd = ArgAddNeededList.end();
+  while(attr != attrEnd) {
+    pOption.appendOption(new mcld::AddNeededOption(
+                                    ArgAddNeededList.getPosition(attr-ArgAddNeededList.begin())));
+    ++attr;
+  }
+
+  // --no-add-needed
+  attr = ArgNoAddNeededList.begin();
+  attrEnd = ArgNoAddNeededList.end();
+  while(attr != attrEnd) {
+    pOption.appendOption(new mcld::NoAddNeededOption(
+                                    ArgNoAddNeededList.getPosition(attr-ArgNoAddNeededList.begin())));
+    ++attr;
+  }
+
+  // -Bdynamic
+  attr = ArgBDynamicList.begin();
+  attrEnd = ArgBDynamicList.end();
+  while(attr != attrEnd) {
+    pOption.appendOption(new mcld::BDynamicOption(
+                                    ArgBDynamicList.getPosition(attr-ArgBDynamicList.begin())));
+  }
+
+  // -Bstatic
+  attr = ArgBStaticList.begin();
+  attrEnd = ArgBStaticList.end();
+  while(attr != attrEnd) {
+    pOption.appendOption(new mcld::BStaticOption(
+                                    ArgBStaticList.getPosition(attr-ArgBStaticList.begin())));
+    ++attr;
+  }
+
+  // -----  Set up Scripting Options  ----- //
+
+  return false;
+}
+
+int main( int argc, char* argv[] )
+{
+
+  LLVMContext &Context = getGlobalContext();
+  llvm_shutdown_obj Y;  // Call llvm_shutdown() on exit.
+  // Initialize targets first, so that --version shows registered targets.
+  InitializeAllTargets();
+  InitializeAllAsmPrinters();
+  InitializeAllAsmParsers();
+  InitializeAllTargetMCs();
+  mcld::InitializeAllTargets();
+  mcld::InitializeAllLinkers();
+  cl::ParseCommandLineOptions(argc, argv, "llvm MCLinker\n");
+
+#ifdef ENABLE_UNITTEST
+  if (UnitTest) {
+    return unit_test( argc, argv );
+  }
+#endif
+
+  // Load the module to be compiled...
+  std::auto_ptr<Module> M;
+
+  if (InputFilename.empty() && (FileType != mcld::CGFT_DSOFile)) {
+    // Read from stdin
+    InputFilename = "-";
+  }
+
+  if (!InputFilename.empty()) {
+    SMDiagnostic Err;
+    M.reset(ParseIRFile(InputFilename, Err, Context));
+
+    if (M.get() == 0) {
+      Err.print(argv[0], errs());
+      errs() << "** Failed to to the given bitcode/llvm asm file '"
+             << InputFilename << "'. **\n";
+      return 1;
+    }
+  } else {
+    // If here, output must be dynamic shared object (mcld::CGFT_DSOFile).
+
+    // Create an empty Module
+    M.reset(new Module("Empty Module", Context));
+  }
+  Module &mod = *M.get();
+
+  // If we are supposed to override the target triple, do so now.
+  Triple TheTriple;
+  if (!TargetTriple.empty()) {
+    TheTriple.setTriple(TargetTriple);
+    mod.setTargetTriple(TargetTriple);
+  }
+
+  // User doesn't specify the triple from command.
+  if (TheTriple.getTriple().empty()) {
+    // Try to get one from the input Module.
+    const std::string &TripleStr = mod.getTargetTriple();
+
+    if (TripleStr.empty())
+      TheTriple.setTriple(sys::getDefaultTargetTriple());
+    else
+      TheTriple.setTriple(TripleStr);
+  }
+
+  // Allocate target machine.  First, check whether the user has explicitly
+  // specified an architecture to compile for. If so we have to look it up by
+  // name, because it might be a backend that has no mapping to a target triple.
+  const mcld::Target *TheTarget = 0;
+  if (!MArch.empty()) {
+    for (mcld::TargetRegistry::iterator it = mcld::TargetRegistry::begin(),
+           ie = mcld::TargetRegistry::end(); it != ie; ++it) {
+      if (MArch == (*it)->get()->getName()) {
+        TheTarget = *it;
+        break;
+      }
+    }
+
+    if (!TheTarget) {
+      errs() << argv[0] << ": error: invalid target '" << MArch << "'.\n";
+      return 1;
+    }
+
+    // Adjust the triple to match (if known), otherwise stick with the
+    // module/host triple.
+    Triple::ArchType Type = Triple::getArchTypeForLLVMName(MArch);
+    if (Type != Triple::UnknownArch)
+      TheTriple.setArch(Type);
+  }
+  else {
+    std::string Err;
+    TheTarget = mcld::TargetRegistry::lookupTarget(TheTriple.getTriple(), Err);
+    if (TheTarget == 0) {
+      errs() << argv[0] << ": error auto-selecting target for module '"
+             << Err << "'.  Please use the -march option to explicitly "
+             << "pick a target.\n";
+      return 1;
+    }
+  }
+
+  // Package up features to be passed to target/subtarget
+  std::string FeaturesStr;
+  if (MAttrs.size()) {
+    SubtargetFeatures Features;
+    for (unsigned i = 0; i != MAttrs.size(); ++i)
+      Features.AddFeature(MAttrs[i]);
+    FeaturesStr = Features.getString();
+  }
+
+  CodeGenOpt::Level OLvl = CodeGenOpt::Default;
+  switch (OptLevel) {
+  default:
+    errs() << argv[0] << ": invalid optimization level.\n";
+    return 1;
+  case ' ': break;
+  case '0': OLvl = CodeGenOpt::None; break;
+  case '1': OLvl = CodeGenOpt::Less; break;
+  case '2': OLvl = CodeGenOpt::Default; break;
+  case '3': OLvl = CodeGenOpt::Aggressive; break;
+  }
+
+  TargetOptions Options;
+  Options.LessPreciseFPMADOption = EnableFPMAD;
+  Options.PrintMachineCode = PrintCode;
+  Options.NoFramePointerElim = DisableFPElim;
+  Options.NoFramePointerElimNonLeaf = DisableFPElimNonLeaf;
+  Options.NoExcessFPPrecision = DisableExcessPrecision;
+  Options.UnsafeFPMath = EnableUnsafeFPMath;
+  Options.NoInfsFPMath = EnableNoInfsFPMath;
+  Options.NoNaNsFPMath = EnableNoNaNsFPMath;
+  Options.HonorSignDependentRoundingFPMathOption =
+      EnableHonorSignDependentRoundingFPMath;
+  Options.UseSoftFloat = GenerateSoftFloatCalls;
+  if (FloatABIForCalls != FloatABI::Default)
+    Options.FloatABIType = FloatABIForCalls;
+  Options.NoZerosInBSS = DontPlaceZerosInBSS;
+  Options.JITExceptionHandling = EnableJITExceptionHandling;
+  Options.JITEmitDebugInfo = EmitJitDebugInfo;
+  Options.JITEmitDebugInfoToDisk = EmitJitDebugInfoToDisk;
+  Options.GuaranteedTailCallOpt = EnableGuaranteedTailCallOpt;
+  Options.StackAlignmentOverride = OverrideStackAlignment;
+  Options.RealignStack = EnableRealignStack;
+  Options.DisableJumpTables = DisableSwitchTables;
+  Options.TrapFuncName = TrapFuncName;
+  Options.EnableSegmentedStacks = SegmentedStacks;
+
+  std::auto_ptr<mcld::LLVMTargetMachine> target_machine(
+          TheTarget->createTargetMachine(TheTriple.getTriple(),
+                                         MCPU, FeaturesStr, Options,
+                                         RelocModel, CMModel, OLvl));
+  assert(target_machine.get() && "Could not allocate target machine!");
+  mcld::LLVMTargetMachine &TheTargetMachine = *target_machine.get();
+
+  TheTargetMachine.getTM().setMCUseLoc(false);
+  TheTargetMachine.getTM().setMCUseCFI(false);
+
+  // Figure out where we are going to send the output...
+  OwningPtr<tool_output_file>
+  Out(GetOutputStream(TheTarget->get()->getName(),
+                      TheTriple.getOS(),
+                      FileType,
+                      InputFilename,
+                      OutputFilename));
+  if (!Out) return 1;
+
+  // Build up all of the passes that we want to do to the module.
+  PassManager PM;
+
+  // Add the target data from the target machine, if it exists, or the module.
+  if (const TargetData *TD = TheTargetMachine.getTM().getTargetData())
+    PM.add(new TargetData(*TD));
+  else
+    PM.add(new TargetData(&mod));
+
+  // Override default to generate verbose assembly.
+  TheTargetMachine.getTM().setAsmVerbosityDefault(true);
+
+  // Process the linker input from the command line
+  mcld::SectLinkerOption *LinkerOpt =
+      new mcld::SectLinkerOption(TheTargetMachine.getLDInfo());
+
+  if (ProcessLinkerInputsFromCommand(*LinkerOpt)) {
+    errs() << argv[0] << ": failed to process inputs from command line!\n";
+    return 1;
+  }
+
+  {
+    formatted_raw_ostream FOS(Out->os());
+
+    // Ask the target to add backend passes as necessary.
+    if( TheTargetMachine.addPassesToEmitFile(PM,
+                                             FOS,
+                                             OutputFilename,
+                                             FileType,
+                                             OLvl,
+                                             LinkerOpt,
+                                             NoVerify)) {
+      errs() << argv[0] << ": target does not support generation of this"
+             << " file type!\n";
+      return 1;
+    }
+
+    // Before executing passes, print the final values of the LLVM options.
+    cl::PrintOptionValues();
+
+    PM.run(mod);
+  }
+
+  // Declare success.
+  Out->keep();
+
+  // clean up
+  delete LinkerOpt;
+
+  return 0;
+}
+