Vendor import of lld release_39 branch r276489:vendor/lld/lld-release_39-r276489

https://llvm.org/svn/llvm-project/lld/branches/release_39@276489

1685 files changed, 30937 insertions, 78902 deletions

diff --git a/.arcconfig b/.arcconfig
index 787b339a9f20..ebf4a4a6f8b7 100644
--- a/.arcconfig
+++ b/.arcconfig
@@ -1,4 +1,4 @@
 {
   "project_id" : "lld",
-  "conduit_uri" : "http://reviews.llvm.org/"
+  "conduit_uri" : "https://reviews.llvm.org/"
 }
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7458de08fc16..46ca748f8fac 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -94,7 +94,7 @@ endmacro(add_lld_library)
 
 
 add_subdirectory(lib)
-add_subdirectory(tools)
+add_subdirectory(tools/lld)
 
 if (LLVM_INCLUDE_TESTS)
   add_subdirectory(test)
diff --git a/COFF/CMakeLists.txt b/COFF/CMakeLists.txt
index 3f31ba9ba1fb..3319f392efe1 100644
--- a/COFF/CMakeLists.txt
+++ b/COFF/CMakeLists.txt
@@ -10,6 +10,7 @@ add_lld_library(lldCOFF
   Error.cpp
   ICF.cpp
   InputFiles.cpp
+  Librarian.cpp
   MarkLive.cpp
   ModuleDef.cpp
   PDB.cpp
@@ -28,6 +29,8 @@ add_lld_library(lldCOFF
   Target
   Option
   Support
+
+  LINK_LIBS ${PTHREAD_LIB}
   )
 
 add_dependencies(lldCOFF COFFOptionsTableGen)
diff --git a/COFF/Chunks.cpp b/COFF/Chunks.cpp
index f9f768d69866..1c1b18176aa2 100644
--- a/COFF/Chunks.cpp
+++ b/COFF/Chunks.cpp
@@ -34,10 +34,7 @@ SectionChunk::SectionChunk(ObjectFile *F, const coff_section *H)
   // Initialize SectionName.
   File->getCOFFObj()->getSectionName(Header, SectionName);
 
-  // Bit [20:24] contains section alignment. Both 0 and 1 mean alignment 1.
-  unsigned Shift = (Header->Characteristics >> 20) & 0xF;
-  if (Shift > 0)
-    Align = uint32_t(1) << (Shift - 1);
+  Align = Header->getAlignment();
 
   // Only COMDAT sections are subject of dead-stripping.
   Live = !isCOMDAT();
@@ -64,7 +61,7 @@ void SectionChunk::applyRelX64(uint8_t *Off, uint16_t Type, Defined *Sym,
   case IMAGE_REL_AMD64_SECTION:  add16(Off, Sym->getSectionIndex()); break;
   case IMAGE_REL_AMD64_SECREL:   add32(Off, Sym->getSecrel()); break;
   default:
-    error("Unsupported relocation type");
+    fatal("unsupported relocation type");
   }
 }
 
@@ -79,7 +76,7 @@ void SectionChunk::applyRelX86(uint8_t *Off, uint16_t Type, Defined *Sym,
   case IMAGE_REL_I386_SECTION:  add16(Off, Sym->getSectionIndex()); break;
   case IMAGE_REL_I386_SECREL:   add32(Off, Sym->getSecrel()); break;
   default:
-    error("Unsupported relocation type");
+    fatal("unsupported relocation type");
   }
 }
 
@@ -123,7 +120,7 @@ void SectionChunk::applyRelARM(uint8_t *Off, uint16_t Type, Defined *Sym,
   case IMAGE_REL_ARM_BRANCH24T: applyBranch24T(Off, S - P - 4); break;
   case IMAGE_REL_ARM_BLX23T:    applyBranch24T(Off, S - P - 4); break;
   default:
-    error("Unsupported relocation type");
+    fatal("unsupported relocation type");
   }
 }
 
@@ -310,7 +307,7 @@ void SEHTableChunk::writeTo(uint8_t *Buf) const {
 BaserelChunk::BaserelChunk(uint32_t Page, Baserel *Begin, Baserel *End) {
   // Block header consists of 4 byte page RVA and 4 byte block size.
   // Each entry is 2 byte. Last entry may be padding.
-  Data.resize(align((End - Begin) * 2 + 8, 4));
+  Data.resize(alignTo((End - Begin) * 2 + 8, 4));
   uint8_t *P = Data.data();
   write32le(P, Page);
   write32le(P + 4, Data.size());
diff --git a/COFF/Chunks.h b/COFF/Chunks.h
index 274135516eb9..cd0e2e69ef5d 100644
--- a/COFF/Chunks.h
+++ b/COFF/Chunks.h
@@ -18,6 +18,7 @@
 #include "llvm/ADT/iterator_range.h"
 #include "llvm/Object/COFF.h"
 #include <atomic>
+#include <utility>
 #include <vector>
 
 namespace lld {
@@ -138,6 +139,7 @@ public:
   SectionChunk(ObjectFile *File, const coff_section *Header);
   static bool classof(const Chunk *C) { return C->kind() == SectionKind; }
   size_t getSize() const override { return Header->SizeOfRawData; }
+  ArrayRef<uint8_t> getContents() const;
   void writeTo(uint8_t *Buf) const override;
   bool hasData() const override;
   uint32_t getPermissions() const override;
@@ -186,8 +188,6 @@ public:
   uint32_t Checksum = 0;
 
 private:
-  ArrayRef<uint8_t> getContents() const;
-
   // A file this chunk was created from.
   ObjectFile *File;
 
@@ -295,7 +295,7 @@ private:
 // functions. x86-only.
 class SEHTableChunk : public Chunk {
 public:
-  explicit SEHTableChunk(std::set<Defined *> S) : Syms(S) {}
+  explicit SEHTableChunk(std::set<Defined *> S) : Syms(std::move(S)) {}
   size_t getSize() const override { return Syms.size() * 4; }
   void writeTo(uint8_t *Buf) const override;
 
@@ -326,10 +326,6 @@ public:
   uint8_t Type;
 };
 
-inline uint64_t align(uint64_t Value, uint64_t Align) {
-  return llvm::RoundUpToAlignment(Value, Align);
-}
-
 } // namespace coff
 } // namespace lld
 
diff --git a/COFF/Config.h b/COFF/Config.h
index 9cfccadba5fa..a5472e937fa1 100644
--- a/COFF/Config.h
+++ b/COFF/Config.h
@@ -106,11 +106,15 @@ struct Configuration {
   // Used for /merge:from=to (e.g. /merge:.rdata=.text)
   std::map<StringRef, StringRef> Merge;
 
+  // Used for /section=.name,{DEKPRSW} to set section attributes.
+  std::map<StringRef, uint32_t> Section;
+
   // Options for manifest files.
   ManifestKind Manifest = SideBySide;
   int ManifestID = 1;
   StringRef ManifestDependency;
   bool ManifestUAC = true;
+  std::vector<std::string> ManifestInput;
   StringRef ManifestLevel = "'asInvoker'";
   StringRef ManifestUIAccess = "'false'";
   StringRef ManifestFile;
diff --git a/COFF/DLL.cpp b/COFF/DLL.cpp
index 8f3383d75c7b..9ac370c11d59 100644
--- a/COFF/DLL.cpp
+++ b/COFF/DLL.cpp
@@ -45,7 +45,7 @@ public:
   size_t getSize() const override {
     // Starts with 2 byte Hint field, followed by a null-terminated string,
     // ends with 0 or 1 byte padding.
-    return align(Name.size() + 3, 2);
+    return alignTo(Name.size() + 3, 2);
   }
 
   void writeTo(uint8_t *Buf) const override {
diff --git a/COFF/Driver.cpp b/COFF/Driver.cpp
index 4cacf0ff552a..bb6a60e4fc4c 100644
--- a/COFF/Driver.cpp
+++ b/COFF/Driver.cpp
@@ -14,6 +14,7 @@
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "Writer.h"
+#include "lld/Driver/Driver.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/LibDriver/LibDriver.h"
 #include "llvm/Option/Arg.h"
@@ -40,27 +41,28 @@ namespace coff {
 Configuration *Config;
 LinkerDriver *Driver;
 
-void link(llvm::ArrayRef<const char *> Args) {
+bool link(llvm::ArrayRef<const char *> Args) {
   Configuration C;
   LinkerDriver D;
   Config = &C;
   Driver = &D;
-  return Driver->link(Args);
+  Driver->link(Args);
+  return true;
 }
 
-// Drop directory components and replace extension with ".exe".
+// Drop directory components and replace extension with ".exe" or ".dll".
 static std::string getOutputPath(StringRef Path) {
   auto P = Path.find_last_of("\\/");
   StringRef S = (P == StringRef::npos) ? Path : Path.substr(P + 1);
-  return (S.substr(0, S.rfind('.')) + ".exe").str();
+  const char* E = Config->DLL ? ".dll" : ".exe";
+  return (S.substr(0, S.rfind('.')) + E).str();
 }
 
 // Opens a file. Path has to be resolved already.
 // Newly created memory buffers are owned by this driver.
 MemoryBufferRef LinkerDriver::openFile(StringRef Path) {
-  auto MBOrErr = MemoryBuffer::getFile(Path);
-  error(MBOrErr, Twine("Could not open ") + Path);
-  std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
+  std::unique_ptr<MemoryBuffer> MB =
+      check(MemoryBuffer::getFile(Path), "could not open " + Path);
   MemoryBufferRef MBRef = MB->getMemBufferRef();
   OwningMBs.push_back(std::move(MB)); // take ownership
   return MBRef;
@@ -116,12 +118,16 @@ void LinkerDriver::parseDirectives(StringRef S) {
     case OPT_nodefaultlib:
       Config->NoDefaultLibs.insert(doFindLib(Arg->getValue()));
       break;
+    case OPT_section:
+      parseSection(Arg->getValue());
+      break;
     case OPT_editandcontinue:
+    case OPT_fastfail:
     case OPT_guardsym:
     case OPT_throwingnew:
       break;
     default:
-      error(Twine(Arg->getSpelling()) + " is not allowed in .drectve");
+      fatal(Arg->getSpelling() + " is not allowed in .drectve");
     }
   }
 }
@@ -246,7 +252,7 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   // We call our own implementation of lib.exe that understands bitcode files.
   if (ArgsArr.size() > 1 && StringRef(ArgsArr[1]).equals_lower("/lib")) {
     if (llvm::libDriverMain(ArgsArr.slice(1)) != 0)
-      error("lib failed");
+      fatal("lib failed");
     return;
   }
 
@@ -268,7 +274,7 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   }
 
   if (Args.filtered_begin(OPT_INPUT) == Args.filtered_end())
-    error("no input files.");
+    fatal("no input files");
 
   // Construct search path list.
   SearchPaths.push_back("");
@@ -295,7 +301,7 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   // Handle /noentry
   if (Args.hasArg(OPT_noentry)) {
     if (!Args.hasArg(OPT_dll))
-      error("/noentry must be specified with /dll");
+      fatal("/noentry must be specified with /dll");
     Config->NoEntry = true;
   }
 
@@ -308,7 +314,7 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   // Handle /fixed
   if (Args.hasArg(OPT_fixed)) {
     if (Args.hasArg(OPT_dynamicbase))
-      error("/fixed must not be specified with /dynamicbase");
+      fatal("/fixed must not be specified with /dynamicbase");
     Config->Relocatable = false;
     Config->DynamicBase = false;
   }
@@ -382,17 +388,17 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
         StringRef OptLevel = StringRef(S).substr(7);
         if (OptLevel.getAsInteger(10, Config->LTOOptLevel) ||
             Config->LTOOptLevel > 3)
-          error("/opt:lldlto: invalid optimization level: " + OptLevel);
+          fatal("/opt:lldlto: invalid optimization level: " + OptLevel);
         continue;
       }
       if (StringRef(S).startswith("lldltojobs=")) {
         StringRef Jobs = StringRef(S).substr(11);
         if (Jobs.getAsInteger(10, Config->LTOJobs) || Config->LTOJobs == 0)
-          error("/opt:lldltojobs: invalid job count: " + Jobs);
+          fatal("/opt:lldltojobs: invalid job count: " + Jobs);
         continue;
       }
       if (S != "ref" && S != "lbr" && S != "nolbr")
-        error(Twine("/opt: unknown option: ") + S);
+        fatal("/opt: unknown option: " + S);
     }
   }
 
@@ -404,6 +410,10 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   for (auto *Arg : Args.filtered(OPT_merge))
     parseMerge(Arg->getValue());
 
+  // Handle /section
+  for (auto *Arg : Args.filtered(OPT_section))
+    parseSection(Arg->getValue());
+
   // Handle /manifest
   if (auto *Arg = Args.getLastArg(OPT_manifest_colon))
     parseManifest(Arg->getValue());
@@ -420,6 +430,10 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   if (auto *Arg = Args.getLastArg(OPT_manifestfile))
     Config->ManifestFile = Arg->getValue();
 
+  // Handle /manifestinput
+  for (auto *Arg : Args.filtered(OPT_manifestinput))
+    Config->ManifestInput.push_back(Arg->getValue());
+
   // Handle miscellaneous boolean flags.
   if (Args.hasArg(OPT_allowbind_no))
     Config->AllowBind = false;
@@ -485,7 +499,7 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
       continue;
     }
     if (Config->Machine != MT)
-      error(Twine(File->getShortName()) + ": machine type " + machineToStr(MT) +
+      fatal(File->getShortName() + ": machine type " + machineToStr(MT) +
             " conflicts with " + machineToStr(Config->Machine));
   }
   if (Config->Machine == IMAGE_FILE_MACHINE_UNKNOWN) {
@@ -520,7 +534,7 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
     // infer that from user-defined entry name.
     StringRef S = findDefaultEntry();
     if (S.empty())
-      error("entry point must be defined");
+      fatal("entry point must be defined");
     Config->Entry = addUndefined(S);
     if (Config->Verbose)
       llvm::outs() << "Entry name inferred: " << S << "\n";
@@ -627,14 +641,14 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   if (Config->Subsystem == IMAGE_SUBSYSTEM_UNKNOWN) {
     Config->Subsystem = inferSubsystem();
     if (Config->Subsystem == IMAGE_SUBSYSTEM_UNKNOWN)
-      error("subsystem must be defined");
+      fatal("subsystem must be defined");
   }
 
   // Handle /safeseh.
   if (Args.hasArg(OPT_safeseh))
     for (ObjectFile *File : Symtab.ObjectFiles)
       if (!File->SEHCompat)
-        error("/safeseh: " + File->getName() + " is not compatible with SEH");
+        fatal("/safeseh: " + File->getName() + " is not compatible with SEH");
 
   // Windows specific -- when we are creating a .dll file, we also
   // need to create a .lib file.
@@ -668,7 +682,8 @@ void LinkerDriver::link(llvm::ArrayRef<const char *> ArgsArr) {
   if (auto *Arg = Args.getLastArg(OPT_lldmap)) {
     std::error_code EC;
     llvm::raw_fd_ostream Out(Arg->getValue(), EC, OpenFlags::F_Text);
-    error(EC, "Could not create the symbol map");
+    if (EC)
+      fatal(EC, "could not create the symbol map");
     Symtab.printMap(Out);
   }
   // Call exit to avoid calling destructors.
diff --git a/COFF/Driver.h b/COFF/Driver.h
index e50da20cbb04..23969ee802fb 100644
--- a/COFF/Driver.h
+++ b/COFF/Driver.h
@@ -34,9 +34,6 @@ using llvm::COFF::WindowsSubsystem;
 using llvm::Optional;
 class InputFile;
 
-// Entry point of the COFF linker.
-void link(llvm::ArrayRef<const char *> Args);
-
 // Implemented in MarkLive.cpp.
 void markLive(const std::vector<Chunk *> &Chunks);
 
@@ -136,6 +133,7 @@ void parseSubsystem(StringRef Arg, WindowsSubsystem *Sys, uint32_t *Major,
 
 void parseAlternateName(StringRef);
 void parseMerge(StringRef);
+void parseSection(StringRef);
 
 // Parses a string in the form of "EMBED[,=<integer>]|NO".
 void parseManifest(StringRef Arg);
@@ -163,7 +161,6 @@ void checkFailIfMismatch(StringRef Arg);
 std::unique_ptr<MemoryBuffer>
 convertResToCOFF(const std::vector<MemoryBufferRef> &MBs);
 
-void touchFile(StringRef Path);
 void createPDB(StringRef Path);
 
 // Create enum with OPT_xxx values for each option in Options.td
diff --git a/COFF/DriverUtils.cpp b/COFF/DriverUtils.cpp
index 014fee7fefd7..5d7dc2bc65af 100644
--- a/COFF/DriverUtils.cpp
+++ b/COFF/DriverUtils.cpp
@@ -19,15 +19,12 @@
 #include "Symbols.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringSwitch.h"
-#include "llvm/Object/Archive.h"
-#include "llvm/Object/ArchiveWriter.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Option/Arg.h"
 #include "llvm/Option/ArgList.h"
 #include "llvm/Option/Option.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileUtilities.h"
-#include "llvm/Support/Path.h"
 #include "llvm/Support/Process.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/raw_ostream.h"
@@ -53,7 +50,8 @@ public:
 
   void run() {
     ErrorOr<std::string> ExeOrErr = llvm::sys::findProgramByName(Prog);
-    error(ExeOrErr, Twine("unable to find ") + Prog + " in PATH: ");
+    if (auto EC = ExeOrErr.getError())
+      fatal(EC, "unable to find " + Prog + " in PATH: ");
     const char *Exe = Saver.save(*ExeOrErr);
     Args.insert(Args.begin(), Exe);
     Args.push_back(nullptr);
@@ -61,7 +59,7 @@ public:
       for (const char *S : Args)
         if (S)
           llvm::errs() << S << " ";
-      error("failed");
+      fatal("ExecuteAndWait failed");
     }
   }
 
@@ -85,7 +83,7 @@ MachineTypes getMachineType(StringRef S) {
                         .Default(IMAGE_FILE_MACHINE_UNKNOWN);
   if (MT != IMAGE_FILE_MACHINE_UNKNOWN)
     return MT;
-  error(Twine("unknown /machine argument: ") + S);
+  fatal("unknown /machine argument: " + S);
 }
 
 StringRef machineToStr(MachineTypes MT) {
@@ -106,9 +104,9 @@ void parseNumbers(StringRef Arg, uint64_t *Addr, uint64_t *Size) {
   StringRef S1, S2;
   std::tie(S1, S2) = Arg.split(',');
   if (S1.getAsInteger(0, *Addr))
-    error(Twine("invalid number: ") + S1);
+    fatal("invalid number: " + S1);
   if (Size && !S2.empty() && S2.getAsInteger(0, *Size))
-    error(Twine("invalid number: ") + S2);
+    fatal("invalid number: " + S2);
 }
 
 // Parses a string in the form of "<integer>[.<integer>]".
@@ -117,10 +115,10 @@ void parseVersion(StringRef Arg, uint32_t *Major, uint32_t *Minor) {
   StringRef S1, S2;
   std::tie(S1, S2) = Arg.split('.');
   if (S1.getAsInteger(0, *Major))
-    error(Twine("invalid number: ") + S1);
+    fatal("invalid number: " + S1);
   *Minor = 0;
   if (!S2.empty() && S2.getAsInteger(0, *Minor))
-    error(Twine("invalid number: ") + S2);
+    fatal("invalid number: " + S2);
 }
 
 // Parses a string in the form of "<subsystem>[,<integer>[.<integer>]]".
@@ -140,7 +138,7 @@ void parseSubsystem(StringRef Arg, WindowsSubsystem *Sys, uint32_t *Major,
     .Case("windows", IMAGE_SUBSYSTEM_WINDOWS_GUI)
     .Default(IMAGE_SUBSYSTEM_UNKNOWN);
   if (*Sys == IMAGE_SUBSYSTEM_UNKNOWN)
-    error(Twine("unknown subsystem: ") + SysStr);
+    fatal("unknown subsystem: " + SysStr);
   if (!Ver.empty())
     parseVersion(Ver, Major, Minor);
 }
@@ -151,10 +149,10 @@ void parseAlternateName(StringRef S) {
   StringRef From, To;
   std::tie(From, To) = S.split('=');
   if (From.empty() || To.empty())
-    error(Twine("/alternatename: invalid argument: ") + S);
+    fatal("/alternatename: invalid argument: " + S);
   auto It = Config->AlternateNames.find(From);
   if (It != Config->AlternateNames.end() && It->second != To)
-    error(Twine("/alternatename: conflicts: ") + S);
+    fatal("/alternatename: conflicts: " + S);
   Config->AlternateNames.insert(It, std::make_pair(From, To));
 }
 
@@ -164,7 +162,7 @@ void parseMerge(StringRef S) {
   StringRef From, To;
   std::tie(From, To) = S.split('=');
   if (From.empty() || To.empty())
-    error(Twine("/merge: invalid argument: ") + S);
+    fatal("/merge: invalid argument: " + S);
   auto Pair = Config->Merge.insert(std::make_pair(From, To));
   bool Inserted = Pair.second;
   if (!Inserted) {
@@ -175,6 +173,47 @@ void parseMerge(StringRef S) {
   }
 }
 
+static uint32_t parseSectionAttributes(StringRef S) {
+  uint32_t Ret = 0;
+  for (char C : S.lower()) {
+    switch (C) {
+    case 'd':
+      Ret |= IMAGE_SCN_MEM_DISCARDABLE;
+      break;
+    case 'e':
+      Ret |= IMAGE_SCN_MEM_EXECUTE;
+      break;
+    case 'k':
+      Ret |= IMAGE_SCN_MEM_NOT_CACHED;
+      break;
+    case 'p':
+      Ret |= IMAGE_SCN_MEM_NOT_PAGED;
+      break;
+    case 'r':
+      Ret |= IMAGE_SCN_MEM_READ;
+      break;
+    case 's':
+      Ret |= IMAGE_SCN_MEM_SHARED;
+      break;
+    case 'w':
+      Ret |= IMAGE_SCN_MEM_WRITE;
+      break;
+    default:
+      fatal("/section: invalid argument: " + S);
+    }
+  }
+  return Ret;
+}
+
+// Parses /section option argument.
+void parseSection(StringRef S) {
+  StringRef Name, Attrs;
+  std::tie(Name, Attrs) = S.split(',');
+  if (Name.empty() || Attrs.empty())
+    fatal("/section: invalid argument: " + S);
+  Config->Section[Name] = parseSectionAttributes(Attrs);
+}
+
 // Parses a string in the form of "EMBED[,=<integer>]|NO".
 // Results are directly written to Config.
 void parseManifest(StringRef Arg) {
@@ -183,16 +222,16 @@ void parseManifest(StringRef Arg) {
     return;
   }
   if (!Arg.startswith_lower("embed"))
-    error(Twine("Invalid option ") + Arg);
+    fatal("invalid option " + Arg);
   Config->Manifest = Configuration::Embed;
   Arg = Arg.substr(strlen("embed"));
   if (Arg.empty())
     return;
   if (!Arg.startswith_lower(",id="))
-    error(Twine("Invalid option ") + Arg);
+    fatal("invalid option " + Arg);
   Arg = Arg.substr(strlen(",id="));
   if (Arg.getAsInteger(0, Config->ManifestID))
-    error(Twine("Invalid option ") + Arg);
+    fatal("invalid option " + Arg);
 }
 
 // Parses a string in the form of "level=<string>|uiAccess=<string>|NO".
@@ -216,7 +255,7 @@ void parseManifestUAC(StringRef Arg) {
       std::tie(Config->ManifestUIAccess, Arg) = Arg.split(" ");
       continue;
     }
-    error(Twine("Invalid option ") + Arg);
+    fatal("invalid option " + Arg);
   }
 }
 
@@ -240,10 +279,19 @@ static void quoteAndPrint(raw_ostream &Out, StringRef S) {
   }
 }
 
-// Create a manifest file contents.
-static std::string createManifestXml() {
-  std::string S;
-  llvm::raw_string_ostream OS(S);
+// Create the default manifest file as a temporary file.
+static std::string createDefaultXml() {
+  // Create a temporary file.
+  SmallString<128> Path;
+  if (auto EC = sys::fs::createTemporaryFile("tmp", "manifest", Path))
+    fatal(EC, "cannot create a temporary file");
+
+  // Open the temporary file for writing.
+  std::error_code EC;
+  llvm::raw_fd_ostream OS(Path, EC, sys::fs::F_Text);
+  if (EC)
+    fatal(EC, "failed to open " + Path);
+
   // Emit the XML. Note that we do *not* verify that the XML attributes are
   // syntactically correct. This is intentional for link.exe compatibility.
   OS << "<?xml version=\"1.0\" standalone=\"yes\"?>\n"
@@ -267,21 +315,57 @@ static std::string createManifestXml() {
     }
   }
   OS << "</assembly>\n";
-  OS.flush();
-  return S;
+  OS.close();
+  return StringRef(Path);
+}
+
+static std::string readFile(StringRef Path) {
+  std::unique_ptr<MemoryBuffer> MB =
+      check(MemoryBuffer::getFile(Path), "could not open " + Path);
+  std::unique_ptr<MemoryBuffer> Buf(std::move(MB));
+  return Buf->getBuffer();
+}
+
+static std::string createManifestXml() {
+  // Create the default manifest file.
+  std::string Path1 = createDefaultXml();
+  if (Config->ManifestInput.empty())
+    return readFile(Path1);
+
+  // If manifest files are supplied by the user using /MANIFESTINPUT
+  // option, we need to merge them with the default manifest.
+  SmallString<128> Path2;
+  if (auto EC = sys::fs::createTemporaryFile("tmp", "manifest", Path2))
+    fatal(EC, "cannot create a temporary file");
+  FileRemover Remover1(Path1);
+  FileRemover Remover2(Path2);
+
+  Executor E("mt.exe");
+  E.add("/manifest");
+  E.add(Path1);
+  for (StringRef Filename : Config->ManifestInput) {
+    E.add("/manifest");
+    E.add(Filename);
+  }
+  E.add("/nologo");
+  E.add("/out:" + StringRef(Path2));
+  E.run();
+  return readFile(Path2);
 }
 
 // Create a resource file containing a manifest XML.
 std::unique_ptr<MemoryBuffer> createManifestRes() {
   // Create a temporary file for the resource script file.
   SmallString<128> RCPath;
-  std::error_code EC = sys::fs::createTemporaryFile("tmp", "rc", RCPath);
-  error(EC, "cannot create a temporary file");
+  if (auto EC = sys::fs::createTemporaryFile("tmp", "rc", RCPath))
+    fatal(EC, "cannot create a temporary file");
   FileRemover RCRemover(RCPath);
 
   // Open the temporary file for writing.
+  std::error_code EC;
   llvm::raw_fd_ostream Out(RCPath, EC, sys::fs::F_Text);
-  error(EC, Twine("failed to open ") + RCPath);
+  if (EC)
+    fatal(EC, "failed to open " + RCPath);
 
   // Write resource script to the RC file.
   Out << "#define LANG_ENGLISH 9\n"
@@ -296,8 +380,8 @@ std::unique_ptr<MemoryBuffer> createManifestRes() {
 
   // Create output resource file.
   SmallString<128> ResPath;
-  EC = sys::fs::createTemporaryFile("tmp", "res", ResPath);
-  error(EC, "cannot create a temporary file");
+  if (auto EC = sys::fs::createTemporaryFile("tmp", "res", ResPath))
+    fatal(EC, "cannot create a temporary file");
 
   Executor E("rc.exe");
   E.add("/fo");
@@ -305,18 +389,17 @@ std::unique_ptr<MemoryBuffer> createManifestRes() {
   E.add("/nologo");
   E.add(RCPath.str());
   E.run();
-  ErrorOr<std::unique_ptr<MemoryBuffer>> Ret = MemoryBuffer::getFile(ResPath);
-  error(Ret, Twine("Could not open ") + ResPath);
-  return std::move(*Ret);
+  return check(MemoryBuffer::getFile(ResPath), "could not open " + ResPath);
 }
 
 void createSideBySideManifest() {
   std::string Path = Config->ManifestFile;
   if (Path == "")
-    Path = (Twine(Config->OutputFile) + ".manifest").str();
+    Path = Config->OutputFile + ".manifest";
   std::error_code EC;
   llvm::raw_fd_ostream Out(Path, EC, llvm::sys::fs::F_Text);
-  error(EC, "failed to create manifest");
+  if (EC)
+    fatal(EC, "failed to create manifest");
   Out << createManifestXml();
 }
 
@@ -380,7 +463,7 @@ Export parseExport(StringRef Arg) {
   return E;
 
 err:
-  error(Twine("invalid /export: ") + Arg);
+  fatal("invalid /export: " + Arg);
 }
 
 static StringRef undecorate(StringRef Sym) {
@@ -398,7 +481,7 @@ void fixupExports() {
     if (E.Ordinal == 0)
       continue;
     if (!Ords.insert(E.Ordinal).second)
-      error("duplicate export ordinal: " + E.Name);
+      fatal("duplicate export ordinal: " + E.Name);
   }
 
   for (Export &E : Config->Exports) {
@@ -459,11 +542,11 @@ void checkFailIfMismatch(StringRef Arg) {
   StringRef K, V;
   std::tie(K, V) = Arg.split('=');
   if (K.empty() || V.empty())
-    error(Twine("/failifmismatch: invalid argument: ") + Arg);
+    fatal("/failifmismatch: invalid argument: " + Arg);
   StringRef Existing = Config->MustMatch[K];
   if (!Existing.empty() && V != Existing)
-    error(Twine("/failifmismatch: mismatch detected: ") + Existing + " and " +
-          V + " for key " + K);
+    fatal("/failifmismatch: mismatch detected: " + Existing + " and " + V +
+          " for key " + K);
   Config->MustMatch[K] = V;
 }
 
@@ -473,8 +556,8 @@ std::unique_ptr<MemoryBuffer>
 convertResToCOFF(const std::vector<MemoryBufferRef> &MBs) {
   // Create an output file path.
   SmallString<128> Path;
-  if (llvm::sys::fs::createTemporaryFile("resource", "obj", Path))
-    error("Could not create temporary file");
+  if (auto EC = llvm::sys::fs::createTemporaryFile("resource", "obj", Path))
+    fatal(EC, "could not create temporary file");
 
   // Execute cvtres.exe.
   Executor E("cvtres.exe");
@@ -485,170 +568,7 @@ convertResToCOFF(const std::vector<MemoryBufferRef> &MBs) {
   for (MemoryBufferRef MB : MBs)
     E.add(MB.getBufferIdentifier());
   E.run();
-  ErrorOr<std::unique_ptr<MemoryBuffer>> Ret = MemoryBuffer::getFile(Path);
-  error(Ret, Twine("Could not open ") + Path);
-  return std::move(*Ret);
-}
-
-static std::string writeToTempFile(StringRef Contents) {
-  SmallString<128> Path;
-  int FD;
-  if (llvm::sys::fs::createTemporaryFile("tmp", "def", FD, Path)) {
-    llvm::errs() << "failed to create a temporary file\n";
-    return "";
-  }
-  llvm::raw_fd_ostream OS(FD, /*shouldClose*/ true);
-  OS << Contents;
-  return Path.str();
-}
-
-void touchFile(StringRef Path) {
-  int FD;
-  std::error_code EC = sys::fs::openFileForWrite(Path, FD, sys::fs::F_Append);
-  error(EC, "failed to create a file");
-  sys::Process::SafelyCloseFileDescriptor(FD);
-}
-
-static std::string getImplibPath() {
-  if (!Config->Implib.empty())
-    return Config->Implib;
-  SmallString<128> Out = StringRef(Config->OutputFile);
-  sys::path::replace_extension(Out, ".lib");
-  return Out.str();
-}
-
-static std::unique_ptr<MemoryBuffer> createEmptyImportLibrary() {
-  std::string S = (Twine("LIBRARY \"") +
-                   llvm::sys::path::filename(Config->OutputFile) + "\"\n")
-                      .str();
-  std::string Path1 = writeToTempFile(S);
-  std::string Path2 = getImplibPath();
-  llvm::FileRemover Remover1(Path1);
-  llvm::FileRemover Remover2(Path2);
-
-  Executor E("lib.exe");
-  E.add("/nologo");
-  E.add("/machine:" + machineToStr(Config->Machine));
-  E.add(Twine("/def:") + Path1);
-  E.add(Twine("/out:") + Path2);
-  E.run();
-
-  ErrorOr<std::unique_ptr<MemoryBuffer>> BufOrErr =
-      MemoryBuffer::getFile(Path2, -1, false);
-  error(BufOrErr, Twine("Failed to open ") + Path2);
-  return MemoryBuffer::getMemBufferCopy((*BufOrErr)->getBuffer());
-}
-
-static std::vector<NewArchiveIterator>
-readMembers(const object::Archive &Archive) {
-  std::vector<NewArchiveIterator> V;
-  for (const auto &ChildOrErr : Archive.children()) {
-    error(ChildOrErr, "Archive::Child::getName failed");
-    const object::Archive::Child C(*ChildOrErr);
-    ErrorOr<StringRef> NameOrErr = C.getName();
-    error(NameOrErr, "Archive::Child::getName failed");
-    V.emplace_back(C, *NameOrErr);
-  }
-  return V;
-}
-
-// This class creates short import files which is described in
-// PE/COFF spec 7. Import Library Format.
-class ShortImportCreator {
-public:
-  ShortImportCreator(object::Archive *A, StringRef S) : Parent(A), DLLName(S) {}
-
-  NewArchiveIterator create(StringRef Sym, uint16_t Ordinal,
-                            ImportNameType NameType, bool isData) {
-    size_t ImpSize = DLLName.size() + Sym.size() + 2; // +2 for NULs
-    size_t Size = sizeof(object::ArchiveMemberHeader) +
-                  sizeof(coff_import_header) + ImpSize;
-    char *Buf = Alloc.Allocate<char>(Size);
-    memset(Buf, 0, Size);
-    char *P = Buf;
-
-    // Write archive member header
-    auto *Hdr = reinterpret_cast<object::ArchiveMemberHeader *>(P);
-    P += sizeof(*Hdr);
-    sprintf(Hdr->Name, "%-12s", "dummy");
-    sprintf(Hdr->LastModified, "%-12d", 0);
-    sprintf(Hdr->UID, "%-6d", 0);
-    sprintf(Hdr->GID, "%-6d", 0);
-    sprintf(Hdr->AccessMode, "%-8d", 0644);
-    sprintf(Hdr->Size, "%-10d", int(sizeof(coff_import_header) + ImpSize));
-
-    // Write short import library.
-    auto *Imp = reinterpret_cast<coff_import_header *>(P);
-    P += sizeof(*Imp);
-    Imp->Sig2 = 0xFFFF;
-    Imp->Machine = Config->Machine;
-    Imp->SizeOfData = ImpSize;
-    if (Ordinal > 0)
-      Imp->OrdinalHint = Ordinal;
-    Imp->TypeInfo = (isData ? IMPORT_DATA : IMPORT_CODE);
-    Imp->TypeInfo |= NameType << 2;
-
-    // Write symbol name and DLL name.
-    memcpy(P, Sym.data(), Sym.size());
-    P += Sym.size() + 1;
-    memcpy(P, DLLName.data(), DLLName.size());
-
-    std::error_code EC;
-    object::Archive::Child C(Parent, Buf, &EC);
-    assert(!EC && "We created an invalid buffer");
-    return NewArchiveIterator(C, DLLName);
-  }
-
-private:
-  BumpPtrAllocator Alloc;
-  object::Archive *Parent;
-  StringRef DLLName;
-};
-
-static ImportNameType getNameType(StringRef Sym, StringRef ExtName) {
-  if (Sym != ExtName)
-    return IMPORT_NAME_UNDECORATE;
-  if (Config->Machine == I386 && Sym.startswith("_"))
-    return IMPORT_NAME_NOPREFIX;
-  return IMPORT_NAME;
-}
-
-static std::string replace(StringRef S, StringRef From, StringRef To) {
-  size_t Pos = S.find(From);
-  assert(Pos != StringRef::npos);
-  return (Twine(S.substr(0, Pos)) + To + S.substr(Pos + From.size())).str();
-}
-
-// Creates an import library for a DLL. In this function, we first
-// create an empty import library using lib.exe and then adds short
-// import files to that file.
-void writeImportLibrary() {
-  std::unique_ptr<MemoryBuffer> Buf = createEmptyImportLibrary();
-  std::error_code EC;
-  object::Archive Archive(Buf->getMemBufferRef(), EC);
-  error(EC, "Error reading an empty import file");
-  std::vector<NewArchiveIterator> Members = readMembers(Archive);
-
-  std::string DLLName = llvm::sys::path::filename(Config->OutputFile);
-  ShortImportCreator ShortImport(&Archive, DLLName);
-  for (Export &E : Config->Exports) {
-    if (E.Private)
-      continue;
-    if (E.ExtName.empty()) {
-      Members.push_back(ShortImport.create(
-          E.SymbolName, E.Ordinal, getNameType(E.SymbolName, E.Name), E.Data));
-    } else {
-      Members.push_back(ShortImport.create(
-          replace(E.SymbolName, E.Name, E.ExtName), E.Ordinal,
-          getNameType(E.SymbolName, E.Name), E.Data));
-    }
-  }
-
-  std::string Path = getImplibPath();
-  std::pair<StringRef, std::error_code> Result =
-      writeArchive(Path, Members, /*WriteSymtab*/ true, object::Archive::K_GNU,
-                   /*Deterministic*/ true, /*Thin*/ false);
-  error(Result.second, Twine("Failed to write ") + Path);
+  return check(MemoryBuffer::getFile(Path), "could not open " + Path);
 }
 
 // Create OptTable
@@ -695,7 +615,7 @@ llvm::opt::InputArgList ArgParser::parse(ArrayRef<const char *> ArgsArr) {
   }
 
   if (MissingCount)
-    error(Twine("missing arg value for \"") + Args.getArgString(MissingIndex) +
+    fatal("missing arg value for \"" + Twine(Args.getArgString(MissingIndex)) +
           "\", expected " + Twine(MissingCount) +
           (MissingCount == 1 ? " argument." : " arguments."));
   for (auto *Arg : Args.filtered(OPT_UNKNOWN))
diff --git a/COFF/Error.cpp b/COFF/Error.cpp
index 255d9bbad9d8..602a8544ce2b 100644
--- a/COFF/Error.cpp
+++ b/COFF/Error.cpp
@@ -10,20 +10,23 @@
 #include "Error.h"
 
 #include "llvm/ADT/Twine.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
 
 namespace lld {
 namespace coff {
 
-void error(const Twine &Msg) {
+void fatal(const Twine &Msg) {
   llvm::errs() << Msg << "\n";
   exit(1);
 }
 
-void error(std::error_code EC, const Twine &Prefix) {
-  if (!EC)
-    return;
-  error(Prefix + ": " + EC.message());
+void fatal(std::error_code EC, const Twine &Msg) {
+  fatal(Msg + ": " + EC.message());
+}
+
+void fatal(llvm::Error &Err, const Twine &Msg) {
+  fatal(errorToErrorCode(std::move(Err)), Msg);
 }
 
 } // namespace coff
diff --git a/COFF/Error.h b/COFF/Error.h
index cb0a185f0917..c9f64c662580 100644
--- a/COFF/Error.h
+++ b/COFF/Error.h
@@ -11,15 +11,25 @@
 #define LLD_COFF_ERROR_H
 
 #include "lld/Core/LLVM.h"
+#include "llvm/Support/Error.h"
 
 namespace lld {
 namespace coff {
 
-LLVM_ATTRIBUTE_NORETURN void error(const Twine &Msg);
-void error(std::error_code EC, const Twine &Prefix);
+LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg);
+LLVM_ATTRIBUTE_NORETURN void fatal(std::error_code EC, const Twine &Prefix);
+LLVM_ATTRIBUTE_NORETURN void fatal(llvm::Error &Err, const Twine &Prefix);
 
-template <typename T> void error(const ErrorOr<T> &V, const Twine &Prefix) {
-  error(V.getError(), Prefix);
+template <class T> T check(ErrorOr<T> &&V, const Twine &Prefix) {
+  if (auto EC = V.getError())
+    fatal(EC, Prefix);
+  return std::move(*V);
+}
+
+template <class T> T check(Expected<T> E, const Twine &Prefix) {
+  if (llvm::Error Err = E.takeError())
+    fatal(Err, Prefix);
+  return std::move(*E);
 }
 
 } // namespace coff
diff --git a/COFF/ICF.cpp b/COFF/ICF.cpp
index f99b41624a84..a2c5a90334d0 100644
--- a/COFF/ICF.cpp
+++ b/COFF/ICF.cpp
@@ -70,7 +70,7 @@ private:
   static bool equalsConstant(const SectionChunk *A, const SectionChunk *B);
   static bool equalsVariable(const SectionChunk *A, const SectionChunk *B);
   bool forEachGroup(std::vector<SectionChunk *> &Chunks, Comparator Eq);
-  bool partition(ChunkIterator Begin, ChunkIterator End, Comparator Eq);
+  bool segregate(ChunkIterator Begin, ChunkIterator End, Comparator Eq);
 
   std::atomic<uint64_t> NextID = { 1 };
 };
@@ -148,7 +148,7 @@ bool ICF::equalsVariable(const SectionChunk *A, const SectionChunk *B) {
   return std::equal(A->Relocs.begin(), A->Relocs.end(), B->Relocs.begin(), Eq);
 }
 
-bool ICF::partition(ChunkIterator Begin, ChunkIterator End, Comparator Eq) {
+bool ICF::segregate(ChunkIterator Begin, ChunkIterator End, Comparator Eq) {
   bool R = false;
   for (auto It = Begin;;) {
     SectionChunk *Head = *It;
@@ -171,7 +171,7 @@ bool ICF::forEachGroup(std::vector<SectionChunk *> &Chunks, Comparator Eq) {
     auto Bound = std::find_if(It + 1, End, [&](SectionChunk *SC) {
       return SC->GroupID != Head->GroupID;
     });
-    if (partition(It, Bound, Eq))
+    if (segregate(It, Bound, Eq))
       R = true;
     It = Bound;
   }
diff --git a/COFF/InputFiles.cpp b/COFF/InputFiles.cpp
index 23af1e89c34d..ff26826371fa 100644
--- a/COFF/InputFiles.cpp
+++ b/COFF/InputFiles.cpp
@@ -8,30 +8,41 @@
 //===----------------------------------------------------------------------===//
 
 #include "Chunks.h"
+#include "Config.h"
 #include "Error.h"
 #include "InputFiles.h"
 #include "Symbols.h"
-#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/ADT/Twine.h"
 #include "llvm/IR/LLVMContext.h"
-#include "llvm/LTO/LTOModule.h"
+#include "llvm/LTO/legacy/LTOModule.h"
+#include "llvm/Object/Binary.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/COFF.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/Endian.h"
-#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/ErrorOr.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Target/TargetOptions.h"
+#include "llvm-c/lto.h"
+#include <cstring>
+#include <system_error>
+#include <utility>
 
 using namespace llvm::COFF;
 using namespace llvm::object;
 using namespace llvm::support::endian;
+
 using llvm::Triple;
 using llvm::support::ulittle32_t;
-using llvm::sys::fs::file_magic;
-using llvm::sys::fs::identify_magic;
 
 namespace lld {
 namespace coff {
 
 int InputFile::NextIndex = 0;
+llvm::LLVMContext BitcodeFile::Context;
 
 // Returns the last element of a path, which is supposed to be a filename.
 static StringRef getBasename(StringRef Path) {
@@ -52,9 +63,7 @@ std::string InputFile::getShortName() {
 
 void ArchiveFile::parse() {
   // Parse a MemoryBufferRef as an archive file.
-  auto ArchiveOrErr = Archive::create(MB);
-  error(ArchiveOrErr, "Failed to parse static library");
-  File = std::move(*ArchiveOrErr);
+  File = check(Archive::create(MB), "failed to parse static library");
 
   // Allocate a buffer for Lazy objects.
   size_t NumSyms = File->getNumberOfSymbols();
@@ -67,40 +76,38 @@ void ArchiveFile::parse() {
   // Seen is a map from member files to boolean values. Initially
   // all members are mapped to false, which indicates all these files
   // are not read yet.
-  for (auto &ChildOrErr : File->children()) {
-    error(ChildOrErr, "Failed to parse static library");
-    const Archive::Child &Child = *ChildOrErr;
+  Error Err;
+  for (auto &Child : File->children(Err))
     Seen[Child.getChildOffset()].clear();
-  }
+  if (Err)
+    fatal(Err, "failed to parse static library");
 }
 
 // Returns a buffer pointing to a member file containing a given symbol.
 // This function is thread-safe.
 MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
-  auto COrErr = Sym->getMember();
-  error(COrErr, Twine("Could not get the member for symbol ") + Sym->getName());
-  const Archive::Child &C = *COrErr;
+  const Archive::Child &C =
+      check(Sym->getMember(),
+            "could not get the member for symbol " + Sym->getName());
 
   // Return an empty buffer if we have already returned the same buffer.
   if (Seen[C.getChildOffset()].test_and_set())
     return MemoryBufferRef();
-  ErrorOr<MemoryBufferRef> Ret = C.getMemoryBufferRef();
-  error(Ret, Twine("Could not get the buffer for the member defining symbol ") +
-                 Sym->getName());
-  return *Ret;
+  return check(C.getMemoryBufferRef(),
+               "could not get the buffer for the member defining symbol " +
+                   Sym->getName());
 }
 
 void ObjectFile::parse() {
   // Parse a memory buffer as a COFF file.
-  auto BinOrErr = createBinary(MB);
-  error(BinOrErr, "Failed to parse object file");
-  std::unique_ptr<Binary> Bin = std::move(*BinOrErr);
+  std::unique_ptr<Binary> Bin =
+      check(createBinary(MB), "failed to parse object file");
 
   if (auto *Obj = dyn_cast<COFFObjectFile>(Bin.get())) {
     Bin.release();
     COFFObj.reset(Obj);
   } else {
-    error(Twine(getName()) + " is not a COFF file.");
+    fatal(getName() + " is not a COFF file");
   }
 
   // Read section and symbol tables.
@@ -116,10 +123,10 @@ void ObjectFile::initializeChunks() {
   for (uint32_t I = 1; I < NumSections + 1; ++I) {
     const coff_section *Sec;
     StringRef Name;
-    std::error_code EC = COFFObj->getSection(I, Sec);
-    error(EC, Twine("getSection failed: #") + Twine(I));
-    EC = COFFObj->getSectionName(Sec, Name);
-    error(EC, Twine("getSectionName failed: #") + Twine(I));
+    if (auto EC = COFFObj->getSection(I, Sec))
+      fatal(EC, "getSection failed: #" + Twine(I));
+    if (auto EC = COFFObj->getSectionName(Sec, Name))
+      fatal(EC, "getSectionName failed: #" + Twine(I));
     if (Name == ".sxdata") {
       SXData = Sec;
       continue;
@@ -149,14 +156,12 @@ void ObjectFile::initializeSymbols() {
   uint32_t NumSymbols = COFFObj->getNumberOfSymbols();
   SymbolBodies.reserve(NumSymbols);
   SparseSymbolBodies.resize(NumSymbols);
-  llvm::SmallVector<Undefined *, 8> WeakAliases;
+  llvm::SmallVector<std::pair<Undefined *, uint32_t>, 8> WeakAliases;
   int32_t LastSectionNumber = 0;
   for (uint32_t I = 0; I < NumSymbols; ++I) {
     // Get a COFFSymbolRef object.
-    auto SymOrErr = COFFObj->getSymbol(I);
-    error(SymOrErr, Twine("broken object file: ") + getName());
-
-    COFFSymbolRef Sym = *SymOrErr;
+    COFFSymbolRef Sym =
+        check(COFFObj->getSymbol(I), "broken object file: " + getName());
 
     const void *AuxP = nullptr;
     if (Sym.getNumberOfAuxSymbols())
@@ -167,8 +172,10 @@ void ObjectFile::initializeSymbols() {
     if (Sym.isUndefined()) {
       Body = createUndefined(Sym);
     } else if (Sym.isWeakExternal()) {
-      Body = createWeakExternal(Sym, AuxP);
-      WeakAliases.push_back((Undefined *)Body);
+      Body = createUndefined(Sym);
+      uint32_t TagIndex =
+          static_cast<const coff_aux_weak_external *>(AuxP)->TagIndex;
+      WeakAliases.emplace_back((Undefined *)Body, TagIndex);
     } else {
       Body = createDefined(Sym, AuxP, IsFirst);
     }
@@ -179,8 +186,8 @@ void ObjectFile::initializeSymbols() {
     I += Sym.getNumberOfAuxSymbols();
     LastSectionNumber = Sym.getSectionNumber();
   }
-  for (Undefined *U : WeakAliases)
-    U->WeakAlias = SparseSymbolBodies[(uintptr_t)U->WeakAlias];
+  for (auto WeakAlias : WeakAliases)
+    WeakAlias.first->WeakAlias = SparseSymbolBodies[WeakAlias.second];
 }
 
 Undefined *ObjectFile::createUndefined(COFFSymbolRef Sym) {
@@ -189,15 +196,6 @@ Undefined *ObjectFile::createUndefined(COFFSymbolRef Sym) {
   return new (Alloc) Undefined(Name);
 }
 
-Undefined *ObjectFile::createWeakExternal(COFFSymbolRef Sym, const void *AuxP) {
-  StringRef Name;
-  COFFObj->getSymbolName(Sym, Name);
-  auto *U = new (Alloc) Undefined(Name);
-  auto *Aux = (const coff_aux_weak_external *)AuxP;
-  U->WeakAlias = (Undefined *)(uintptr_t)Aux->TagIndex;
-  return U;
-}
-
 Defined *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
                                    bool IsFirst) {
   StringRef Name;
@@ -219,11 +217,21 @@ Defined *ObjectFile::createDefined(COFFSymbolRef Sym, const void *AuxP,
     }
     return new (Alloc) DefinedAbsolute(Name, Sym);
   }
-  if (Sym.getSectionNumber() == llvm::COFF::IMAGE_SYM_DEBUG)
+  int32_t SectionNumber = Sym.getSectionNumber();
+  if (SectionNumber == llvm::COFF::IMAGE_SYM_DEBUG)
     return nullptr;
 
+  // Reserved sections numbers don't have contents.
+  if (llvm::COFF::isReservedSectionNumber(SectionNumber))
+    fatal("broken object file: " + getName());
+
+  // This symbol references a section which is not present in the section
+  // header.
+  if ((uint32_t)SectionNumber >= SparseChunks.size())
+    fatal("broken object file: " + getName());
+
   // Nothing else to do without a section chunk.
-  auto *SC = cast_or_null<SectionChunk>(SparseChunks[Sym.getSectionNumber()]);
+  auto *SC = cast_or_null<SectionChunk>(SparseChunks[SectionNumber]);
   if (!SC)
     return nullptr;
 
@@ -250,7 +258,7 @@ void ObjectFile::initializeSEH() {
   ArrayRef<uint8_t> A;
   COFFObj->getSectionContents(SXData, A);
   if (A.size() % 4 != 0)
-    error(".sxdata must be an array of symbol table indices");
+    fatal(".sxdata must be an array of symbol table indices");
   auto *I = reinterpret_cast<const ulittle32_t *>(A.data());
   auto *E = reinterpret_cast<const ulittle32_t *>(A.data() + A.size());
   for (; I != E; ++I)
@@ -276,11 +284,11 @@ void ImportFile::parse() {
 
   // Check if the total size is valid.
   if ((size_t)(End - Buf) != (sizeof(*Hdr) + Hdr->SizeOfData))
-    error("broken import library");
+    fatal("broken import library");
 
   // Read names and create an __imp_ symbol.
   StringRef Name = StringAlloc.save(StringRef(Buf + sizeof(*Hdr)));
-  StringRef ImpName = StringAlloc.save(Twine("__imp_") + Name);
+  StringRef ImpName = StringAlloc.save("__imp_" + Name);
   const char *NameStart = Buf + sizeof(coff_import_header) + Name.size() + 1;
   DLLName = StringRef(NameStart);
   StringRef ExtName;
@@ -315,11 +323,10 @@ void BitcodeFile::parse() {
   // Usually parse() is thread-safe, but bitcode file is an exception.
   std::lock_guard<std::mutex> Lock(Mu);
 
-  ErrorOr<std::unique_ptr<LTOModule>> ModOrErr =
-      LTOModule::createFromBuffer(llvm::getGlobalContext(), MB.getBufferStart(),
-                                  MB.getBufferSize(), llvm::TargetOptions());
-  error(ModOrErr, "Could not create lto module");
-  M = std::move(*ModOrErr);
+  Context.enableDebugTypeODRUniquing();
+  ErrorOr<std::unique_ptr<LTOModule>> ModOrErr = LTOModule::createFromBuffer(
+      Context, MB.getBufferStart(), MB.getBufferSize(), llvm::TargetOptions());
+  M = check(std::move(ModOrErr), "could not create LTO module");
 
   llvm::StringSaver Saver(Alloc);
   for (unsigned I = 0, E = M->getSymbolCount(); I != E; ++I) {
diff --git a/COFF/InputFiles.h b/COFF/InputFiles.h
index 6a263fbaddf6..0ec01b5075f9 100644
--- a/COFF/InputFiles.h
+++ b/COFF/InputFiles.h
@@ -12,7 +12,8 @@
 
 #include "lld/Core/LLVM.h"
 #include "llvm/ADT/ArrayRef.h"
-#include "llvm/LTO/LTOModule.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/LTO/legacy/LTOModule.h"
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/COFF.h"
 #include "llvm/Support/StringSaver.h"
@@ -103,7 +104,7 @@ public:
 
   // All symbols returned by ArchiveFiles are of Lazy type.
   std::vector<SymbolBody *> &getSymbols() override {
-    llvm_unreachable("internal error");
+    llvm_unreachable("internal fatal");
   }
 
 private:
@@ -147,7 +148,6 @@ private:
 
   Defined *createDefined(COFFSymbolRef Sym, const void *Aux, bool IsFirst);
   Undefined *createUndefined(COFFSymbolRef Sym);
-  Undefined *createWeakExternal(COFFSymbolRef Sym, const void *Aux);
 
   std::unique_ptr<COFFObjectFile> COFFObj;
   llvm::BumpPtrAllocator Alloc;
@@ -204,9 +204,10 @@ public:
   static bool classof(const InputFile *F) { return F->kind() == BitcodeKind; }
   std::vector<SymbolBody *> &getSymbols() override { return SymbolBodies; }
   MachineTypes getMachineType() override;
-
   std::unique_ptr<LTOModule> takeModule() { return std::move(M); }
 
+  static llvm::LLVMContext Context;
+
 private:
   void parse() override;
 
diff --git a/COFF/Librarian.cpp b/COFF/Librarian.cpp
new file mode 100644
index 000000000000..25fb4a87b3eb
--- /dev/null
+++ b/COFF/Librarian.cpp
@@ -0,0 +1,489 @@
+//===- Librarian.cpp ------------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains functions for the Librarian.  The librarian creates and
+// manages libraries of the Common Object File Format (COFF) object files.  It
+// primarily is used for creating static libraries and import libraries.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Config.h"
+#include "Driver.h"
+#include "Error.h"
+#include "Symbols.h"
+#include "llvm/Object/Archive.h"
+#include "llvm/Object/ArchiveWriter.h"
+#include "llvm/Object/COFF.h"
+#include "llvm/Support/Path.h"
+
+#include <vector>
+
+using namespace lld::coff;
+using namespace llvm::COFF;
+using namespace llvm::object;
+using namespace llvm;
+
+static bool is32bit() {
+  switch (Config->Machine) {
+  default:
+    llvm_unreachable("unsupported machine");
+  case IMAGE_FILE_MACHINE_AMD64:
+    return false;
+  case IMAGE_FILE_MACHINE_ARMNT:
+  case IMAGE_FILE_MACHINE_I386:
+    return true;
+  }
+}
+
+static uint16_t getImgRelRelocation() {
+  switch (Config->Machine) {
+  default:
+    llvm_unreachable("unsupported machine");
+  case IMAGE_FILE_MACHINE_AMD64:
+    return IMAGE_REL_AMD64_ADDR32NB;
+  case IMAGE_FILE_MACHINE_ARMNT:
+    return IMAGE_REL_ARM_ADDR32NB;
+  case IMAGE_FILE_MACHINE_I386:
+    return IMAGE_REL_I386_DIR32NB;
+  }
+}
+
+template <class T> void append(std::vector<uint8_t> &B, const T &Data) {
+  size_t S = B.size();
+  B.resize(S + sizeof(T));
+  memcpy(&B[S], &Data, sizeof(T));
+}
+
+static void writeStringTable(std::vector<uint8_t> &B,
+                             ArrayRef<const std::string> Strings) {
+  // The COFF string table consists of a 4-byte value which is the size of the
+  // table, including the length field itself.  This value is followed by the
+  // string content itself, which is an array of null-terminated C-style
+  // strings.  The termination is important as they are referenced to by offset
+  // by the symbol entity in the file format.
+
+  std::vector<uint8_t>::size_type Pos = B.size();
+  std::vector<uint8_t>::size_type Offset = B.size();
+
+  // Skip over the length field, we will fill it in later as we will have
+  // computed the length while emitting the string content itself.
+  Pos += sizeof(uint32_t);
+
+  for (const auto &S : Strings) {
+    B.resize(Pos + S.length() + 1);
+    strcpy(reinterpret_cast<char *>(&B[Pos]), S.c_str());
+    Pos += S.length() + 1;
+  }
+
+  // Backfill the length of the table now that it has been computed.
+  support::ulittle32_t Length(B.size() - Offset);
+  memcpy(&B[Offset], &Length, sizeof(Length));
+}
+
+static std::string getImplibPath() {
+  if (!Config->Implib.empty())
+    return Config->Implib;
+  SmallString<128> Out = StringRef(Config->OutputFile);
+  sys::path::replace_extension(Out, ".lib");
+  return Out.str();
+}
+
+static ImportNameType getNameType(StringRef Sym, StringRef ExtName) {
+  if (Sym != ExtName)
+    return IMPORT_NAME_UNDECORATE;
+  if (Config->Machine == I386 && Sym.startswith("_"))
+    return IMPORT_NAME_NOPREFIX;
+  return IMPORT_NAME;
+}
+
+static std::string replace(StringRef S, StringRef From, StringRef To) {
+  size_t Pos = S.find(From);
+  assert(Pos != StringRef::npos);
+  return (Twine(S.substr(0, Pos)) + To + S.substr(Pos + From.size())).str();
+}
+
+static const std::string NullImportDescriptorSymbolName =
+    "__NULL_IMPORT_DESCRIPTOR";
+
+namespace {
+// This class constructs various small object files necessary to support linking
+// symbols imported from a DLL.  The contents are pretty strictly defined and
+// nearly entirely static.  The details of the structures files are defined in
+// WINNT.h and the PE/COFF specification.
+class ObjectFactory {
+  using u16 = support::ulittle16_t;
+  using u32 = support::ulittle32_t;
+
+  BumpPtrAllocator Alloc;
+  StringRef DLLName;
+  StringRef Library;
+  std::string ImportDescriptorSymbolName;
+  std::string NullThunkSymbolName;
+
+public:
+  ObjectFactory(StringRef S)
+      : DLLName(S), Library(S.drop_back(4)),
+        ImportDescriptorSymbolName(("__IMPORT_DESCRIPTOR_" + Library).str()),
+        NullThunkSymbolName(("\x7f" + Library + "_NULL_THUNK_DATA").str()) {}
+
+  // Creates an Import Descriptor.  This is a small object file which contains a
+  // reference to the terminators and contains the library name (entry) for the
+  // import name table.  It will force the linker to construct the necessary
+  // structure to import symbols from the DLL.
+  NewArchiveMember createImportDescriptor(std::vector<uint8_t> &Buffer);
+
+  // Creates a NULL import descriptor.  This is a small object file whcih
+  // contains a NULL import descriptor.  It is used to terminate the imports
+  // from a specific DLL.
+  NewArchiveMember createNullImportDescriptor(std::vector<uint8_t> &Buffer);
+
+  // Create a NULL Thunk Entry.  This is a small object file which contains a
+  // NULL Import Address Table entry and a NULL Import Lookup Table Entry.  It
+  // is used to terminate the IAT and ILT.
+  NewArchiveMember createNullThunk(std::vector<uint8_t> &Buffer);
+
+  // Create a short import file which is described in PE/COFF spec 7. Import
+  // Library Format.
+  NewArchiveMember createShortImport(StringRef Sym, uint16_t Ordinal,
+                                     ImportNameType NameType, bool isData);
+};
+}
+
+NewArchiveMember
+ObjectFactory::createImportDescriptor(std::vector<uint8_t> &Buffer) {
+  static const uint32_t NumberOfSections = 2;
+  static const uint32_t NumberOfSymbols = 7;
+  static const uint32_t NumberOfRelocations = 3;
+
+  // COFF Header
+  coff_file_header Header{
+      u16(Config->Machine), u16(NumberOfSections), u32(0),
+      u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
+          // .idata$2
+          sizeof(coff_import_directory_table_entry) +
+          NumberOfRelocations * sizeof(coff_relocation) +
+          // .idata$4
+          (DLLName.size() + 1)),
+      u32(NumberOfSymbols), u16(0),
+      u16(is32bit() ? IMAGE_FILE_32BIT_MACHINE : 0),
+  };
+  append(Buffer, Header);
+
+  // Section Header Table
+  static const coff_section SectionTable[NumberOfSections] = {
+      {{'.', 'i', 'd', 'a', 't', 'a', '$', '2'},
+       u32(0),
+       u32(0),
+       u32(sizeof(coff_import_directory_table_entry)),
+       u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section)),
+       u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
+           sizeof(coff_import_directory_table_entry)),
+       u32(0),
+       u16(NumberOfRelocations),
+       u16(0),
+       u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
+           IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
+      {{'.', 'i', 'd', 'a', 't', 'a', '$', '6'},
+       u32(0),
+       u32(0),
+       u32(DLLName.size() + 1),
+       u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
+           sizeof(coff_import_directory_table_entry) +
+           NumberOfRelocations * sizeof(coff_relocation)),
+       u32(0),
+       u32(0),
+       u16(0),
+       u16(0),
+       u32(IMAGE_SCN_ALIGN_2BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
+           IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
+  };
+  append(Buffer, SectionTable);
+
+  // .idata$2
+  static const coff_import_directory_table_entry ImportDescriptor{
+      u32(0), u32(0), u32(0), u32(0), u32(0),
+  };
+  append(Buffer, ImportDescriptor);
+
+  static const coff_relocation RelocationTable[NumberOfRelocations] = {
+      {u32(offsetof(coff_import_directory_table_entry, NameRVA)), u32(2),
+       u16(getImgRelRelocation())},
+      {u32(offsetof(coff_import_directory_table_entry, ImportLookupTableRVA)),
+       u32(3), u16(getImgRelRelocation())},
+      {u32(offsetof(coff_import_directory_table_entry, ImportAddressTableRVA)),
+       u32(4), u16(getImgRelRelocation())},
+  };
+  append(Buffer, RelocationTable);
+
+  // .idata$6
+  auto S = Buffer.size();
+  Buffer.resize(S + DLLName.size() + 1);
+  memcpy(&Buffer[S], DLLName.data(), DLLName.size());
+  Buffer[S + DLLName.size()] = '\0';
+
+  // Symbol Table
+  coff_symbol16 SymbolTable[NumberOfSymbols] = {
+      {{{0, 0, 0, 0, 0, 0, 0, 0}},
+       u32(0),
+       u16(1),
+       u16(0),
+       IMAGE_SYM_CLASS_EXTERNAL,
+       0},
+      {{{'.', 'i', 'd', 'a', 't', 'a', '$', '2'}},
+       u32(0),
+       u16(1),
+       u16(0),
+       IMAGE_SYM_CLASS_SECTION,
+       0},
+      {{{'.', 'i', 'd', 'a', 't', 'a', '$', '6'}},
+       u32(0),
+       u16(2),
+       u16(0),
+       IMAGE_SYM_CLASS_STATIC,
+       0},
+      {{{'.', 'i', 'd', 'a', 't', 'a', '$', '4'}},
+       u32(0),
+       u16(0),
+       u16(0),
+       IMAGE_SYM_CLASS_SECTION,
+       0},
+      {{{'.', 'i', 'd', 'a', 't', 'a', '$', '5'}},
+       u32(0),
+       u16(0),
+       u16(0),
+       IMAGE_SYM_CLASS_SECTION,
+       0},
+      {{{0, 0, 0, 0, 0, 0, 0, 0}},
+       u32(0),
+       u16(0),
+       u16(0),
+       IMAGE_SYM_CLASS_EXTERNAL,
+       0},
+      {{{0, 0, 0, 0, 0, 0, 0, 0}},
+       u32(0),
+       u16(0),
+       u16(0),
+       IMAGE_SYM_CLASS_EXTERNAL,
+       0},
+  };
+  reinterpret_cast<StringTableOffset &>(SymbolTable[0].Name).Offset =
+      sizeof(uint32_t);
+  reinterpret_cast<StringTableOffset &>(SymbolTable[5].Name).Offset =
+      sizeof(uint32_t) + ImportDescriptorSymbolName.length() + 1;
+  reinterpret_cast<StringTableOffset &>(SymbolTable[6].Name).Offset =
+      sizeof(uint32_t) + ImportDescriptorSymbolName.length() + 1 +
+      NullImportDescriptorSymbolName.length() + 1;
+  append(Buffer, SymbolTable);
+
+  // String Table
+  writeStringTable(Buffer,
+                   {ImportDescriptorSymbolName, NullImportDescriptorSymbolName,
+                    NullThunkSymbolName});
+
+  StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
+  return {MemoryBufferRef(F, DLLName)};
+}
+
+NewArchiveMember
+ObjectFactory::createNullImportDescriptor(std::vector<uint8_t> &Buffer) {
+  static const uint32_t NumberOfSections = 1;
+  static const uint32_t NumberOfSymbols = 1;
+
+  // COFF Header
+  coff_file_header Header{
+      u16(Config->Machine), u16(NumberOfSections), u32(0),
+      u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
+          // .idata$3
+          sizeof(coff_import_directory_table_entry)),
+      u32(NumberOfSymbols), u16(0),
+      u16(is32bit() ? IMAGE_FILE_32BIT_MACHINE : 0),
+  };
+  append(Buffer, Header);
+
+  // Section Header Table
+  static const coff_section SectionTable[NumberOfSections] = {
+      {{'.', 'i', 'd', 'a', 't', 'a', '$', '3'},
+       u32(0),
+       u32(0),
+       u32(sizeof(coff_import_directory_table_entry)),
+       u32(sizeof(coff_file_header) +
+           (NumberOfSections * sizeof(coff_section))),
+       u32(0),
+       u32(0),
+       u16(0),
+       u16(0),
+       u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
+           IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
+  };
+  append(Buffer, SectionTable);
+
+  // .idata$3
+  static const coff_import_directory_table_entry ImportDescriptor{
+      u32(0), u32(0), u32(0), u32(0), u32(0),
+  };
+  append(Buffer, ImportDescriptor);
+
+  // Symbol Table
+  coff_symbol16 SymbolTable[NumberOfSymbols] = {
+      {{{0, 0, 0, 0, 0, 0, 0, 0}},
+       u32(0),
+       u16(1),
+       u16(0),
+       IMAGE_SYM_CLASS_EXTERNAL,
+       0},
+  };
+  reinterpret_cast<StringTableOffset &>(SymbolTable[0].Name).Offset =
+      sizeof(uint32_t);
+  append(Buffer, SymbolTable);
+
+  // String Table
+  writeStringTable(Buffer, {NullImportDescriptorSymbolName});
+
+  StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
+  return {MemoryBufferRef(F, DLLName)};
+}
+
+NewArchiveMember ObjectFactory::createNullThunk(std::vector<uint8_t> &Buffer) {
+  static const uint32_t NumberOfSections = 2;
+  static const uint32_t NumberOfSymbols = 1;
+
+  // COFF Header
+  coff_file_header Header{
+      u16(Config->Machine), u16(NumberOfSections), u32(0),
+      u32(sizeof(Header) + (NumberOfSections * sizeof(coff_section)) +
+          // .idata$5
+          sizeof(export_address_table_entry) +
+          // .idata$4
+          sizeof(export_address_table_entry)),
+      u32(NumberOfSymbols), u16(0),
+      u16(is32bit() ? IMAGE_FILE_32BIT_MACHINE : 0),
+  };
+  append(Buffer, Header);
+
+  // Section Header Table
+  static const coff_section SectionTable[NumberOfSections] = {
+      {{'.', 'i', 'd', 'a', 't', 'a', '$', '5'},
+       u32(0),
+       u32(0),
+       u32(sizeof(export_address_table_entry)),
+       u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section)),
+       u32(0),
+       u32(0),
+       u16(0),
+       u16(0),
+       u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
+           IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
+      {{'.', 'i', 'd', 'a', 't', 'a', '$', '4'},
+       u32(0),
+       u32(0),
+       u32(sizeof(export_address_table_entry)),
+       u32(sizeof(coff_file_header) + NumberOfSections * sizeof(coff_section) +
+           sizeof(export_address_table_entry)),
+       u32(0),
+       u32(0),
+       u16(0),
+       u16(0),
+       u32(IMAGE_SCN_ALIGN_4BYTES | IMAGE_SCN_CNT_INITIALIZED_DATA |
+           IMAGE_SCN_MEM_READ | IMAGE_SCN_MEM_WRITE)},
+  };
+  append(Buffer, SectionTable);
+
+  // .idata$5
+  static const export_address_table_entry ILT{u32(0)};
+  append(Buffer, ILT);
+
+  // .idata$4
+  static const export_address_table_entry IAT{u32(0)};
+  append(Buffer, IAT);
+
+  // Symbol Table
+  coff_symbol16 SymbolTable[NumberOfSymbols] = {
+      {{{0, 0, 0, 0, 0, 0, 0, 0}},
+       u32(0),
+       u16(1),
+       u16(0),
+       IMAGE_SYM_CLASS_EXTERNAL,
+       0},
+  };
+  reinterpret_cast<StringTableOffset &>(SymbolTable[0].Name).Offset =
+      sizeof(uint32_t);
+  append(Buffer, SymbolTable);
+
+  // String Table
+  writeStringTable(Buffer, {NullThunkSymbolName});
+
+  StringRef F{reinterpret_cast<const char *>(Buffer.data()), Buffer.size()};
+  return {MemoryBufferRef{F, DLLName}};
+}
+
+NewArchiveMember ObjectFactory::createShortImport(StringRef Sym,
+                                                  uint16_t Ordinal,
+                                                  ImportNameType NameType,
+                                                  bool isData) {
+  size_t ImpSize = DLLName.size() + Sym.size() + 2; // +2 for NULs
+  size_t Size = sizeof(coff_import_header) + ImpSize;
+  char *Buf = Alloc.Allocate<char>(Size);
+  memset(Buf, 0, Size);
+  char *P = Buf;
+
+  // Write short import library.
+  auto *Imp = reinterpret_cast<coff_import_header *>(P);
+  P += sizeof(*Imp);
+  Imp->Sig2 = 0xFFFF;
+  Imp->Machine = Config->Machine;
+  Imp->SizeOfData = ImpSize;
+  if (Ordinal > 0)
+    Imp->OrdinalHint = Ordinal;
+  Imp->TypeInfo = (isData ? IMPORT_DATA : IMPORT_CODE);
+  Imp->TypeInfo |= NameType << 2;
+
+  // Write symbol name and DLL name.
+  memcpy(P, Sym.data(), Sym.size());
+  P += Sym.size() + 1;
+  memcpy(P, DLLName.data(), DLLName.size());
+
+  return {MemoryBufferRef(StringRef(Buf, Size), DLLName)};
+}
+
+// Creates an import library for a DLL. In this function, we first
+// create an empty import library using lib.exe and then adds short
+// import files to that file.
+void lld::coff::writeImportLibrary() {
+  std::vector<NewArchiveMember> Members;
+
+  std::string Path = getImplibPath();
+  std::string DLLName = llvm::sys::path::filename(Config->OutputFile);
+  ObjectFactory OF(DLLName);
+
+  std::vector<uint8_t> ImportDescriptor;
+  Members.push_back(OF.createImportDescriptor(ImportDescriptor));
+
+  std::vector<uint8_t> NullImportDescriptor;
+  Members.push_back(OF.createNullImportDescriptor(NullImportDescriptor));
+
+  std::vector<uint8_t> NullThunk;
+  Members.push_back(OF.createNullThunk(NullThunk));
+
+  for (Export &E : Config->Exports) {
+    if (E.Private)
+      continue;
+
+    ImportNameType Type = getNameType(E.SymbolName, E.Name);
+    std::string Name = E.ExtName.empty()
+                           ? std::string(E.SymbolName)
+                           : replace(E.SymbolName, E.Name, E.ExtName);
+    Members.push_back(OF.createShortImport(Name, E.Ordinal, Type, E.Data));
+  }
+
+  std::pair<StringRef, std::error_code> Result =
+      writeArchive(Path, Members, /*WriteSymtab*/ true, object::Archive::K_GNU,
+                   /*Deterministic*/ true, /*Thin*/ false);
+  if (auto EC = Result.second)
+    fatal(EC, "failed to write " + Path);
+}
diff --git a/COFF/ModuleDef.cpp b/COFF/ModuleDef.cpp
index d117e961f89a..5e393f45d184 100644
--- a/COFF/ModuleDef.cpp
+++ b/COFF/ModuleDef.cpp
@@ -134,13 +134,13 @@ private:
   void readAsInt(uint64_t *I) {
     read();
     if (Tok.K != Identifier || Tok.Value.getAsInteger(10, *I))
-      error("integer expected");
+      fatal("integer expected");
   }
 
   void expect(Kind Expected, StringRef Msg) {
     read();
     if (Tok.K != Expected)
-      error(Msg);
+      fatal(Msg);
   }
 
   void unget() { Stack.push_back(Tok); }
@@ -177,7 +177,7 @@ private:
       parseVersion(&Config->MajorImageVersion, &Config->MinorImageVersion);
       return;
     default:
-      error(Twine("unknown directive: ") + Tok.Value);
+      fatal("unknown directive: " + Tok.Value);
     }
   }
 
@@ -188,7 +188,7 @@ private:
     if (Tok.K == Equal) {
       read();
       if (Tok.K != Identifier)
-        error(Twine("identifier expected, but got ") + Tok.Value);
+        fatal("identifier expected, but got " + Tok.Value);
       E.ExtName = E.Name;
       E.Name = Tok.Value;
     } else {
@@ -264,15 +264,15 @@ private:
   void parseVersion(uint32_t *Major, uint32_t *Minor) {
     read();
     if (Tok.K != Identifier)
-      error(Twine("identifier expected, but got ") + Tok.Value);
+      fatal("identifier expected, but got " + Tok.Value);
     StringRef V1, V2;
     std::tie(V1, V2) = Tok.Value.split('.');
     if (V1.getAsInteger(10, *Major))
-      error(Twine("integer expected, but got ") + Tok.Value);
+      fatal("integer expected, but got " + Tok.Value);
     if (V2.empty())
       *Minor = 0;
     else if (V2.getAsInteger(10, *Minor))
-      error(Twine("integer expected, but got ") + Tok.Value);
+      fatal("integer expected, but got " + Tok.Value);
   }
 
   Lexer Lex;
diff --git a/COFF/Options.td b/COFF/Options.td
index a21b8de76afb..e5c9c5b4635b 100644
--- a/COFF/Options.td
+++ b/COFF/Options.td
@@ -48,6 +48,7 @@ def manifestuac : P<"manifestuac", "User access control">;
 def manifestfile : P<"manifestfile", "Manifest file path">;
 def manifestdependency : P<"manifestdependency",
                            "Attributes for <dependency> in manifest file">;
+def manifestinput : P<"manifestinput", "Specify manifest file">;
 
 // We cannot use multiclass P because class name "incl" is different
 // from its command line option name. We do this because "include" is
@@ -110,6 +111,7 @@ def no_incremental : F<"incremental:no">;
 def nologo : F<"nologo">;
 def throwingnew : F<"throwingnew">;
 def editandcontinue : F<"editandcontinue">;
+def fastfail : F<"fastfail">;
 
 def delay : QF<"delay">;
 def errorreport : QF<"errorreport">;
diff --git a/COFF/PDB.cpp b/COFF/PDB.cpp
index 786d28798bab..7606ccc680d3 100644
--- a/COFF/PDB.cpp
+++ b/COFF/PDB.cpp
@@ -38,7 +38,8 @@ void lld::coff::createPDB(StringRef Path) {
   size_t FileSize = PageSize * 3;
   ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
       FileOutputBuffer::create(Path, FileSize);
-  error(BufferOrErr, Twine("failed to open ") + Path);
+  if (auto EC = BufferOrErr.getError())
+    fatal(EC, "failed to open " + Path);
   std::unique_ptr<FileOutputBuffer> Buffer = std::move(*BufferOrErr);
 
   // Write the file header.
diff --git a/COFF/README.md b/COFF/README.md
index c1be560f4405..f1bfc9c15263 100644
--- a/COFF/README.md
+++ b/COFF/README.md
@@ -1,265 +1 @@
-The PE/COFF Linker
-==================
-
-This directory contains a linker for Windows operating system.
-Because the fundamental design of this port is different from
-the other ports of LLD, this port is separated to this directory.
-
-The linker is command-line compatible with MSVC linker and is
-generally 2x faster than that. It can be used to link real-world
-programs such as LLD itself or Clang, or even web browsers which
-are probably the largest open-source programs for Windows.
-
-This document is also applicable to ELF linker because the linker
-shares the same design as this COFF linker.
-
-Overall Design
---------------
-
-This is a list of important data types in this linker.
-
-* SymbolBody
-
-  SymbolBody is a class for symbols. They may be created for symbols
-  in object files or in archive file headers. The linker may create
-  them out of nothing.
-
-  There are mainly three types of SymbolBodies: Defined, Undefined, or
-  Lazy. Defined symbols are for all symbols that are considered as
-  "resolved", including real defined symbols, COMDAT symbols, common
-  symbols, absolute symbols, linker-created symbols, etc. Undefined
-  symbols are for undefined symbols, which need to be replaced by
-  Defined symbols by the resolver. Lazy symbols represent symbols we
-  found in archive file headers -- which can turn into Defined symbols
-  if we read archieve members, but we haven't done that yet.
-
-* Symbol
-
-  Symbol is a pointer to a SymbolBody. There's only one Symbol for
-  each unique symbol name (this uniqueness is guaranteed by the symbol
-  table). Because SymbolBodies are created for each file
-  independently, there can be many SymbolBodies for the same
-  name. Thus, the relationship between Symbols and SymbolBodies is 1:N.
-
-  The resolver keeps the Symbol's pointer to always point to the "best"
-  SymbolBody. Pointer mutation is the resolve operation in this
-  linker.
-
-  SymbolBodies have pointers to their Symbols. That means you can
-  always find the best SymbolBody from any SymbolBody by following
-  pointers twice. This structure makes it very easy to find
-  replacements for symbols. For example, if you have an Undefined
-  SymbolBody, you can find a Defined SymbolBody for that symbol just
-  by going to its Symbol and then to SymbolBody, assuming the resolver
-  have successfully resolved all undefined symbols.
-
-* Chunk
-
-  Chunk represents a chunk of data that will occupy space in an
-  output. Each regular section becomes a chunk.
-  Chunks created for common or BSS symbols are not backed by sections.
-  The linker may create chunks out of nothing to append additional
-  data to an output.
-
-  Chunks know about their size, how to copy their data to mmap'ed
-  outputs, and how to apply relocations to them. Specifically,
-  section-based chunks know how to read relocation tables and how to
-  apply them.
-
-* SymbolTable
-
-  SymbolTable is basically a hash table from strings to Symbols, with
-  a logic to resolve symbol conflicts. It resolves conflicts by symbol
-  type. For example, if we add Undefined and Defined symbols, the
-  symbol table will keep the latter. If we add Defined and Lazy
-  symbols, it will keep the former. If we add Lazy and Undefined, it
-  will keep the former, but it will also trigger the Lazy symbol to
-  load the archive member to actually resolve the symbol.
-
-* OutputSection
-
-  OutputSection is a container of Chunks. A Chunk belongs to at most
-  one OutputSection.
-
-There are mainly three actors in this linker.
-
-* InputFile
-
-  InputFile is a superclass of file readers. We have a different
-  subclass for each input file type, such as regular object file,
-  archive file, etc. They are responsible for creating and owning
-  SymbolBodies and Chunks.
-
-* Writer
-
-  The writer is responsible for writing file headers and Chunks to a
-  file. It creates OutputSections, put all Chunks into them, assign
-  unique, non-overlapping addresses and file offsets to them, and then
-  write them down to a file.
-
-* Driver
-
-  The linking process is drived by the driver. The driver
-
-  - processes command line options,
-  - creates a symbol table,
-  - creates an InputFile for each input file and put all symbols in it
-    into the symbol table,
-  - checks if there's no remaining undefined symbols,
-  - creates a writer,
-  - and passes the symbol table to the writer to write the result to a
-    file.
-
-Performance
------------
-
-It's generally 2x faster than MSVC link.exe. It takes 3.5 seconds to
-self-host on my Xeon 2580 machine. MSVC linker takes 7.0 seconds to
-link the same executable. The resulting output is 65MB.
-The old LLD is buggy that it produces 120MB executable for some reason,
-and it takes 30 seconds to do that.
-
-We believe the performance difference comes from simplification and
-optimizations we made to the new port. Notable differences are listed
-below.
-
-* Reduced number of relocation table reads
-
-  In the old design, relocation tables are read from beginning to
-  construct graphs because they consist of graph edges. In the new
-  design, they are not read until we actually apply relocations.
-
-  This simplification has two benefits. One is that we don't create
-  additional objects for relocations but instead consume relocation
-  tables directly. The other is that it reduces number of relocation
-  entries we have to read, because we won't read relocations for
-  dead-stripped COMDAT sections. Large C++ programs tend to consist of
-  lots of COMDAT sections. In the old design, the time to process
-  relocation table is linear to size of input. In this new model, it's
-  linear to size of output.
-
-* Reduced number of symbol table lookup
-
-  Symbol table lookup can be a heavy operation because number of
-  symbols can be very large and each symbol name can be very long
-  (think of C++ mangled symbols -- time to compute a hash value for a
-  string is linear to the length.)
-
-  We look up the symbol table exactly only once for each symbol in the
-  new design. This is I believe the minimum possible number. This is
-  achieved by the separation of Symbol and SymbolBody. Once you get a
-  pointer to a Symbol by looking up the symbol table, you can always
-  get the latest symbol resolution result by just dereferencing a
-  pointer. (I'm not sure if the idea is new to the linker. At least,
-  all other linkers I've investigated so far seem to look up hash
-  tables or sets more than once for each new symbol, but I may be
-  wrong.)
-
-* Reduced number of file visits
-
-  The symbol table implements the Windows linker semantics. We treat
-  the symbol table as a bucket of all known symbols, including symbols
-  in archive file headers. We put all symbols into one bucket as we
-  visit new files. That means we visit each file only once.
-
-  This is different from the Unix linker semantics, in which we only
-  keep undefined symbols and visit each file one by one until we
-  resolve all undefined symbols. In the Unix model, we have to visit
-  archive files many times if there are circular dependencies between
-  archives.
-
-* Avoiding creating additional objects or copying data
-
-  The data structures described in the previous section are all thin
-  wrappers for classes that LLVM libObject provides. We avoid copying
-  data from libObject's objects to our objects. We read much less data
-  than before. For example, we don't read symbol values until we apply
-  relocations because these values are not relevant to symbol
-  resolution. Again, COMDAT symbols may be discarded during symbol
-  resolution, so reading their attributes too early could result in a
-  waste. We use underlying objects directly where doing so makes
-  sense.
-
-Parallelism
------------
-
-The abovementioned data structures are also chosen with
-multi-threading in mind. It should relatively be easy to make the
-symbol table a concurrent hash map, so that we let multiple workers
-work on symbol table concurrently. Symbol resolution in this design is
-a single pointer mutation, which allows the resolver work concurrently
-in a lock-free manner using atomic pointer compare-and-swap.
-
-It should also be easy to apply relocations and write chunks concurrently.
-
-We created an experimental multi-threaded linker using the Microsoft
-ConcRT concurrency library, and it was able to link itself in 0.5
-seconds, so we think the design is promising.
-
-Link-Time Optimization
-----------------------
-
-LTO is implemented by handling LLVM bitcode files as object files.
-The linker resolves symbols in bitcode files normally. If all symbols
-are successfully resolved, it then calls an LLVM libLTO function
-with all bitcode files to convert them to one big regular COFF file.
-Finally, the linker replaces bitcode symbols with COFF symbols,
-so that we can link the input files as if they were in the native
-format from the beginning.
-
-The details are described in this document.
-http://llvm.org/docs/LinkTimeOptimization.html
-
-Glossary
---------
-
-* RVA
-
-  Short for Relative Virtual Address.
-
-  Windows executables or DLLs are not position-independent; they are
-  linked against a fixed address called an image base. RVAs are
-  offsets from an image base.
-
-  Default image bases are 0x140000000 for executables and 0x18000000
-  for DLLs. For example, when we are creating an executable, we assume
-  that the executable will be loaded at address 0x140000000 by the
-  loader, so we apply relocations accordingly. Result texts and data
-  will contain raw absolute addresses.
-
-* VA
-
-  Short for Virtual Address. Equivalent to RVA + image base. It is
-  rarely used. We almost always use RVAs instead.
-
-* Base relocations
-
-  Relocation information for the loader. If the loader decides to map
-  an executable or a DLL to a different address than their image
-  bases, it fixes up binaries using information contained in the base
-  relocation table. A base relocation table consists of a list of
-  locations containing addresses. The loader adds a difference between
-  RVA and actual load address to all locations listed there.
-
-  Note that this run-time relocation mechanism is much simpler than ELF.
-  There's no PLT or GOT. Images are relocated as a whole just
-  by shifting entire images in memory by some offsets. Although doing
-  this breaks text sharing, I think this mechanism is not actually bad
-  on today's computers.
-
-* ICF
-
-  Short for Identical COMDAT Folding.
-
-  ICF is an optimization to reduce output size by merging COMDAT sections
-  by not only their names but by their contents. If two COMDAT sections
-  happen to have the same metadata, actual contents and relocations,
-  they are merged by ICF. It is known as an effective technique,
-  and it usually reduces C++ program's size by a few percent or more.
-
-  Note that this is not entirely sound optimization. C/C++ require
-  different functions have different addresses. If a program depends on
-  that property, it would fail at runtime. However, that's not really an
-  issue on Windows because MSVC link.exe enabled the optimization by
-  default. As long as your program works with the linker's default
-  settings, your program should be safe with ICF.
+See docs/NewLLD.rst
diff --git a/COFF/SymbolTable.cpp b/COFF/SymbolTable.cpp
index 5b7b89cd360a..df9da4c36650 100644
--- a/COFF/SymbolTable.cpp
+++ b/COFF/SymbolTable.cpp
@@ -14,7 +14,7 @@
 #include "Symbols.h"
 #include "lld/Core/Parallel.h"
 #include "llvm/IR/LLVMContext.h"
-#include "llvm/LTO/LTOCodeGenerator.h"
+#include "llvm/LTO/legacy/LTOCodeGenerator.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/raw_ostream.h"
 #include <utility>
@@ -164,7 +164,7 @@ void SymbolTable::reportRemainingUndefines(bool Resolve) {
           llvm::errs() << File->getShortName() << ": undefined symbol: "
                        << Sym->getName() << "\n";
   if (!Config->Force)
-    error("Link failed");
+    fatal("link failed");
 }
 
 void SymbolTable::addLazy(Lazy *New, std::vector<Symbol *> *Accum) {
@@ -211,7 +211,7 @@ void SymbolTable::addSymbol(SymbolBody *New) {
   // equivalent (conflicting), or more preferable, respectively.
   int Comp = Existing->compare(New);
   if (Comp == 0)
-    error(Twine("duplicate symbol: ") + Existing->getDebugName() + " and " +
+    fatal("duplicate symbol: " + Existing->getDebugName() + " and " +
           New->getDebugName());
   if (Comp < 0)
     Sym->Body = New;
@@ -338,21 +338,25 @@ void SymbolTable::addCombinedLTOObject(ObjectFile *Obj) {
     // diagnose them later in reportRemainingUndefines().
     StringRef Name = Body->getName();
     Symbol *Sym = insert(Body);
+    SymbolBody *Existing = Sym->Body;
+
+    if (Existing == Body)
+      continue;
 
-    if (isa<DefinedBitcode>(Sym->Body)) {
+    if (isa<DefinedBitcode>(Existing)) {
       Sym->Body = Body;
       continue;
     }
-    if (auto *L = dyn_cast<Lazy>(Sym->Body)) {
+    if (auto *L = dyn_cast<Lazy>(Existing)) {
       // We may see new references to runtime library symbols such as __chkstk
       // here. These symbols must be wholly defined in non-bitcode files.
       addMemberFile(L);
       continue;
     }
-    SymbolBody *Existing = Sym->Body;
+
     int Comp = Existing->compare(Body);
     if (Comp == 0)
-      error(Twine("LTO: unexpected duplicate symbol: ") + Name);
+      fatal("LTO: unexpected duplicate symbol: " + Name);
     if (Comp < 0)
       Sym->Body = Body;
   }
@@ -369,7 +373,7 @@ void SymbolTable::addCombinedLTOObjects() {
 
   // Create an object file and add it to the symbol table by replacing any
   // DefinedBitcode symbols with the definitions in the object file.
-  LTOCodeGenerator CG(getGlobalContext());
+  LTOCodeGenerator CG(BitcodeFile::Context);
   CG.setOptLevel(Config->LTOOptLevel);
   std::vector<ObjectFile *> Objs = createLTOObjects(&CG);
 
@@ -379,7 +383,7 @@ void SymbolTable::addCombinedLTOObjects() {
   size_t NumBitcodeFiles = BitcodeFiles.size();
   run();
   if (BitcodeFiles.size() != NumBitcodeFiles)
-    error("LTO: late loaded symbol created new bitcode reference");
+    fatal("LTO: late loaded symbol created new bitcode reference");
 }
 
 // Combine and compile bitcode files and then return the result
@@ -414,24 +418,23 @@ std::vector<ObjectFile *> SymbolTable::createLTOObjects(LTOCodeGenerator *CG) {
   DisableVerify = false;
 #endif
   if (!CG->optimize(DisableVerify, false, false, false))
-    error(""); // optimize() should have emitted any error message.
+    fatal(""); // optimize() should have emitted any error message.
 
   Objs.resize(Config->LTOJobs);
   // Use std::list to avoid invalidation of pointers in OSPtrs.
   std::list<raw_svector_ostream> OSs;
   std::vector<raw_pwrite_stream *> OSPtrs;
-  for (SmallVector<char, 0> &Obj : Objs) {
+  for (SmallString<0> &Obj : Objs) {
     OSs.emplace_back(Obj);
     OSPtrs.push_back(&OSs.back());
   }
 
   if (!CG->compileOptimized(OSPtrs))
-    error(""); // compileOptimized() should have emitted any error message.
+    fatal(""); // compileOptimized() should have emitted any error message.
 
   std::vector<ObjectFile *> ObjFiles;
-  for (SmallVector<char, 0> &Obj : Objs) {
-    auto *ObjFile = new ObjectFile(
-        MemoryBufferRef(StringRef(Obj.data(), Obj.size()), "<LTO object>"));
+  for (SmallString<0> &Obj : Objs) {
+    auto *ObjFile = new ObjectFile(MemoryBufferRef(Obj, "<LTO object>"));
     Files.emplace_back(ObjFile);
     ObjectFiles.push_back(ObjFile);
     ObjFile->parse();
diff --git a/COFF/SymbolTable.h b/COFF/SymbolTable.h
index ce305bfa8743..8bf4387cdfff 100644
--- a/COFF/SymbolTable.h
+++ b/COFF/SymbolTable.h
@@ -115,7 +115,7 @@ private:
   std::vector<std::future<InputFile *>> ObjectQueue;
 
   std::vector<BitcodeFile *> BitcodeFiles;
-  std::vector<SmallVector<char, 0>> Objs;
+  std::vector<SmallString<0>> Objs;
   llvm::BumpPtrAllocator Alloc;
 };
 
diff --git a/COFF/Symbols.cpp b/COFF/Symbols.cpp
index d732d76cfb06..6e2db6631ce7 100644
--- a/COFF/Symbols.cpp
+++ b/COFF/Symbols.cpp
@@ -162,32 +162,6 @@ std::string SymbolBody::getDebugName() {
   return N;
 }
 
-uint64_t Defined::getFileOff() {
-  switch (kind()) {
-  case DefinedImportDataKind:
-    return cast<DefinedImportData>(this)->getFileOff();
-  case DefinedImportThunkKind:
-    return cast<DefinedImportThunk>(this)->getFileOff();
-  case DefinedLocalImportKind:
-    return cast<DefinedLocalImport>(this)->getFileOff();
-  case DefinedCommonKind:
-    return cast<DefinedCommon>(this)->getFileOff();
-  case DefinedRegularKind:
-    return cast<DefinedRegular>(this)->getFileOff();
-
-  case DefinedBitcodeKind:
-    llvm_unreachable("There is no file offset for a bitcode symbol.");
-  case DefinedAbsoluteKind:
-    llvm_unreachable("Cannot get a file offset for an absolute symbol.");
-  case DefinedRelativeKind:
-    llvm_unreachable("Cannot get a file offset for a relative symbol.");
-  case LazyKind:
-  case UndefinedKind:
-    llvm_unreachable("Cannot get a file offset for an undefined symbol.");
-  }
-  llvm_unreachable("unknown symbol kind");
-}
-
 COFFSymbolRef DefinedCOFF::getCOFFSymbol() {
   size_t SymSize = File->getCOFFObj()->getSymbolTableEntrySize();
   if (SymSize == sizeof(coff_symbol16))
@@ -225,7 +199,7 @@ std::unique_ptr<InputFile> Lazy::getMember() {
   else if (Magic == file_magic::bitcode)
     Obj.reset(new BitcodeFile(MBRef));
   else
-    error(Twine(File->getName()) + ": unknown file type");
+    fatal("unknown file type: " + File->getName());
 
   Obj->setParentName(File->getName());
   return Obj;
diff --git a/COFF/Symbols.h b/COFF/Symbols.h
index 7059fbc8bb15..f96c1fb3cc1d 100644
--- a/COFF/Symbols.h
+++ b/COFF/Symbols.h
@@ -125,10 +125,6 @@ public:
   // writer sets and uses RVAs.
   uint64_t getRVA();
 
-  // Returns the file offset of this symbol in the final executable.
-  // The writer uses this information to apply relocations.
-  uint64_t getFileOff();
-
   // Returns the RVA relative to the beginning of the output section.
   // Used to implement SECREL relocation type.
   uint64_t getSecrel();
diff --git a/COFF/Writer.cpp b/COFF/Writer.cpp
index 5575c8d6b320..d8077df95701 100644
--- a/COFF/Writer.cpp
+++ b/COFF/Writer.cpp
@@ -59,6 +59,7 @@ private:
   void openFile(StringRef OutputPath);
   template <typename PEHeaderTy> void writeHeader();
   void fixSafeSEHSymbols();
+  void setSectionPermissions();
   void writeSections();
   void sortExceptionTable();
   void applyRelocations();
@@ -114,6 +115,7 @@ public:
   StringRef getName() { return Name; }
   std::vector<Chunk *> &getChunks() { return Chunks; }
   void addPermissions(uint32_t C);
+  void setPermissions(uint32_t C);
   uint32_t getPermissions() { return Header.Characteristics & PermMask; }
   uint32_t getCharacteristics() { return Header.Characteristics; }
   uint64_t getRVA() { return Header.VirtualAddress; }
@@ -163,19 +165,23 @@ void OutputSection::addChunk(Chunk *C) {
   Chunks.push_back(C);
   C->setOutputSection(this);
   uint64_t Off = Header.VirtualSize;
-  Off = align(Off, C->getAlign());
+  Off = alignTo(Off, C->getAlign());
   C->setRVA(Off);
   C->setOutputSectionOff(Off);
   Off += C->getSize();
   Header.VirtualSize = Off;
   if (C->hasData())
-    Header.SizeOfRawData = align(Off, SectorSize);
+    Header.SizeOfRawData = alignTo(Off, SectorSize);
 }
 
 void OutputSection::addPermissions(uint32_t C) {
   Header.Characteristics |= C & PermMask;
 }
 
+void OutputSection::setPermissions(uint32_t C) {
+  Header.Characteristics = C & PermMask;
+}
+
 // Write the section header to a given buffer.
 void OutputSection::writeHeaderTo(uint8_t *Buf) {
   auto *Hdr = reinterpret_cast<coff_section *>(Buf);
@@ -193,13 +199,13 @@ void OutputSection::writeHeaderTo(uint8_t *Buf) {
 uint64_t Defined::getSecrel() {
   if (auto *D = dyn_cast<DefinedRegular>(this))
     return getRVA() - D->getChunk()->getOutputSection()->getRVA();
-  error("SECREL relocation points to a non-regular symbol");
+  fatal("SECREL relocation points to a non-regular symbol");
 }
 
 uint64_t Defined::getSectionIndex() {
   if (auto *D = dyn_cast<DefinedRegular>(this))
     return D->getChunk()->getOutputSection()->SectionIndex;
-  error("SECTION relocation points to a non-regular symbol");
+  fatal("SECTION relocation points to a non-regular symbol");
 }
 
 bool Defined::isExecutable() {
@@ -222,6 +228,7 @@ void Writer::run() {
     createSection(".reloc");
   assignAddresses();
   removeEmptySections();
+  setSectionPermissions();
   createSymbolAndStringTable();
   openFile(Config->OutputFile);
   if (Config->is64()) {
@@ -232,7 +239,8 @@ void Writer::run() {
   fixSafeSEHSymbols();
   writeSections();
   sortExceptionTable();
-  error(Buffer->commit(), "Failed to write the output file");
+  if (auto EC = Buffer->commit())
+    fatal(EC, "failed to write the output file");
 }
 
 static StringRef getOutputSection(StringRef Name) {
@@ -447,15 +455,15 @@ void Writer::createSymbolAndStringTable() {
 
   OutputSection *LastSection = OutputSections.back();
   // We position the symbol table to be adjacent to the end of the last section.
-  uint64_t FileOff =
-      LastSection->getFileOff() + align(LastSection->getRawSize(), SectorSize);
+  uint64_t FileOff = LastSection->getFileOff() +
+                     alignTo(LastSection->getRawSize(), SectorSize);
   if (!OutputSymtab.empty()) {
     PointerToSymbolTable = FileOff;
     FileOff += OutputSymtab.size() * sizeof(coff_symbol16);
   }
   if (!Strtab.empty())
     FileOff += Strtab.size() + 4;
-  FileSize = align(FileOff, SectorSize);
+  FileSize = alignTo(FileOff, SectorSize);
 }
 
 // Visits all sections to assign incremental, non-overlapping RVAs and
@@ -466,7 +474,7 @@ void Writer::assignAddresses() {
                   sizeof(coff_section) * OutputSections.size();
   SizeOfHeaders +=
       Config->is64() ? sizeof(pe32plus_header) : sizeof(pe32_header);
-  SizeOfHeaders = align(SizeOfHeaders, SectorSize);
+  SizeOfHeaders = alignTo(SizeOfHeaders, SectorSize);
   uint64_t RVA = 0x1000; // The first page is kept unmapped.
   FileSize = SizeOfHeaders;
   // Move DISCARDABLE (or non-memory-mapped) sections to the end of file because
@@ -480,10 +488,10 @@ void Writer::assignAddresses() {
       addBaserels(Sec);
     Sec->setRVA(RVA);
     Sec->setFileOffset(FileSize);
-    RVA += align(Sec->getVirtualSize(), PageSize);
-    FileSize += align(Sec->getRawSize(), SectorSize);
+    RVA += alignTo(Sec->getVirtualSize(), PageSize);
+    FileSize += alignTo(Sec->getRawSize(), SectorSize);
   }
-  SizeOfImage = SizeOfHeaders + align(RVA - 0x1000, PageSize);
+  SizeOfImage = SizeOfHeaders + alignTo(RVA - 0x1000, PageSize);
 }
 
 template <typename PEHeaderTy> void Writer::writeHeader() {
@@ -596,13 +604,26 @@ template <typename PEHeaderTy> void Writer::writeHeader() {
   if (Symbol *Sym = Symtab->findUnderscore("_tls_used")) {
     if (Defined *B = dyn_cast<Defined>(Sym->Body)) {
       Dir[TLS_TABLE].RelativeVirtualAddress = B->getRVA();
-      Dir[TLS_TABLE].Size = 40;
+      Dir[TLS_TABLE].Size = Config->is64()
+                                ? sizeof(object::coff_tls_directory64)
+                                : sizeof(object::coff_tls_directory32);
     }
   }
   if (Symbol *Sym = Symtab->findUnderscore("_load_config_used")) {
-    if (Defined *B = dyn_cast<Defined>(Sym->Body)) {
+    if (auto *B = dyn_cast<DefinedRegular>(Sym->Body)) {
+      SectionChunk *SC = B->getChunk();
+      assert(B->getRVA() >= SC->getRVA());
+      uint64_t OffsetInChunk = B->getRVA() - SC->getRVA();
+      if (!SC->hasData() || OffsetInChunk + 4 > SC->getSize())
+        fatal("_load_config_used is malformed");
+
+      ArrayRef<uint8_t> SecContents = SC->getContents();
+      uint32_t LoadConfigSize =
+          *reinterpret_cast<const ulittle32_t *>(&SecContents[OffsetInChunk]);
+      if (OffsetInChunk + LoadConfigSize > SC->getSize())
+        fatal("_load_config_used is too large");
       Dir[LOAD_CONFIG_TABLE].RelativeVirtualAddress = B->getRVA();
-      Dir[LOAD_CONFIG_TABLE].Size = Config->is64() ? 112 : 64;
+      Dir[LOAD_CONFIG_TABLE].Size = LoadConfigSize;
     }
   }
 
@@ -626,14 +647,14 @@ template <typename PEHeaderTy> void Writer::writeHeader() {
   // The first 4 bytes is length including itself.
   Buf = reinterpret_cast<uint8_t *>(&SymbolTable[NumberOfSymbols]);
   write32le(Buf, Strtab.size() + 4);
-  memcpy(Buf + 4, Strtab.data(), Strtab.size());
+  if (!Strtab.empty())
+    memcpy(Buf + 4, Strtab.data(), Strtab.size());
 }
 
 void Writer::openFile(StringRef Path) {
-  ErrorOr<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
-      FileOutputBuffer::create(Path, FileSize, FileOutputBuffer::F_executable);
-  error(BufferOrErr, Twine("failed to open ") + Path);
-  Buffer = std::move(*BufferOrErr);
+  Buffer = check(
+      FileOutputBuffer::create(Path, FileSize, FileOutputBuffer::F_executable),
+      "failed to open " + Path);
 }
 
 void Writer::fixSafeSEHSymbols() {
@@ -643,6 +664,17 @@ void Writer::fixSafeSEHSymbols() {
   Config->SEHCount->setVA(SEHTable->getSize() / 4);
 }
 
+// Handles /section options to allow users to overwrite
+// section attributes.
+void Writer::setSectionPermissions() {
+  for (auto &P : Config->Section) {
+    StringRef Name = P.first;
+    uint32_t Perm = P.second;
+    if (auto *Sec = findSection(Name))
+      Sec->setPermissions(Perm);
+  }
+}
+
 // Write section contents to a mmap'ed file.
 void Writer::writeSections() {
   uint8_t *Buf = Buffer->getBufferStart();
diff --git a/ELF/CMakeLists.txt b/ELF/CMakeLists.txt
index 3dcb65ff8957..a1b65adc7400 100644
--- a/ELF/CMakeLists.txt
+++ b/ELF/CMakeLists.txt
@@ -2,25 +2,49 @@ set(LLVM_TARGET_DEFINITIONS Options.td)
 tablegen(LLVM Options.inc -gen-opt-parser-defs)
 add_public_tablegen_target(ELFOptionsTableGen)
 
-add_lld_library(lldELF2
+add_lld_library(lldELF
   Driver.cpp
   DriverUtils.cpp
+  EhFrame.cpp
   Error.cpp
+  ICF.cpp
   InputFiles.cpp
   InputSection.cpp
+  LTO.cpp
   LinkerScript.cpp
   MarkLive.cpp
   OutputSections.cpp
+  Relocations.cpp
+  ScriptParser.cpp
+  Strings.cpp
+  SymbolListFile.cpp
   SymbolTable.cpp
   Symbols.cpp
   Target.cpp
+  Thunks.cpp
   Writer.cpp
 
   LINK_COMPONENTS
+  ${LLVM_TARGETS_TO_BUILD}
+  Analysis
+  BitReader
+  BitWriter
+  Codegen
+  Core
+  IPO
+  Linker
+  LTO
   Object
   Option
+  Passes
   MC
   Support
+  Target
+  TransformUtils
+
+  LINK_LIBS
+  lldConfig
+  ${PTHREAD_LIB}
   )
 
-add_dependencies(lldELF2 ELFOptionsTableGen)
+add_dependencies(lldELF intrinsics_gen ELFOptionsTableGen)
diff --git a/ELF/Config.h b/ELF/Config.h
index c279b99b43c1..2ccd95e88775 100644
--- a/ELF/Config.h
+++ b/ELF/Config.h
@@ -17,10 +17,10 @@
 #include <vector>
 
 namespace lld {
-namespace elf2 {
+namespace elf {
 
 class InputFile;
-class SymbolBody;
+struct Symbol;
 
 enum ELFKind {
   ELFNoneKind,
@@ -30,60 +30,105 @@ enum ELFKind {
   ELF64BEKind
 };
 
+enum class BuildIdKind { None, Fnv1, Md5, Sha1, Hexstring };
+
+enum class UnresolvedPolicy { NoUndef, Error, Warn, Ignore };
+
+struct SymbolVersion {
+  llvm::StringRef Name;
+  bool IsExternCpp;
+};
+
+// This struct contains symbols version definition that
+// can be found in version script if it is used for link.
+struct VersionDefinition {
+  VersionDefinition(llvm::StringRef Name, size_t Id) : Name(Name), Id(Id) {}
+  llvm::StringRef Name;
+  size_t Id;
+  std::vector<SymbolVersion> Globals;
+  size_t NameOff; // Offset in string table.
+};
+
 // This struct contains the global configuration for the linker.
 // Most fields are direct mapping from the command line options
 // and such fields have the same name as the corresponding options.
 // Most fields are initialized by the driver.
 struct Configuration {
-  SymbolBody *EntrySym = nullptr;
-  SymbolBody *MipsGpDisp = nullptr;
+  Symbol *EntrySym = nullptr;
   InputFile *FirstElf = nullptr;
   llvm::StringRef DynamicLinker;
   llvm::StringRef Entry;
   llvm::StringRef Emulation;
   llvm::StringRef Fini;
   llvm::StringRef Init;
+  llvm::StringRef LtoAAPipeline;
+  llvm::StringRef LtoNewPmPasses;
   llvm::StringRef OutputFile;
   llvm::StringRef SoName;
   llvm::StringRef Sysroot;
   std::string RPath;
-  llvm::MapVector<llvm::StringRef, std::vector<llvm::StringRef>> OutputSections;
+  std::vector<VersionDefinition> VersionDefinitions;
+  std::vector<llvm::StringRef> DynamicList;
   std::vector<llvm::StringRef> SearchPaths;
   std::vector<llvm::StringRef> Undefined;
+  std::vector<SymbolVersion> VersionScriptGlobals;
+  std::vector<uint8_t> BuildIdVector;
   bool AllowMultipleDefinition;
   bool AsNeeded = false;
   bool Bsymbolic;
+  bool BsymbolicFunctions;
+  bool Demangle = true;
+  bool DisableVerify;
   bool DiscardAll;
   bool DiscardLocals;
   bool DiscardNone;
+  bool EhFrameHdr;
   bool EnableNewDtags;
   bool ExportDynamic;
+  bool FatalWarnings;
   bool GcSections;
   bool GnuHash = false;
+  bool ICF;
   bool Mips64EL = false;
-  bool NoInhibitExec;
-  bool NoUndefined;
+  bool NoGnuUnique;
+  bool NoUndefinedVersion;
+  bool Pic;
+  bool Pie;
   bool PrintGcSections;
+  bool Rela;
+  bool Relocatable;
+  bool SaveTemps;
   bool Shared;
   bool Static = false;
   bool StripAll;
+  bool StripDebug;
   bool SysvHash = true;
+  bool Threads;
+  bool Trace;
   bool Verbose;
+  bool WarnCommon;
+  bool ZCombreloc;
   bool ZExecStack;
   bool ZNodelete;
   bool ZNow;
   bool ZOrigin;
   bool ZRelro;
+  UnresolvedPolicy UnresolvedSymbols;
+  BuildIdKind BuildId = BuildIdKind::None;
   ELFKind EKind = ELFNoneKind;
+  uint16_t DefaultSymbolVersion = llvm::ELF::VER_NDX_GLOBAL;
   uint16_t EMachine = llvm::ELF::EM_NONE;
   uint64_t EntryAddr = -1;
-  unsigned Optimize = 0;
+  uint64_t ImageBase;
+  unsigned LtoJobs;
+  unsigned LtoO;
+  unsigned Optimize;
 };
 
 // The only instance of Configuration struct.
 extern Configuration *Config;
 
-} // namespace elf2
+} // namespace elf
 } // namespace lld
 
 #endif
diff --git a/ELF/Driver.cpp b/ELF/Driver.cpp
index f00d97851e4a..c6ca2639236f 100644
--- a/ELF/Driver.cpp
+++ b/ELF/Driver.cpp
@@ -10,119 +10,218 @@
 #include "Driver.h"
 #include "Config.h"
 #include "Error.h"
+#include "ICF.h"
 #include "InputFiles.h"
+#include "InputSection.h"
+#include "LinkerScript.h"
+#include "Strings.h"
+#include "SymbolListFile.h"
 #include "SymbolTable.h"
 #include "Target.h"
 #include "Writer.h"
-#include "llvm/ADT/STLExtras.h"
+#include "lld/Driver/Driver.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/raw_ostream.h"
+#include <cstdlib>
 #include <utility>
 
 using namespace llvm;
 using namespace llvm::ELF;
 using namespace llvm::object;
+using namespace llvm::sys;
 
 using namespace lld;
-using namespace lld::elf2;
+using namespace lld::elf;
 
-Configuration *elf2::Config;
-LinkerDriver *elf2::Driver;
+Configuration *elf::Config;
+LinkerDriver *elf::Driver;
+
+bool elf::link(ArrayRef<const char *> Args, raw_ostream &Error) {
+  HasError = false;
+  ErrorOS = &Error;
 
-void elf2::link(ArrayRef<const char *> Args) {
   Configuration C;
   LinkerDriver D;
+  ScriptConfiguration SC;
   Config = &C;
   Driver = &D;
-  Driver->main(Args.slice(1));
+  ScriptConfig = &SC;
+
+  Driver->main(Args);
+  return !HasError;
 }
 
+// Parses a linker -m option.
 static std::pair<ELFKind, uint16_t> parseEmulation(StringRef S) {
-  if (S == "elf32btsmip")
-    return {ELF32BEKind, EM_MIPS};
-  if (S == "elf32ltsmip")
-    return {ELF32LEKind, EM_MIPS};
-  if (S == "elf32ppc" || S == "elf32ppc_fbsd")
-    return {ELF32BEKind, EM_PPC};
-  if (S == "elf64ppc" || S == "elf64ppc_fbsd")
-    return {ELF64BEKind, EM_PPC64};
-  if (S == "elf_i386")
-    return {ELF32LEKind, EM_386};
-  if (S == "elf_x86_64")
-    return {ELF64LEKind, EM_X86_64};
-  if (S == "aarch64linux")
-    return {ELF64LEKind, EM_AARCH64};
-  if (S == "i386pe" || S == "i386pep" || S == "thumb2pe")
-    error("Windows targets are not supported on the ELF frontend: " + S);
-  error("Unknown emulation: " + S);
+  if (S.endswith("_fbsd"))
+    S = S.drop_back(5);
+
+  std::pair<ELFKind, uint16_t> Ret =
+      StringSwitch<std::pair<ELFKind, uint16_t>>(S)
+          .Case("aarch64linux", {ELF64LEKind, EM_AARCH64})
+          .Case("armelf_linux_eabi", {ELF32LEKind, EM_ARM})
+          .Case("elf32_x86_64", {ELF32LEKind, EM_X86_64})
+          .Case("elf32btsmip", {ELF32BEKind, EM_MIPS})
+          .Case("elf32ltsmip", {ELF32LEKind, EM_MIPS})
+          .Case("elf32ppc", {ELF32BEKind, EM_PPC})
+          .Case("elf64btsmip", {ELF64BEKind, EM_MIPS})
+          .Case("elf64ltsmip", {ELF64LEKind, EM_MIPS})
+          .Case("elf64ppc", {ELF64BEKind, EM_PPC64})
+          .Case("elf_i386", {ELF32LEKind, EM_386})
+          .Case("elf_x86_64", {ELF64LEKind, EM_X86_64})
+          .Default({ELFNoneKind, EM_NONE});
+
+  if (Ret.first == ELFNoneKind) {
+    if (S == "i386pe" || S == "i386pep" || S == "thumb2pe")
+      error("Windows targets are not supported on the ELF frontend: " + S);
+    else
+      error("unknown emulation: " + S);
+  }
+  return Ret;
 }
 
 // Returns slices of MB by parsing MB as an archive file.
 // Each slice consists of a member file in the archive.
-static std::vector<MemoryBufferRef> getArchiveMembers(MemoryBufferRef MB) {
-  ErrorOr<std::unique_ptr<Archive>> FileOrErr = Archive::create(MB);
-  error(FileOrErr, "Failed to parse archive");
-  std::unique_ptr<Archive> File = std::move(*FileOrErr);
+std::vector<MemoryBufferRef>
+LinkerDriver::getArchiveMembers(MemoryBufferRef MB) {
+  std::unique_ptr<Archive> File =
+      check(Archive::create(MB), "failed to parse archive");
 
   std::vector<MemoryBufferRef> V;
-  for (const ErrorOr<Archive::Child> &C : File->children()) {
-    error(C, "Could not get the child of the archive " + File->getFileName());
-    ErrorOr<MemoryBufferRef> MbOrErr = C->getMemoryBufferRef();
-    error(MbOrErr, "Could not get the buffer for a child of the archive " +
-                       File->getFileName());
-    V.push_back(*MbOrErr);
+  Error Err;
+  for (const ErrorOr<Archive::Child> &COrErr : File->children(Err)) {
+    Archive::Child C = check(COrErr, "could not get the child of the archive " +
+                                         File->getFileName());
+    MemoryBufferRef MBRef =
+        check(C.getMemoryBufferRef(),
+              "could not get the buffer for a child of the archive " +
+                  File->getFileName());
+    V.push_back(MBRef);
   }
+  if (Err)
+    Error(Err);
+
+  // Take ownership of memory buffers created for members of thin archives.
+  for (std::unique_ptr<MemoryBuffer> &MB : File->takeThinBuffers())
+    OwningMBs.push_back(std::move(MB));
+
   return V;
 }
 
 // Opens and parses a file. Path has to be resolved already.
 // Newly created memory buffers are owned by this driver.
 void LinkerDriver::addFile(StringRef Path) {
-  using namespace llvm::sys::fs;
+  using namespace sys::fs;
   if (Config->Verbose)
-    llvm::outs() << Path << "\n";
-  auto MBOrErr = MemoryBuffer::getFile(Path);
-  error(MBOrErr, "cannot open " + Path);
-  std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
-  MemoryBufferRef MBRef = MB->getMemBufferRef();
-  OwningMBs.push_back(std::move(MB)); // take MB ownership
+    outs() << Path << "\n";
+
+  Optional<MemoryBufferRef> Buffer = readFile(Path);
+  if (!Buffer.hasValue())
+    return;
+  MemoryBufferRef MBRef = *Buffer;
 
   switch (identify_magic(MBRef.getBuffer())) {
   case file_magic::unknown:
-    readLinkerScript(&Alloc, MBRef);
+    readLinkerScript(MBRef);
     return;
   case file_magic::archive:
     if (WholeArchive) {
       for (MemoryBufferRef MB : getArchiveMembers(MBRef))
-        Files.push_back(createObjectFile(MB));
+        Files.push_back(createObjectFile(MB, Path));
       return;
     }
     Files.push_back(make_unique<ArchiveFile>(MBRef));
     return;
   case file_magic::elf_shared_object:
+    if (Config->Relocatable) {
+      error("attempted static link of dynamic object " + Path);
+      return;
+    }
     Files.push_back(createSharedFile(MBRef));
     return;
   default:
-    Files.push_back(createObjectFile(MBRef));
+    if (InLib)
+      Files.push_back(make_unique<LazyObjectFile>(MBRef));
+    else
+      Files.push_back(createObjectFile(MBRef));
+  }
+}
+
+Optional<MemoryBufferRef> LinkerDriver::readFile(StringRef Path) {
+  auto MBOrErr = MemoryBuffer::getFile(Path);
+  if (auto EC = MBOrErr.getError()) {
+    error(EC, "cannot open " + Path);
+    return None;
   }
+  std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
+  MemoryBufferRef MBRef = MB->getMemBufferRef();
+  OwningMBs.push_back(std::move(MB)); // take MB ownership
+
+  if (Cpio)
+    Cpio->append(relativeToRoot(Path), MBRef.getBuffer());
+
+  return MBRef;
+}
+
+// Add a given library by searching it from input search paths.
+void LinkerDriver::addLibrary(StringRef Name) {
+  std::string Path = searchLibrary(Name);
+  if (Path.empty())
+    error("unable to find library -l" + Name);
+  else
+    addFile(Path);
+}
+
+// This function is called on startup. We need this for LTO since
+// LTO calls LLVM functions to compile bitcode files to native code.
+// Technically this can be delayed until we read bitcode files, but
+// we don't bother to do lazily because the initialization is fast.
+static void initLLVM(opt::InputArgList &Args) {
+  InitializeAllTargets();
+  InitializeAllTargetMCs();
+  InitializeAllAsmPrinters();
+  InitializeAllAsmParsers();
+
+  // This is a flag to discard all but GlobalValue names.
+  // We want to enable it by default because it saves memory.
+  // Disable it only when a developer option (-save-temps) is given.
+  Driver->Context.setDiscardValueNames(!Config->SaveTemps);
+  Driver->Context.enableDebugTypeODRUniquing();
+
+  // Parse and evaluate -mllvm options.
+  std::vector<const char *> V;
+  V.push_back("lld (LLVM option parsing)");
+  for (auto *Arg : Args.filtered(OPT_mllvm))
+    V.push_back(Arg->getValue());
+  cl::ParseCommandLineOptions(V.size(), V.data());
 }
 
 // Some command line options or some combinations of them are not allowed.
 // This function checks for such errors.
 static void checkOptions(opt::InputArgList &Args) {
-  // Traditional linkers can generate re-linkable object files instead
-  // of executables or DSOs. We don't support that since the feature
-  // does not seem to provide more value than the static archiver.
-  if (Args.hasArg(OPT_relocatable))
-    error("-r option is not supported. Use 'ar' command instead.");
-
   // The MIPS ABI as of 2016 does not support the GNU-style symbol lookup
   // table which is a relatively new feature.
   if (Config->EMachine == EM_MIPS && Config->GnuHash)
-    error("The .gnu.hash section is not compatible with the MIPS target.");
+    error("the .gnu.hash section is not compatible with the MIPS target.");
 
   if (Config->EMachine == EM_AMDGPU && !Config->Entry.empty())
     error("-e option is not valid for AMDGPU.");
+
+  if (Config->Pie && Config->Shared)
+    error("-shared and -pie may not be used together");
+
+  if (Config->Relocatable) {
+    if (Config->Shared)
+      error("-r and -shared may not be used together");
+    if (Config->GcSections)
+      error("-r and --gc-sections may not be used together");
+    if (Config->ICF)
+      error("-r and --icf may not be used together");
+    if (Config->Pie)
+      error("-r and -pie may not be used together");
+  }
 }
 
 static StringRef
@@ -132,6 +231,22 @@ getString(opt::InputArgList &Args, unsigned Key, StringRef Default = "") {
   return Default;
 }
 
+static int getInteger(opt::InputArgList &Args, unsigned Key, int Default) {
+  int V = Default;
+  if (auto *Arg = Args.getLastArg(Key)) {
+    StringRef S = Arg->getValue();
+    if (S.getAsInteger(10, V))
+      error(Arg->getSpelling() + ": number expected, but got " + S);
+  }
+  return V;
+}
+
+static const char *getReproduceOption(opt::InputArgList &Args) {
+  if (auto *Arg = Args.getLastArg(OPT_reproduce))
+    return Arg->getValue();
+  return getenv("LLD_REPRODUCE");
+}
+
 static bool hasZOption(opt::InputArgList &Args, StringRef Key) {
   for (auto *Arg : Args.filtered(OPT_z))
     if (Key == Arg->getValue())
@@ -140,12 +255,33 @@ static bool hasZOption(opt::InputArgList &Args, StringRef Key) {
 }
 
 void LinkerDriver::main(ArrayRef<const char *> ArgsArr) {
-  initSymbols();
+  ELFOptTable Parser;
+  opt::InputArgList Args = Parser.parse(ArgsArr.slice(1));
+  if (Args.hasArg(OPT_help)) {
+    printHelp(ArgsArr[0]);
+    return;
+  }
+  if (Args.hasArg(OPT_version)) {
+    outs() << getVersionString();
+    return;
+  }
+
+  if (const char *Path = getReproduceOption(Args)) {
+    // Note that --reproduce is a debug option so you can ignore it
+    // if you are trying to understand the whole picture of the code.
+    Cpio.reset(CpioFile::create(Path));
+    if (Cpio) {
+      Cpio->append("response.txt", createResponseFile(Args));
+      Cpio->append("version.txt", getVersionString());
+    }
+  }
 
-  opt::InputArgList Args = parseArgs(&Alloc, ArgsArr);
   readConfigs(Args);
+  initLLVM(Args);
   createFiles(Args);
   checkOptions(Args);
+  if (HasError)
+    return;
 
   switch (Config->EKind) {
   case ELF32LEKind:
@@ -165,6 +301,25 @@ void LinkerDriver::main(ArrayRef<const char *> ArgsArr) {
   }
 }
 
+static UnresolvedPolicy getUnresolvedSymbolOption(opt::InputArgList &Args) {
+  if (Args.hasArg(OPT_noinhibit_exec))
+    return UnresolvedPolicy::Warn;
+  if (Args.hasArg(OPT_no_undefined) || hasZOption(Args, "defs"))
+    return UnresolvedPolicy::NoUndef;
+  if (Config->Relocatable)
+    return UnresolvedPolicy::Ignore;
+
+  if (auto *Arg = Args.getLastArg(OPT_unresolved_symbols)) {
+    StringRef S = Arg->getValue();
+    if (S == "ignore-all" || S == "ignore-in-object-files")
+      return UnresolvedPolicy::Ignore;
+    if (S == "ignore-in-shared-libs" || S == "report-all")
+      return UnresolvedPolicy::Error;
+    error("unknown --unresolved-symbols value: " + S);
+  }
+  return UnresolvedPolicy::Error;
+}
+
 // Initializes Config members by the command line options.
 void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   for (auto *Arg : Args.filtered(OPT_L))
@@ -185,38 +340,66 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
 
   Config->AllowMultipleDefinition = Args.hasArg(OPT_allow_multiple_definition);
   Config->Bsymbolic = Args.hasArg(OPT_Bsymbolic);
+  Config->BsymbolicFunctions = Args.hasArg(OPT_Bsymbolic_functions);
+  Config->Demangle = !Args.hasArg(OPT_no_demangle);
+  Config->DisableVerify = Args.hasArg(OPT_disable_verify);
   Config->DiscardAll = Args.hasArg(OPT_discard_all);
   Config->DiscardLocals = Args.hasArg(OPT_discard_locals);
   Config->DiscardNone = Args.hasArg(OPT_discard_none);
+  Config->EhFrameHdr = Args.hasArg(OPT_eh_frame_hdr);
   Config->EnableNewDtags = !Args.hasArg(OPT_disable_new_dtags);
   Config->ExportDynamic = Args.hasArg(OPT_export_dynamic);
+  Config->FatalWarnings = Args.hasArg(OPT_fatal_warnings);
   Config->GcSections = Args.hasArg(OPT_gc_sections);
-  Config->NoInhibitExec = Args.hasArg(OPT_noinhibit_exec);
-  Config->NoUndefined = Args.hasArg(OPT_no_undefined);
+  Config->ICF = Args.hasArg(OPT_icf);
+  Config->NoGnuUnique = Args.hasArg(OPT_no_gnu_unique);
+  Config->NoUndefinedVersion = Args.hasArg(OPT_no_undefined_version);
+  Config->Pie = Args.hasArg(OPT_pie);
   Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
+  Config->Relocatable = Args.hasArg(OPT_relocatable);
+  Config->SaveTemps = Args.hasArg(OPT_save_temps);
   Config->Shared = Args.hasArg(OPT_shared);
   Config->StripAll = Args.hasArg(OPT_strip_all);
+  Config->StripDebug = Args.hasArg(OPT_strip_debug);
+  Config->Threads = Args.hasArg(OPT_threads);
+  Config->Trace = Args.hasArg(OPT_trace);
   Config->Verbose = Args.hasArg(OPT_verbose);
+  Config->WarnCommon = Args.hasArg(OPT_warn_common);
 
   Config->DynamicLinker = getString(Args, OPT_dynamic_linker);
   Config->Entry = getString(Args, OPT_entry);
   Config->Fini = getString(Args, OPT_fini, "_fini");
   Config->Init = getString(Args, OPT_init, "_init");
+  Config->LtoAAPipeline = getString(Args, OPT_lto_aa_pipeline);
+  Config->LtoNewPmPasses = getString(Args, OPT_lto_newpm_passes);
   Config->OutputFile = getString(Args, OPT_o);
   Config->SoName = getString(Args, OPT_soname);
   Config->Sysroot = getString(Args, OPT_sysroot);
 
+  Config->Optimize = getInteger(Args, OPT_O, 1);
+  Config->LtoO = getInteger(Args, OPT_lto_O, 2);
+  if (Config->LtoO > 3)
+    error("invalid optimization level for LTO: " + getString(Args, OPT_lto_O));
+  Config->LtoJobs = getInteger(Args, OPT_lto_jobs, 1);
+  if (Config->LtoJobs == 0)
+    error("number of threads must be > 0");
+
+  Config->ZCombreloc = !hasZOption(Args, "nocombreloc");
   Config->ZExecStack = hasZOption(Args, "execstack");
   Config->ZNodelete = hasZOption(Args, "nodelete");
   Config->ZNow = hasZOption(Args, "now");
   Config->ZOrigin = hasZOption(Args, "origin");
   Config->ZRelro = !hasZOption(Args, "norelro");
 
-  if (auto *Arg = Args.getLastArg(OPT_O)) {
-    StringRef Val = Arg->getValue();
-    if (Val.getAsInteger(10, Config->Optimize))
-      error("Invalid optimization level");
-  }
+  if (Config->Relocatable)
+    Config->StripAll = false;
+
+  // --strip-all implies --strip-debug.
+  if (Config->StripAll)
+    Config->StripDebug = true;
+
+  // Config->Pic is true if we are generating position-independent code.
+  Config->Pic = Config->Pie || Config->Shared;
 
   if (auto *Arg = Args.getLastArg(OPT_hash_style)) {
     StringRef S = Arg->getValue();
@@ -226,19 +409,52 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
     } else if (S == "both") {
       Config->GnuHash = true;
     } else if (S != "sysv")
-      error("Unknown hash style: " + S);
+      error("unknown hash style: " + S);
+  }
+
+  // Parse --build-id or --build-id=<style>.
+  if (Args.hasArg(OPT_build_id))
+    Config->BuildId = BuildIdKind::Fnv1;
+  if (auto *Arg = Args.getLastArg(OPT_build_id_eq)) {
+    StringRef S = Arg->getValue();
+    if (S == "md5") {
+      Config->BuildId = BuildIdKind::Md5;
+    } else if (S == "sha1") {
+      Config->BuildId = BuildIdKind::Sha1;
+    } else if (S == "none") {
+      Config->BuildId = BuildIdKind::None;
+    } else if (S.startswith("0x")) {
+      Config->BuildId = BuildIdKind::Hexstring;
+      Config->BuildIdVector = parseHex(S.substr(2));
+    } else {
+      error("unknown --build-id style: " + S);
+    }
   }
 
   for (auto *Arg : Args.filtered(OPT_undefined))
     Config->Undefined.push_back(Arg->getValue());
+
+  Config->UnresolvedSymbols = getUnresolvedSymbolOption(Args);
+
+  if (auto *Arg = Args.getLastArg(OPT_dynamic_list))
+    if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
+      parseDynamicList(*Buffer);
+
+  for (auto *Arg : Args.filtered(OPT_export_dynamic_symbol))
+    Config->DynamicList.push_back(Arg->getValue());
+
+  if (auto *Arg = Args.getLastArg(OPT_version_script))
+    if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
+      parseVersionScript(*Buffer);
 }
 
 void LinkerDriver::createFiles(opt::InputArgList &Args) {
   for (auto *Arg : Args) {
     switch (Arg->getOption().getID()) {
     case OPT_l:
-      addFile(searchLibrary(Arg->getValue()));
+      addLibrary(Arg->getValue());
       break;
+    case OPT_alias_script_T:
     case OPT_INPUT:
     case OPT_script:
       addFile(Arg->getValue());
@@ -261,75 +477,112 @@ void LinkerDriver::createFiles(opt::InputArgList &Args) {
     case OPT_no_whole_archive:
       WholeArchive = false;
       break;
+    case OPT_start_lib:
+      InLib = true;
+      break;
+    case OPT_end_lib:
+      InLib = false;
+      break;
     }
   }
 
-  if (Files.empty())
+  if (Files.empty() && !HasError)
     error("no input files.");
+
+  // If -m <machine_type> was not given, infer it from object files.
+  if (Config->EKind == ELFNoneKind) {
+    for (std::unique_ptr<InputFile> &F : Files) {
+      if (F->EKind == ELFNoneKind)
+        continue;
+      Config->EKind = F->EKind;
+      Config->EMachine = F->EMachine;
+      break;
+    }
+  }
 }
 
+// Do actual linking. Note that when this function is called,
+// all linker scripts have already been parsed.
 template <class ELFT> void LinkerDriver::link(opt::InputArgList &Args) {
   SymbolTable<ELFT> Symtab;
-  Target.reset(createTarget());
-
-  if (!Config->Shared) {
-    // Add entry symbol.
-    //
-    // There is no entry symbol for AMDGPU binaries, so skip adding one to avoid
-    // having and undefined symbol.
-    if (Config->Entry.empty() && Config->EMachine != EM_AMDGPU)
-      Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
-
-    // In the assembly for 32 bit x86 the _GLOBAL_OFFSET_TABLE_ symbol
-    // is magical and is used to produce a R_386_GOTPC relocation.
-    // The R_386_GOTPC relocation value doesn't actually depend on the
-    // symbol value, so it could use an index of STN_UNDEF which, according
-    // to the spec, means the symbol value is 0.
-    // Unfortunately both gas and MC keep the _GLOBAL_OFFSET_TABLE_ symbol in
-    // the object file.
-    // The situation is even stranger on x86_64 where the assembly doesn't
-    // need the magical symbol, but gas still puts _GLOBAL_OFFSET_TABLE_ as
-    // an undefined symbol in the .o files.
-    // Given that the symbol is effectively unused, we just create a dummy
-    // hidden one to avoid the undefined symbol error.
-    Symtab.addIgnored("_GLOBAL_OFFSET_TABLE_");
-  }
+  elf::Symtab<ELFT>::X = &Symtab;
+
+  std::unique_ptr<TargetInfo> TI(createTarget());
+  Target = TI.get();
+  LinkerScript<ELFT> LS;
+  Script<ELFT>::X = &LS;
+
+  Config->Rela = ELFT::Is64Bits || Config->EMachine == EM_X86_64;
+  Config->Mips64EL =
+      (Config->EMachine == EM_MIPS && Config->EKind == ELF64LEKind);
+
+  // Add entry symbol. Note that AMDGPU binaries have no entry points.
+  if (Config->Entry.empty() && !Config->Shared && !Config->Relocatable &&
+      Config->EMachine != EM_AMDGPU)
+    Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
+
+  // Default output filename is "a.out" by the Unix tradition.
+  if (Config->OutputFile.empty())
+    Config->OutputFile = "a.out";
+
+  // Handle --trace-symbol.
+  for (auto *Arg : Args.filtered(OPT_trace_symbol))
+    Symtab.trace(Arg->getValue());
 
+  // Set either EntryAddr (if S is a number) or EntrySym (otherwise).
   if (!Config->Entry.empty()) {
-    // Set either EntryAddr (if S is a number) or EntrySym (otherwise).
     StringRef S = Config->Entry;
     if (S.getAsInteger(0, Config->EntryAddr))
       Config->EntrySym = Symtab.addUndefined(S);
   }
 
-  if (Config->EMachine == EM_MIPS) {
-    // On MIPS O32 ABI, _gp_disp is a magic symbol designates offset between
-    // start of function and gp pointer into GOT. Use 'strong' variant of
-    // the addIgnored to prevent '_gp_disp' substitution.
-    Config->MipsGpDisp = Symtab.addIgnoredStrong("_gp_disp");
-
-    // Define _gp for MIPS. st_value of _gp symbol will be updated by Writer
-    // so that it points to an absolute address which is relative to GOT.
-    // See "Global Data Symbols" in Chapter 6 in the following document:
-    // ftp://www.linux-mips.org/pub/linux/mips/doc/ABI/mipsabi.pdf
-    Symtab.addAbsolute("_gp", ElfSym<ELFT>::MipsGp);
+  // Initialize Config->ImageBase.
+  if (auto *Arg = Args.getLastArg(OPT_image_base)) {
+    StringRef S = Arg->getValue();
+    if (S.getAsInteger(0, Config->ImageBase))
+      error(Arg->getSpelling() + ": number expected, but got " + S);
+    else if ((Config->ImageBase % Target->PageSize) != 0)
+      warning(Arg->getSpelling() + ": address isn't multiple of page size");
+  } else {
+    Config->ImageBase = Config->Pic ? 0 : Target->DefaultImageBase;
   }
 
   for (std::unique_ptr<InputFile> &F : Files)
     Symtab.addFile(std::move(F));
+  if (HasError)
+    return; // There were duplicate symbols or incompatible files
 
-  for (StringRef S : Config->Undefined)
-    Symtab.addUndefinedOpt(S);
+  Symtab.scanUndefinedFlags();
+  Symtab.scanShlibUndefined();
+  Symtab.scanDynamicList();
+  Symtab.scanVersionScript();
+  Symtab.scanSymbolVersions();
+
+  Symtab.addCombinedLtoObject();
+  if (HasError)
+    return;
 
   for (auto *Arg : Args.filtered(OPT_wrap))
     Symtab.wrap(Arg->getValue());
 
-  if (Config->OutputFile.empty())
-    Config->OutputFile = "a.out";
-
   // Write the result to the file.
-  Symtab.scanShlibUndefined();
   if (Config->GcSections)
-    markLive<ELFT>(&Symtab);
+    markLive<ELFT>();
+  if (Config->ICF)
+    doIcf<ELFT>();
+
+  // MergeInputSection::splitIntoPieces needs to be called before
+  // any call of MergeInputSection::getOffset. Do that.
+  for (const std::unique_ptr<elf::ObjectFile<ELFT>> &F :
+       Symtab.getObjectFiles())
+    for (InputSectionBase<ELFT> *S : F->getSections()) {
+      if (!S || S == &InputSection<ELFT>::Discarded || !S->Live)
+        continue;
+      if (S->Compressed)
+        S->uncompress();
+      if (auto *MS = dyn_cast<MergeInputSection<ELFT>>(S))
+        MS->splitIntoPieces();
+    }
+
   writeResult<ELFT>(&Symtab);
 }
diff --git a/ELF/Driver.h b/ELF/Driver.h
index 720ef46dc710..6b9b9bb208e5 100644
--- a/ELF/Driver.h
+++ b/ELF/Driver.h
@@ -12,36 +12,54 @@
 
 #include "SymbolTable.h"
 #include "lld/Core/LLVM.h"
+#include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/StringSet.h"
 #include "llvm/Option/ArgList.h"
+#include "llvm/Support/raw_ostream.h"
 
 namespace lld {
-namespace elf2 {
+namespace elf {
 
 extern class LinkerDriver *Driver;
 
-// Entry point of the ELF linker.
-void link(ArrayRef<const char *> Args);
+class CpioFile;
 
 class LinkerDriver {
 public:
   void main(ArrayRef<const char *> Args);
   void addFile(StringRef Path);
+  void addLibrary(StringRef Name);
+  llvm::LLVMContext Context;      // to parse bitcode ifles
+  std::unique_ptr<CpioFile> Cpio; // for reproduce
 
 private:
+  std::vector<MemoryBufferRef> getArchiveMembers(MemoryBufferRef MB);
+  llvm::Optional<MemoryBufferRef> readFile(StringRef Path);
   void readConfigs(llvm::opt::InputArgList &Args);
   void createFiles(llvm::opt::InputArgList &Args);
   template <class ELFT> void link(llvm::opt::InputArgList &Args);
 
-  llvm::BumpPtrAllocator Alloc;
+  // True if we are in --whole-archive and --no-whole-archive.
   bool WholeArchive = false;
+
+  // True if we are in --start-lib and --end-lib.
+  bool InLib = false;
+
+  llvm::BumpPtrAllocator Alloc;
   std::vector<std::unique_ptr<InputFile>> Files;
   std::vector<std::unique_ptr<MemoryBuffer>> OwningMBs;
 };
 
 // Parses command line options.
-llvm::opt::InputArgList parseArgs(llvm::BumpPtrAllocator *A,
-                                  ArrayRef<const char *> Args);
+class ELFOptTable : public llvm::opt::OptTable {
+public:
+  ELFOptTable();
+  llvm::opt::InputArgList parse(ArrayRef<const char *> Argv);
+
+private:
+  llvm::BumpPtrAllocator Alloc;
+};
 
 // Create enum with OPT_xxx values for each option in Options.td
 enum {
@@ -51,14 +69,43 @@ enum {
 #undef OPTION
 };
 
-// Parses a linker script. Calling this function updates the Symtab and Config.
-void readLinkerScript(llvm::BumpPtrAllocator *A, MemoryBufferRef MB);
+// This is the class to create a .cpio file for --reproduce.
+//
+// If "--reproduce foo" is given, we create a file "foo.cpio" and
+// copy all input files to the archive, along with a response file
+// to re-run the same command with the same inputs.
+// It is useful for reporting issues to LLD developers.
+//
+// Cpio as a file format is a deliberate choice. It's standardized in
+// POSIX and very easy to create. cpio command is available virtually
+// on all Unix systems. See
+// http://pubs.opengroup.org/onlinepubs/9699919799/utilities/pax.html#tag_20_92_13_07
+// for the format details.
+class CpioFile {
+public:
+  static CpioFile *create(StringRef OutputPath);
+  void append(StringRef Path, StringRef Data);
+
+private:
+  CpioFile(std::unique_ptr<llvm::raw_fd_ostream> OS, StringRef Basename);
+
+  std::unique_ptr<llvm::raw_fd_ostream> OS;
+  llvm::StringSet<> Seen;
+  std::string Basename;
+};
+
+void printHelp(const char *Argv0);
+std::string getVersionString();
+std::vector<uint8_t> parseHexstring(StringRef S);
+
+std::string createResponseFile(const llvm::opt::InputArgList &Args);
+std::string relativeToRoot(StringRef Path);
 
 std::string findFromSearchPaths(StringRef Path);
 std::string searchLibrary(StringRef Path);
 std::string buildSysrootedPath(llvm::StringRef Dir, llvm::StringRef File);
 
-} // namespace elf2
+} // namespace elf
 } // namespace lld
 
 #endif
diff --git a/ELF/DriverUtils.cpp b/ELF/DriverUtils.cpp
index 965ed4f00a61..3f18259b4ae7 100644
--- a/ELF/DriverUtils.cpp
+++ b/ELF/DriverUtils.cpp
@@ -15,16 +15,20 @@
 
 #include "Driver.h"
 #include "Error.h"
+#include "lld/Config/Version.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Option/Option.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/StringSaver.h"
 
 using namespace llvm;
+using namespace llvm::sys;
 
 using namespace lld;
-using namespace lld::elf2;
+using namespace lld::elf;
 
 // Create OptTable
 
@@ -34,55 +38,208 @@ using namespace lld::elf2;
 #undef PREFIX
 
 // Create table mapping all options defined in Options.td
-static const opt::OptTable::Info infoTable[] = {
+static const opt::OptTable::Info OptInfo[] = {
 #define OPTION(X1, X2, ID, KIND, GROUP, ALIAS, X6, X7, X8, X9, X10)            \
   {                                                                            \
     X1, X2, X9, X10, OPT_##ID, opt::Option::KIND##Class, X8, X7, OPT_##GROUP,  \
         OPT_##ALIAS, X6                                                        \
-  }                                                                            \
-  ,
+  },
 #include "Options.inc"
 #undef OPTION
 };
 
-class ELFOptTable : public opt::OptTable {
-public:
-  ELFOptTable() : OptTable(infoTable) {}
-};
+ELFOptTable::ELFOptTable() : OptTable(OptInfo) {}
+
+static cl::TokenizerCallback getQuotingStyle(opt::InputArgList &Args) {
+  if (auto *Arg = Args.getLastArg(OPT_rsp_quoting)) {
+    StringRef S = Arg->getValue();
+    if (S != "windows" && S != "posix")
+      error("invalid response file quoting: " + S);
+    if (S == "windows")
+      return cl::TokenizeWindowsCommandLine;
+    return cl::TokenizeGNUCommandLine;
+  }
+  if (Triple(sys::getProcessTriple()).getOS() == Triple::Win32)
+    return cl::TokenizeWindowsCommandLine;
+  return cl::TokenizeGNUCommandLine;
+}
 
 // Parses a given list of options.
-opt::InputArgList elf2::parseArgs(llvm::BumpPtrAllocator *A,
-                                  ArrayRef<const char *> Argv) {
+opt::InputArgList ELFOptTable::parse(ArrayRef<const char *> Argv) {
   // Make InputArgList from string vectors.
-  ELFOptTable Table;
   unsigned MissingIndex;
   unsigned MissingCount;
+  SmallVector<const char *, 256> Vec(Argv.data(), Argv.data() + Argv.size());
+
+  // We need to get the quoting style for response files before parsing all
+  // options so we parse here before and ignore all the options but
+  // --rsp-quoting.
+  opt::InputArgList Args = this->ParseArgs(Vec, MissingIndex, MissingCount);
 
   // Expand response files. '@<filename>' is replaced by the file's contents.
-  SmallVector<const char *, 256> Vec(Argv.data(), Argv.data() + Argv.size());
-  StringSaver Saver(*A);
-  llvm::cl::ExpandResponseFiles(Saver, llvm::cl::TokenizeGNUCommandLine, Vec);
+  StringSaver Saver(Alloc);
+  cl::ExpandResponseFiles(Saver, getQuotingStyle(Args), Vec);
 
   // Parse options and then do error checking.
-  opt::InputArgList Args = Table.ParseArgs(Vec, MissingIndex, MissingCount);
+  Args = this->ParseArgs(Vec, MissingIndex, MissingCount);
   if (MissingCount)
     error(Twine("missing arg value for \"") + Args.getArgString(MissingIndex) +
           "\", expected " + Twine(MissingCount) +
           (MissingCount == 1 ? " argument.\n" : " arguments"));
 
-  iterator_range<opt::arg_iterator> Unknowns = Args.filtered(OPT_UNKNOWN);
-  for (auto *Arg : Unknowns)
-    warning("warning: unknown argument: " + Arg->getSpelling());
-  if (Unknowns.begin() != Unknowns.end())
-    error("unknown argument(s) found");
-
+  for (auto *Arg : Args.filtered(OPT_UNKNOWN))
+    error("unknown argument: " + Arg->getSpelling());
   return Args;
 }
 
-std::string elf2::findFromSearchPaths(StringRef Path) {
+void elf::printHelp(const char *Argv0) {
+  ELFOptTable Table;
+  Table.PrintHelp(outs(), Argv0, "lld", false);
+}
+
+std::string elf::getVersionString() {
+  std::string Version = getLLDVersion();
+  std::string Repo = getLLDRepositoryVersion();
+  if (Repo.empty())
+    return "LLD " + Version + "\n";
+  return "LLD " + Version + " " + Repo + "\n";
+}
+
+// Makes a given pathname an absolute path first, and then remove
+// beginning /. For example, "../foo.o" is converted to "home/john/foo.o",
+// assuming that the current directory is "/home/john/bar".
+std::string elf::relativeToRoot(StringRef Path) {
+  SmallString<128> Abs = Path;
+  if (std::error_code EC = fs::make_absolute(Abs))
+    fatal("make_absolute failed: " + EC.message());
+  path::remove_dots(Abs, /*remove_dot_dot=*/true);
+
+  // This is Windows specific. root_name() returns a drive letter
+  // (e.g. "c:") or a UNC name (//net). We want to keep it as part
+  // of the result.
+  SmallString<128> Res;
+  StringRef Root = path::root_name(Abs);
+  if (Root.endswith(":"))
+    Res = Root.drop_back();
+  else if (Root.startswith("//"))
+    Res = Root.substr(2);
+
+  path::append(Res, path::relative_path(Abs));
+  return Res.str();
+}
+
+CpioFile::CpioFile(std::unique_ptr<raw_fd_ostream> OS, StringRef S)
+    : OS(std::move(OS)), Basename(S) {}
+
+CpioFile *CpioFile::create(StringRef OutputPath) {
+  std::string Path = (OutputPath + ".cpio").str();
+  std::error_code EC;
+  auto OS = llvm::make_unique<raw_fd_ostream>(Path, EC, fs::F_None);
+  if (EC) {
+    error(EC, "--reproduce: failed to open " + Path);
+    return nullptr;
+  }
+  return new CpioFile(std::move(OS), path::filename(OutputPath));
+}
+
+static void writeMember(raw_fd_ostream &OS, StringRef Path, StringRef Data) {
+  // The c_dev/c_ino pair should be unique according to the spec,
+  // but no one seems to care.
+  OS << "070707";                        // c_magic
+  OS << "000000";                        // c_dev
+  OS << "000000";                        // c_ino
+  OS << "100664";                        // c_mode: C_ISREG | rw-rw-r--
+  OS << "000000";                        // c_uid
+  OS << "000000";                        // c_gid
+  OS << "000001";                        // c_nlink
+  OS << "000000";                        // c_rdev
+  OS << "00000000000";                   // c_mtime
+  OS << format("%06o", Path.size() + 1); // c_namesize
+  OS << format("%011o", Data.size());    // c_filesize
+  OS << Path << '\0';                    // c_name
+  OS << Data;                            // c_filedata
+}
+
+void CpioFile::append(StringRef Path, StringRef Data) {
+  if (!Seen.insert(Path).second)
+    return;
+
+  // Construct an in-archive filename so that /home/foo/bar is stored
+  // as baz/home/foo/bar where baz is the basename of the output file.
+  // (i.e. in that case we are creating baz.cpio.)
+  SmallString<128> Fullpath;
+  path::append(Fullpath, Basename, Path);
+
+  // Use unix path separators so the cpio can be extracted on both unix and
+  // windows.
+  std::replace(Fullpath.begin(), Fullpath.end(), '\\', '/');
+
+  writeMember(*OS, Fullpath, Data);
+
+  // Print the trailer and seek back.
+  // This way we have a valid archive if we crash.
+  uint64_t Pos = OS->tell();
+  writeMember(*OS, "TRAILER!!!", "");
+  OS->seek(Pos);
+}
+
+// Quote a given string if it contains a space character.
+static std::string quote(StringRef S) {
+  if (S.find(' ') == StringRef::npos)
+    return S;
+  return ("\"" + S + "\"").str();
+}
+
+static std::string rewritePath(StringRef S) {
+  if (fs::exists(S))
+    return relativeToRoot(S);
+  return S;
+}
+
+static std::string stringize(opt::Arg *Arg) {
+  std::string K = Arg->getSpelling();
+  if (Arg->getNumValues() == 0)
+    return K;
+  std::string V = quote(Arg->getValue());
+  if (Arg->getOption().getRenderStyle() == opt::Option::RenderJoinedStyle)
+    return K + V;
+  return K + " " + V;
+}
+
+// Reconstructs command line arguments so that so that you can re-run
+// the same command with the same inputs. This is for --reproduce.
+std::string elf::createResponseFile(const opt::InputArgList &Args) {
+  SmallString<0> Data;
+  raw_svector_ostream OS(Data);
+
+  // Copy the command line to the output while rewriting paths.
+  for (auto *Arg : Args) {
+    switch (Arg->getOption().getID()) {
+    case OPT_reproduce:
+      break;
+    case OPT_INPUT:
+      OS << quote(rewritePath(Arg->getValue())) << "\n";
+      break;
+    case OPT_L:
+    case OPT_dynamic_list:
+    case OPT_rpath:
+    case OPT_alias_script_T:
+    case OPT_script:
+    case OPT_version_script:
+      OS << Arg->getSpelling() << " "
+         << quote(rewritePath(Arg->getValue())) << "\n";
+      break;
+    default:
+      OS << stringize(Arg) << "\n";
+    }
+  }
+  return Data.str();
+}
+
+std::string elf::findFromSearchPaths(StringRef Path) {
   for (StringRef Dir : Config->SearchPaths) {
     std::string FullPath = buildSysrootedPath(Dir, Path);
-    if (sys::fs::exists(FullPath))
+    if (fs::exists(FullPath))
       return FullPath;
   }
   return "";
@@ -90,31 +247,30 @@ std::string elf2::findFromSearchPaths(StringRef Path) {
 
 // Searches a given library from input search paths, which are filled
 // from -L command line switches. Returns a path to an existent library file.
-std::string elf2::searchLibrary(StringRef Path) {
-  std::vector<std::string> Names;
-  if (Path[0] == ':') {
-    Names.push_back(Path.drop_front());
-  } else {
-    if (!Config->Static)
-      Names.push_back(("lib" + Path + ".so").str());
-    Names.push_back(("lib" + Path + ".a").str());
-  }
-  for (const std::string &Name : Names) {
-    std::string S = findFromSearchPaths(Name);
-    if (!S.empty())
+std::string elf::searchLibrary(StringRef Path) {
+  if (Path.startswith(":"))
+    return findFromSearchPaths(Path.substr(1));
+  for (StringRef Dir : Config->SearchPaths) {
+    if (!Config->Static) {
+      std::string S = buildSysrootedPath(Dir, ("lib" + Path + ".so").str());
+      if (fs::exists(S))
+        return S;
+    }
+    std::string S = buildSysrootedPath(Dir, ("lib" + Path + ".a").str());
+    if (fs::exists(S))
       return S;
   }
-  error("Unable to find library -l" + Path);
+  return "";
 }
 
 // Makes a path by concatenating Dir and File.
 // If Dir starts with '=' the result will be preceded by Sysroot,
 // which can be set with --sysroot command line switch.
-std::string elf2::buildSysrootedPath(StringRef Dir, StringRef File) {
+std::string elf::buildSysrootedPath(StringRef Dir, StringRef File) {
   SmallString<128> Path;
   if (Dir.startswith("="))
-    sys::path::append(Path, Config->Sysroot, Dir.substr(1), File);
+    path::append(Path, Config->Sysroot, Dir.substr(1), File);
   else
-    sys::path::append(Path, Dir, File);
+    path::append(Path, Dir, File);
   return Path.str();
 }
diff --git a/ELF/EhFrame.cpp b/ELF/EhFrame.cpp
new file mode 100644
index 000000000000..b130ac1ca22d
--- /dev/null
+++ b/ELF/EhFrame.cpp
@@ -0,0 +1,167 @@
+//===- EhFrame.cpp -------------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// .eh_frame section contains information on how to unwind the stack when
+// an exception is thrown. The section consists of sequence of CIE and FDE
+// records. The linker needs to merge CIEs and associate FDEs to CIEs.
+// That means the linker has to understand the format of the section.
+//
+// This file contains a few utility functions to read .eh_frame contents.
+//
+//===----------------------------------------------------------------------===//
+
+#include "EhFrame.h"
+#include "Error.h"
+
+#include "llvm/Object/ELF.h"
+#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Endian.h"
+
+using namespace llvm;
+using namespace llvm::ELF;
+using namespace llvm::dwarf;
+using namespace llvm::object;
+using namespace llvm::support::endian;
+
+namespace lld {
+namespace elf {
+
+// .eh_frame section is a sequence of records. Each record starts with
+// a 4 byte length field. This function reads the length.
+template <class ELFT> size_t readEhRecordSize(ArrayRef<uint8_t> D) {
+  const endianness E = ELFT::TargetEndianness;
+  if (D.size() < 4)
+    fatal("CIE/FDE too small");
+
+  // First 4 bytes of CIE/FDE is the size of the record.
+  // If it is 0xFFFFFFFF, the next 8 bytes contain the size instead,
+  // but we do not support that format yet.
+  uint64_t V = read32<E>(D.data());
+  if (V == UINT32_MAX)
+    fatal("CIE/FDE too large");
+  uint64_t Size = V + 4;
+  if (Size > D.size())
+    fatal("CIE/FIE ends past the end of the section");
+  return Size;
+}
+
+// Read a byte and advance D by one byte.
+static uint8_t readByte(ArrayRef<uint8_t> &D) {
+  if (D.empty())
+    fatal("corrupted or unsupported CIE information");
+  uint8_t B = D.front();
+  D = D.slice(1);
+  return B;
+}
+
+// Skip an integer encoded in the LEB128 format.
+// Actual number is not of interest because only the runtime needs it.
+// But we need to be at least able to skip it so that we can read
+// the field that follows a LEB128 number.
+static void skipLeb128(ArrayRef<uint8_t> &D) {
+  while (!D.empty()) {
+    uint8_t Val = D.front();
+    D = D.slice(1);
+    if ((Val & 0x80) == 0)
+      return;
+  }
+  fatal("corrupted or unsupported CIE information");
+}
+
+template <class ELFT> static size_t getAugPSize(unsigned Enc) {
+  switch (Enc & 0x0f) {
+  case DW_EH_PE_absptr:
+  case DW_EH_PE_signed:
+    return ELFT::Is64Bits ? 8 : 4;
+  case DW_EH_PE_udata2:
+  case DW_EH_PE_sdata2:
+    return 2;
+  case DW_EH_PE_udata4:
+  case DW_EH_PE_sdata4:
+    return 4;
+  case DW_EH_PE_udata8:
+  case DW_EH_PE_sdata8:
+    return 8;
+  }
+  fatal("unknown FDE encoding");
+}
+
+template <class ELFT> static void skipAugP(ArrayRef<uint8_t> &D) {
+  uint8_t Enc = readByte(D);
+  if ((Enc & 0xf0) == DW_EH_PE_aligned)
+    fatal("DW_EH_PE_aligned encoding is not supported");
+  size_t Size = getAugPSize<ELFT>(Enc);
+  if (Size >= D.size())
+    fatal("corrupted CIE");
+  D = D.slice(Size);
+}
+
+template <class ELFT> uint8_t getFdeEncoding(ArrayRef<uint8_t> D) {
+  if (D.size() < 8)
+    fatal("CIE too small");
+  D = D.slice(8);
+
+  uint8_t Version = readByte(D);
+  if (Version != 1 && Version != 3)
+    fatal("FDE version 1 or 3 expected, but got " + Twine((unsigned)Version));
+
+  const unsigned char *AugEnd = std::find(D.begin(), D.end(), '\0');
+  if (AugEnd == D.end())
+    fatal("corrupted CIE");
+  StringRef Aug(reinterpret_cast<const char *>(D.begin()), AugEnd - D.begin());
+  D = D.slice(Aug.size() + 1);
+
+  // Code alignment factor should always be 1 for .eh_frame.
+  if (readByte(D) != 1)
+    fatal("CIE code alignment must be 1");
+
+  // Skip data alignment factor.
+  skipLeb128(D);
+
+  // Skip the return address register. In CIE version 1 this is a single
+  // byte. In CIE version 3 this is an unsigned LEB128.
+  if (Version == 1)
+    readByte(D);
+  else
+    skipLeb128(D);
+
+  // We only care about an 'R' value, but other records may precede an 'R'
+  // record. Unfortunately records are not in TLV (type-length-value) format,
+  // so we need to teach the linker how to skip records for each type.
+  for (char C : Aug) {
+    if (C == 'R')
+      return readByte(D);
+    if (C == 'z') {
+      skipLeb128(D);
+      continue;
+    }
+    if (C == 'P') {
+      skipAugP<ELFT>(D);
+      continue;
+    }
+    if (C == 'L') {
+      readByte(D);
+      continue;
+    }
+    fatal("unknown .eh_frame augmentation string: " + Aug);
+  }
+  return DW_EH_PE_absptr;
+}
+
+template size_t readEhRecordSize<ELF32LE>(ArrayRef<uint8_t>);
+template size_t readEhRecordSize<ELF32BE>(ArrayRef<uint8_t>);
+template size_t readEhRecordSize<ELF64LE>(ArrayRef<uint8_t>);
+template size_t readEhRecordSize<ELF64BE>(ArrayRef<uint8_t>);
+
+template uint8_t getFdeEncoding<ELF32LE>(ArrayRef<uint8_t>);
+template uint8_t getFdeEncoding<ELF32BE>(ArrayRef<uint8_t>);
+template uint8_t getFdeEncoding<ELF64LE>(ArrayRef<uint8_t>);
+template uint8_t getFdeEncoding<ELF64BE>(ArrayRef<uint8_t>);
+}
+}
diff --git a/ELF/EhFrame.h b/ELF/EhFrame.h
new file mode 100644
index 000000000000..0d5a2ff2f417
--- /dev/null
+++ b/ELF/EhFrame.h
@@ -0,0 +1,22 @@
+//===- EhFrame.h ------------------------------------------------*- C++ -*-===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_ELF_EHFRAME_H
+#define LLD_ELF_EHFRAME_H
+
+#include "lld/Core/LLVM.h"
+
+namespace lld {
+namespace elf {
+template <class ELFT> size_t readEhRecordSize(ArrayRef<uint8_t> Data);
+template <class ELFT> uint8_t getFdeEncoding(ArrayRef<uint8_t> Data);
+}
+}
+
+#endif
diff --git a/ELF/Error.cpp b/ELF/Error.cpp
index e0701f7f4cc6..59a49c17b97c 100644
--- a/ELF/Error.cpp
+++ b/ELF/Error.cpp
@@ -8,31 +8,58 @@
 //===----------------------------------------------------------------------===//
 
 #include "Error.h"
+#include "Config.h"
 
 #include "llvm/ADT/Twine.h"
+#include "llvm/Support/Error.h"
 #include "llvm/Support/raw_ostream.h"
 
+using namespace llvm;
+
 namespace lld {
-namespace elf2 {
+namespace elf {
+
+bool HasError;
+raw_ostream *ErrorOS;
 
-void warning(const Twine &Msg) { llvm::errs() << Msg << "\n"; }
+void log(const Twine &Msg) {
+  if (Config->Verbose)
+    outs() << Msg << "\n";
+}
+
+void warning(const Twine &Msg) {
+  if (Config->FatalWarnings)
+    error(Msg);
+  else
+    *ErrorOS << Msg << "\n";
+}
 
 void error(const Twine &Msg) {
-  llvm::errs() << Msg << "\n";
-  exit(1);
+  *ErrorOS << Msg << "\n";
+  HasError = true;
 }
 
 void error(std::error_code EC, const Twine &Prefix) {
-  if (!EC)
-    return;
   error(Prefix + ": " + EC.message());
 }
 
-void error(std::error_code EC) {
-  if (!EC)
-    return;
-  error(EC.message());
+void fatal(const Twine &Msg) {
+  *ErrorOS << Msg << "\n";
+  exit(1);
+}
+
+void fatal(const Twine &Msg, const Twine &Prefix) {
+  fatal(Prefix + ": " + Msg);
+}
+
+void check(std::error_code EC) {
+  if (EC)
+    fatal(EC.message());
+}
+
+void check(Error Err) {
+  check(errorToErrorCode(std::move(Err)));
 }
 
-} // namespace elf2
+} // namespace elf
 } // namespace lld
diff --git a/ELF/Error.h b/ELF/Error.h
index b1d2e7a8fc5b..552f50498464 100644
--- a/ELF/Error.h
+++ b/ELF/Error.h
@@ -13,20 +13,49 @@
 #include "lld/Core/LLVM.h"
 
 namespace lld {
-namespace elf2 {
+namespace elf {
 
+extern bool HasError;
+extern llvm::raw_ostream *ErrorOS;
+
+void log(const Twine &Msg);
 void warning(const Twine &Msg);
 
-LLVM_ATTRIBUTE_NORETURN void error(const Twine &Msg);
+void error(const Twine &Msg);
 void error(std::error_code EC, const Twine &Prefix);
-void error(std::error_code EC);
 
 template <typename T> void error(const ErrorOr<T> &V, const Twine &Prefix) {
   error(V.getError(), Prefix);
 }
-template <typename T> void error(const ErrorOr<T> &V) { error(V.getError()); }
 
-} // namespace elf2
+LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg);
+LLVM_ATTRIBUTE_NORETURN void fatal(const Twine &Msg, const Twine &Prefix);
+
+template <class T> T check(ErrorOr<T> E) {
+  if (auto EC = E.getError())
+    fatal(EC.message());
+  return std::move(*E);
+}
+
+template <class T> T check(Expected<T> E) {
+  if (!E)
+    fatal(errorToErrorCode(E.takeError()).message());
+  return std::move(*E);
+}
+
+template <class T> T check(ErrorOr<T> E, const Twine &Prefix) {
+  if (auto EC = E.getError())
+    fatal(EC.message(), Prefix);
+  return std::move(*E);
+}
+
+template <class T> T check(Expected<T> E, const Twine &Prefix) {
+  if (!E)
+    fatal(errorToErrorCode(E.takeError()).message(), Prefix);
+  return std::move(*E);
+}
+
+} // namespace elf
 } // namespace lld
 
 #endif
diff --git a/ELF/ICF.cpp b/ELF/ICF.cpp
new file mode 100644
index 000000000000..10a2603b3b3e
--- /dev/null
+++ b/ELF/ICF.cpp
@@ -0,0 +1,345 @@
+//===- ICF.cpp ------------------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Identical Code Folding is a feature to merge sections not by name (which
+// is regular comdat handling) but by contents. If two non-writable sections
+// have the same data, relocations, attributes, etc., then the two
+// are considered identical and merged by the linker. This optimization
+// makes outputs smaller.
+//
+// ICF is theoretically a problem of reducing graphs by merging as many
+// identical subgraphs as possible if we consider sections as vertices and
+// relocations as edges. It may sound simple, but it is a bit more
+// complicated than you might think. The order of processing sections
+// matters because merging two sections can make other sections, whose
+// relocations now point to the same section, mergeable. Graphs may contain
+// cycles. We need a sophisticated algorithm to do this properly and
+// efficiently.
+//
+// What we do in this file is this. We split sections into groups. Sections
+// in the same group are considered identical.
+//
+// We begin by optimistically putting all sections into a single equivalence
+// class. Then we apply a series of checks that split this initial
+// equivalence class into more and more refined equivalence classes based on
+// the properties by which a section can be distinguished.
+//
+// We begin by checking that the section contents and flags are the
+// same. This only needs to be done once since these properties don't depend
+// on the current equivalence class assignment.
+//
+// Then we split the equivalence classes based on checking that their
+// relocations are the same, where relocation targets are compared by their
+// equivalence class, not the concrete section. This may need to be done
+// multiple times because as the equivalence classes are refined, two
+// sections that had a relocation target in the same equivalence class may
+// now target different equivalence classes, and hence these two sections
+// must be put in different equivalence classes (whereas in the previous
+// iteration they were not since the relocation target was the same.)
+//
+// Our algorithm is smart enough to merge the following mutually-recursive
+// functions.
+//
+//   void foo() { bar(); }
+//   void bar() { foo(); }
+//
+// This algorithm is so-called "optimistic" algorithm described in
+// http://research.google.com/pubs/pub36912.html. (Note that what GNU
+// gold implemented is different from the optimistic algorithm.)
+//
+//===----------------------------------------------------------------------===//
+
+#include "ICF.h"
+#include "Config.h"
+#include "OutputSections.h"
+#include "SymbolTable.h"
+
+#include "llvm/ADT/Hashing.h"
+#include "llvm/Object/ELF.h"
+#include "llvm/Support/ELF.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace lld;
+using namespace lld::elf;
+using namespace llvm;
+using namespace llvm::ELF;
+using namespace llvm::object;
+
+namespace lld {
+namespace elf {
+template <class ELFT> class ICF {
+  typedef typename ELFT::Shdr Elf_Shdr;
+  typedef typename ELFT::Sym Elf_Sym;
+  typedef typename ELFT::uint uintX_t;
+  typedef Elf_Rel_Impl<ELFT, false> Elf_Rel;
+
+  using Comparator = std::function<bool(const InputSection<ELFT> *,
+                                        const InputSection<ELFT> *)>;
+
+public:
+  void run();
+
+private:
+  uint64_t NextId = 1;
+
+  static void setLive(SymbolTable<ELFT> *S);
+  static uint64_t relSize(InputSection<ELFT> *S);
+  static uint64_t getHash(InputSection<ELFT> *S);
+  static bool isEligible(InputSectionBase<ELFT> *Sec);
+  static std::vector<InputSection<ELFT> *> getSections();
+
+  void segregate(InputSection<ELFT> **Begin, InputSection<ELFT> **End,
+                 Comparator Eq);
+
+  void forEachGroup(std::vector<InputSection<ELFT> *> &V, Comparator Eq);
+
+  template <class RelTy>
+  static bool relocationEq(ArrayRef<RelTy> RA, ArrayRef<RelTy> RB);
+
+  template <class RelTy>
+  static bool variableEq(const InputSection<ELFT> *A,
+                         const InputSection<ELFT> *B, ArrayRef<RelTy> RA,
+                         ArrayRef<RelTy> RB);
+
+  static bool equalsConstant(const InputSection<ELFT> *A,
+                             const InputSection<ELFT> *B);
+
+  static bool equalsVariable(const InputSection<ELFT> *A,
+                             const InputSection<ELFT> *B);
+};
+}
+}
+
+// Returns a hash value for S. Note that the information about
+// relocation targets is not included in the hash value.
+template <class ELFT> uint64_t ICF<ELFT>::getHash(InputSection<ELFT> *S) {
+  uint64_t Flags = S->getSectionHdr()->sh_flags;
+  uint64_t H = hash_combine(Flags, S->getSize());
+  for (const Elf_Shdr *Rel : S->RelocSections)
+    H = hash_combine(H, (uint64_t)Rel->sh_size);
+  return H;
+}
+
+// Returns true if Sec is subject of ICF.
+template <class ELFT> bool ICF<ELFT>::isEligible(InputSectionBase<ELFT> *Sec) {
+  if (!Sec || Sec == &InputSection<ELFT>::Discarded || !Sec->Live)
+    return false;
+  auto *S = dyn_cast<InputSection<ELFT>>(Sec);
+  if (!S)
+    return false;
+
+  // .init and .fini contains instructions that must be executed to
+  // initialize and finalize the process. They cannot and should not
+  // be merged.
+  StringRef Name = S->getSectionName();
+  if (Name == ".init" || Name == ".fini")
+    return false;
+
+  const Elf_Shdr &H = *S->getSectionHdr();
+  return (H.sh_flags & SHF_ALLOC) && (~H.sh_flags & SHF_WRITE);
+}
+
+template <class ELFT>
+std::vector<InputSection<ELFT> *> ICF<ELFT>::getSections() {
+  std::vector<InputSection<ELFT> *> V;
+  for (const std::unique_ptr<ObjectFile<ELFT>> &F :
+       Symtab<ELFT>::X->getObjectFiles())
+    for (InputSectionBase<ELFT> *S : F->getSections())
+      if (isEligible(S))
+        V.push_back(cast<InputSection<ELFT>>(S));
+  return V;
+}
+
+// All sections between Begin and End must have the same group ID before
+// you call this function. This function compare sections between Begin
+// and End using Eq and assign new group IDs for new groups.
+template <class ELFT>
+void ICF<ELFT>::segregate(InputSection<ELFT> **Begin, InputSection<ELFT> **End,
+                          Comparator Eq) {
+  // This loop rearranges [Begin, End) so that all sections that are
+  // equal in terms of Eq are contiguous. The algorithm is quadratic in
+  // the worst case, but that is not an issue in practice because the
+  // number of distinct sections in [Begin, End) is usually very small.
+  InputSection<ELFT> **I = Begin;
+  for (;;) {
+    InputSection<ELFT> *Head = *I;
+    auto Bound = std::stable_partition(
+        I + 1, End, [&](InputSection<ELFT> *S) { return Eq(Head, S); });
+    if (Bound == End)
+      return;
+    uint64_t Id = NextId++;
+    for (; I != Bound; ++I)
+      (*I)->GroupId = Id;
+  }
+}
+
+template <class ELFT>
+void ICF<ELFT>::forEachGroup(std::vector<InputSection<ELFT> *> &V,
+                             Comparator Eq) {
+  for (InputSection<ELFT> **I = V.data(), **E = I + V.size(); I != E;) {
+    InputSection<ELFT> *Head = *I;
+    auto Bound = std::find_if(I + 1, E, [&](InputSection<ELFT> *S) {
+      return S->GroupId != Head->GroupId;
+    });
+    segregate(I, Bound, Eq);
+    I = Bound;
+  }
+}
+
+// Compare two lists of relocations.
+template <class ELFT>
+template <class RelTy>
+bool ICF<ELFT>::relocationEq(ArrayRef<RelTy> RelsA, ArrayRef<RelTy> RelsB) {
+  const RelTy *IA = RelsA.begin();
+  const RelTy *EA = RelsA.end();
+  const RelTy *IB = RelsB.begin();
+  const RelTy *EB = RelsB.end();
+  if (EA - IA != EB - IB)
+    return false;
+  for (; IA != EA; ++IA, ++IB)
+    if (IA->r_offset != IB->r_offset ||
+        IA->getType(Config->Mips64EL) != IB->getType(Config->Mips64EL) ||
+        getAddend<ELFT>(*IA) != getAddend<ELFT>(*IB))
+      return false;
+  return true;
+}
+
+// Compare "non-moving" part of two InputSections, namely everything
+// except relocation targets.
+template <class ELFT>
+bool ICF<ELFT>::equalsConstant(const InputSection<ELFT> *A,
+                               const InputSection<ELFT> *B) {
+  if (A->RelocSections.size() != B->RelocSections.size())
+    return false;
+
+  for (size_t I = 0, E = A->RelocSections.size(); I != E; ++I) {
+    const Elf_Shdr *RA = A->RelocSections[I];
+    const Elf_Shdr *RB = B->RelocSections[I];
+    ELFFile<ELFT> &FileA = A->File->getObj();
+    ELFFile<ELFT> &FileB = B->File->getObj();
+    if (RA->sh_type == SHT_RELA) {
+      if (!relocationEq(FileA.relas(RA), FileB.relas(RB)))
+        return false;
+    } else {
+      if (!relocationEq(FileA.rels(RA), FileB.rels(RB)))
+        return false;
+    }
+  }
+
+  return A->getSectionHdr()->sh_flags == B->getSectionHdr()->sh_flags &&
+         A->getSize() == B->getSize() &&
+         A->getSectionData() == B->getSectionData();
+}
+
+template <class ELFT>
+template <class RelTy>
+bool ICF<ELFT>::variableEq(const InputSection<ELFT> *A,
+                           const InputSection<ELFT> *B, ArrayRef<RelTy> RelsA,
+                           ArrayRef<RelTy> RelsB) {
+  const RelTy *IA = RelsA.begin();
+  const RelTy *EA = RelsA.end();
+  const RelTy *IB = RelsB.begin();
+  for (; IA != EA; ++IA, ++IB) {
+    SymbolBody &SA = A->File->getRelocTargetSym(*IA);
+    SymbolBody &SB = B->File->getRelocTargetSym(*IB);
+    if (&SA == &SB)
+      continue;
+
+    // Or, the symbols should be pointing to the same section
+    // in terms of the group ID.
+    auto *DA = dyn_cast<DefinedRegular<ELFT>>(&SA);
+    auto *DB = dyn_cast<DefinedRegular<ELFT>>(&SB);
+    if (!DA || !DB)
+      return false;
+    if (DA->Value != DB->Value)
+      return false;
+    InputSection<ELFT> *X = dyn_cast<InputSection<ELFT>>(DA->Section);
+    InputSection<ELFT> *Y = dyn_cast<InputSection<ELFT>>(DB->Section);
+    if (X && Y && X->GroupId && X->GroupId == Y->GroupId)
+      continue;
+    return false;
+  }
+  return true;
+}
+
+// Compare "moving" part of two InputSections, namely relocation targets.
+template <class ELFT>
+bool ICF<ELFT>::equalsVariable(const InputSection<ELFT> *A,
+                               const InputSection<ELFT> *B) {
+  for (size_t I = 0, E = A->RelocSections.size(); I != E; ++I) {
+    const Elf_Shdr *RA = A->RelocSections[I];
+    const Elf_Shdr *RB = B->RelocSections[I];
+    ELFFile<ELFT> &FileA = A->File->getObj();
+    ELFFile<ELFT> &FileB = B->File->getObj();
+    if (RA->sh_type == SHT_RELA) {
+      if (!variableEq(A, B, FileA.relas(RA), FileB.relas(RB)))
+        return false;
+    } else {
+      if (!variableEq(A, B, FileA.rels(RA), FileB.rels(RB)))
+        return false;
+    }
+  }
+  return true;
+}
+
+// The main function of ICF.
+template <class ELFT> void ICF<ELFT>::run() {
+  // Initially, we use hash values as section group IDs. Therefore,
+  // if two sections have the same ID, they are likely (but not
+  // guaranteed) to have the same static contents in terms of ICF.
+  std::vector<InputSection<ELFT> *> V = getSections();
+  for (InputSection<ELFT> *S : V)
+    // Set MSB on to avoid collisions with serial group IDs
+    S->GroupId = getHash(S) | (uint64_t(1) << 63);
+
+  // From now on, sections in V are ordered so that sections in
+  // the same group are consecutive in the vector.
+  std::stable_sort(V.begin(), V.end(),
+                   [](InputSection<ELFT> *A, InputSection<ELFT> *B) {
+                     return A->GroupId < B->GroupId;
+                   });
+
+  // Compare static contents and assign unique IDs for each static content.
+  forEachGroup(V, equalsConstant);
+
+  // Split groups by comparing relocations until we get a convergence.
+  int Cnt = 1;
+  for (;;) {
+    ++Cnt;
+    uint64_t Id = NextId;
+    forEachGroup(V, equalsVariable);
+    if (Id == NextId)
+      break;
+  }
+  log("ICF needed " + Twine(Cnt) + " iterations.");
+
+  // Merge sections in the same group.
+  for (auto I = V.begin(), E = V.end(); I != E;) {
+    InputSection<ELFT> *Head = *I++;
+    auto Bound = std::find_if(I, E, [&](InputSection<ELFT> *S) {
+      return Head->GroupId != S->GroupId;
+    });
+    if (I == Bound)
+      continue;
+    log("selected " + Head->getSectionName());
+    while (I != Bound) {
+      InputSection<ELFT> *S = *I++;
+      log("  removed " + S->getSectionName());
+      Head->replace(S);
+    }
+  }
+}
+
+// ICF entry point function.
+template <class ELFT> void elf::doIcf() { ICF<ELFT>().run(); }
+
+template void elf::doIcf<ELF32LE>();
+template void elf::doIcf<ELF32BE>();
+template void elf::doIcf<ELF64LE>();
+template void elf::doIcf<ELF64BE>();
diff --git a/ELF/ICF.h b/ELF/ICF.h
new file mode 100644
index 000000000000..502e128c8109
--- /dev/null
+++ b/ELF/ICF.h
@@ -0,0 +1,19 @@
+//===- ICF.h --------------------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_ELF_ICF_H
+#define LLD_ELF_ICF_H
+
+namespace lld {
+namespace elf {
+template <class ELFT> void doIcf();
+}
+}
+
+#endif
diff --git a/ELF/InputFiles.cpp b/ELF/InputFiles.cpp
index 6a908d450f60..57e556395937 100644
--- a/ELF/InputFiles.cpp
+++ b/ELF/InputFiles.cpp
@@ -8,10 +8,17 @@
 //===----------------------------------------------------------------------===//
 
 #include "InputFiles.h"
-#include "InputSection.h"
+#include "Driver.h"
 #include "Error.h"
+#include "InputSection.h"
+#include "SymbolTable.h"
 #include "Symbols.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/CodeGen/Analysis.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 using namespace llvm::ELF;
@@ -19,43 +26,52 @@ using namespace llvm::object;
 using namespace llvm::sys::fs;
 
 using namespace lld;
-using namespace lld::elf2;
-
-namespace {
-class ECRAII {
-  std::error_code EC;
-
-public:
-  std::error_code &getEC() { return EC; }
-  ~ECRAII() { error(EC); }
-};
+using namespace lld::elf;
+
+// Returns "(internal)", "foo.a(bar.o)" or "baz.o".
+std::string elf::getFilename(const InputFile *F) {
+  if (!F)
+    return "(internal)";
+  if (!F->ArchiveName.empty())
+    return (F->ArchiveName + "(" + F->getName() + ")").str();
+  return F->getName();
 }
 
 template <class ELFT>
-ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef M)
-    : InputFile(K, M), ELFObj(MB.getBuffer(), ECRAII().getEC()) {}
+static ELFFile<ELFT> createELFObj(MemoryBufferRef MB) {
+  std::error_code EC;
+  ELFFile<ELFT> F(MB.getBuffer(), EC);
+  if (EC)
+    error(EC, "failed to read " + MB.getBufferIdentifier());
+  return F;
+}
 
-template <class ELFT>
-ELFKind ELFFileBase<ELFT>::getELFKind() {
+template <class ELFT> static ELFKind getELFKind() {
   if (ELFT::TargetEndianness == support::little)
     return ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
   return ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
 }
 
 template <class ELFT>
-typename ELFFileBase<ELFT>::Elf_Sym_Range
-ELFFileBase<ELFT>::getSymbolsHelper(bool Local) {
+ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef MB)
+    : InputFile(K, MB), ELFObj(createELFObj<ELFT>(MB)) {
+  EKind = getELFKind<ELFT>();
+  EMachine = ELFObj.getHeader()->e_machine;
+}
+
+template <class ELFT>
+typename ELFT::SymRange ELFFileBase<ELFT>::getElfSymbols(bool OnlyGlobals) {
   if (!Symtab)
     return Elf_Sym_Range(nullptr, nullptr);
   Elf_Sym_Range Syms = ELFObj.symbols(Symtab);
   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
   uint32_t FirstNonLocal = Symtab->sh_info;
   if (FirstNonLocal > NumSymbols)
-    error("Invalid sh_info in symbol table");
-  if (!Local)
-    return make_range(Syms.begin() + FirstNonLocal, Syms.end());
-  // +1 to skip over dummy symbol.
-  return make_range(Syms.begin() + 1, Syms.begin() + FirstNonLocal);
+    fatal(getFilename(this) + ": invalid sh_info in symbol table");
+
+  if (OnlyGlobals)
+    return makeArrayRef(Syms.begin() + FirstNonLocal, Syms.end());
+  return makeArrayRef(Syms.begin(), Syms.end());
 }
 
 template <class ELFT>
@@ -63,7 +79,7 @@ uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
   uint32_t I = Sym.st_shndx;
   if (I == ELF::SHN_XINDEX)
     return ELFObj.getExtendedSymbolTableIndex(&Sym, Symtab, SymtabSHNDX);
-  if (I >= ELF::SHN_LORESERVE || I == ELF::SHN_ABS)
+  if (I >= ELF::SHN_LORESERVE)
     return 0;
   return I;
 }
@@ -71,44 +87,46 @@ uint32_t ELFFileBase<ELFT>::getSectionIndex(const Elf_Sym &Sym) const {
 template <class ELFT> void ELFFileBase<ELFT>::initStringTable() {
   if (!Symtab)
     return;
-  ErrorOr<StringRef> StringTableOrErr = ELFObj.getStringTableForSymtab(*Symtab);
-  error(StringTableOrErr);
-  StringTable = *StringTableOrErr;
+  StringTable = check(ELFObj.getStringTableForSymtab(*Symtab));
 }
 
 template <class ELFT>
-typename ELFFileBase<ELFT>::Elf_Sym_Range
-ELFFileBase<ELFT>::getNonLocalSymbols() {
-  return getSymbolsHelper(false);
+elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
+    : ELFFileBase<ELFT>(Base::ObjectKind, M) {}
+
+template <class ELFT>
+ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getNonLocalSymbols() {
+  if (!this->Symtab)
+    return this->SymbolBodies;
+  uint32_t FirstNonLocal = this->Symtab->sh_info;
+  return makeArrayRef(this->SymbolBodies).slice(FirstNonLocal);
 }
 
 template <class ELFT>
-ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
-    : ELFFileBase<ELFT>(Base::ObjectKind, M) {}
+ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getLocalSymbols() {
+  if (!this->Symtab)
+    return this->SymbolBodies;
+  uint32_t FirstNonLocal = this->Symtab->sh_info;
+  return makeArrayRef(this->SymbolBodies).slice(1, FirstNonLocal - 1);
+}
 
 template <class ELFT>
-typename ObjectFile<ELFT>::Elf_Sym_Range ObjectFile<ELFT>::getLocalSymbols() {
-  return this->getSymbolsHelper(true);
+ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getSymbols() {
+  if (!this->Symtab)
+    return this->SymbolBodies;
+  return makeArrayRef(this->SymbolBodies).slice(1);
 }
 
-template <class ELFT> uint32_t ObjectFile<ELFT>::getMipsGp0() const {
-  if (MipsReginfo)
+template <class ELFT> uint32_t elf::ObjectFile<ELFT>::getMipsGp0() const {
+  if (ELFT::Is64Bits && MipsOptions && MipsOptions->Reginfo)
+    return MipsOptions->Reginfo->ri_gp_value;
+  if (!ELFT::Is64Bits && MipsReginfo && MipsReginfo->Reginfo)
     return MipsReginfo->Reginfo->ri_gp_value;
   return 0;
 }
 
 template <class ELFT>
-const typename ObjectFile<ELFT>::Elf_Sym *
-ObjectFile<ELFT>::getLocalSymbol(uintX_t SymIndex) {
-  uint32_t FirstNonLocal = this->Symtab->sh_info;
-  if (SymIndex >= FirstNonLocal)
-    return nullptr;
-  Elf_Sym_Range Syms = this->ELFObj.symbols(this->Symtab);
-  return Syms.begin() + SymIndex;
-}
-
-template <class ELFT>
-void ObjectFile<ELFT>::parse(DenseSet<StringRef> &ComdatGroups) {
+void elf::ObjectFile<ELFT>::parse(DenseSet<StringRef> &ComdatGroups) {
   // Read section and symbol tables.
   initializeSections(ComdatGroups);
   initializeSymbols();
@@ -118,63 +136,57 @@ void ObjectFile<ELFT>::parse(DenseSet<StringRef> &ComdatGroups) {
 // They are identified and deduplicated by group name. This function
 // returns a group name.
 template <class ELFT>
-StringRef ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
+StringRef elf::ObjectFile<ELFT>::getShtGroupSignature(const Elf_Shdr &Sec) {
   const ELFFile<ELFT> &Obj = this->ELFObj;
-  uint32_t SymtabdSectionIndex = Sec.sh_link;
-  ErrorOr<const Elf_Shdr *> SecOrErr = Obj.getSection(SymtabdSectionIndex);
-  error(SecOrErr);
-  const Elf_Shdr *SymtabSec = *SecOrErr;
-  uint32_t SymIndex = Sec.sh_info;
-  const Elf_Sym *Sym = Obj.getSymbol(SymtabSec, SymIndex);
-  ErrorOr<StringRef> StringTableOrErr = Obj.getStringTableForSymtab(*SymtabSec);
-  error(StringTableOrErr);
-  ErrorOr<StringRef> SignatureOrErr = Sym->getName(*StringTableOrErr);
-  error(SignatureOrErr);
-  return *SignatureOrErr;
+  const Elf_Shdr *Symtab = check(Obj.getSection(Sec.sh_link));
+  const Elf_Sym *Sym = Obj.getSymbol(Symtab, Sec.sh_info);
+  StringRef Strtab = check(Obj.getStringTableForSymtab(*Symtab));
+  return check(Sym->getName(Strtab));
 }
 
 template <class ELFT>
-ArrayRef<typename ObjectFile<ELFT>::uint32_X>
-ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
+ArrayRef<typename elf::ObjectFile<ELFT>::Elf_Word>
+elf::ObjectFile<ELFT>::getShtGroupEntries(const Elf_Shdr &Sec) {
   const ELFFile<ELFT> &Obj = this->ELFObj;
-  ErrorOr<ArrayRef<uint32_X>> EntriesOrErr =
-      Obj.template getSectionContentsAsArray<uint32_X>(&Sec);
-  error(EntriesOrErr);
-  ArrayRef<uint32_X> Entries = *EntriesOrErr;
+  ArrayRef<Elf_Word> Entries =
+      check(Obj.template getSectionContentsAsArray<Elf_Word>(&Sec));
   if (Entries.empty() || Entries[0] != GRP_COMDAT)
-    error("Unsupported SHT_GROUP format");
+    fatal(getFilename(this) + ": unsupported SHT_GROUP format");
   return Entries.slice(1);
 }
 
 template <class ELFT>
-static bool shouldMerge(const typename ELFFile<ELFT>::Elf_Shdr &Sec) {
-  typedef typename ELFFile<ELFT>::uintX_t uintX_t;
+bool elf::ObjectFile<ELFT>::shouldMerge(const Elf_Shdr &Sec) {
+  // We don't merge sections if -O0 (default is -O1). This makes sometimes
+  // the linker significantly faster, although the output will be bigger.
+  if (Config->Optimize == 0)
+    return false;
+
   uintX_t Flags = Sec.sh_flags;
   if (!(Flags & SHF_MERGE))
     return false;
   if (Flags & SHF_WRITE)
-    error("Writable SHF_MERGE sections are not supported");
+    fatal(getFilename(this) + ": writable SHF_MERGE section is not supported");
   uintX_t EntSize = Sec.sh_entsize;
   if (!EntSize || Sec.sh_size % EntSize)
-    error("SHF_MERGE section size must be a multiple of sh_entsize");
+    fatal(getFilename(this) +
+          ": SHF_MERGE section size must be a multiple of sh_entsize");
 
-  // Don't try to merge if the aligment is larger than the sh_entsize.
+  // Don't try to merge if the alignment is larger than the sh_entsize and this
+  // is not SHF_STRINGS.
   //
-  // If this is not a SHF_STRINGS, we would need to pad after every entity. It
-  // would be equivalent for the producer of the .o to just set a larger
+  // Since this is not a SHF_STRINGS, we would need to pad after every entity.
+  // It would be equivalent for the producer of the .o to just set a larger
   // sh_entsize.
-  //
-  // If this is a SHF_STRINGS, the larger alignment makes sense. Unfortunately
-  // it would complicate tail merging. This doesn't seem that common to
-  // justify the effort.
-  if (Sec.sh_addralign > EntSize)
-    return false;
+  if (Flags & SHF_STRINGS)
+    return true;
 
-  return true;
+  return Sec.sh_addralign <= EntSize;
 }
 
 template <class ELFT>
-void ObjectFile<ELFT>::initializeSections(DenseSet<StringRef> &ComdatGroups) {
+void elf::ObjectFile<ELFT>::initializeSections(
+    DenseSet<StringRef> &ComdatGroups) {
   uint64_t Size = this->ELFObj.getNumSections();
   Sections.resize(Size);
   unsigned I = -1;
@@ -191,53 +203,85 @@ void ObjectFile<ELFT>::initializeSections(DenseSet<StringRef> &ComdatGroups) {
         continue;
       for (uint32_t SecIndex : getShtGroupEntries(Sec)) {
         if (SecIndex >= Size)
-          error("Invalid section index in group");
+          fatal(getFilename(this) + ": invalid section index in group: " +
+                Twine(SecIndex));
         Sections[SecIndex] = &InputSection<ELFT>::Discarded;
       }
       break;
     case SHT_SYMTAB:
       this->Symtab = &Sec;
       break;
-    case SHT_SYMTAB_SHNDX: {
-      ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
-      error(ErrorOrTable);
-      this->SymtabSHNDX = *ErrorOrTable;
+    case SHT_SYMTAB_SHNDX:
+      this->SymtabSHNDX = check(Obj.getSHNDXTable(Sec));
       break;
-    }
     case SHT_STRTAB:
     case SHT_NULL:
       break;
     case SHT_RELA:
     case SHT_REL: {
-      uint32_t RelocatedSectionIndex = Sec.sh_info;
-      if (RelocatedSectionIndex >= Size)
-        error("Invalid relocated section index");
-      InputSectionBase<ELFT> *RelocatedSection =
-          Sections[RelocatedSectionIndex];
-      if (!RelocatedSection)
-        error("Unsupported relocation reference");
-      if (auto *S = dyn_cast<InputSection<ELFT>>(RelocatedSection)) {
+      // This section contains relocation information.
+      // If -r is given, we do not interpret or apply relocation
+      // but just copy relocation sections to output.
+      if (Config->Relocatable) {
+        Sections[I] = new (IAlloc.Allocate()) InputSection<ELFT>(this, &Sec);
+        break;
+      }
+
+      // Find the relocation target section and associate this
+      // section with it.
+      InputSectionBase<ELFT> *Target = getRelocTarget(Sec);
+      if (!Target)
+        break;
+      if (auto *S = dyn_cast<InputSection<ELFT>>(Target)) {
         S->RelocSections.push_back(&Sec);
-      } else if (auto *S = dyn_cast<EHInputSection<ELFT>>(RelocatedSection)) {
+        break;
+      }
+      if (auto *S = dyn_cast<EhInputSection<ELFT>>(Target)) {
         if (S->RelocSection)
-          error("Multiple relocation sections to .eh_frame are not supported");
+          fatal(
+              getFilename(this) +
+              ": multiple relocation sections to .eh_frame are not supported");
         S->RelocSection = &Sec;
-      } else {
-        error("Relocations pointing to SHF_MERGE are not supported");
+        break;
       }
-      break;
+      fatal(getFilename(this) +
+            ": relocations pointing to SHF_MERGE are not supported");
     }
+    case SHT_ARM_ATTRIBUTES:
+      // FIXME: ARM meta-data section. At present attributes are ignored,
+      // they can be used to reason about object compatibility.
+      Sections[I] = &InputSection<ELFT>::Discarded;
+      break;
     default:
       Sections[I] = createInputSection(Sec);
     }
   }
 }
 
-template <class ELFT> InputSectionBase<ELFT> *
-ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec) {
-  ErrorOr<StringRef> NameOrErr = this->ELFObj.getSectionName(&Sec);
-  error(NameOrErr);
-  StringRef Name = *NameOrErr;
+template <class ELFT>
+InputSectionBase<ELFT> *
+elf::ObjectFile<ELFT>::getRelocTarget(const Elf_Shdr &Sec) {
+  uint32_t Idx = Sec.sh_info;
+  if (Idx >= Sections.size())
+    fatal(getFilename(this) + ": invalid relocated section index: " +
+          Twine(Idx));
+  InputSectionBase<ELFT> *Target = Sections[Idx];
+
+  // Strictly speaking, a relocation section must be included in the
+  // group of the section it relocates. However, LLVM 3.3 and earlier
+  // would fail to do so, so we gracefully handle that case.
+  if (Target == &InputSection<ELFT>::Discarded)
+    return nullptr;
+
+  if (!Target)
+    fatal(getFilename(this) + ": unsupported relocation reference");
+  return Target;
+}
+
+template <class ELFT>
+InputSectionBase<ELFT> *
+elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec) {
+  StringRef Name = check(this->ELFObj.getSectionName(&Sec));
 
   // .note.GNU-stack is a marker section to control the presence of
   // PT_GNU_STACK segment in outputs. Since the presence of the segment
@@ -246,98 +290,129 @@ ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec) {
   if (Name == ".note.GNU-stack")
     return &InputSection<ELFT>::Discarded;
 
-  // A MIPS object file has a special section that contains register
-  // usage info, which needs to be handled by the linker specially.
-  if (Config->EMachine == EM_MIPS && Name == ".reginfo") {
-    MipsReginfo = new (Alloc) MipsReginfoInputSection<ELFT>(this, &Sec);
-    return MipsReginfo;
+  if (Name == ".note.GNU-split-stack") {
+    error("objects using splitstacks are not supported");
+    return &InputSection<ELFT>::Discarded;
   }
 
-  if (Name == ".eh_frame")
-    return new (EHAlloc.Allocate()) EHInputSection<ELFT>(this, &Sec);
-  if (shouldMerge<ELFT>(Sec))
+  if (Config->StripDebug && Name.startswith(".debug"))
+    return &InputSection<ELFT>::Discarded;
+
+  // A MIPS object file has a special sections that contain register
+  // usage info, which need to be handled by the linker specially.
+  if (Config->EMachine == EM_MIPS) {
+    if (Name == ".reginfo") {
+      MipsReginfo.reset(new MipsReginfoInputSection<ELFT>(this, &Sec));
+      return MipsReginfo.get();
+    }
+    if (Name == ".MIPS.options") {
+      MipsOptions.reset(new MipsOptionsInputSection<ELFT>(this, &Sec));
+      return MipsOptions.get();
+    }
+  }
+
+  // The linker merges EH (exception handling) frames and creates a
+  // .eh_frame_hdr section for runtime. So we handle them with a special
+  // class. For relocatable outputs, they are just passed through.
+  if (Name == ".eh_frame" && !Config->Relocatable)
+    return new (EHAlloc.Allocate()) EhInputSection<ELFT>(this, &Sec);
+
+  if (shouldMerge(Sec))
     return new (MAlloc.Allocate()) MergeInputSection<ELFT>(this, &Sec);
-  return new (Alloc) InputSection<ELFT>(this, &Sec);
+  return new (IAlloc.Allocate()) InputSection<ELFT>(this, &Sec);
 }
 
-template <class ELFT> void ObjectFile<ELFT>::initializeSymbols() {
+template <class ELFT> void elf::ObjectFile<ELFT>::initializeSymbols() {
   this->initStringTable();
-  Elf_Sym_Range Syms = this->getNonLocalSymbols();
+  Elf_Sym_Range Syms = this->getElfSymbols(false);
   uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
   SymbolBodies.reserve(NumSymbols);
   for (const Elf_Sym &Sym : Syms)
-    SymbolBodies.push_back(createSymbolBody(this->StringTable, &Sym));
+    SymbolBodies.push_back(createSymbolBody(&Sym));
 }
 
 template <class ELFT>
 InputSectionBase<ELFT> *
-ObjectFile<ELFT>::getSection(const Elf_Sym &Sym) const {
+elf::ObjectFile<ELFT>::getSection(const Elf_Sym &Sym) const {
   uint32_t Index = this->getSectionIndex(Sym);
   if (Index == 0)
     return nullptr;
   if (Index >= Sections.size() || !Sections[Index])
-    error("Invalid section index");
-  return Sections[Index];
+    fatal(getFilename(this) + ": invalid section index: " + Twine(Index));
+  InputSectionBase<ELFT> *S = Sections[Index];
+  if (S == &InputSectionBase<ELFT>::Discarded)
+    return S;
+  return S->Repl;
 }
 
 template <class ELFT>
-SymbolBody *ObjectFile<ELFT>::createSymbolBody(StringRef StringTable,
-                                                     const Elf_Sym *Sym) {
-  ErrorOr<StringRef> NameOrErr = Sym->getName(StringTable);
-  error(NameOrErr);
-  StringRef Name = *NameOrErr;
+SymbolBody *elf::ObjectFile<ELFT>::createSymbolBody(const Elf_Sym *Sym) {
+  int Binding = Sym->getBinding();
+  InputSectionBase<ELFT> *Sec = getSection(*Sym);
+  if (Binding == STB_LOCAL) {
+    if (Sym->st_shndx == SHN_UNDEF)
+      return new (this->Alloc)
+          Undefined(Sym->st_name, Sym->st_other, Sym->getType(), this);
+    return new (this->Alloc) DefinedRegular<ELFT>(*Sym, Sec);
+  }
+
+  StringRef Name = check(Sym->getName(this->StringTable));
 
   switch (Sym->st_shndx) {
   case SHN_UNDEF:
-    return new (Alloc) UndefinedElf<ELFT>(Name, *Sym);
+    return elf::Symtab<ELFT>::X
+        ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
+                       /*CanOmitFromDynSym*/ false, this)
+        ->body();
   case SHN_COMMON:
-    return new (Alloc) DefinedCommon(Name, Sym->st_size, Sym->st_value,
-                                     Sym->getBinding() == llvm::ELF::STB_WEAK,
-                                     Sym->getVisibility());
+    return elf::Symtab<ELFT>::X
+        ->addCommon(Name, Sym->st_size, Sym->st_value, Binding, Sym->st_other,
+                    Sym->getType(), this)
+        ->body();
   }
 
-  switch (Sym->getBinding()) {
+  switch (Binding) {
   default:
-    error("unexpected binding");
+    fatal(getFilename(this) + ": unexpected binding: " + Twine(Binding));
   case STB_GLOBAL:
   case STB_WEAK:
-  case STB_GNU_UNIQUE: {
-    InputSectionBase<ELFT> *Sec = getSection(*Sym);
+  case STB_GNU_UNIQUE:
     if (Sec == &InputSection<ELFT>::Discarded)
-      return new (Alloc) UndefinedElf<ELFT>(Name, *Sym);
-    return new (Alloc) DefinedRegular<ELFT>(Name, *Sym, Sec);
-  }
+      return elf::Symtab<ELFT>::X
+          ->addUndefined(Name, Binding, Sym->st_other, Sym->getType(),
+                         /*CanOmitFromDynSym*/ false, this)
+          ->body();
+    return elf::Symtab<ELFT>::X->addRegular(Name, *Sym, Sec)->body();
   }
 }
 
-void ArchiveFile::parse() {
-  ErrorOr<std::unique_ptr<Archive>> FileOrErr = Archive::create(MB);
-  error(FileOrErr, "Failed to parse archive");
-  File = std::move(*FileOrErr);
-
-  // Allocate a buffer for Lazy objects.
-  size_t NumSyms = File->getNumberOfSymbols();
-  LazySymbols.reserve(NumSyms);
+template <class ELFT> void ArchiveFile::parse() {
+  File = check(Archive::create(MB), "failed to parse archive");
 
   // Read the symbol table to construct Lazy objects.
   for (const Archive::Symbol &Sym : File->symbols())
-    LazySymbols.emplace_back(this, Sym);
+    Symtab<ELFT>::X->addLazyArchive(this, Sym);
 }
 
 // Returns a buffer pointing to a member file containing a given symbol.
 MemoryBufferRef ArchiveFile::getMember(const Archive::Symbol *Sym) {
-  ErrorOr<Archive::Child> COrErr = Sym->getMember();
-  error(COrErr, "Could not get the member for symbol " + Sym->getName());
-  const Archive::Child &C = *COrErr;
+  Archive::Child C =
+      check(Sym->getMember(),
+            "could not get the member for symbol " + Sym->getName());
 
   if (!Seen.insert(C.getChildOffset()).second)
     return MemoryBufferRef();
 
-  ErrorOr<MemoryBufferRef> RefOrErr = C.getMemoryBufferRef();
-  if (!RefOrErr)
-    error(RefOrErr, "Could not get the buffer for the member defining symbol " +
-          Sym->getName());
-  return *RefOrErr;
+  MemoryBufferRef Ret =
+      check(C.getMemoryBufferRef(),
+            "could not get the buffer for the member defining symbol " +
+                Sym->getName());
+
+  if (C.getParent()->isThin() && Driver->Cpio)
+    Driver->Cpio->append(relativeToRoot(check(C.getFullName())),
+                         Ret.getBuffer());
+
+  return Ret;
 }
 
 template <class ELFT>
@@ -345,21 +420,19 @@ SharedFile<ELFT>::SharedFile(MemoryBufferRef M)
     : ELFFileBase<ELFT>(Base::SharedKind, M), AsNeeded(Config->AsNeeded) {}
 
 template <class ELFT>
-const typename ELFFile<ELFT>::Elf_Shdr *
+const typename ELFT::Shdr *
 SharedFile<ELFT>::getSection(const Elf_Sym &Sym) const {
   uint32_t Index = this->getSectionIndex(Sym);
   if (Index == 0)
     return nullptr;
-  ErrorOr<const Elf_Shdr *> Ret = this->ELFObj.getSection(Index);
-  error(Ret);
-  return *Ret;
+  return check(this->ELFObj.getSection(Index));
 }
 
 // Partially parse the shared object file so that we can call
 // getSoName on this object.
 template <class ELFT> void SharedFile<ELFT>::parseSoName() {
-  typedef typename ELFFile<ELFT>::Elf_Dyn Elf_Dyn;
-  typedef typename ELFFile<ELFT>::uintX_t uintX_t;
+  typedef typename ELFT::Dyn Elf_Dyn;
+  typedef typename ELFT::uint uintX_t;
   const Elf_Shdr *DynamicSec = nullptr;
 
   const ELFFile<ELFT> Obj = this->ELFObj;
@@ -373,12 +446,15 @@ template <class ELFT> void SharedFile<ELFT>::parseSoName() {
     case SHT_DYNAMIC:
       DynamicSec = &Sec;
       break;
-    case SHT_SYMTAB_SHNDX: {
-      ErrorOr<ArrayRef<Elf_Word>> ErrorOrTable = Obj.getSHNDXTable(Sec);
-      error(ErrorOrTable);
-      this->SymtabSHNDX = *ErrorOrTable;
+    case SHT_SYMTAB_SHNDX:
+      this->SymtabSHNDX = check(Obj.getSHNDXTable(Sec));
+      break;
+    case SHT_GNU_versym:
+      this->VersymSec = &Sec;
+      break;
+    case SHT_GNU_verdef:
+      this->VerdefSec = &Sec;
       break;
-    }
     }
   }
 
@@ -395,83 +471,358 @@ template <class ELFT> void SharedFile<ELFT>::parseSoName() {
     if (Dyn.d_tag == DT_SONAME) {
       uintX_t Val = Dyn.getVal();
       if (Val >= this->StringTable.size())
-        error("Invalid DT_SONAME entry");
+        fatal(getFilename(this) + ": invalid DT_SONAME entry");
       SoName = StringRef(this->StringTable.data() + Val);
       return;
     }
   }
 }
 
+// Parse the version definitions in the object file if present. Returns a vector
+// whose nth element contains a pointer to the Elf_Verdef for version identifier
+// n. Version identifiers that are not definitions map to nullptr. The array
+// always has at least length 1.
+template <class ELFT>
+std::vector<const typename ELFT::Verdef *>
+SharedFile<ELFT>::parseVerdefs(const Elf_Versym *&Versym) {
+  std::vector<const Elf_Verdef *> Verdefs(1);
+  // We only need to process symbol versions for this DSO if it has both a
+  // versym and a verdef section, which indicates that the DSO contains symbol
+  // version definitions.
+  if (!VersymSec || !VerdefSec)
+    return Verdefs;
+
+  // The location of the first global versym entry.
+  Versym = reinterpret_cast<const Elf_Versym *>(this->ELFObj.base() +
+                                                VersymSec->sh_offset) +
+           this->Symtab->sh_info;
+
+  // We cannot determine the largest verdef identifier without inspecting
+  // every Elf_Verdef, but both bfd and gold assign verdef identifiers
+  // sequentially starting from 1, so we predict that the largest identifier
+  // will be VerdefCount.
+  unsigned VerdefCount = VerdefSec->sh_info;
+  Verdefs.resize(VerdefCount + 1);
+
+  // Build the Verdefs array by following the chain of Elf_Verdef objects
+  // from the start of the .gnu.version_d section.
+  const uint8_t *Verdef = this->ELFObj.base() + VerdefSec->sh_offset;
+  for (unsigned I = 0; I != VerdefCount; ++I) {
+    auto *CurVerdef = reinterpret_cast<const Elf_Verdef *>(Verdef);
+    Verdef += CurVerdef->vd_next;
+    unsigned VerdefIndex = CurVerdef->vd_ndx;
+    if (Verdefs.size() <= VerdefIndex)
+      Verdefs.resize(VerdefIndex + 1);
+    Verdefs[VerdefIndex] = CurVerdef;
+  }
+
+  return Verdefs;
+}
+
 // Fully parse the shared object file. This must be called after parseSoName().
 template <class ELFT> void SharedFile<ELFT>::parseRest() {
-  Elf_Sym_Range Syms = this->getNonLocalSymbols();
-  uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
-  SymbolBodies.reserve(NumSymbols);
+  // Create mapping from version identifiers to Elf_Verdef entries.
+  const Elf_Versym *Versym = nullptr;
+  std::vector<const Elf_Verdef *> Verdefs = parseVerdefs(Versym);
+
+  Elf_Sym_Range Syms = this->getElfSymbols(true);
   for (const Elf_Sym &Sym : Syms) {
-    ErrorOr<StringRef> NameOrErr = Sym.getName(this->StringTable);
-    error(NameOrErr.getError());
-    StringRef Name = *NameOrErr;
+    unsigned VersymIndex = 0;
+    if (Versym) {
+      VersymIndex = Versym->vs_index;
+      ++Versym;
+    }
 
-    if (Sym.isUndefined())
+    StringRef Name = check(Sym.getName(this->StringTable));
+    if (Sym.isUndefined()) {
       Undefs.push_back(Name);
-    else
-      SymbolBodies.emplace_back(this, Name, Sym);
+      continue;
+    }
+
+    if (Versym) {
+      // Ignore local symbols and non-default versions.
+      if (VersymIndex == VER_NDX_LOCAL || (VersymIndex & VERSYM_HIDDEN))
+        continue;
+    }
+
+    const Elf_Verdef *V =
+        VersymIndex == VER_NDX_GLOBAL ? nullptr : Verdefs[VersymIndex];
+    elf::Symtab<ELFT>::X->addShared(this, Name, Sym, V);
   }
 }
 
-template <typename T>
-static std::unique_ptr<InputFile> createELFFileAux(MemoryBufferRef MB) {
-  std::unique_ptr<T> Ret = llvm::make_unique<T>(MB);
+static ELFKind getELFKind(MemoryBufferRef MB) {
+  std::string TripleStr = getBitcodeTargetTriple(MB, Driver->Context);
+  Triple TheTriple(TripleStr);
+  bool Is64Bits = TheTriple.isArch64Bit();
+  if (TheTriple.isLittleEndian())
+    return Is64Bits ? ELF64LEKind : ELF32LEKind;
+  return Is64Bits ? ELF64BEKind : ELF32BEKind;
+}
 
-  if (!Config->FirstElf)
-    Config->FirstElf = Ret.get();
+static uint8_t getMachineKind(MemoryBufferRef MB) {
+  std::string TripleStr = getBitcodeTargetTriple(MB, Driver->Context);
+  switch (Triple(TripleStr).getArch()) {
+  case Triple::aarch64:
+    return EM_AARCH64;
+  case Triple::arm:
+    return EM_ARM;
+  case Triple::mips:
+  case Triple::mipsel:
+  case Triple::mips64:
+  case Triple::mips64el:
+    return EM_MIPS;
+  case Triple::ppc:
+    return EM_PPC;
+  case Triple::ppc64:
+    return EM_PPC64;
+  case Triple::x86:
+    return EM_386;
+  case Triple::x86_64:
+    return EM_X86_64;
+  default:
+    fatal(MB.getBufferIdentifier() +
+          ": could not infer e_machine from bitcode target triple " +
+          TripleStr);
+  }
+}
+
+BitcodeFile::BitcodeFile(MemoryBufferRef MB) : InputFile(BitcodeKind, MB) {
+  EKind = getELFKind(MB);
+  EMachine = getMachineKind(MB);
+}
 
-  if (Config->EKind == ELFNoneKind) {
-    Config->EKind = Ret->getELFKind();
-    Config->EMachine = Ret->getEMachine();
+static uint8_t getGvVisibility(const GlobalValue *GV) {
+  switch (GV->getVisibility()) {
+  case GlobalValue::DefaultVisibility:
+    return STV_DEFAULT;
+  case GlobalValue::HiddenVisibility:
+    return STV_HIDDEN;
+  case GlobalValue::ProtectedVisibility:
+    return STV_PROTECTED;
   }
+  llvm_unreachable("unknown visibility");
+}
+
+template <class ELFT>
+Symbol *BitcodeFile::createSymbol(const DenseSet<const Comdat *> &KeptComdats,
+                                  const IRObjectFile &Obj,
+                                  const BasicSymbolRef &Sym) {
+  const GlobalValue *GV = Obj.getSymbolGV(Sym.getRawDataRefImpl());
+
+  SmallString<64> Name;
+  raw_svector_ostream OS(Name);
+  Sym.printName(OS);
+  StringRef NameRef = Saver.save(StringRef(Name));
+
+  uint32_t Flags = Sym.getFlags();
+  bool IsWeak = Flags & BasicSymbolRef::SF_Weak;
+  uint32_t Binding = IsWeak ? STB_WEAK : STB_GLOBAL;
+
+  uint8_t Type = STT_NOTYPE;
+  bool CanOmitFromDynSym = false;
+  // FIXME: Expose a thread-local flag for module asm symbols.
+  if (GV) {
+    if (GV->isThreadLocal())
+      Type = STT_TLS;
+    CanOmitFromDynSym = canBeOmittedFromSymbolTable(GV);
+  }
+
+  uint8_t Visibility;
+  if (GV)
+    Visibility = getGvVisibility(GV);
+  else
+    // FIXME: Set SF_Hidden flag correctly for module asm symbols, and expose
+    // protected visibility.
+    Visibility = STV_DEFAULT;
+
+  if (GV)
+    if (const Comdat *C = GV->getComdat())
+      if (!KeptComdats.count(C))
+        return Symtab<ELFT>::X->addUndefined(NameRef, Binding, Visibility, Type,
+                                             CanOmitFromDynSym, this);
+
+  const Module &M = Obj.getModule();
+  if (Flags & BasicSymbolRef::SF_Undefined)
+    return Symtab<ELFT>::X->addUndefined(NameRef, Binding, Visibility, Type,
+                                         CanOmitFromDynSym, this);
+  if (Flags & BasicSymbolRef::SF_Common) {
+    // FIXME: Set SF_Common flag correctly for module asm symbols, and expose
+    // size and alignment.
+    assert(GV);
+    const DataLayout &DL = M.getDataLayout();
+    uint64_t Size = DL.getTypeAllocSize(GV->getValueType());
+    return Symtab<ELFT>::X->addCommon(NameRef, Size, GV->getAlignment(),
+                                      Binding, Visibility, STT_OBJECT, this);
+  }
+  return Symtab<ELFT>::X->addBitcode(NameRef, IsWeak, Visibility, Type,
+                                     CanOmitFromDynSym, this);
+}
 
-  return std::move(Ret);
+bool BitcodeFile::shouldSkip(uint32_t Flags) {
+  return !(Flags & BasicSymbolRef::SF_Global) ||
+         (Flags & BasicSymbolRef::SF_FormatSpecific);
+}
+
+template <class ELFT>
+void BitcodeFile::parse(DenseSet<StringRef> &ComdatGroups) {
+  Obj = check(IRObjectFile::create(MB, Driver->Context));
+  const Module &M = Obj->getModule();
+
+  DenseSet<const Comdat *> KeptComdats;
+  for (const auto &P : M.getComdatSymbolTable()) {
+    StringRef N = Saver.save(P.first());
+    if (ComdatGroups.insert(N).second)
+      KeptComdats.insert(&P.second);
+  }
+
+  for (const BasicSymbolRef &Sym : Obj->symbols())
+    if (!shouldSkip(Sym.getFlags()))
+      Symbols.push_back(createSymbol<ELFT>(KeptComdats, *Obj, Sym));
 }
 
 template <template <class> class T>
 static std::unique_ptr<InputFile> createELFFile(MemoryBufferRef MB) {
-  std::pair<unsigned char, unsigned char> Type = getElfArchType(MB.getBuffer());
-  if (Type.second != ELF::ELFDATA2LSB && Type.second != ELF::ELFDATA2MSB)
-    error("Invalid data encoding: " + MB.getBufferIdentifier());
-
-  if (Type.first == ELF::ELFCLASS32) {
-    if (Type.second == ELF::ELFDATA2LSB)
-      return createELFFileAux<T<ELF32LE>>(MB);
-    return createELFFileAux<T<ELF32BE>>(MB);
-  }
-  if (Type.first == ELF::ELFCLASS64) {
-    if (Type.second == ELF::ELFDATA2LSB)
-      return createELFFileAux<T<ELF64LE>>(MB);
-    return createELFFileAux<T<ELF64BE>>(MB);
-  }
-  error("Invalid file class: " + MB.getBufferIdentifier());
+  unsigned char Size;
+  unsigned char Endian;
+  std::tie(Size, Endian) = getElfArchType(MB.getBuffer());
+  if (Endian != ELFDATA2LSB && Endian != ELFDATA2MSB)
+    fatal("invalid data encoding: " + MB.getBufferIdentifier());
+
+  std::unique_ptr<InputFile> Obj;
+  if (Size == ELFCLASS32 && Endian == ELFDATA2LSB)
+    Obj.reset(new T<ELF32LE>(MB));
+  else if (Size == ELFCLASS32 && Endian == ELFDATA2MSB)
+    Obj.reset(new T<ELF32BE>(MB));
+  else if (Size == ELFCLASS64 && Endian == ELFDATA2LSB)
+    Obj.reset(new T<ELF64LE>(MB));
+  else if (Size == ELFCLASS64 && Endian == ELFDATA2MSB)
+    Obj.reset(new T<ELF64BE>(MB));
+  else
+    fatal("invalid file class: " + MB.getBufferIdentifier());
+
+  if (!Config->FirstElf)
+    Config->FirstElf = Obj.get();
+  return Obj;
+}
+
+static bool isBitcode(MemoryBufferRef MB) {
+  using namespace sys::fs;
+  return identify_magic(MB.getBuffer()) == file_magic::bitcode;
 }
 
-std::unique_ptr<InputFile> elf2::createObjectFile(MemoryBufferRef MB) {
-  return createELFFile<ObjectFile>(MB);
+std::unique_ptr<InputFile> elf::createObjectFile(MemoryBufferRef MB,
+                                                 StringRef ArchiveName) {
+  std::unique_ptr<InputFile> F;
+  if (isBitcode(MB))
+    F.reset(new BitcodeFile(MB));
+  else
+    F = createELFFile<ObjectFile>(MB);
+  F->ArchiveName = ArchiveName;
+  return F;
 }
 
-std::unique_ptr<InputFile> elf2::createSharedFile(MemoryBufferRef MB) {
+std::unique_ptr<InputFile> elf::createSharedFile(MemoryBufferRef MB) {
   return createELFFile<SharedFile>(MB);
 }
 
-template class elf2::ELFFileBase<ELF32LE>;
-template class elf2::ELFFileBase<ELF32BE>;
-template class elf2::ELFFileBase<ELF64LE>;
-template class elf2::ELFFileBase<ELF64BE>;
+MemoryBufferRef LazyObjectFile::getBuffer() {
+  if (Seen)
+    return MemoryBufferRef();
+  Seen = true;
+  return MB;
+}
 
-template class elf2::ObjectFile<ELF32LE>;
-template class elf2::ObjectFile<ELF32BE>;
-template class elf2::ObjectFile<ELF64LE>;
-template class elf2::ObjectFile<ELF64BE>;
+template <class ELFT>
+void LazyObjectFile::parse() {
+  for (StringRef Sym : getSymbols())
+    Symtab<ELFT>::X->addLazyObject(Sym, *this);
+}
+
+template <class ELFT> std::vector<StringRef> LazyObjectFile::getElfSymbols() {
+  typedef typename ELFT::Shdr Elf_Shdr;
+  typedef typename ELFT::Sym Elf_Sym;
+  typedef typename ELFT::SymRange Elf_Sym_Range;
+
+  const ELFFile<ELFT> Obj = createELFObj<ELFT>(this->MB);
+  for (const Elf_Shdr &Sec : Obj.sections()) {
+    if (Sec.sh_type != SHT_SYMTAB)
+      continue;
+    Elf_Sym_Range Syms = Obj.symbols(&Sec);
+    uint32_t FirstNonLocal = Sec.sh_info;
+    StringRef StringTable = check(Obj.getStringTableForSymtab(Sec));
+    std::vector<StringRef> V;
+    for (const Elf_Sym &Sym : Syms.slice(FirstNonLocal))
+      if (Sym.st_shndx != SHN_UNDEF)
+        V.push_back(check(Sym.getName(StringTable)));
+    return V;
+  }
+  return {};
+}
+
+std::vector<StringRef> LazyObjectFile::getBitcodeSymbols() {
+  LLVMContext Context;
+  std::unique_ptr<IRObjectFile> Obj =
+      check(IRObjectFile::create(this->MB, Context));
+  std::vector<StringRef> V;
+  for (const BasicSymbolRef &Sym : Obj->symbols()) {
+    uint32_t Flags = Sym.getFlags();
+    if (BitcodeFile::shouldSkip(Flags))
+      continue;
+    if (Flags & BasicSymbolRef::SF_Undefined)
+      continue;
+    SmallString<64> Name;
+    raw_svector_ostream OS(Name);
+    Sym.printName(OS);
+    V.push_back(Saver.save(StringRef(Name)));
+  }
+  return V;
+}
+
+// Returns a vector of globally-visible defined symbol names.
+std::vector<StringRef> LazyObjectFile::getSymbols() {
+  if (isBitcode(this->MB))
+    return getBitcodeSymbols();
+
+  unsigned char Size;
+  unsigned char Endian;
+  std::tie(Size, Endian) = getElfArchType(this->MB.getBuffer());
+  if (Size == ELFCLASS32) {
+    if (Endian == ELFDATA2LSB)
+      return getElfSymbols<ELF32LE>();
+    return getElfSymbols<ELF32BE>();
+  }
+  if (Endian == ELFDATA2LSB)
+    return getElfSymbols<ELF64LE>();
+  return getElfSymbols<ELF64BE>();
+}
 
-template class elf2::SharedFile<ELF32LE>;
-template class elf2::SharedFile<ELF32BE>;
-template class elf2::SharedFile<ELF64LE>;
-template class elf2::SharedFile<ELF64BE>;
+template void ArchiveFile::parse<ELF32LE>();
+template void ArchiveFile::parse<ELF32BE>();
+template void ArchiveFile::parse<ELF64LE>();
+template void ArchiveFile::parse<ELF64BE>();
+
+template void BitcodeFile::parse<ELF32LE>(DenseSet<StringRef> &);
+template void BitcodeFile::parse<ELF32BE>(DenseSet<StringRef> &);
+template void BitcodeFile::parse<ELF64LE>(DenseSet<StringRef> &);
+template void BitcodeFile::parse<ELF64BE>(DenseSet<StringRef> &);
+
+template void LazyObjectFile::parse<ELF32LE>();
+template void LazyObjectFile::parse<ELF32BE>();
+template void LazyObjectFile::parse<ELF64LE>();
+template void LazyObjectFile::parse<ELF64BE>();
+
+template class elf::ELFFileBase<ELF32LE>;
+template class elf::ELFFileBase<ELF32BE>;
+template class elf::ELFFileBase<ELF64LE>;
+template class elf::ELFFileBase<ELF64BE>;
+
+template class elf::ObjectFile<ELF32LE>;
+template class elf::ObjectFile<ELF32BE>;
+template class elf::ObjectFile<ELF64LE>;
+template class elf::ObjectFile<ELF64BE>;
+
+template class elf::SharedFile<ELF32LE>;
+template class elf::SharedFile<ELF32BE>;
+template class elf::SharedFile<ELF64LE>;
+template class elf::SharedFile<ELF64BE>;
diff --git a/ELF/InputFiles.h b/ELF/InputFiles.h
index 45d403c0125c..79cb751494b3 100644
--- a/ELF/InputFiles.h
+++ b/ELF/InputFiles.h
@@ -18,11 +18,16 @@
 #include "lld/Core/LLVM.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/IR/Comdat.h"
 #include "llvm/Object/Archive.h"
 #include "llvm/Object/ELF.h"
+#include "llvm/Object/IRObjectFile.h"
+#include "llvm/Support/StringSaver.h"
+
+#include <map>
 
 namespace lld {
-namespace elf2 {
+namespace elf {
 
 using llvm::object::Archive;
 
@@ -33,25 +38,45 @@ class SymbolBody;
 // The root class of input files.
 class InputFile {
 public:
-  enum Kind { ObjectKind, SharedKind, ArchiveKind };
+  enum Kind {
+    ObjectKind,
+    SharedKind,
+    LazyObjectKind,
+    ArchiveKind,
+    BitcodeKind,
+  };
+
   Kind kind() const { return FileKind; }
 
   StringRef getName() const { return MB.getBufferIdentifier(); }
+  MemoryBufferRef MB;
+
+  // Filename of .a which contained this file. If this file was
+  // not in an archive file, it is the empty string. We use this
+  // string for creating error messages.
+  StringRef ArchiveName;
+
+  // If this is an architecture-specific file, the following members
+  // have ELF type (i.e. ELF{32,64}{LE,BE}) and target machine type.
+  ELFKind EKind = ELFNoneKind;
+  uint16_t EMachine = llvm::ELF::EM_NONE;
 
 protected:
   InputFile(Kind K, MemoryBufferRef M) : MB(M), FileKind(K) {}
-  MemoryBufferRef MB;
 
 private:
   const Kind FileKind;
 };
 
+// Returns "(internal)", "foo.a(bar.o)" or "baz.o".
+std::string getFilename(const InputFile *F);
+
 template <typename ELFT> class ELFFileBase : public InputFile {
 public:
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Word Elf_Word;
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym_Range Elf_Sym_Range;
+  typedef typename ELFT::Shdr Elf_Shdr;
+  typedef typename ELFT::Sym Elf_Sym;
+  typedef typename ELFT::Word Elf_Word;
+  typedef typename ELFT::SymRange Elf_Sym_Range;
 
   ELFFileBase(Kind K, MemoryBufferRef M);
   static bool classof(const InputFile *F) {
@@ -59,11 +84,9 @@ public:
     return K == ObjectKind || K == SharedKind;
   }
 
-  static ELFKind getELFKind();
   const llvm::object::ELFFile<ELFT> &getObj() const { return ELFObj; }
   llvm::object::ELFFile<ELFT> &getObj() { return ELFObj; }
 
-  uint16_t getEMachine() const { return getObj().getHeader()->e_machine; }
   uint8_t getOSABI() const {
     return getObj().getHeader()->e_ident[llvm::ELF::EI_OSABI];
   }
@@ -72,39 +95,36 @@ public:
 
   uint32_t getSectionIndex(const Elf_Sym &Sym) const;
 
+  Elf_Sym_Range getElfSymbols(bool OnlyGlobals);
+
 protected:
   llvm::object::ELFFile<ELFT> ELFObj;
   const Elf_Shdr *Symtab = nullptr;
   ArrayRef<Elf_Word> SymtabSHNDX;
   StringRef StringTable;
   void initStringTable();
-  Elf_Sym_Range getNonLocalSymbols();
-  Elf_Sym_Range getSymbolsHelper(bool);
 };
 
 // .o file.
 template <class ELFT> class ObjectFile : public ELFFileBase<ELFT> {
   typedef ELFFileBase<ELFT> Base;
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym Elf_Sym;
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Shdr Elf_Shdr;
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Sym_Range Elf_Sym_Range;
-  typedef typename llvm::object::ELFFile<ELFT>::Elf_Word Elf_Word;
-  typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
-
-  // uint32 in ELFT's byte order
-  typedef llvm::support::detail::packed_endian_specific_integral<
-      uint32_t, ELFT::TargetEndianness, 2>
-      uint32_X;
+  typedef typename ELFT::Sym Elf_Sym;
+  typedef typename ELFT::Shdr Elf_Shdr;
+  typedef typename ELFT::SymRange Elf_Sym_Range;
+  typedef typename ELFT::Word Elf_Word;
+  typedef typename ELFT::uint uintX_t;
 
   StringRef getShtGroupSignature(const Elf_Shdr &Sec);
-  ArrayRef<uint32_X> getShtGroupEntries(const Elf_Shdr &Sec);
+  ArrayRef<Elf_Word> getShtGroupEntries(const Elf_Shdr &Sec);
 
 public:
   static bool classof(const InputFile *F) {
     return F->kind() == Base::ObjectKind;
   }
 
-  ArrayRef<SymbolBody *> getSymbols() { return SymbolBodies; }
+  ArrayRef<SymbolBody *> getSymbols();
+  ArrayRef<SymbolBody *> getLocalSymbols();
+  ArrayRef<SymbolBody *> getNonLocalSymbols();
 
   explicit ObjectFile(MemoryBufferRef M);
   void parse(llvm::DenseSet<StringRef> &ComdatGroups);
@@ -112,15 +132,14 @@ public:
   ArrayRef<InputSectionBase<ELFT> *> getSections() const { return Sections; }
   InputSectionBase<ELFT> *getSection(const Elf_Sym &Sym) const;
 
-  SymbolBody *getSymbolBody(uint32_t SymbolIndex) const {
-    uint32_t FirstNonLocal = this->Symtab->sh_info;
-    if (SymbolIndex < FirstNonLocal)
-      return nullptr;
-    return SymbolBodies[SymbolIndex - FirstNonLocal];
+  SymbolBody &getSymbolBody(uint32_t SymbolIndex) const {
+    return *SymbolBodies[SymbolIndex];
   }
 
-  Elf_Sym_Range getLocalSymbols();
-  const Elf_Sym *getLocalSymbol(uintX_t SymIndex);
+  template <typename RelT> SymbolBody &getRelocTargetSym(const RelT &Rel) const {
+    uint32_t SymIndex = Rel.getSymbol(Config->Mips64EL);
+    return getSymbolBody(SymIndex);
+  }
 
   const Elf_Shdr *getSymbolTable() const { return this->Symtab; };
 
@@ -129,12 +148,22 @@ public:
   // R_MIPS_GPREL16 / R_MIPS_GPREL32 relocations.
   uint32_t getMipsGp0() const;
 
+  // The number is the offset in the string table. It will be used as the
+  // st_name of the symbol.
+  std::vector<std::pair<const DefinedRegular<ELFT> *, unsigned>> KeptLocalSyms;
+
+  // SymbolBodies and Thunks for sections in this file are allocated
+  // using this buffer.
+  llvm::BumpPtrAllocator Alloc;
+
 private:
   void initializeSections(llvm::DenseSet<StringRef> &ComdatGroups);
   void initializeSymbols();
+  InputSectionBase<ELFT> *getRelocTarget(const Elf_Shdr &Sec);
   InputSectionBase<ELFT> *createInputSection(const Elf_Shdr &Sec);
 
-  SymbolBody *createSymbolBody(StringRef StringTable, const Elf_Sym *Sym);
+  bool shouldMerge(const Elf_Shdr &Sec);
+  SymbolBody *createSymbolBody(const Elf_Sym *Sym);
 
   // List of all sections defined by this file.
   std::vector<InputSectionBase<ELFT> *> Sections;
@@ -143,49 +172,97 @@ private:
   std::vector<SymbolBody *> SymbolBodies;
 
   // MIPS .reginfo section defined by this file.
-  MipsReginfoInputSection<ELFT> *MipsReginfo = nullptr;
+  std::unique_ptr<MipsReginfoInputSection<ELFT>> MipsReginfo;
+  // MIPS .MIPS.options section defined by this file.
+  std::unique_ptr<MipsOptionsInputSection<ELFT>> MipsOptions;
 
-  llvm::BumpPtrAllocator Alloc;
+  llvm::SpecificBumpPtrAllocator<InputSection<ELFT>> IAlloc;
   llvm::SpecificBumpPtrAllocator<MergeInputSection<ELFT>> MAlloc;
-  llvm::SpecificBumpPtrAllocator<EHInputSection<ELFT>> EHAlloc;
+  llvm::SpecificBumpPtrAllocator<EhInputSection<ELFT>> EHAlloc;
+};
+
+// LazyObjectFile is analogous to ArchiveFile in the sense that
+// the file contains lazy symbols. The difference is that
+// LazyObjectFile wraps a single file instead of multiple files.
+//
+// This class is used for --start-lib and --end-lib options which
+// instruct the linker to link object files between them with the
+// archive file semantics.
+class LazyObjectFile : public InputFile {
+public:
+  explicit LazyObjectFile(MemoryBufferRef M) : InputFile(LazyObjectKind, M) {}
+
+  static bool classof(const InputFile *F) {
+    return F->kind() == LazyObjectKind;
+  }
+
+  template <class ELFT> void parse();
+  MemoryBufferRef getBuffer();
+
+private:
+  std::vector<StringRef> getSymbols();