diff --git a/COFF/Chunks.cpp b/COFF/Chunks.cpp
index 2e49f417a20..791d96ee92a 100644
--- a/COFF/Chunks.cpp
+++ b/COFF/Chunks.cpp
@@ -326,41 +326,38 @@ void SEHTableChunk::writeTo(uint8_t *Buf) const {
 // usually loaded to that address. However, if there's already another
 // DLL that overlaps, the loader has to relocate it. To do that, DLLs
 // contain .reloc sections which contain offsets that need to be fixed
-// up at runtime. If the loader find that a DLL cannot be loaded to its
+// up at runtime. If the loader finds that a DLL cannot be loaded to its
 // desired base address, it loads it to somewhere else, and add <actual
 // base address> - <desired base address> to each offset that is
-// specified by .reloc section.
+// specified by the .reloc section. In ELF terms, .reloc sections
+// contain relative relocations in REL format (as opposed to RELA.)
 //
-// In ELF terms, .reloc sections contain arrays of relocation offsets.
-// All these offsets in the section are implicitly R_*_RELATIVE, and
-// addends are read from section contents (so it is REL as opposed to
-// RELA).
+// This already significantly reduces the size of relocations compared
+// to ELF .rel.dyn, but Windows does more to reduce it (probably because
+// it was invented for PCs in the late '80s or early '90s.)  Offsets in
+// .reloc are grouped by page where the page size is 12 bits, and
+// offsets sharing the same page address are stored consecutively to
+// represent them with less space. This is very similar to the page
+// table which is grouped by (multiple stages of) pages.
 //
-// This already reduce the size of relocations to 1/3 compared to ELF
-// .dynrel, but Windows does more to reduce it (probably because it was
-// invented for PCs in the late '80s or early '90s.) Offsets in .reloc
-// are grouped by page where page size is 16 bits, and offsets sharing
-// the same page address are stored consecutively to represent them with
-// less space. This is a very similar to the page table which is grouped
-// by (multiple stages of) pages.
-//
-// For example, let's say we have 0x00030, 0x00500, 0x01000, 0x01100,
-// 0x20004, and 0x20008 in a .reloc section. In the section, they are
-// represented like this:
+// For example, let's say we have 0x00030, 0x00500, 0x00700, 0x00A00,
+// 0x20004, and 0x20008 in a .reloc section for x64. The uppermost 4
+// bits have a type IMAGE_REL_BASED_DIR64 or 0xA. In the section, they
+// are represented like this:
 //
 //   0x00000  -- page address (4 bytes)
 //   16       -- size of this block (4 bytes)
-//     0x0030 -- entries (2 bytes each)
-//     0x0500
-//     0x1000
-//     0x1100
+//     0xA030 -- entries (2 bytes each)
+//     0xA500
+//     0xA700
+//     0xAA00
 //   0x20000  -- page address (4 bytes)
 //   12       -- size of this block (4 bytes)
-//     0x0004 -- entries (2 bytes each)
-//     0x0008
+//     0xA004 -- entries (2 bytes each)
+//     0xA008
 //
-// Usually we have a lot of relocatinos for each page, so the number of
-// bytes for one .reloc entry is close to 2 bytes.
+// Usually we have a lot of relocations for each page, so the number of
+// bytes for one .reloc entry is close to 2 bytes on average.
 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.
diff --git a/COFF/Error.cpp b/COFF/Error.cpp
index b2c7c89bd36..166b1971e77 100644
--- a/COFF/Error.cpp
+++ b/COFF/Error.cpp
@@ -59,6 +59,7 @@ void log(const Twine &Msg) {
   if (Config->Verbose) {
     std::lock_guard<std::mutex> Lock(Mu);
     outs() << Argv0 << ": " << Msg << "\n";
+    outs().flush();
   }
 }
 
diff --git a/COFF/ICF.cpp b/COFF/ICF.cpp
index 19468c0fac5..fe59de6efa5 100644
--- a/COFF/ICF.cpp
+++ b/COFF/ICF.cpp
@@ -71,10 +71,18 @@ uint32_t ICF::getHash(SectionChunk *C) {
 }
 
 // Returns true if section S is subject of ICF.
+//
+// Microsoft's documentation
+// (https://msdn.microsoft.com/en-us/library/bxwfs976.aspx; visited April
+// 2017) says that /opt:icf folds both functions and read-only data.
+// Despite that, the MSVC linker folds only functions. We found
+// a few instances of programs that are not safe for data merging.
+// Therefore, we merge only functions just like the MSVC tool.
 bool ICF::isEligible(SectionChunk *C) {
   bool Global = C->Sym && C->Sym->isExternal();
+  bool Executable = C->getPermissions() & llvm::COFF::IMAGE_SCN_MEM_EXECUTE;
   bool Writable = C->getPermissions() & llvm::COFF::IMAGE_SCN_MEM_WRITE;
-  return C->isCOMDAT() && C->isLive() && Global && !Writable;
+  return C->isCOMDAT() && C->isLive() && Global && Executable && !Writable;
 }
 
 // Split a range into smaller ranges by recoloring sections
diff --git a/COFF/InputFiles.cpp b/COFF/InputFiles.cpp
index cb56e13014d..df3b6a032cf 100644
--- a/COFF/InputFiles.cpp
+++ b/COFF/InputFiles.cpp
@@ -327,6 +327,9 @@ void ImportFile::parse() {
 
   ImpSym = cast<DefinedImportData>(
       Symtab->addImportData(ImpName, this)->body());
+  if (Hdr->getType() == llvm::COFF::IMPORT_CONST)
+    ConstSym =
+        cast<DefinedImportData>(Symtab->addImportData(Name, this)->body());
 
   // If type is function, we need to create a thunk which jump to an
   // address pointed by the __imp_ symbol. (This allows you to call
diff --git a/COFF/InputFiles.h b/COFF/InputFiles.h
index 3078de68752..a2fd3f59ad7 100644
--- a/COFF/InputFiles.h
+++ b/COFF/InputFiles.h
@@ -167,6 +167,7 @@ public:
   static bool classof(const InputFile *F) { return F->kind() == ImportKind; }
 
   DefinedImportData *ImpSym = nullptr;
+  DefinedImportData *ConstSym = nullptr;
   DefinedImportThunk *ThunkSym = nullptr;
   std::string DLLName;
 
diff --git a/COFF/MapFile.cpp b/COFF/MapFile.cpp
index 43dd8dc3581..4e596e602fe 100644
--- a/COFF/MapFile.cpp
+++ b/COFF/MapFile.cpp
@@ -11,21 +11,21 @@
 // hierarchically the output sections, input sections, input files and
 // symbol:
 //
-// Address  Size     Align Out     In      File    Symbol
-// =================================================================
-// 00201000 00000015     4 .text
-// 00201000 0000000e     4         .text
-// 00201000 0000000e     4                 test.o
-// 0020100e 00000000     0                         local
-// 00201005 00000000     0                         f(int)
+//   Address  Size     Align Out     File    Symbol
+//   00201000 00000015     4 .text
+//   00201000 0000000e     4         test.o:(.text)
+//   0020100e 00000000     0                 local
+//   00201005 00000000     0                 f(int)
 //
 //===----------------------------------------------------------------------===//
 
 #include "MapFile.h"
 #include "Error.h"
+#include "SymbolTable.h"
 #include "Symbols.h"
 #include "Writer.h"
 
+#include "lld/Core/Parallel.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
@@ -34,72 +34,58 @@ using namespace llvm::object;
 using namespace lld;
 using namespace lld::coff;
 
-static void writeOutSecLine(raw_fd_ostream &OS, uint64_t Address, uint64_t Size,
-                            uint64_t Align, StringRef Name) {
-  OS << format("%08llx %08llx %5lld ", Address, Size, Align)
-     << left_justify(Name, 7);
+typedef DenseMap<const SectionChunk *, SmallVector<DefinedRegular *, 4>>
+    SymbolMapTy;
+
+// Print out the first three columns of a line.
+static void writeHeader(raw_ostream &OS, uint64_t Addr, uint64_t Size,
+                        uint64_t Align) {
+  OS << format("%08llx %08llx %5lld ", Addr, Size, Align);
 }
 
-static void writeInSecLine(raw_fd_ostream &OS, uint64_t Address, uint64_t Size,
-                           uint64_t Align, StringRef Name) {
-  // Pass an empty name to align the text to the correct column.
-  writeOutSecLine(OS, Address, Size, Align, "");
-  OS << ' ' << left_justify(Name, 7);
+static std::string indent(int Depth) { return std::string(Depth * 8, ' '); }
+
+// Returns a list of all symbols that we want to print out.
+static std::vector<DefinedRegular *> getSymbols() {
+  std::vector<DefinedRegular *> V;
+  for (coff::ObjectFile *File : Symtab->ObjectFiles)
+    for (SymbolBody *B : File->getSymbols())
+      if (auto *Sym = dyn_cast<DefinedRegular>(B))
+        if (Sym && !Sym->getCOFFSymbol().isSectionDefinition())
+          V.push_back(Sym);
+  return V;
 }
 
-static void writeFileLine(raw_fd_ostream &OS, uint64_t Address, uint64_t Size,
-                          uint64_t Align, StringRef Name) {
-  // Pass an empty name to align the text to the correct column.
-  writeInSecLine(OS, Address, Size, Align, "");
-  OS << ' ' << left_justify(Name, 7);
-}
+// Returns a map from sections to their symbols.
+static SymbolMapTy getSectionSyms(ArrayRef<DefinedRegular *> Syms) {
+  SymbolMapTy Ret;
+  for (DefinedRegular *S : Syms)
+    Ret[S->getChunk()].push_back(S);
 
-static void writeSymbolLine(raw_fd_ostream &OS, uint64_t Address, uint64_t Size,
-                            StringRef Name) {
-  // Pass an empty name to align the text to the correct column.
-  writeFileLine(OS, Address, Size, 0, "");
-  OS << ' ' << left_justify(Name, 7);
-}
-
-static void writeSectionChunk(raw_fd_ostream &OS, const SectionChunk *SC,
-                              StringRef &PrevName) {
-  StringRef Name = SC->getSectionName();
-  if (Name != PrevName) {
-    writeInSecLine(OS, SC->getRVA(), SC->getSize(), SC->getAlign(), Name);
-    OS << '\n';
-    PrevName = Name;
-  }
-  coff::ObjectFile *File = SC->File;
-  if (!File)
-    return;
-  writeFileLine(OS, SC->getRVA(), SC->getSize(), SC->getAlign(),
-                toString(File));
-  OS << '\n';
-  ArrayRef<SymbolBody *> Syms = File->getSymbols();
-  for (SymbolBody *Sym : Syms) {
-    auto *DR = dyn_cast<DefinedRegular>(Sym);
-    if (!DR || DR->getChunk() != SC ||
-        DR->getCOFFSymbol().isSectionDefinition())
-      continue;
-    writeSymbolLine(OS, DR->getRVA(), SC->getSize(), toString(*Sym));
-    OS << '\n';
+  // Sort symbols by address.
+  for (auto &It : Ret) {
+    SmallVectorImpl<DefinedRegular *> &V = It.second;
+    std::sort(V.begin(), V.end(), [](DefinedRegular *A, DefinedRegular *B) {
+      return A->getRVA() < B->getRVA();
+    });
   }
+  return Ret;
 }
 
-static void writeMapFile2(raw_fd_ostream &OS,
-                          ArrayRef<OutputSection *> OutputSections) {
-  OS << "Address  Size     Align Out     In      File    Symbol\n";
+// Construct a map from symbols to their stringified representations.
+static DenseMap<DefinedRegular *, std::string>
+getSymbolStrings(ArrayRef<DefinedRegular *> Syms) {
+  std::vector<std::string> Str(Syms.size());
+  parallel_for((size_t)0, Syms.size(), [&](size_t I) {
+    raw_string_ostream OS(Str[I]);
+    writeHeader(OS, Syms[I]->getRVA(), 0, 0);
+    OS << indent(2) << toString(*Syms[I]);
+  });
 
-  for (OutputSection *Sec : OutputSections) {
-    uint32_t VA = Sec->getRVA();
-    writeOutSecLine(OS, VA, Sec->getVirtualSize(), /*Align=*/PageSize,
-                    Sec->getName());
-    OS << '\n';
-    StringRef PrevName = "";
-    for (Chunk *C : Sec->getChunks())
-      if (const auto *SC = dyn_cast<SectionChunk>(C))
-        writeSectionChunk(OS, SC, PrevName);
-  }
+  DenseMap<DefinedRegular *, std::string> Ret;
+  for (size_t I = 0, E = Syms.size(); I < E; ++I)
+    Ret[Syms[I]] = std::move(Str[I]);
+  return Ret;
 }
 
 void coff::writeMapFile(ArrayRef<OutputSection *> OutputSections) {
@@ -110,5 +96,30 @@ void coff::writeMapFile(ArrayRef<OutputSection *> OutputSections) {
   raw_fd_ostream OS(Config->MapFile, EC, sys::fs::F_None);
   if (EC)
     fatal("cannot open " + Config->MapFile + ": " + EC.message());
-  writeMapFile2(OS, OutputSections);
+
+  // Collect symbol info that we want to print out.
+  std::vector<DefinedRegular *> Syms = getSymbols();
+  SymbolMapTy SectionSyms = getSectionSyms(Syms);
+  DenseMap<DefinedRegular *, std::string> SymStr = getSymbolStrings(Syms);
+
+  // Print out the header line.
+  OS << "Address  Size     Align Out     In      Symbol\n";
+
+  // Print out file contents.
+  for (OutputSection *Sec : OutputSections) {
+    writeHeader(OS, Sec->getRVA(), Sec->getVirtualSize(), /*Align=*/PageSize);
+    OS << Sec->getName() << '\n';
+
+    for (Chunk *C : Sec->getChunks()) {
+      auto *SC = dyn_cast<SectionChunk>(C);
+      if (!SC)
+        continue;
+
+      writeHeader(OS, SC->getRVA(), SC->getSize(), SC->getAlign());
+      OS << indent(1) << SC->File->getName() << ":(" << SC->getSectionName()
+         << ")\n";
+      for (DefinedRegular *Sym : SectionSyms[SC])
+        OS << SymStr[Sym] << '\n';
+    }
+  }
 }
diff --git a/ELF/Config.h b/ELF/Config.h
index d25c63c3c0d..1ace4aa26fd 100644
--- a/ELF/Config.h
+++ b/ELF/Config.h
@@ -89,7 +89,7 @@ struct Configuration {
   llvm::StringRef SoName;
   llvm::StringRef Sysroot;
   llvm::StringRef ThinLTOCacheDir;
-  std::string RPath;
+  std::string Rpath;
   std::vector<VersionDefinition> VersionDefinitions;
   std::vector<llvm::StringRef> AuxiliaryList;
   std::vector<llvm::StringRef> SearchPaths;
diff --git a/ELF/Driver.cpp b/ELF/Driver.cpp
index 68eb5616a5c..6a71eb3ee49 100644
--- a/ELF/Driver.cpp
+++ b/ELF/Driver.cpp
@@ -124,7 +124,7 @@ static std::tuple<ELFKind, uint16_t, uint8_t> parseEmulation(StringRef Emul) {
 // Returns slices of MB by parsing MB as an archive file.
 // Each slice consists of a member file in the archive.
 std::vector<MemoryBufferRef>
-LinkerDriver::getArchiveMembers(MemoryBufferRef MB) {
+static getArchiveMembers(MemoryBufferRef MB) {
   std::unique_ptr<Archive> File =
       check(Archive::create(MB),
             MB.getBufferIdentifier() + ": failed to parse archive");
@@ -242,6 +242,9 @@ static void checkOptions(opt::InputArgList &Args) {
   if (Config->Pie && Config->Shared)
     error("-shared and -pie may not be used together");
 
+  if (!Config->Shared && !Config->AuxiliaryList.empty())
+    error("-f may not be used without -shared");
+
   if (Config->Relocatable) {
     if (Config->Shared)
       error("-r and -shared may not be used together");
@@ -396,7 +399,7 @@ static std::vector<StringRef> getArgs(opt::InputArgList &Args, int Id) {
   return V;
 }
 
-static std::string getRPath(opt::InputArgList &Args) {
+static std::string getRpath(opt::InputArgList &Args) {
   std::vector<StringRef> V = getArgs(Args, OPT_rpath);
   return llvm::join(V.begin(), V.end(), ":");
 }
@@ -444,16 +447,14 @@ static UnresolvedPolicy getUnresolvedSymbolPolicy(opt::InputArgList &Args) {
 }
 
 static Target2Policy getTarget2(opt::InputArgList &Args) {
-  if (auto *Arg = Args.getLastArg(OPT_target2)) {
-    StringRef S = Arg->getValue();
-    if (S == "rel")
-      return Target2Policy::Rel;
-    if (S == "abs")
-      return Target2Policy::Abs;
-    if (S == "got-rel")
-      return Target2Policy::GotRel;
-    error("unknown --target2 option: " + S);
-  }
+  StringRef S = getString(Args, OPT_target2, "got-rel");
+  if (S == "rel")
+    return Target2Policy::Rel;
+  if (S == "abs")
+    return Target2Policy::Abs;
+  if (S == "got-rel")
+    return Target2Policy::GotRel;
+  error("unknown --target2 option: " + S);
   return Target2Policy::GotRel;
 }
 
@@ -550,6 +551,29 @@ static std::pair<bool, bool> getHashStyle(opt::InputArgList &Args) {
   return {true, true};
 }
 
+// Parse --build-id or --build-id=<style>. We handle "tree" as a
+// synonym for "sha1" because all our hash functions including
+// -build-id=sha1 are actually tree hashes for performance reasons.
+static std::pair<BuildIdKind, std::vector<uint8_t>>
+getBuildId(opt::InputArgList &Args) {
+  if (Args.hasArg(OPT_build_id))
+    return {BuildIdKind::Fast, {}};
+
+  StringRef S = getString(Args, OPT_build_id_eq, "none");
+  if (S == "md5")
+    return {BuildIdKind::Md5, {}};
+  if (S == "sha1" || S == "tree")
+    return {BuildIdKind::Sha1, {}};
+  if (S == "uuid")
+    return {BuildIdKind::Uuid, {}};
+  if (S.startswith("0x"))
+    return {BuildIdKind::Hexstring, parseHex(S.substr(2))};
+
+  if (S != "none")
+    error("unknown --build-id style: " + S);
+  return {BuildIdKind::None, {}};
+}
+
 static std::vector<StringRef> getLines(MemoryBufferRef MB) {
   SmallVector<StringRef, 0> Arr;
   MB.getBuffer().split(Arr, '\n');
@@ -564,14 +588,14 @@ static std::vector<StringRef> getLines(MemoryBufferRef MB) {
 }
 
 static bool getCompressDebugSections(opt::InputArgList &Args) {
-  if (auto *Arg = Args.getLastArg(OPT_compress_debug_sections)) {
-    StringRef S = Arg->getValue();
-    if (S == "zlib")
-      return zlib::isAvailable();
-    if (S != "none")
-      error("unknown --compress-debug-sections value: " + S);
-  }
-  return false;
+  StringRef S = getString(Args, OPT_compress_debug_sections, "none");
+  if (S == "none")
+    return false;
+  if (S != "zlib")
+    error("unknown --compress-debug-sections value: " + S);
+  if (!zlib::isAvailable())
+    error("--compress-debug-sections: zlib is not available");
+  return true;
 }
 
 // Initializes Config members by the command line options.
@@ -616,7 +640,7 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->OutputFile = getString(Args, OPT_o);
   Config->Pie = getArg(Args, OPT_pie, OPT_nopie, false);
   Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
-  Config->RPath = getRPath(Args);
+  Config->Rpath = getRpath(Args);
   Config->Relocatable = Args.hasArg(OPT_relocatable);
   Config->SaveTemps = Args.hasArg(OPT_save_temps);
   Config->SearchPaths = getArgs(Args, OPT_L);
@@ -679,32 +703,7 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
     Config->ZRelro = false;
 
   std::tie(Config->SysvHash, Config->GnuHash) = getHashStyle(Args);
-
-  // Parse --build-id or --build-id=<style>. We handle "tree" as a
-  // synonym for "sha1" because all of our hash functions including
-  // -build-id=sha1 are tree hashes for performance reasons.
-  if (Args.hasArg(OPT_build_id))
-    Config->BuildId = BuildIdKind::Fast;
-  if (auto *Arg = Args.getLastArg(OPT_build_id_eq)) {
-    StringRef S = Arg->getValue();
-    if (S == "md5") {
-      Config->BuildId = BuildIdKind::Md5;
-    } else if (S == "sha1" || S == "tree") {
-      Config->BuildId = BuildIdKind::Sha1;
-    } else if (S == "uuid") {
-      Config->BuildId = BuildIdKind::Uuid;
-    } 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);
-    }
-  }
-
-  if (!Config->Shared && !Config->AuxiliaryList.empty())
-    error("-f may not be used without -shared");
+  std::tie(Config->BuildId, Config->BuildIdVector) = getBuildId(Args);
 
   if (auto *Arg = Args.getLastArg(OPT_symbol_ordering_file))
     if (Optional<MemoryBufferRef> Buffer = readFile(Arg->getValue()))
diff --git a/ELF/Driver.h b/ELF/Driver.h
index 6a75a8942ca..58bd2ab5219 100644
--- a/ELF/Driver.h
+++ b/ELF/Driver.h
@@ -31,7 +31,6 @@ public:
   void addLibrary(StringRef Name);
 
 private:
-  std::vector<MemoryBufferRef> getArchiveMembers(MemoryBufferRef MB);
   void readConfigs(llvm::opt::InputArgList &Args);
   void createFiles(llvm::opt::InputArgList &Args);
   void inferMachineType();
diff --git a/ELF/Error.cpp b/ELF/Error.cpp
index 2c61b58dfed..7a58668bdcc 100644
--- a/ELF/Error.cpp
+++ b/ELF/Error.cpp
@@ -60,6 +60,7 @@ void elf::log(const Twine &Msg) {
   if (Config->Verbose) {
     std::lock_guard<std::mutex> Lock(Mu);
     outs() << Argv0 << ": " << Msg << "\n";
+    outs().flush();
   }
 }
 
diff --git a/ELF/InputFiles.cpp b/ELF/InputFiles.cpp
index d99f71eb4aa..12867bbd071 100644
--- a/ELF/InputFiles.cpp
+++ b/ELF/InputFiles.cpp
@@ -123,10 +123,10 @@ std::string elf::ObjectFile<ELFT>::getLineInfo(InputSectionBase *S,
   return "";
 }
 
-// Returns "(internal)", "foo.a(bar.o)" or "baz.o".
+// Returns "<internal>", "foo.a(bar.o)" or "baz.o".
 std::string lld::toString(const InputFile *F) {
   if (!F)
-    return "(internal)";
+    return "<internal>";
 
   if (F->ToStringCache.empty()) {
     if (F->ArchiveName.empty())
@@ -137,15 +137,13 @@ std::string lld::toString(const InputFile *F) {
   return F->ToStringCache;
 }
 
-template <class ELFT> static ELFKind getELFKind() {
-  if (ELFT::TargetEndianness == support::little)
-    return ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
-  return ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
-}
-
 template <class ELFT>
 ELFFileBase<ELFT>::ELFFileBase(Kind K, MemoryBufferRef MB) : InputFile(K, MB) {
-  EKind = getELFKind<ELFT>();
+  if (ELFT::TargetEndianness == support::little)
+    EKind = ELFT::Is64Bits ? ELF64LEKind : ELF32LEKind;
+  else
+    EKind = ELFT::Is64Bits ? ELF64BEKind : ELF32BEKind;
+
   EMachine = getObj().getHeader()->e_machine;
   OSABI = getObj().getHeader()->e_ident[llvm::ELF::EI_OSABI];
 }
@@ -174,8 +172,10 @@ void ELFFileBase<ELFT>::initSymtab(ArrayRef<Elf_Shdr> Sections,
 }
 
 template <class ELFT>
-elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M)
-    : ELFFileBase<ELFT>(Base::ObjectKind, M) {}
+elf::ObjectFile<ELFT>::ObjectFile(MemoryBufferRef M, StringRef ArchiveName)
+    : ELFFileBase<ELFT>(Base::ObjectKind, M) {
+  this->ArchiveName = ArchiveName;
+}
 
 template <class ELFT>
 ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getLocalSymbols() {
@@ -361,6 +361,15 @@ InputSectionBase *elf::ObjectFile<ELFT>::getRelocTarget(const Elf_Shdr &Sec) {
   return Target;
 }
 
+// Create a regular InputSection class that has the same contents
+// as a given section.
+InputSectionBase *toRegularSection(MergeInputSection *Sec) {
+  auto *Ret = make<InputSection>(Sec->Flags, Sec->Type, Sec->Alignment,
+                                 Sec->Data, Sec->Name);
+  Ret->File = Sec->File;
+  return Ret;
+}
+
 template <class ELFT>
 InputSectionBase *
 elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec,
@@ -398,9 +407,18 @@ elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec,
     if (Target->FirstRelocation)
       fatal(toString(this) +
             ": multiple relocation sections to one section are not supported");
-    if (isa<MergeInputSection>(Target))
-      fatal(toString(this) +
-            ": relocations pointing to SHF_MERGE are not supported");
+
+    // Mergeable sections with relocations are tricky because relocations
+    // need to be taken into account when comparing section contents for
+    // merging. It doesn't worth supporting such mergeable sections because
+    // they are rare and it'd complicates the internal design (we usually
+    // have to determine if two sections are mergeable early in the link
+    // process much before applying relocations). We simply handle mergeable
+    // sections with relocations as non-mergeable.
+    if (auto *MS = dyn_cast<MergeInputSection>(Target)) {
+      Target = toRegularSection(MS);
+      this->Sections[Sec.sh_info] = Target;
+    }
 
     size_t NumRelocations;
     if (Sec.sh_type == SHT_RELA) {
@@ -461,6 +479,15 @@ elf::ObjectFile<ELFT>::createInputSection(const Elf_Shdr &Sec,
   if (Config->Strip != StripPolicy::None && Name.startswith(".debug"))
     return &InputSection::Discarded;
 
+  // If -gdb-index is given, LLD creates .gdb_index section, and that
+  // section serves the same purpose as .debug_gnu_pub{names,types} sections.
+  // If that's the case, we want to eliminate .debug_gnu_pub{names,types}
+  // because they are redundant and can waste large amount of disk space
+  // (for example, they are about 400 MiB in total for a clang debug build.)
+  if (Config->GdbIndex &&
+      (Name == ".debug_gnu_pubnames" || Name == ".debug_gnu_pubtypes"))
+    return &InputSection::Discarded;
+
   // The linkonce feature is a sort of proto-comdat. Some glibc i386 object
   // files contain definitions of symbol "__x86.get_pc_thunk.bx" in linkonce
   // sections. Drop those sections to avoid duplicate symbol errors.
@@ -665,7 +692,7 @@ template <class ELFT> void SharedFile<ELFT>::parseSoName() {
       uint64_t Val = Dyn.getVal();
       if (Val >= this->StringTable.size())
         fatal(toString(this) + ": invalid DT_SONAME entry");
-      SoName = StringRef(this->StringTable.data() + Val);
+      SoName = this->StringTable.data() + Val;
       return;
     }
   }
@@ -748,7 +775,7 @@ template <class ELFT> void SharedFile<ELFT>::parseRest() {
     // with explicit versions.
     if (V) {
       StringRef VerName = this->StringTable.data() + V->getAux()->vda_name;
-      Name = Saver.save(Twine(Name) + "@" + VerName);
+      Name = Saver.save(Name + "@" + VerName);
       elf::Symtab<ELFT>::X->addShared(this, Name, Sym, V);
     }
   }
@@ -862,76 +889,50 @@ void BitcodeFile::parse(DenseSet<CachedHashStringRef> &ComdatGroups) {
     Symbols.push_back(createBitcodeSymbol<ELFT>(KeptComdats, ObjSym, this));
 }
 
-// Small bit of template meta programming to handle the SharedFile constructor
-// being the only one with a DefaultSoName parameter.
-template <template <class> class T, class E>
-typename std::enable_if<std::is_same<T<E>, SharedFile<E>>::value,
-                        InputFile *>::type
-createELFAux(MemoryBufferRef MB, StringRef DefaultSoName) {
-  return make<T<E>>(MB, DefaultSoName);
-}
-template <template <class> class T, class E>
-typename std::enable_if<!std::is_same<T<E>, SharedFile<E>>::value,
-                        InputFile *>::type
-createELFAux(MemoryBufferRef MB, StringRef DefaultSoName) {
-  return make<T<E>>(MB);
-}
-
-template <template <class> class T>
-static InputFile *createELFFile(MemoryBufferRef MB, StringRef DefaultSoName) {
+static ELFKind getELFKind(MemoryBufferRef MB) {
   unsigned char Size;
   unsigned char Endian;
   std::tie(Size, Endian) = getElfArchType(MB.getBuffer());
+
   if (Endian != ELFDATA2LSB && Endian != ELFDATA2MSB)
     fatal(MB.getBufferIdentifier() + ": invalid data encoding");
+  if (Size != ELFCLASS32 && Size != ELFCLASS64)
+    fatal(MB.getBufferIdentifier() + ": invalid file class");
 
   size_t BufSize = MB.getBuffer().size();
   if ((Size == ELFCLASS32 && BufSize < sizeof(Elf32_Ehdr)) ||
       (Size == ELFCLASS64 && BufSize < sizeof(Elf64_Ehdr)))
     fatal(MB.getBufferIdentifier() + ": file is too short");
 
-  InputFile *Obj;
-  if (Size == ELFCLASS32 && Endian == ELFDATA2LSB)
-    Obj = createELFAux<T, ELF32LE>(MB, DefaultSoName);
-  else if (Size == ELFCLASS32 && Endian == ELFDATA2MSB)
-    Obj = createELFAux<T, ELF32BE>(MB, DefaultSoName);
-  else if (Size == ELFCLASS64 && Endian == ELFDATA2LSB)
-    Obj = createELFAux<T, ELF64LE>(MB, DefaultSoName);
-  else if (Size == ELFCLASS64 && Endian == ELFDATA2MSB)
-    Obj = createELFAux<T, ELF64BE>(MB, DefaultSoName);
-  else
-    fatal(MB.getBufferIdentifier() + ": invalid file class");
-
-  if (!Config->FirstElf)
-    Config->FirstElf = Obj;
-  return Obj;
+  if (Size == ELFCLASS32)
+    return (Endian == ELFDATA2LSB) ? ELF32LEKind : ELF32BEKind;
+  return (Endian == ELFDATA2LSB) ? ELF64LEKind : ELF64BEKind;
 }
 
 template <class ELFT> void BinaryFile::parse() {
-  StringRef Buf = MB.getBuffer();
-  ArrayRef<uint8_t> Data =
-      makeArrayRef<uint8_t>((const uint8_t *)Buf.data(), Buf.size());
-
-  std::string Filename = MB.getBufferIdentifier();
-  std::transform(Filename.begin(), Filename.end(), Filename.begin(),
-                 [](char C) { return isalnum(C) ? C : '_'; });
-  Filename = "_binary_" + Filename;
-  StringRef StartName = Saver.save(Twine(Filename) + "_start");
-  StringRef EndName = Saver.save(Twine(Filename) + "_end");
-  StringRef SizeName = Saver.save(Twine(Filename) + "_size");
-
+  ArrayRef<uint8_t> Data = toArrayRef(MB.getBuffer());
   auto *Section =
       make<InputSection>(SHF_ALLOC | SHF_WRITE, SHT_PROGBITS, 8, Data, ".data");
   Sections.push_back(Section);
 
-  elf::Symtab<ELFT>::X->addRegular(StartName, STV_DEFAULT, STT_OBJECT, 0, 0,
-                                   STB_GLOBAL, Section, nullptr);
-  elf::Symtab<ELFT>::X->addRegular(EndName, STV_DEFAULT, STT_OBJECT,
-                                   Data.size(), 0, STB_GLOBAL, Section,
-                                   nullptr);
-  elf::Symtab<ELFT>::X->addRegular(SizeName, STV_DEFAULT, STT_OBJECT,
-                                   Data.size(), 0, STB_GLOBAL, nullptr,
+  // For each input file foo that is embedded to a result as a binary
+  // blob, we define _binary_foo_{start,end,size} symbols, so that
+  // user programs can access blobs by name. Non-alphanumeric
+  // characters in a filename are replaced with underscore.
+  std::string S = "_binary_" + MB.getBufferIdentifier().str();
+  for (size_t I = 0; I < S.size(); ++I)
+    if (!isalnum(S[I]))
+      S[I] = '_';
+
+  elf::Symtab<ELFT>::X->addRegular(Saver.save(S + "_start"), STV_DEFAULT,
+                                   STT_OBJECT, 0, 0, STB_GLOBAL, Section,
                                    nullptr);
+  elf::Symtab<ELFT>::X->addRegular(Saver.save(S + "_end"), STV_DEFAULT,
+                                   STT_OBJECT, Data.size(), 0, STB_GLOBAL,
+                                   Section, nullptr);
+  elf::Symtab<ELFT>::X->addRegular(Saver.save(S + "_size"), STV_DEFAULT,
+                                   STT_OBJECT, Data.size(), 0, STB_GLOBAL,
+                                   nullptr, nullptr);
 }
 
 static bool isBitcode(MemoryBufferRef MB) {
@@ -941,15 +942,36 @@ static bool isBitcode(MemoryBufferRef MB) {
 
 InputFile *elf::createObjectFile(MemoryBufferRef MB, StringRef ArchiveName,
                                  uint64_t OffsetInArchive) {
-  InputFile *F = isBitcode(MB)
-                     ? make<BitcodeFile>(MB, ArchiveName, OffsetInArchive)
-                     : createELFFile<ObjectFile>(MB, "");
-  F->ArchiveName = ArchiveName;
-  return F;
+  if (isBitcode(MB))
+    return make<BitcodeFile>(MB, ArchiveName, OffsetInArchive);
+
+  switch (getELFKind(MB)) {
+  case ELF32LEKind:
+    return make<ObjectFile<ELF32LE>>(MB, ArchiveName);
+  case ELF32BEKind:
+    return make<ObjectFile<ELF32BE>>(MB, ArchiveName);
+  case ELF64LEKind:
+    return make<ObjectFile<ELF64LE>>(MB, ArchiveName);
+  case ELF64BEKind:
+    return make<ObjectFile<ELF64BE>>(MB, ArchiveName);
+  default:
+    llvm_unreachable("getELFKind");
+  }
 }
 
 InputFile *elf::createSharedFile(MemoryBufferRef MB, StringRef DefaultSoName) {
-  return createELFFile<SharedFile>(MB, DefaultSoName);
+  switch (getELFKind(MB)) {
+  case ELF32LEKind:
+    return make<SharedFile<ELF32LE>>(MB, DefaultSoName);
+  case ELF32BEKind:
+    return make<SharedFile<ELF32BE>>(MB, DefaultSoName);
+  case ELF64LEKind:
+    return make<SharedFile<ELF64LE>>(MB, DefaultSoName);
+  case ELF64BEKind:
+    return make<SharedFile<ELF64BE>>(MB, DefaultSoName);
+  default:
+    llvm_unreachable("getELFKind");
+  }
 }
 
 MemoryBufferRef LazyObjectFile::getBuffer() {
@@ -1004,17 +1026,18 @@ 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>();
+  switch (getELFKind(this->MB)) {
+  case ELF32LEKind:
+    return getElfSymbols<ELF32LE>();
+  case ELF32BEKind:
     return getElfSymbols<ELF32BE>();
-  }
-  if (Endian == ELFDATA2LSB)
+  case ELF64LEKind:
     return getElfSymbols<ELF64LE>();
-  return getElfSymbols<ELF64BE>();
+  case ELF64BEKind:
+    return getElfSymbols<ELF64BE>();
+  default:
+    llvm_unreachable("getELFKind");
+  }
 }
 
 template void ArchiveFile::parse<ELF32LE>();
diff --git a/ELF/InputFiles.h b/ELF/InputFiles.h
index 4552270316d..d0a45a4a98c 100644
--- a/ELF/InputFiles.h
+++ b/ELF/InputFiles.h
@@ -156,7 +156,7 @@ public:
   ArrayRef<SymbolBody *> getSymbols();
   ArrayRef<SymbolBody *> getLocalSymbols();
 
-  explicit ObjectFile(MemoryBufferRef M);
+  ObjectFile(MemoryBufferRef M, StringRef ArchiveName);
   void parse(llvm::DenseSet<llvm::CachedHashStringRef> &ComdatGroups);
 
   InputSectionBase *getSection(const Elf_Sym &Sym) const;
diff --git a/ELF/InputSection.cpp b/ELF/InputSection.cpp
index aff57551a8b..c082f128a9b 100644
--- a/ELF/InputSection.cpp
+++ b/ELF/InputSection.cpp
@@ -39,9 +39,7 @@ std::vector<InputSectionBase *> elf::InputSections;
 
 // Returns a string to construct an error message.
 std::string lld::toString(const InputSectionBase *Sec) {
-  // File can be absent if section is synthetic.
-  std::string FileName = Sec->File ? Sec->File->getName() : "<internal>";
-  return (FileName + ":(" + Sec->Name + ")").str();
+  return (toString(Sec->File) + ":(" + Sec->Name + ")").str();
 }
 
 template <class ELFT>
diff --git a/ELF/LTO.cpp b/ELF/LTO.cpp
index dd435173101..de0d45bea1c 100644
--- a/ELF/LTO.cpp
+++ b/ELF/LTO.cpp
@@ -105,6 +105,11 @@ BitcodeCompiler::~BitcodeCompiler() = default;
 static void undefine(Symbol *S) {
   replaceBody<Undefined>(S, S->body()->getName(), /*IsLocal=*/false,
                          STV_DEFAULT, S->body()->Type, nullptr);
+  // It shouldn't normally matter what the binding is, but if a bug in the LTO
+  // implementation causes it to fail to provide a definition for a symbol,
+  // setting the binding to STB_GLOBAL will cause the linker to report an
+  // undefined symbol error, even if the definition was weak.
+  S->Binding = STB_GLOBAL;
 }
 
 void BitcodeCompiler::add(BitcodeFile &F) {
diff --git a/ELF/LinkerScript.cpp b/ELF/LinkerScript.cpp
index 63eb90456e1..22a5b639469 100644
--- a/ELF/LinkerScript.cpp
+++ b/ELF/LinkerScript.cpp
@@ -406,8 +406,15 @@ void LinkerScript::processCommands(OutputSectionFactory &Factory) {
       }
 
       // Add input sections to an output section.
-      for (InputSectionBase *S : V)
-        Factory.addInputSec(S, Cmd->Name);
+      unsigned Pos = 0;
+      for (InputSectionBase *S : V) {
+        // The actual offset will be computed during
+        // assignAddresses. For now, use the index as a very crude
+        // approximation so that it is at least easy for other code to
+        // know the section order.
+        cast<InputSection>(S)->OutSecOff = Pos++;
+        Factory.addInputSec(S, Cmd->Name, Cmd->Sec);
+      }
     }
   }
   CurOutSec = nullptr;
@@ -465,9 +472,26 @@ void LinkerScript::fabricateDefaultCommands(bool AllocateHeader) {
 
 // Add sections that didn't match any sections command.
 void LinkerScript::addOrphanSections(OutputSectionFactory &Factory) {
-  for (InputSectionBase *S : InputSections)
-    if (S->Live && !S->OutSec)
-      Factory.addInputSec(S, getOutputSectionName(S->Name));
+  for (InputSectionBase *S : InputSections) {
+    if (!S->Live || S->OutSec)
+      continue;
+    StringRef Name = getOutputSectionName(S->Name);
+    auto I = std::find_if(
+        Opt.Commands.begin(), Opt.Commands.end(), [&](BaseCommand *Base) {
+          if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
+            return Cmd->Name == Name;
+          return false;
+        });
+    if (I == Opt.Commands.end()) {
+      Factory.addInputSec(S, Name);
+    } else {
+      auto *Cmd = cast<OutputSectionCommand>(*I);
+      Factory.addInputSec(S, Name, Cmd->Sec);
+      auto *ISD = make<InputSectionDescription>("");
+      ISD->Sections.push_back(S);
+      Cmd->Commands.push_back(ISD);
+    }
+  }
 }
 
 static bool isTbss(OutputSection *Sec) {
@@ -475,8 +499,6 @@ static bool isTbss(OutputSection *Sec) {
 }
 
 void LinkerScript::output(InputSection *S) {
-  if (!AlreadyOutputIS.insert(S).second)
-    return;
   bool IsTbss = isTbss(CurOutSec);
 
   uint64_t Pos = IsTbss ? Dot + ThreadBssOffset : Dot;
@@ -508,19 +530,9 @@ void LinkerScript::output(InputSection *S) {
     Dot = Pos;
 }
 
-void LinkerScript::flush() {
-  assert(CurOutSec);
-  if (!AlreadyOutputOS.insert(CurOutSec).second)
-    return;
-  for (InputSection *I : CurOutSec->Sections)
-    output(I);
-}
-
 void LinkerScript::switchTo(OutputSection *Sec) {
   if (CurOutSec == Sec)
     return;
-  if (AlreadyOutputOS.count(Sec))
-    return;
 
   CurOutSec = Sec;
 
@@ -571,19 +583,11 @@ void LinkerScript::process(BaseCommand &Base) {
 
     if (!Sec->Live)
       continue;
-    assert(CurOutSec == Sec->OutSec || AlreadyOutputOS.count(Sec->OutSec));
+    assert(CurOutSec == Sec->OutSec);
     output(cast<InputSection>(Sec));
   }
 }
 
-static OutputSection *
-findSection(StringRef Name, const std::vector<OutputSection *> &Sections) {
-  for (OutputSection *Sec : Sections)
-    if (Sec->Name == Name)
-      return Sec;
-  return nullptr;
-}
-
 // This function searches for a memory region to place the given output
 // section in. If found, a pointer to the appropriate memory region is
 // returned. Otherwise, a nullptr is returned.
@@ -638,19 +642,8 @@ void LinkerScript::assignOffsets(OutputSectionCommand *Cmd) {
     Dot = CurMemRegion->Offset;
   switchTo(Sec);
 
-  // flush() may add orphan sections, so the order of flush() and
-  // symbol assignments is important. We want to call flush() first so
-  // that symbols pointing the end of the current section points to
-  // the location after orphan sections.
-  auto Mid =
-      std::find_if(Cmd->Commands.rbegin(), Cmd->Commands.rend(),
-                   [](BaseCommand *Cmd) { return !isa<SymbolAssignment>(Cmd); })
-          .base();
-  for (auto I = Cmd->Commands.begin(); I != Mid; ++I)
-    process(**I);
-  flush();
-  for (auto I = Mid, E = Cmd->Commands.end(); I != E; ++I)
-    process(**I);
+  for (BaseCommand *C : Cmd->Commands)
+    process(*C);
 }
 
 void LinkerScript::removeEmptyCommands() {
@@ -663,7 +656,8 @@ void LinkerScript::removeEmptyCommands() {
   auto Pos = std::remove_if(
       Opt.Commands.begin(), Opt.Commands.end(), [&](BaseCommand *Base) {
         if (auto *Cmd = dyn_cast<OutputSectionCommand>(Base))
-          return !Cmd->Sec;
+          return std::find(OutputSections->begin(), OutputSections->end(),
+                           Cmd->Sec) == OutputSections->end();
         return false;
       });
   Opt.Commands.erase(Pos, Opt.Commands.end());
@@ -687,8 +681,7 @@ void LinkerScript::adjustSectionsBeforeSorting() {
     auto *Cmd = dyn_cast<OutputSectionCommand>(Base);
     if (!Cmd)
       continue;
-    if (OutputSection *Sec = findSection(Cmd->Name, *OutputSections)) {
-      Cmd->Sec = Sec;
+    if (OutputSection *Sec = Cmd->Sec) {
       Flags = Sec->Flags;
       Type = Sec->Type;
       continue;
@@ -820,15 +813,24 @@ void LinkerScript::placeOrphanSections() {
       ++CmdIndex;
     }
 
+    // If there is no command corresponding to this output section,
+    // create one and put a InputSectionDescription in it so that both
+    // representations agree on which input sections to use.
     auto Pos = std::find_if(CmdIter, E, [&](BaseCommand *Base) {
       auto *Cmd = dyn_cast<OutputSectionCommand>(Base);
       return Cmd && Cmd->Name == Name;
     });
     if (Pos == E) {
       auto *Cmd = make<OutputSectionCommand>(Name);
-      Cmd->Sec = Sec;
       Opt.Commands.insert(CmdIter, Cmd);
       ++CmdIndex;
+
+      Cmd->Sec = Sec;
+      auto *ISD = make<InputSectionDescription>("");
+      for (InputSection *IS : Sec->Sections)
+        ISD->Sections.push_back(IS);
+      Cmd->Commands.push_back(ISD);
+
       continue;
     }
 
@@ -846,6 +848,51 @@ void LinkerScript::processNonSectionCommands() {
   }
 }
 
+// Do a last effort at synchronizing the linker script "AST" and the section
+// list. This is needed to account for last minute changes, like adding a
+// .ARM.exidx terminator and sorting SHF_LINK_ORDER sections.
+//
+// FIXME: We should instead create the "AST" earlier and the above changes would
+// be done directly in the "AST".
+//
+// This can only handle new sections being added and sections being reordered.
+void LinkerScript::synchronize() {
+  for (BaseCommand *Base : Opt.Commands) {
+    auto *Cmd = dyn_cast<OutputSectionCommand>(Base);
+    if (!Cmd)
+      continue;
+    ArrayRef<InputSection *> Sections = Cmd->Sec->Sections;
+    std::vector<InputSectionBase **> ScriptSections;
+    DenseSet<InputSectionBase *> ScriptSectionsSet;
+    for (BaseCommand *Base : Cmd->Commands) {
+      auto *ISD = dyn_cast<InputSectionDescription>(Base);
+      if (!ISD)
+        continue;
+      for (InputSectionBase *&IS : ISD->Sections) {
+        if (IS->Live) {
+          ScriptSections.push_back(&IS);
+          ScriptSectionsSet.insert(IS);
+        }
+      }
+    }
+    std::vector<InputSectionBase *> Missing;
+    for (InputSection *IS : Sections)
+      if (!ScriptSectionsSet.count(IS))
+        Missing.push_back(IS);
+    if (!Missing.empty()) {
+      auto ISD = make<InputSectionDescription>("");
+      ISD->Sections = Missing;
+      Cmd->Commands.push_back(ISD);
+      for (InputSectionBase *&IS : ISD->Sections)
+        if (IS->Live)
+          ScriptSections.push_back(&IS);
+    }
+    assert(ScriptSections.size() == Sections.size());
+    for (int I = 0, N = Sections.size(); I < N; ++I)
+      *ScriptSections[I] = Sections[I];
+  }
+}
+
 void LinkerScript::assignAddresses(std::vector<PhdrEntry> &Phdrs) {
   // Assign addresses as instructed by linker script SECTIONS sub-commands.
   Dot = 0;
diff --git a/ELF/LinkerScript.h b/ELF/LinkerScript.h
index 61942b2db35..dd96d335a66 100644
--- a/ELF/LinkerScript.h
+++ b/ELF/LinkerScript.h
@@ -228,7 +228,6 @@ protected:
   MemoryRegion *findMemoryRegion(OutputSectionCommand *Cmd);
 
   void switchTo(OutputSection *Sec);
-  void flush();
   void output(InputSection *Sec);
   void process(BaseCommand &Base);
 
@@ -242,9 +241,6 @@ protected:
   OutputSection *CurOutSec = nullptr;
   MemoryRegion *CurMemRegion = nullptr;
 
-  llvm::DenseSet<OutputSection *> AlreadyOutputOS;
-  llvm::DenseSet<InputSectionBase *> AlreadyOutputIS;
-
 public:
   bool hasPhdrsCommands() { return !Opt.PhdrsCommands.empty(); }
   uint64_t getDot() { return Dot; }
@@ -271,6 +267,7 @@ public:
   void assignOffsets(OutputSectionCommand *Cmd);
   void placeOrphanSections();
   void processNonSectionCommands();
+  void synchronize();
   void assignAddresses(std::vector<PhdrEntry> &Phdrs);
   int getSectionIndex(StringRef Name);
 
diff --git a/ELF/MapFile.cpp b/ELF/MapFile.cpp
index 31c8091bb6a..af5bc3c2c81 100644
--- a/ELF/MapFile.cpp
+++ b/ELF/MapFile.cpp
@@ -11,19 +11,19 @@
 // hierarchically the output sections, input sections, input files and
 // symbol:
 //
-// Address  Size     Align Out     In      File    Symbol
-// =================================================================
-// 00201000 00000015     4 .text
-// 00201000 0000000e     4         .text
-// 00201000 0000000e     4                 test.o
-// 0020100e 00000000     0                         local
-// 00201005 00000000     0                         f(int)
+//   Address  Size     Align Out     In      Symbol
+//   00201000 00000015     4 .text
+//   00201000 0000000e     4         test.o:(.text)
+//   0020100e 00000000     0                 local
+//   00201005 00000000     0                 f(int)
 //
 //===----------------------------------------------------------------------===//
 
 #include "MapFile.h"
 #include "InputFiles.h"
 #include "Strings.h"
+#include "SymbolTable.h"
+#include "Threads.h"
 
 #include "llvm/Support/raw_ostream.h"
 
@@ -33,83 +33,68 @@ using namespace llvm::object;
 using namespace lld;
 using namespace lld::elf;
 
-static void writeOutSecLine(raw_fd_ostream &OS, int Width, uint64_t Address,
-                            uint64_t Size, uint64_t Align, StringRef Name) {
-  OS << format("%0*llx %0*llx %5lld ", Width, Address, Width, Size, Align)
-     << left_justify(Name, 7);
-}
-
-static void writeInSecLine(raw_fd_ostream &OS, int Width, uint64_t Address,
-                           uint64_t Size, uint64_t Align, StringRef Name) {
-  // Pass an empty name to align the text to the correct column.
-  writeOutSecLine(OS, Width, Address, Size, Align, "");
-  OS << ' ' << left_justify(Name, 7);
-}
-
-static void writeFileLine(raw_fd_ostream &OS, int Width, uint64_t Address,
-                          uint64_t Size, uint64_t Align, StringRef Name) {
-  // Pass an empty name to align the text to the correct column.
-  writeInSecLine(OS, Width, Address, Size, Align, "");
-  OS << ' ' << left_justify(Name, 7);
-}
-
-static void writeSymbolLine(raw_fd_ostream &OS, int Width, uint64_t Address,
-                            uint64_t Size, StringRef Name) {
-  // Pass an empty name to align the text to the correct column.
-  writeFileLine(OS, Width, Address, Size, 0, "");
-  OS << ' ' << left_justify(Name, 7);
-}
+typedef DenseMap<const SectionBase *, SmallVector<DefinedRegular *, 4>>
+    SymbolMapTy;
 
+// Print out the first three columns of a line.
 template <class ELFT>
-static void writeInputSection(raw_fd_ostream &OS, const InputSection *IS,
-                              StringRef &PrevName) {
-  int Width = ELFT::Is64Bits ? 16 : 8;
-  StringRef Name = IS->Name;
-  if (Name != PrevName) {
-    writeInSecLine(OS, Width, IS->OutSec->Addr + IS->OutSecOff, IS->getSize(),
-                   IS->Alignment, Name);
-    OS << '\n';
-    PrevName = Name;
-  }
-
-  elf::ObjectFile<ELFT> *File = IS->template getFile<ELFT>();
-  if (!File)
-    return;
-  writeFileLine(OS, Width, IS->OutSec->Addr + IS->OutSecOff, IS->getSize(),
-                IS->Alignment, toString(File));
-  OS << '\n';
-
-  for (SymbolBody *Sym : File->getSymbols()) {
-    auto *DR = dyn_cast<DefinedRegular>(Sym);
-    if (!DR)
-      continue;
-    if (DR->Section != IS)
-      continue;
-    if (DR->isSection())
-      continue;
-    writeSymbolLine(OS, Width, Sym->getVA(), Sym->getSize<ELFT>(),
-                    toString(*Sym));
-    OS << '\n';
-  }
+static void writeHeader(raw_ostream &OS, uint64_t Addr, uint64_t Size,
+                        uint64_t Align) {
+  int W = ELFT::Is64Bits ? 16 : 8;
+  OS << format("%0*llx %0*llx %5lld ", W, Addr, W, Size, Align);
 }
 
+static std::string indent(int Depth) { return std::string(Depth * 8, ' '); }
+
+// Returns a list of all symbols that we want to print out.
+template <class ELFT> std::vector<DefinedRegular *> getSymbols() {
+  std::vector<DefinedRegular *> V;
+  for (elf::ObjectFile<ELFT> *File : Symtab<ELFT>::X->getObjectFiles())
+    for (SymbolBody *B : File->getSymbols())
+      if (B->File == File && !B->isSection())
+        if (auto *Sym = dyn_cast<DefinedRegular>(B))
+          if (Sym->Section)
+            V.push_back(Sym);
+  return V;
+}
+
+// Returns a map from sections to their symbols.
 template <class ELFT>
-static void writeMapFile2(raw_fd_ostream &OS,
-                          ArrayRef<OutputSection *> OutputSections) {
-  int Width = ELFT::Is64Bits ? 16 : 8;
+SymbolMapTy getSectionSyms(ArrayRef<DefinedRegular *> Syms) {
+  SymbolMapTy Ret;
+  for (DefinedRegular *S : Syms)
+    Ret[S->Section].push_back(S);
 
-  OS << left_justify("Address", Width) << ' ' << left_justify("Size", Width)
-     << " Align Out     In      File    Symbol\n";
-
-  for (OutputSection *Sec : OutputSections) {
-    writeOutSecLine(OS, Width, Sec->Addr, Sec->Size, Sec->Alignment, Sec->Name);
-    OS << '\n';
-
-    StringRef PrevName = "";
-    for (InputSection *IS : Sec->Sections) {
-      writeInputSection<ELFT>(OS, IS, PrevName);
-    }
+  // Sort symbols by address. We want to print out symbols in the
+  // order in the output file rather than the order they appeared
+  // in the input files.
+  for (auto &It : Ret) {
+    SmallVectorImpl<DefinedRegular *> &V = It.second;
+    std::sort(V.begin(), V.end(), [](DefinedRegular *A, DefinedRegular *B) {
+      return A->getVA() < B->getVA();
+    });
   }
+  return Ret;
+}
+
+// Construct a map from symbols to their stringified representations.
+// Demangling symbols (which is what toString() does) is slow, so
+// we do that in batch using parallel-for.
+template <class ELFT>
+DenseMap<DefinedRegular *, std::string>
+getSymbolStrings(ArrayRef<DefinedRegular *> Syms) {
+  std::vector<std::string> Str(Syms.size());
+  parallelFor(0, Syms.size(), [&](size_t I) {
+    raw_string_ostream OS(Str[I]);
+    writeHeader<ELFT>(OS, Syms[I]->getVA(), Syms[I]->template getSize<ELFT>(),
+                      0);
+    OS << indent(2) << toString(*Syms[I]);
+  });
+
+  DenseMap<DefinedRegular *, std::string> Ret;
+  for (size_t I = 0, E = Syms.size(); I < E; ++I)
+    Ret[Syms[I]] = std::move(Str[I]);
+  return Ret;
 }
 
 template <class ELFT>
@@ -117,12 +102,38 @@ void elf::writeMapFile(ArrayRef<OutputSection *> OutputSections) {
   if (Config->MapFile.empty())
     return;
 
+  // Open a map file for writing.
   std::error_code EC;
   raw_fd_ostream OS(Config->MapFile, EC, sys::fs::F_None);
-  if (EC)
+  if (EC) {
     error("cannot open " + Config->MapFile + ": " + EC.message());
-  else
-    writeMapFile2<ELFT>(OS, OutputSections);
+    return;
+  }
+
+  // Collect symbol info that we want to print out.
+  std::vector<DefinedRegular *> Syms = getSymbols<ELFT>();
+  SymbolMapTy SectionSyms = getSectionSyms<ELFT>(Syms);
+  DenseMap<DefinedRegular *, std::string> SymStr = getSymbolStrings<ELFT>(Syms);
+
+  // Print out the header line.
+  int W = ELFT::Is64Bits ? 16 : 8;
+  OS << left_justify("Address", W) << ' ' << left_justify("Size", W)
+     << " Align Out     In      Symbol\n";
+
+  // Print out file contents.
+  for (OutputSection *OSec : OutputSections) {
+    writeHeader<ELFT>(OS, OSec->Addr, OSec->Size, OSec->Alignment);
+    OS << OSec->Name << '\n';
+
+    // Dump symbols for each input section.
+    for (InputSection *IS : OSec->Sections) {
+      writeHeader<ELFT>(OS, OSec->Addr + IS->OutSecOff, IS->getSize(),
+                        IS->Alignment);
+      OS << indent(1) << toString(IS) << '\n';
+      for (DefinedRegular *Sym : SectionSyms[IS])
+        OS << SymStr[Sym] << '\n';
+    }
+  }
 }
 
 template void elf::writeMapFile<ELF32LE>(ArrayRef<OutputSection *>);
diff --git a/ELF/Options.td b/ELF/Options.td
index fda67544995..8863912c179 100644
--- a/ELF/Options.td
+++ b/ELF/Options.td
@@ -344,6 +344,26 @@ def end_group_paren: Flag<["-"], ")">;
 def start_group: F<"start-group">;
 def start_group_paren: Flag<["-"], "(">;
 
+// LTO-related options.
+def lto_aa_pipeline: J<"lto-aa-pipeline=">,
+  HelpText<"AA pipeline to run during LTO. Used in conjunction with -lto-newpm-passes">;
+def lto_newpm_passes: J<"lto-newpm-passes=">,
+  HelpText<"Passes to run during LTO">;
+def lto_partitions: J<"lto-partitions=">,
+  HelpText<"Number of LTO codegen partitions">;
+def disable_verify: F<"disable-verify">;
+def mllvm: S<"mllvm">;
+def opt_remarks_filename: Separate<["--"], "opt-remarks-filename">,
+  HelpText<"YAML output file for optimization remarks">;
+def opt_remarks_with_hotness: Flag<["--"], "opt-remarks-with-hotness">,
+  HelpText<"Include hotness informations in the optimization remarks file">;
+def save_temps: F<"save-temps">;
+def thinlto_cache_dir: J<"thinlto-cache-dir=">,
+  HelpText<"Path to ThinLTO cached object file directory">;
+def thinlto_cache_policy: S<"thinlto-cache-policy">,
+  HelpText<"Pruning policy for the ThinLTO cache">;
+def thinlto_jobs: J<"thinlto-jobs=">, HelpText<"Number of ThinLTO jobs">;
+
 // Ignore LTO plugin-related options.
 // clang -flto passes -plugin and -plugin-opt to the linker. This is required
 // for ld.gold and ld.bfd to get LTO working. But it's not for lld which doesn't
@@ -365,6 +385,7 @@ def no_add_needed: F<"no-add-needed">;
 def no_allow_shlib_undefined: F<"no-allow-shlib-undefined">;
 def no_copy_dt_needed_entries: F<"no-copy-dt-needed-entries">,
   Alias<no_add_needed>;
+def no_keep_memory: F<"no-keep-memory">;
 def no_mmap_output_file: F<"no-mmap-output-file">;
 def no_warn_common: F<"no-warn-common">;
 def no_warn_mismatch: F<"no-warn-mismatch">;
@@ -382,23 +403,3 @@ def Qy : F<"Qy">;
 // Aliases for ignored options
 def alias_version_script_version_script: J<"version-script=">,
   Alias<version_script>;
-
-// LTO-related options.
-def lto_aa_pipeline: J<"lto-aa-pipeline=">,
-  HelpText<"AA pipeline to run during LTO. Used in conjunction with -lto-newpm-passes">;
-def lto_newpm_passes: J<"lto-newpm-passes=">,
-  HelpText<"Passes to run during LTO">;
-def lto_partitions: J<"lto-partitions=">,
-  HelpText<"Number of LTO codegen partitions">;
-def disable_verify: F<"disable-verify">;
-def mllvm: S<"mllvm">;
-def opt_remarks_filename: Separate<["--"], "opt-remarks-filename">,
-  HelpText<"YAML output file for optimization remarks">;
-def opt_remarks_with_hotness: Flag<["--"], "opt-remarks-with-hotness">,
-  HelpText<"Include hotness informations in the optimization remarks file">;
-def save_temps: F<"save-temps">;
-def thinlto_cache_dir: J<"thinlto-cache-dir=">,
-  HelpText<"Path to ThinLTO cached object file directory">;
-def thinlto_cache_policy: S<"thinlto-cache-policy">,
-  HelpText<"Pruning policy for the ThinLTO cache">;
-def thinlto_jobs: J<"thinlto-jobs=">, HelpText<"Number of ThinLTO jobs">;
diff --git a/ELF/OutputSections.cpp b/ELF/OutputSections.cpp
index 71fc00ac35e..839f68f2da5 100644
--- a/ELF/OutputSections.cpp
+++ b/ELF/OutputSections.cpp
@@ -395,14 +395,20 @@ static void reportDiscarded(InputSectionBase *IS) {
 
 void OutputSectionFactory::addInputSec(InputSectionBase *IS,
                                        StringRef OutsecName) {
+  SectionKey Key = createKey(IS, OutsecName);
+  OutputSection *&Sec = Map[Key];
+  return addInputSec(IS, OutsecName, Sec);
+}
+
+void OutputSectionFactory::addInputSec(InputSectionBase *IS,
+                                       StringRef OutsecName,
+                                       OutputSection *&Sec) {
   if (!IS->Live) {
     reportDiscarded(IS);
     return;
   }
 
-  SectionKey Key = createKey(IS, OutsecName);
   uint64_t Flags = getOutFlags(IS);
-  OutputSection *&Sec = Map[Key];
   if (Sec) {
     if (getIncompatibleFlags(Sec->Flags) != getIncompatibleFlags(IS->Flags))
       error("incompatible section flags for " + Sec->Name +
@@ -418,7 +424,7 @@ void OutputSectionFactory::addInputSec(InputSectionBase *IS,
     }
     Sec->Flags |= Flags;
   } else {
-    Sec = make<OutputSection>(Key.Name, IS->Type, Flags);
+    Sec = make<OutputSection>(OutsecName, IS->Type, Flags);
     OutputSections.push_back(Sec);
   }
 
diff --git a/ELF/OutputSections.h b/ELF/OutputSections.h
index bcda77d1a26..6405fb38c6d 100644
--- a/ELF/OutputSections.h
+++ b/ELF/OutputSections.h
@@ -141,6 +141,8 @@ public:
   ~OutputSectionFactory();
 
   void addInputSec(InputSectionBase *IS, StringRef OutsecName);
+  void addInputSec(InputSectionBase *IS, StringRef OutsecName,
+                   OutputSection *&Sec);
 
 private:
   llvm::SmallDenseMap<SectionKey, OutputSection *> Map;
diff --git a/ELF/Strings.h b/ELF/Strings.h
index 934b6427105..bcfa2814498 100644
--- a/ELF/Strings.h
+++ b/ELF/Strings.h
@@ -76,6 +76,10 @@ llvm::Optional<std::string> demangle(StringRef Name);
 inline StringRef toStringRef(ArrayRef<uint8_t> Arr) {
   return {(const char *)Arr.data(), Arr.size()};
 }
+
+inline ArrayRef<uint8_t> toArrayRef(StringRef S) {
+  return {(const uint8_t *)S.data(), S.size()};
+}
 }
 }
 
diff --git a/ELF/SymbolTable.cpp b/ELF/SymbolTable.cpp
index e55b8bf52c1..541fc1bf647 100644
--- a/ELF/SymbolTable.cpp
+++ b/ELF/SymbolTable.cpp
@@ -52,6 +52,9 @@ template <class ELFT> static bool isCompatible(InputFile *F) {
 
 // Add symbols in File to the symbol table.
 template <class ELFT> void SymbolTable<ELFT>::addFile(InputFile *File) {
+  if (!Config->FirstElf && isa<ELFFileBase<ELFT>>(File))
+    Config->FirstElf = File;
+
   if (!isCompatible<ELFT>(File))
     return;
 
diff --git a/ELF/SyntheticSections.cpp b/ELF/SyntheticSections.cpp
index e1f81940bb5..a271d31048f 100644
--- a/ELF/SyntheticSections.cpp
+++ b/ELF/SyntheticSections.cpp
@@ -97,7 +97,7 @@ static ArrayRef<uint8_t> getVersion() {
 
 // Creates a .comment section containing LLD version info.
 // With this feature, you can identify LLD-generated binaries easily
-// by "objdump -s -j .comment <file>".
+// by "readelf --string-dump .comment <file>".
 // The returned object is a mergeable string section.
 template <class ELFT> MergeInputSection *elf::createCommentSection() {
   typename ELFT::Shdr Hdr = {};
@@ -541,6 +541,13 @@ template <class ELFT> void EhFrameSection<ELFT>::finalizeContents() {
       Off += alignTo(Fde->size(), Config->Wordsize);
     }
   }
+
+  // The LSB standard does not allow a .eh_frame section with zero
+  // Call Frame Information records. Therefore add a CIE record length
+  // 0 as a terminator if this .eh_frame section is empty.
+  if (Off == 0)
+    Off = 4;
+
   this->Size = Off;
 }
 
@@ -1022,9 +1029,9 @@ template <class ELFT> void DynamicSection<ELFT>::addEntries() {
   // fixed early.
   for (StringRef S : Config->AuxiliaryList)
     add({DT_AUXILIARY, In<ELFT>::DynStrTab->addString(S)});
-  if (!Config->RPath.empty())
+  if (!Config->Rpath.empty())
     add({Config->EnableNewDtags ? DT_RUNPATH : DT_RPATH,
-         In<ELFT>::DynStrTab->addString(Config->RPath)});
+         In<ELFT>::DynStrTab->addString(Config->Rpath)});
   for (SharedFile<ELFT> *F : Symtab<ELFT>::X->getSharedFiles())
     if (F->isNeeded())
       add({DT_NEEDED, In<ELFT>::DynStrTab->addString(F->SoName)});
diff --git a/ELF/Writer.cpp b/ELF/Writer.cpp
index 989a55af167..e2ab48433a5 100644
--- a/ELF/Writer.cpp
+++ b/ELF/Writer.cpp
@@ -101,7 +101,7 @@ StringRef elf::getOutputSectionName(StringRef Name) {
     for (StringRef V : {".rel.", ".rela."}) {
       if (Name.startswith(V)) {
         StringRef Inner = getOutputSectionName(Name.substr(V.size() - 1));
-        return Saver.save(Twine(V.drop_back()) + Inner);
+        return Saver.save(V.drop_back() + Inner);
       }
     }
   }
@@ -123,7 +123,7 @@ StringRef elf::getOutputSectionName(StringRef Name) {
   // ".zdebug_" is a prefix for ZLIB-compressed sections.
   // Because we decompressed input sections, we want to remove 'z'.
   if (Name.startswith(".zdebug_"))
-    return Saver.save(Twine(".") + Name.substr(2));
+    return Saver.save("." + Name.substr(2));
   return Name;
 }
 
@@ -254,6 +254,7 @@ template <class ELFT> void Writer<ELFT>::run() {
       fixSectionAlignments();
       Script->fabricateDefaultCommands(Config->MaxPageSize);
     }
+    Script->synchronize();
     Script->assignAddresses(Phdrs);
 
     // Remove empty PT_LOAD to avoid causing the dynamic linker to try to mmap a
@@ -1080,6 +1081,7 @@ static void removeUnusedSyntheticSections(std::vector<OutputSection *> &V) {
 
     SS->OutSec->Sections.erase(std::find(SS->OutSec->Sections.begin(),
                                          SS->OutSec->Sections.end(), SS));
+    SS->Live = false;
     // If there are no other sections in the output section, remove it from the
     // output.
     if (SS->OutSec->Sections.empty())
diff --git a/docs/index.rst b/docs/index.rst
index 6d9780458d1..fbdade7daf2 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -135,7 +135,7 @@ LDFLAGS when building your programs.
 
 LLD leaves its name and version number to a ``.comment`` section in an
 output. If you are in doubt whether you are successfully using LLD or
-not, run ``objdump -s -j .comment <output-file>`` and examine the
+not, run ``readelf --string-dump .comment <output-file>`` and examine the
 output. If the string "Linker: LLD" is included in the output, you are
 using LLD.
 
diff --git a/test/COFF/Inputs/constant-import.s b/test/COFF/Inputs/constant-import.s
new file mode 100644
index 00000000000..4249d74c9cb
--- /dev/null
+++ b/test/COFF/Inputs/constant-import.s
@@ -0,0 +1,21 @@
+
+	.def __DllMainCRTStartup@12
+		.type 32
+		.scl 2
+	.endef
+	.global __DllMainCRTStartup@12
+__DllMainCRTStartup@12:
+	ret
+
+	.data
+	.def _Data
+		.type 0
+		.scl 2
+	.endef
+	.global _Data
+_Data:
+	.long ___CFConstantStringClassReference
+
+	.section .drectve
+	.ascii " -export:_Data"
+
diff --git a/test/COFF/constant.test b/test/COFF/constant.test
new file mode 100644
index 00000000000..3c8956beac9
--- /dev/null
+++ b/test/COFF/constant.test
@@ -0,0 +1,5 @@
+RUN: mkdir -p %t
+RUN: llvm-mc -triple i686-unknown-windows-msvc -filetype obj -o %t/import.o %S/Inputs/constant-import.s
+RUN: llc -mtriple i686-unknown-windows-msvc -filetype obj -o %t/export.o %S/Inputs/constant-export.ll
+RUN: lld-link -machine:x86 -dll -out:%t/export.dll %t/export.o -entry:__CFConstantStringClassReference
+RUN: lld-link -machine:x86 -dll -out:%t/import.dll %t/import.o %t/export.lib
diff --git a/test/COFF/icf-data.test b/test/COFF/icf-data.test
new file mode 100644
index 00000000000..20bdecaf3cf
--- /dev/null
+++ b/test/COFF/icf-data.test
@@ -0,0 +1,61 @@
+# RUN: yaml2obj < %s > %t.obj
+# RUN: lld-link /entry:foo /out:%t.exe /subsystem:console /include:bar \
+# RUN:   /verbose %t.obj > %t.log 2>&1
+# RUN: FileCheck %s < %t.log
+
+# CHECK-NOT: Removed foo
+# CHECK-NOT: Removed bar
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+  Characteristics: []
+sections:
+  - Name:            '.text$mn'
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     4883EC28E8000000004883C428C3
+  - Name:            '.text$mn'
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_LNK_COMDAT, IMAGE_SCN_MEM_READ ]
+    Alignment:       16
+    SectionData:     4883EC28E8000000004883C428C3
+symbols:
+  - Name:            '.text$mn'
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          14
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        1682752513
+      Number:          0
+      Selection:       IMAGE_COMDAT_SELECT_NODUPLICATES
+  - Name:            '.text$mn'
+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          14
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        1682752513
+      Number:          0
+      Selection:       IMAGE_COMDAT_SELECT_NODUPLICATES
+  - Name:            foo
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            bar
+    Value:           0
+    SectionNumber:   2
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...
diff --git a/test/COFF/lldmap.test b/test/COFF/lldmap.test
index 69080fd639a..d705a16c6c2 100644
--- a/test/COFF/lldmap.test
+++ b/test/COFF/lldmap.test
@@ -1,11 +1,10 @@
 # RUN: yaml2obj < %p/Inputs/ret42.yaml > %t.obj
 # RUN: lld-link /out:%t.exe /entry:main /lldmap:%T/foo.map %t.obj
-# RUN: FileCheck %s < %T/foo.map
+# RUN: FileCheck -strict-whitespace %s < %T/foo.map
 # RUN: lld-link /out:%T/bar.exe /entry:main /lldmap %t.obj
-# RUN: FileCheck %s < %T/bar.map
+# RUN: FileCheck -strict-whitespace %s < %T/bar.map
 
-# CHECK:      Address  Size     Align Out     In      File    Symbol
+# CHECK:      Address  Size     Align Out     In      Symbol
 # CHECK-NEXT: 00001000 00000006  4096 .text
-# CHECK-NEXT: 00001000 00000006    16         .text$mn
-# CHECK-NEXT: 00001000 00000006    16                 {{.*}}lldmap.test.tmp.obj
-# CHECK-NEXT: 00001000 00000006     0                         main   
+# CHECK-NEXT: 00001000 00000006    16         {{.*}}lldmap.test.tmp.obj:(.text$mn)
+# CHECK-NEXT: 00001000 00000000     0                 main
diff --git a/test/ELF/Inputs/eh-frame-end.s b/test/ELF/Inputs/eh-frame-end.s
new file mode 100644
index 00000000000..b7334d8ffbb
--- /dev/null
+++ b/test/ELF/Inputs/eh-frame-end.s
@@ -0,0 +1,2 @@
+	.section ".eh_frame", "a", @progbits
+	.long 0
diff --git a/test/ELF/abs-conflict.s b/test/ELF/abs-conflict.s
index 17a53020003..4662c48a4e4 100644
--- a/test/ELF/abs-conflict.s
+++ b/test/ELF/abs-conflict.s
@@ -15,4 +15,4 @@ foo = 0x123
 
 // DUP:      duplicate symbol: foo
 // DUP-NEXT: >>> defined in {{.*}}.o
-// DUP-NEXT: >>> defined in (internal)
+// DUP-NEXT: >>> defined in <internal>
diff --git a/test/ELF/debug-gnu-pubnames.s b/test/ELF/debug-gnu-pubnames.s
new file mode 100644
index 00000000000..0a8693c97eb
--- /dev/null
+++ b/test/ELF/debug-gnu-pubnames.s
@@ -0,0 +1,10 @@
+# REQUIRES: x86
+# RUN: ld.lld -e main %p/Inputs/gdb-index-a.elf %p/Inputs/gdb-index-b.elf -o %t1.exe
+# RUN: llvm-readobj -sections %t1.exe | FileCheck -check-prefix=CHECK1 %s
+# CHECK1: Name: .debug_gnu_pubnames
+# CHECK1: Name: .debug_gnu_pubtypes
+
+# RUN: ld.lld -gdb-index -e main %p/Inputs/gdb-index-a.elf %p/Inputs/gdb-index-b.elf -o %t2.exe
+# RUN: llvm-readobj -sections %t2.exe | FileCheck -check-prefix=CHECK2 %s
+# CHECK2-NOT: Name: .debug_gnu_pubnames
+# CHECK2-NOT: Name: .debug_gnu_pubtypes
diff --git a/test/ELF/driver-access.test b/test/ELF/driver-access.test
index 3c976a66d0f..5209483ae48 100644
--- a/test/ELF/driver-access.test
+++ b/test/ELF/driver-access.test
@@ -8,6 +8,7 @@
 # RUN: chmod 100 %t.dir
 # RUN: cd %t.dir
 # RUN: ld.lld %t.o -o %t.exe
+# RUN: chmod 755 %t.dir
 
 .globl _start
 _start:
diff --git a/test/ELF/eh-frame-begin-end.s b/test/ELF/eh-frame-begin-end.s
new file mode 100644
index 00000000000..a7f0bb7d3ef
--- /dev/null
+++ b/test/ELF/eh-frame-begin-end.s
@@ -0,0 +1,17 @@
+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=amd64-unknown-openbsd %s -o %t.o
+// RUN: llvm-mc -filetype=obj -triple=amd64-unknown-openbsd %p/Inputs/eh-frame-end.s -o %t2.o
+// RUN: ld.lld %t.o %t2.o -o %t
+// RUN: llvm-readobj -sections %t | FileCheck %s
+
+// CHECK:      Name: .eh_frame
+// CHECK-NEXT: Type: SHT_PROGBITS
+// CHECK-NEXT: Flags [
+// CHECK-NEXT:   SHF_ALLOC
+// CHECK-NEXT: ]
+// CHECK-NEXT: Address: 0x200120
+// CHECK-NEXT: Offset: 0x120
+// CHECK-NEXT: Size: 4
+
+	.section ".eh_frame", "a", @progbits
+__EH_FRAME_BEGIN__:
diff --git a/test/ELF/gdb-index.s b/test/ELF/gdb-index.s
index 4ad5c13d315..b7d8a708ace 100644
--- a/test/ELF/gdb-index.s
+++ b/test/ELF/gdb-index.s
@@ -34,8 +34,8 @@
 # CHECK-NEXT:    0: Offset = 0x0, Length = 0x34
 # CHECK-NEXT:    1: Offset = 0x34, Length = 0x34
 # CHECK:       Address area offset = 0x38, has 2 entries:
-# CHECK-NEXT:    Low address = 0x201000, High address = 0x20100b, CU index = 0
-# CHECK-NEXT:    Low address = 0x20100b, High address = 0x201016, CU index = 1
+# CHECK-NEXT:    Low/High address = [0x201000, 0x20100b) (Size: 0xb), CU id = 0
+# CHECK-NEXT:    Low/High address = [0x20100b, 0x201016) (Size: 0xb), CU id = 1
 # CHECK:       Symbol table offset = 0x60, size = 1024, filled slots:
 # CHECK-NEXT:    489: Name offset = 0x1d, CU vector offset = 0x0
 # CHECK-NEXT:      String name: main, CU vector index: 0
diff --git a/test/ELF/linkerscript/section-metadata.s b/test/ELF/linkerscript/section-metadata.s
new file mode 100644
index 00000000000..f447240ac3a
--- /dev/null
+++ b/test/ELF/linkerscript/section-metadata.s
@@ -0,0 +1,33 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+
+# RUN: echo "SECTIONS { .text : { *(.text.bar) *(.text.foo)  } }" > %t.script
+# RUN: ld.lld -o %t --script %t.script %t.o
+# RUN: llvm-objdump -s %t | FileCheck %s
+
+# RUN: echo "SECTIONS { .text : { *(.text.foo) *(.text.bar) } }" > %t.script
+# RUN: ld.lld -o %t --script %t.script %t.o
+# RUN: llvm-objdump -s %t | FileCheck --check-prefix=INV %s
+
+
+# CHECK:      Contents of section .text:
+# CHECK-NEXT: 02000000 00000000 01000000 00000000
+# CHECK:      Contents of section .rodata:
+# CHECK-NEXT: 02000000 00000000 01000000 00000000
+
+# INV:      Contents of section .text:
+# INV-NEXT: 01000000 00000000 02000000 00000000
+# INV:      Contents of section .rodata:
+# INV-NEXT: 01000000 00000000 02000000 00000000
+
+.global _start
+_start:
+
+.section .text.bar,"a",@progbits
+.quad 2
+.section .text.foo,"a",@progbits
+.quad 1
+.section .rodata.foo,"ao",@progbits,.text.foo
+.quad 1
+.section .rodata.bar,"ao",@progbits,.text.bar
+.quad 2
diff --git a/test/ELF/linkerscript/sections.s b/test/ELF/linkerscript/sections.s
index b7d396fdec9..69c6f19d078 100644
--- a/test/ELF/linkerscript/sections.s
+++ b/test/ELF/linkerscript/sections.s
@@ -86,7 +86,8 @@
 
 #           Idx Name          Size
 # SEC-MULTI:      1 .text         0000000e {{[0-9a-f]*}} TEXT DATA
-# SEC-MULTI-NEXT:   .data         00000023 {{[0-9a-f]*}} DATA
+# SEC-MULTI-NEXT:   .data         00000020 {{[0-9a-f]*}} DATA
+# SEC-MULTI-NEXT:   .data         00000003 {{[0-9a-f]*}} DATA
 # SEC-MULTI-NEXT:   .bss          00000002 {{[0-9a-f]*}} BSS
 # SEC-MULTI-NEXT:   .comment      00000008 {{[0-9a-f]*}}
 # SEC-MULTI-NEXT:   .symtab       00000030 {{[0-9a-f]*}}
diff --git a/test/ELF/map-file.s b/test/ELF/map-file.s
index e74c91645cb..9dbbda0ff0e 100644
--- a/test/ELF/map-file.s
+++ b/test/ELF/map-file.s
@@ -6,10 +6,10 @@
 // RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %p/Inputs/map-file4.s -o %t4.o
 // RUN: rm -f %t4.a
 // RUN: llvm-ar rc %t4.a %t4.o
-// RUN: ld.lld %t1.o %t2.o %t3.o %t4.a -o %t -M | FileCheck %s
-// RUN: ld.lld %t1.o %t2.o %t3.o %t4.a -o %t -print-map | FileCheck %s
+// RUN: ld.lld %t1.o %t2.o %t3.o %t4.a -o %t -M | FileCheck -strict-whitespace %s
+// RUN: ld.lld %t1.o %t2.o %t3.o %t4.a -o %t -print-map | FileCheck -strict-whitespace %s
 // RUN: ld.lld %t1.o %t2.o %t3.o %t4.a -o %t -Map=%t.map
-// RUN: FileCheck %s < %t.map
+// RUN: FileCheck -strict-whitespace %s < %t.map
 
 .global _start
 _start:
@@ -26,36 +26,33 @@ bar:
 local:
 .comm   common,4,16
 
-// CHECK:      Address          Size             Align Out     In      File    Symbol
+// CHECK:      Address          Size             Align Out     In      Symbol
 // CHECK-NEXT: 0000000000200158 0000000000000030     8 .eh_frame
-// CHECK-NEXT: 0000000000200158 0000000000000030     8         .eh_frame
+// CHECK-NEXT: 0000000000200158 0000000000000030     8         <internal>:(.eh_frame)
 // CHECK-NEXT: 0000000000201000 0000000000000015     4 .text
-// CHECK-NEXT: 0000000000201000 000000000000000e     4         .text
-// CHECK-NEXT: 0000000000201000 000000000000000e     4                 {{.*}}{{/|\\}}map-file.s.tmp1.o
-// CHECK-NEXT: 000000000020100e 0000000000000000     0                         local
-// CHECK-NEXT: 0000000000201005 0000000000000000     0                         f(int)
-// CHECK-NEXT: 0000000000201000 0000000000000000     0                         _start
-// CHECK-NEXT: 0000000000201010 0000000000000002     4                 {{.*}}{{/|\\}}map-file.s.tmp2.o
-// CHECK-NEXT: 0000000000201010 0000000000000000     0                         foo
-// CHECK-NEXT: 0000000000201011 0000000000000000     0                         bar
-// CHECK-NEXT: 0000000000201012 0000000000000000     1         .text.zed
-// CHECK-NEXT: 0000000000201012 0000000000000000     1                 {{.*}}{{/|\\}}map-file.s.tmp2.o
-// CHECK-NEXT: 0000000000201012 0000000000000000     0                         zed
-// CHECK-NEXT: 0000000000201014 0000000000000000     4         .text
-// CHECK-NEXT: 0000000000201014 0000000000000000     4                 {{.*}}{{/|\\}}map-file.s.tmp3.o
-// CHECK-NEXT: 0000000000201014 0000000000000000     0                         bah
-// CHECK-NEXT: 0000000000201014 0000000000000001     4                 {{.*}}{{/|\\}}map-file.s.tmp4.a(map-file.s.tmp4.o)
-// CHECK-NEXT: 0000000000201014 0000000000000000     0                         baz
+// CHECK-NEXT: 0000000000201000 000000000000000e     4         {{.*}}{{/|\\}}map-file.s.tmp1.o:(.text)
+// CHECK-NEXT: 0000000000201000 0000000000000000     0                 _start
+// CHECK-NEXT: 0000000000201005 0000000000000000     0                 f(int)
+// CHECK-NEXT: 000000000020100e 0000000000000000     0                 local
+// CHECK-NEXT: 0000000000201010 0000000000000002     4         {{.*}}{{/|\\}}map-file.s.tmp2.o:(.text)
+// CHECK-NEXT: 0000000000201010 0000000000000000     0                 foo
+// CHECK-NEXT: 0000000000201011 0000000000000000     0                 bar
+// CHECK-NEXT: 0000000000201012 0000000000000000     1         {{.*}}{{/|\\}}map-file.s.tmp2.o:(.text.zed)
+// CHECK-NEXT: 0000000000201012 0000000000000000     0                 zed
+// CHECK-NEXT: 0000000000201014 0000000000000000     4         {{.*}}{{/|\\}}map-file.s.tmp3.o:(.text)
+// CHECK-NEXT: 0000000000201014 0000000000000000     0                 bah
+// CHECK-NEXT: 0000000000201014 0000000000000001     4         {{.*}}{{/|\\}}map-file.s.tmp4.a(map-file.s.tmp4.o):(.text)
+// CHECK-NEXT: 0000000000201014 0000000000000000     0                 baz
 // CHECK-NEXT: 0000000000202000 0000000000000004    16 .bss
-// CHECK-NEXT: 0000000000202000 0000000000000004    16         COMMON
+// CHECK-NEXT: 0000000000202000 0000000000000004    16         <internal>:(COMMON)
 // CHECK-NEXT: 0000000000000000 0000000000000008     1 .comment
-// CHECK-NEXT: 0000000000000000 0000000000000008     1         .comment
+// CHECK-NEXT: 0000000000000000 0000000000000008     1         <internal>:(.comment)
 // CHECK-NEXT: 0000000000000000 00000000000000f0     8 .symtab
-// CHECK-NEXT: 0000000000000000 00000000000000f0     8         .symtab
+// CHECK-NEXT: 0000000000000000 00000000000000f0     8         <internal>:(.symtab)
 // CHECK-NEXT: 0000000000000000 0000000000000039     1 .shstrtab
-// CHECK-NEXT: 0000000000000000 0000000000000039     1         .shstrtab
+// CHECK-NEXT: 0000000000000000 0000000000000039     1         <internal>:(.shstrtab)
 // CHECK-NEXT: 0000000000000000 000000000000002f     1 .strtab
-// CHECK-NEXT: 0000000000000000 000000000000002f     1         .strtab
+// CHECK-NEXT: 0000000000000000 000000000000002f     1         <internal>:(.strtab)
 
 // RUN: not ld.lld %t1.o %t2.o %t3.o %t4.a -o %t -Map=/ 2>&1 \
 // RUN:  | FileCheck -check-prefix=FAIL %s
diff --git a/test/ELF/relocation-in-merge.s b/test/ELF/relocation-in-merge.s
index 9ce2e4f7915..b37eff3ab89 100644
--- a/test/ELF/relocation-in-merge.s
+++ b/test/ELF/relocation-in-merge.s
@@ -1,7 +1,12 @@
 // REQUIRES: x86
 // RUN: llvm-mc %s -o %t.o -filetype=obj -triple=x86_64-pc-linux
-// RUN: not ld.lld %t.o -o %t 2>&1 | FileCheck %s
-// CHECK: relocations pointing to SHF_MERGE are not supported
+// RUN: ld.lld %t.o -o %t -shared
+// RUN: llvm-objdump -section-headers %t | FileCheck %s
 
-        .section	.foo,"aM",@progbits,4
-        .long bar
+// Test that we accept this by just not merging the section.
+// CHECK:  .foo          00000008
+
+bar:
+        .section	.foo,"aM",@progbits,8
+        .long bar - .
+        .long bar - .