Merge clang, llvm, lld, lldb, compiler-rt and libc++ 5.0.0 release.

MFC r309126 (by emaste):

  Correct lld llvm-tblgen dependency file name

MFC r309169:

  Get rid of separate Subversion mergeinfo properties for llvm-dwarfdump
  and llvm-lto.  The mergeinfo confuses Subversion enormously, and these
  directories will just use the mergeinfo for llvm itself.

MFC r312765:

  Pull in r276136 from upstream llvm trunk (by Wei Mi):

    Use ValueOffsetPair to enhance value reuse during SCEV expansion.

    In D12090, the ExprValueMap was added to reuse existing value during
    SCEV expansion. However, const folding and sext/zext distribution can
    make the reuse still difficult.

    A simplified case is: suppose we know S1 expands to V1 in
    ExprValueMap, and
      S1 = S2 + C_a
      S3 = S2 + C_b
    where C_a and C_b are different SCEVConstants. Then we'd like to
    expand S3 as V1 - C_a + C_b instead of expanding S2 literally. It is
    helpful when S2 is a complex SCEV expr and S2 has no entry in
    ExprValueMap, which is usually caused by the fact that S3 is
    generated from S1 after const folding.

    In order to do that, we represent ExprValueMap as a mapping from SCEV
    to ValueOffsetPair. We will save both S1->{V1, 0} and S2->{V1, C_a}
    into the ExprValueMap when we create SCEV for V1. When S3 is
    expanded, it will first expand S2 to V1 - C_a because of S2->{V1,
    C_a} in the map, then expand S3 to V1 - C_a + C_b.

    Differential Revision: https://reviews.llvm.org/D21313

  This should fix assertion failures when building OpenCV >= 3.1.

  PR:		215649

MFC r312831:

  Revert r312765 for now, since it causes assertions when building
  lang/spidermonkey24.

  Reported by:	antoine
  PR:		215649

MFC r316511 (by jhb):

  Add an implementation of __ffssi2() derived from __ffsdi2().

  Newer versions of GCC include an __ffssi2() symbol in libgcc and the
  compiler can emit calls to it in generated code.  This is true for at
  least GCC 6.2 when compiling world for mips and mips64.

  Reviewed by:	jmallett, dim
  Sponsored by:	DARPA / AFRL
  Differential Revision:	https://reviews.freebsd.org/D10086

MFC r318601 (by adrian):

  [libcompiler-rt] add bswapdi2/bswapsi2

  This is required for mips gcc 6.3 userland to build/run.

  Reviewed by:	emaste, dim
  Approved by:	emaste
  Differential Revision:	https://reviews.freebsd.org/D10838

MFC r318884 (by emaste):

  lldb: map TRAP_CAP to a trace trap

  In the absense of a more specific handler for TRAP_CAP (generated by
  ENOTCAPABLE or ECAPMODE while in capability mode) treat it as a trace
  trap.

  Example usage (testing the bug in PR219173):

  % proccontrol -m trapcap lldb usr.bin/hexdump/obj/hexdump -- -Cv -s 1 /bin/ls
  ...
  (lldb) run
  Process 12980 launching
  Process 12980 launched: '.../usr.bin/hexdump/obj/hexdump' (x86_64)
  Process 12980 stopped
  * thread #1, stop reason = trace
      frame #0: 0x0000004b80c65f1a libc.so.7`__sys_lseek + 10
  ...

  In the future we should have LLDB control the trapcap procctl itself
  (as it does with ASLR), as well as report a specific stop reason.
  This change eliminates an assertion failure from LLDB for now.

MFC r319796:

  Remove a few unneeded files from libllvm, libclang and liblldb.

MFC r319885 (by emaste):

  lld: ELF: Fix ICF crash on absolute symbol relocations.

  If two sections contained relocations to absolute symbols with the same
  value we would crash when trying to access their sections. Add a check that
  both symbols point to sections before accessing their sections, and treat
  absolute symbols as equal if their values are equal.

  Obtained from:	LLD commit r292578

MFC r319918:

  Revert r319796 for now, it can cause undefined references when linking
  in some circumstances.

  Reported by:	Shawn Webb <shawn.webb@hardenedbsd.org>

MFC r319957 (by emaste):

  lld: Add armelf emulation mode

  Obtained from:	LLD r305375

MFC r321369:

  Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
  5.0.0 (trunk r308421).  Upstream has branched for the 5.0.0 release,
  which should be in about a month.  Please report bugs and regressions,
  so we can get them into the release.

  Please note that from 3.5.0 onwards, clang, llvm and lldb require C++11
  support to build; see UPDATING for more information.

MFC r321420:

  Add a few more object files to liblldb, which should solve errors when
  linking the lldb executable in some cases.  In particular, when the
  -ffunction-sections -fdata-sections options are turned off, or
  ineffective.

  Reported by:	Shawn Webb, Mark Millard

MFC r321433:

  Cleanup stale Options.inc files from the previous libllvm build for
  clang 4.0.0.  Otherwise, these can get included before the two newly
  generated ones (which are different) for clang 5.0.0.

  Reported by:	Mark Millard

MFC r321439 (by bdrewery):

  Move llvm Options.inc hack from r321433 for NO_CLEAN to lib/clang/libllvm.

  The files are only ever generated to .OBJDIR, not to WORLDTMP (as a
  sysroot) and are only ever included from a compilation.  So using
  a beforebuild target here removes the file before the compilation
  tries to include it.

MFC r321664:

  Pull in r308891 from upstream llvm trunk (by Benjamin Kramer):

    [CodeGenPrepare] Cut off FindAllMemoryUses if there are too many uses.

    This avoids excessive compile time. The case I'm looking at is
    Function.cpp from an old version of LLVM that still had the giant
    memcmp string matcher in it. Before r308322 this compiled in about 2
    minutes, after it, clang takes infinite* time to compile it. With
    this patch we're at 5 min, which is still bad but this is a
    pathological case.

    The cut off at 20 uses was chosen by looking at other cut-offs in LLVM
    for user scanning. It's probably too high, but does the job and is
    very unlikely to regress anything.

    Fixes PR33900.

    * I'm impatient and aborted after 15 minutes, on the bug report it was
      killed after 2h.

  Pull in r308986 from upstream llvm trunk (by Simon Pilgrim):

    [X86][CGP] Reduce memcmp() expansion to 2 load pairs (PR33914)

    D35067/rL308322 attempted to support up to 4 load pairs for memcmp
    inlining which resulted in regressions for some optimized libc memcmp
    implementations (PR33914).

    Until we can match these more optimal cases, this patch reduces the
    memcmp expansion to a maximum of 2 load pairs (which matches what we
    do for -Os).

    This patch should be considered for the 5.0.0 release branch as well

    Differential Revision: https://reviews.llvm.org/D35830

  These fix a hang (or extremely long compile time) when building older
  LLVM ports.

  Reported by:    antoine
  PR:             219139

MFC r321719:

  Pull in r309503 from upstream clang trunk (by Richard Smith):

    PR33902: Invalidate line number cache when adding more text to
    existing buffer.

    This led to crashes as the line number cache would report a bogus
    line number for a line of code, and we'd try to find a nonexistent
    column within the line when printing diagnostics.

  This fixes an assertion when building the graphics/champlain port.

  Reported by:	antoine, kwm
  PR:		219139

MFC r321723:

  Upgrade our copies of clang, llvm, lld and lldb to r309439 from the
  upstream release_50 branch.  This is just after upstream's 5.0.0-rc1.

MFC r322320:

  Upgrade our copies of clang, llvm and libc++ to r310316 from the
  upstream release_50 branch.

MFC r322326 (by emaste):

  lldb: Make i386-*-freebsd expression work on JIT path

  * Enable i386 ABI creation for freebsd
  * Added an extra argument in ABISysV_i386::PrepareTrivialCall for mmap
    syscall
  * Unlike linux, the last argument of mmap is actually 64-bit(off_t).
    This requires us to push an additional word for the higher order bits.
  * Prior to this change, ktrace dump will show mmap failures due to
    invalid argument coming from the 6th mmap argument.

  Submitted by:	Karnajit Wangkhem
  Differential Revision:	https://reviews.llvm.org/D34776

MFC r322360 (by emaste):

  lldb: Report inferior signals as signals, not exceptions, on FreeBSD

  This is the FreeBSD equivalent of LLVM r238549.

  This serves 2 purposes:

  * LLDB should handle inferior process signals SIGSEGV/SIGILL/SIGBUS/
    SIGFPE the way it is suppose to be handled. Prior to this fix these
    signals will neither create a coredump, nor exit from the debugger
    or work for signal handling scenario.
  * eInvalidCrashReason need not report "unknown crash reason" if we have
    a valid si_signo

  llvm.org/pr23699

  Patch by Karnajit Wangkhem

  Differential Revision:  https://reviews.llvm.org/D35223

  Submitted by:	Karnajit Wangkhem
  Obtained from:	LLVM r310591

MFC r322474 (by emaste):

  lld: Add `-z muldefs` option.

  Obtained from:	LLVM r310757

MFC r322740:

  Upgrade our copies of clang, llvm, lld and libc++ to r311219 from the
  upstream release_50 branch.

MFC r322855:

  Upgrade our copies of clang, llvm, lldb and compiler-rt to r311606 from
  the upstream release_50 branch.

  As of this version, lib/msun's trig test should also work correctly
  again (see bug 220989 for more information).

  PR:		220989

MFC r323112:

  Upgrade our copies of clang, llvm, lldb and compiler-rt to r312293 from
  the upstream release_50 branch.  This corresponds to 5.0.0 rc4.

  As of this version, the cad/stepcode port should now compile in a more
  reasonable time on i386 (see bug 221836 for more information).

  PR:		221836

MFC r323245:

  Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
  5.0.0 release (upstream r312559).

  Release notes for llvm, clang and lld will be available here soon:
  <http://releases.llvm.org/5.0.0/docs/ReleaseNotes.html>
  <http://releases.llvm.org/5.0.0/tools/clang/docs/ReleaseNotes.html>
  <http://releases.llvm.org/5.0.0/tools/lld/docs/ReleaseNotes.html>

  Relnotes:	yes

(cherry picked from commit 12cd91cf4c6b96a24427c0de5374916f2808d263)

1 files changed, 420 insertions, 0 deletions

diff --git a/contrib/llvm/lib/DebugInfo/PDB/Native/DbiStreamBuilder.cpp b/contrib/llvm/lib/DebugInfo/PDB/Native/DbiStreamBuilder.cpp
new file mode 100644
index 0000000..25076e4
--- /dev/null
+++ b/contrib/llvm/lib/DebugInfo/PDB/Native/DbiStreamBuilder.cpp
@@ -0,0 +1,420 @@
+//===- DbiStreamBuilder.cpp - PDB Dbi Stream Creation -----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/PDB/Native/DbiStreamBuilder.h"
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/BinaryFormat/COFF.h"
+#include "llvm/DebugInfo/MSF/MSFBuilder.h"
+#include "llvm/DebugInfo/MSF/MappedBlockStream.h"
+#include "llvm/DebugInfo/PDB/Native/DbiModuleDescriptorBuilder.h"
+#include "llvm/DebugInfo/PDB/Native/DbiStream.h"
+#include "llvm/DebugInfo/PDB/Native/RawError.h"
+#include "llvm/Object/COFF.h"
+#include "llvm/Support/BinaryStreamWriter.h"
+
+using namespace llvm;
+using namespace llvm::codeview;
+using namespace llvm::msf;
+using namespace llvm::pdb;
+
+DbiStreamBuilder::DbiStreamBuilder(msf::MSFBuilder &Msf)
+    : Msf(Msf), Allocator(Msf.getAllocator()), Age(1), BuildNumber(0),
+      PdbDllVersion(0), PdbDllRbld(0), Flags(0), MachineType(PDB_Machine::x86),
+      Header(nullptr), DbgStreams((int)DbgHeaderType::Max) {}
+
+DbiStreamBuilder::~DbiStreamBuilder() {}
+
+void DbiStreamBuilder::setVersionHeader(PdbRaw_DbiVer V) { VerHeader = V; }
+
+void DbiStreamBuilder::setAge(uint32_t A) { Age = A; }
+
+void DbiStreamBuilder::setBuildNumber(uint16_t B) { BuildNumber = B; }
+
+void DbiStreamBuilder::setPdbDllVersion(uint16_t V) { PdbDllVersion = V; }
+
+void DbiStreamBuilder::setPdbDllRbld(uint16_t R) { PdbDllRbld = R; }
+
+void DbiStreamBuilder::setFlags(uint16_t F) { Flags = F; }
+
+void DbiStreamBuilder::setMachineType(PDB_Machine M) { MachineType = M; }
+
+void DbiStreamBuilder::setSectionMap(ArrayRef<SecMapEntry> SecMap) {
+  SectionMap = SecMap;
+}
+
+void DbiStreamBuilder::setSymbolRecordStreamIndex(uint32_t Index) {
+  SymRecordStreamIndex = Index;
+}
+
+void DbiStreamBuilder::setPublicsStreamIndex(uint32_t Index) {
+  PublicsStreamIndex = Index;
+}
+
+Error DbiStreamBuilder::addDbgStream(pdb::DbgHeaderType Type,
+                                     ArrayRef<uint8_t> Data) {
+  if (DbgStreams[(int)Type].StreamNumber != kInvalidStreamIndex)
+    return make_error<RawError>(raw_error_code::duplicate_entry,
+                                "The specified stream type already exists");
+  auto ExpectedIndex = Msf.addStream(Data.size());
+  if (!ExpectedIndex)
+    return ExpectedIndex.takeError();
+  uint32_t Index = std::move(*ExpectedIndex);
+  DbgStreams[(int)Type].Data = Data;
+  DbgStreams[(int)Type].StreamNumber = Index;
+  return Error::success();
+}
+
+uint32_t DbiStreamBuilder::addECName(StringRef Name) {
+  return ECNamesBuilder.insert(Name);
+}
+
+uint32_t DbiStreamBuilder::calculateSerializedLength() const {
+  // For now we only support serializing the header.
+  return sizeof(DbiStreamHeader) + calculateFileInfoSubstreamSize() +
+         calculateModiSubstreamSize() + calculateSectionContribsStreamSize() +
+         calculateSectionMapStreamSize() + calculateDbgStreamsSize() +
+         ECNamesBuilder.calculateSerializedSize();
+}
+
+Expected<DbiModuleDescriptorBuilder &>
+DbiStreamBuilder::addModuleInfo(StringRef ModuleName) {
+  uint32_t Index = ModiList.size();
+  auto MIB =
+      llvm::make_unique<DbiModuleDescriptorBuilder>(ModuleName, Index, Msf);
+  auto M = MIB.get();
+  auto Result = ModiMap.insert(std::make_pair(ModuleName, std::move(MIB)));
+
+  if (!Result.second)
+    return make_error<RawError>(raw_error_code::duplicate_entry,
+                                "The specified module already exists");
+  ModiList.push_back(M);
+  return *M;
+}
+
+Error DbiStreamBuilder::addModuleSourceFile(StringRef Module, StringRef File) {
+  auto ModIter = ModiMap.find(Module);
+  if (ModIter == ModiMap.end())
+    return make_error<RawError>(raw_error_code::no_entry,
+                                "The specified module was not found");
+  return addModuleSourceFile(*ModIter->second, File);
+}
+
+Error DbiStreamBuilder::addModuleSourceFile(DbiModuleDescriptorBuilder &Module,
+                                            StringRef File) {
+  uint32_t Index = SourceFileNames.size();
+  SourceFileNames.insert(std::make_pair(File, Index));
+  Module.addSourceFile(File);
+  return Error::success();
+}
+
+Expected<uint32_t> DbiStreamBuilder::getSourceFileNameIndex(StringRef File) {
+  auto NameIter = SourceFileNames.find(File);
+  if (NameIter == SourceFileNames.end())
+    return make_error<RawError>(raw_error_code::no_entry,
+                                "The specified source file was not found");
+  return NameIter->getValue();
+}
+
+uint32_t DbiStreamBuilder::calculateModiSubstreamSize() const {
+  uint32_t Size = 0;
+  for (const auto &M : ModiList)
+    Size += M->calculateSerializedLength();
+  return Size;
+}
+
+uint32_t DbiStreamBuilder::calculateSectionContribsStreamSize() const {
+  if (SectionContribs.empty())
+    return 0;
+  return sizeof(enum PdbRaw_DbiSecContribVer) +
+         sizeof(SectionContribs[0]) * SectionContribs.size();
+}
+
+uint32_t DbiStreamBuilder::calculateSectionMapStreamSize() const {
+  if (SectionMap.empty())
+    return 0;
+  return sizeof(SecMapHeader) + sizeof(SecMapEntry) * SectionMap.size();
+}
+
+uint32_t DbiStreamBuilder::calculateNamesOffset() const {
+  uint32_t Offset = 0;
+  Offset += sizeof(ulittle16_t);                         // NumModules
+  Offset += sizeof(ulittle16_t);                         // NumSourceFiles
+  Offset += ModiList.size() * sizeof(ulittle16_t);       // ModIndices
+  Offset += ModiList.size() * sizeof(ulittle16_t);       // ModFileCounts
+  uint32_t NumFileInfos = 0;
+  for (const auto &M : ModiList)
+    NumFileInfos += M->source_files().size();
+  Offset += NumFileInfos * sizeof(ulittle32_t); // FileNameOffsets
+  return Offset;
+}
+
+uint32_t DbiStreamBuilder::calculateFileInfoSubstreamSize() const {
+  uint32_t Size = calculateNamesOffset();
+  Size += calculateNamesBufferSize();
+  return alignTo(Size, sizeof(uint32_t));
+}
+
+uint32_t DbiStreamBuilder::calculateNamesBufferSize() const {
+  uint32_t Size = 0;
+  for (const auto &F : SourceFileNames) {
+    Size += F.getKeyLength() + 1; // Names[I];
+  }
+  return Size;
+}
+
+uint32_t DbiStreamBuilder::calculateDbgStreamsSize() const {
+  return DbgStreams.size() * sizeof(uint16_t);
+}
+
+Error DbiStreamBuilder::generateFileInfoSubstream() {
+  uint32_t Size = calculateFileInfoSubstreamSize();
+  auto Data = Allocator.Allocate<uint8_t>(Size);
+  uint32_t NamesOffset = calculateNamesOffset();
+
+  FileInfoBuffer = MutableBinaryByteStream(MutableArrayRef<uint8_t>(Data, Size),
+                                           llvm::support::little);
+
+  WritableBinaryStreamRef MetadataBuffer =
+      WritableBinaryStreamRef(FileInfoBuffer).keep_front(NamesOffset);
+  BinaryStreamWriter MetadataWriter(MetadataBuffer);
+
+  uint16_t ModiCount = std::min<uint32_t>(UINT16_MAX, ModiList.size());
+  uint16_t FileCount = std::min<uint32_t>(UINT16_MAX, SourceFileNames.size());
+  if (auto EC = MetadataWriter.writeInteger(ModiCount)) // NumModules
+    return EC;
+  if (auto EC = MetadataWriter.writeInteger(FileCount)) // NumSourceFiles
+    return EC;
+  for (uint16_t I = 0; I < ModiCount; ++I) {
+    if (auto EC = MetadataWriter.writeInteger(I)) // Mod Indices
+      return EC;
+  }
+  for (const auto &MI : ModiList) {
+    FileCount = static_cast<uint16_t>(MI->source_files().size());
+    if (auto EC = MetadataWriter.writeInteger(FileCount)) // Mod File Counts
+      return EC;
+  }
+
+  // Before writing the FileNameOffsets array, write the NamesBuffer array.
+  // A side effect of this is that this will actually compute the various
+  // file name offsets, so we can then go back and write the FileNameOffsets
+  // array to the other substream.
+  NamesBuffer = WritableBinaryStreamRef(FileInfoBuffer).drop_front(NamesOffset);
+  BinaryStreamWriter NameBufferWriter(NamesBuffer);
+  for (auto &Name : SourceFileNames) {
+    Name.second = NameBufferWriter.getOffset();
+    if (auto EC = NameBufferWriter.writeCString(Name.getKey()))
+      return EC;
+  }
+
+  for (const auto &MI : ModiList) {
+    for (StringRef Name : MI->source_files()) {
+      auto Result = SourceFileNames.find(Name);
+      if (Result == SourceFileNames.end())
+        return make_error<RawError>(raw_error_code::no_entry,
+                                    "The source file was not found.");
+      if (auto EC = MetadataWriter.writeInteger(Result->second))
+        return EC;
+    }
+  }
+
+  if (auto EC = NameBufferWriter.padToAlignment(sizeof(uint32_t)))
+    return EC;
+
+  if (NameBufferWriter.bytesRemaining() > 0)
+    return make_error<RawError>(raw_error_code::invalid_format,
+                                "The names buffer contained unexpected data.");
+
+  if (MetadataWriter.bytesRemaining() > sizeof(uint32_t))
+    return make_error<RawError>(
+        raw_error_code::invalid_format,
+        "The metadata buffer contained unexpected data.");
+
+  return Error::success();
+}
+
+Error DbiStreamBuilder::finalize() {
+  if (Header)
+    return Error::success();
+
+  for (auto &MI : ModiList)
+    MI->finalize();
+
+  if (auto EC = generateFileInfoSubstream())
+    return EC;
+
+  DbiStreamHeader *H = Allocator.Allocate<DbiStreamHeader>();
+  ::memset(H, 0, sizeof(DbiStreamHeader));
+  H->VersionHeader = *VerHeader;
+  H->VersionSignature = -1;
+  H->Age = Age;
+  H->BuildNumber = BuildNumber;
+  H->Flags = Flags;
+  H->PdbDllRbld = PdbDllRbld;
+  H->PdbDllVersion = PdbDllVersion;
+  H->MachineType = static_cast<uint16_t>(MachineType);
+
+  H->ECSubstreamSize = ECNamesBuilder.calculateSerializedSize();
+  H->FileInfoSize = FileInfoBuffer.getLength();
+  H->ModiSubstreamSize = calculateModiSubstreamSize();
+  H->OptionalDbgHdrSize = DbgStreams.size() * sizeof(uint16_t);
+  H->SecContrSubstreamSize = calculateSectionContribsStreamSize();
+  H->SectionMapSize = calculateSectionMapStreamSize();
+  H->TypeServerSize = 0;
+  H->SymRecordStreamIndex = SymRecordStreamIndex;
+  H->PublicSymbolStreamIndex = PublicsStreamIndex;
+  H->MFCTypeServerIndex = kInvalidStreamIndex;
+  H->GlobalSymbolStreamIndex = kInvalidStreamIndex;
+
+  Header = H;
+  return Error::success();
+}
+
+Error DbiStreamBuilder::finalizeMsfLayout() {
+  for (auto &MI : ModiList) {
+    if (auto EC = MI->finalizeMsfLayout())
+      return EC;
+  }
+
+  uint32_t Length = calculateSerializedLength();
+  if (auto EC = Msf.setStreamSize(StreamDBI, Length))
+    return EC;
+  return Error::success();
+}
+
+static uint16_t toSecMapFlags(uint32_t Flags) {
+  uint16_t Ret = 0;
+  if (Flags & COFF::IMAGE_SCN_MEM_READ)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Read);
+  if (Flags & COFF::IMAGE_SCN_MEM_WRITE)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Write);
+  if (Flags & COFF::IMAGE_SCN_MEM_EXECUTE)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Execute);
+  if (Flags & COFF::IMAGE_SCN_MEM_EXECUTE)
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::Execute);
+  if (!(Flags & COFF::IMAGE_SCN_MEM_16BIT))
+    Ret |= static_cast<uint16_t>(OMFSegDescFlags::AddressIs32Bit);
+
+  // This seems always 1.
+  Ret |= static_cast<uint16_t>(OMFSegDescFlags::IsSelector);
+
+  return Ret;
+}
+
+void DbiStreamBuilder::addSectionContrib(DbiModuleDescriptorBuilder *ModuleDbi,
+                                         const object::coff_section *SecHdr) {
+  SectionContrib SC;
+  memset(&SC, 0, sizeof(SC));
+  SC.ISect = (uint16_t)~0U; // This represents nil.
+  SC.Off = SecHdr->PointerToRawData;
+  SC.Size = SecHdr->SizeOfRawData;
+  SC.Characteristics = SecHdr->Characteristics;
+  // Use the module index in the module dbi stream or nil (-1).
+  SC.Imod = ModuleDbi ? ModuleDbi->getModuleIndex() : (uint16_t)~0U;
+  SectionContribs.emplace_back(SC);
+}
+
+// A utility function to create a Section Map for a given list of COFF sections.
+//
+// A Section Map seem to be a copy of a COFF section list in other format.
+// I don't know why a PDB file contains both a COFF section header and
+// a Section Map, but it seems it must be present in a PDB.
+std::vector<SecMapEntry> DbiStreamBuilder::createSectionMap(
+    ArrayRef<llvm::object::coff_section> SecHdrs) {
+  std::vector<SecMapEntry> Ret;
+  int Idx = 0;
+
+  auto Add = [&]() -> SecMapEntry & {
+    Ret.emplace_back();
+    auto &Entry = Ret.back();
+    memset(&Entry, 0, sizeof(Entry));
+
+    Entry.Frame = Idx + 1;
+
+    // We don't know the meaning of these fields yet.
+    Entry.SecName = UINT16_MAX;
+    Entry.ClassName = UINT16_MAX;
+
+    return Entry;
+  };
+
+  for (auto &Hdr : SecHdrs) {
+    auto &Entry = Add();
+    Entry.Flags = toSecMapFlags(Hdr.Characteristics);
+    Entry.SecByteLength = Hdr.VirtualSize;
+    ++Idx;
+  }
+
+  // The last entry is for absolute symbols.
+  auto &Entry = Add();
+  Entry.Flags = static_cast<uint16_t>(OMFSegDescFlags::AddressIs32Bit) |
+                static_cast<uint16_t>(OMFSegDescFlags::IsAbsoluteAddress);
+  Entry.SecByteLength = UINT32_MAX;
+
+  return Ret;
+}
+
+Error DbiStreamBuilder::commit(const msf::MSFLayout &Layout,
+                               WritableBinaryStreamRef MsfBuffer) {
+  if (auto EC = finalize())
+    return EC;
+
+  auto DbiS = WritableMappedBlockStream::createIndexedStream(
+      Layout, MsfBuffer, StreamDBI, Allocator);
+
+  BinaryStreamWriter Writer(*DbiS);
+  if (auto EC = Writer.writeObject(*Header))
+    return EC;
+
+  for (auto &M : ModiList) {
+    if (auto EC = M->commit(Writer, Layout, MsfBuffer))
+      return EC;
+  }
+
+  if (!SectionContribs.empty()) {
+    if (auto EC = Writer.writeEnum(DbiSecContribVer60))
+      return EC;
+    if (auto EC = Writer.writeArray(makeArrayRef(SectionContribs)))
+      return EC;
+  }
+
+  if (!SectionMap.empty()) {
+    ulittle16_t Size = static_cast<ulittle16_t>(SectionMap.size());
+    SecMapHeader SMHeader = {Size, Size};
+    if (auto EC = Writer.writeObject(SMHeader))
+      return EC;
+    if (auto EC = Writer.writeArray(SectionMap))
+      return EC;
+  }
+
+  if (auto EC = Writer.writeStreamRef(FileInfoBuffer))
+    return EC;
+
+  if (auto EC = ECNamesBuilder.commit(Writer))
+    return EC;
+
+  for (auto &Stream : DbgStreams)
+    if (auto EC = Writer.writeInteger(Stream.StreamNumber))
+      return EC;
+
+  for (auto &Stream : DbgStreams) {
+    if (Stream.StreamNumber == kInvalidStreamIndex)
+      continue;
+    auto WritableStream = WritableMappedBlockStream::createIndexedStream(
+        Layout, MsfBuffer, Stream.StreamNumber, Allocator);
+    BinaryStreamWriter DbgStreamWriter(*WritableStream);
+    if (auto EC = DbgStreamWriter.writeArray(Stream.Data))
+      return EC;
+  }
+
+  if (Writer.bytesRemaining() > 0)
+    return make_error<RawError>(raw_error_code::invalid_format,
+                                "Unexpected bytes found in DBI Stream");
+  return Error::success();
+}