Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release:

MFC r309142 (by emaste):

Add WITH_LLD_AS_LD build knob

If set it installs LLD as /usr/bin/ld.  LLD (as of version 3.9) is not
capable of linking the world and kernel, but can self-host and link many
substantial applications. GNU ld continues to be used for the world and
kernel build, regardless of how this knob is set.

It is on by default for arm64, and off for all other CPU architectures.

Sponsored by:	The FreeBSD Foundation

MFC r310840:

Reapply 310775, now it also builds correctly if lldb is disabled:

Move llvm-objdump from CLANG_EXTRAS to installed by default

We currently install three tools from binutils 2.17.50: as, ld, and
objdump. Work is underway to migrate to a permissively-licensed
tool-chain, with one goal being the retirement of binutils 2.17.50.

LLVM's llvm-objdump is intended to be compatible with GNU objdump
although it is currently missing some options and may have formatting
differences. Enable it by default for testing and further investigation.
It may later be changed to install as /usr/bin/objdump, it becomes a
fully viable replacement.

Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D8879

MFC r312855 (by emaste):

Rename LLD_AS_LD to LLD_IS_LD, for consistency with CLANG_IS_CC

Reported by:	Dan McGregor <dan.mcgregor usask.ca>

MFC r313559 | glebius | 2017-02-10 18:34:48 +0100 (Fri, 10 Feb 2017) | 5 lines

Don't check struct rtentry on FreeBSD, it is an internal kernel structure.
On other systems it may be API structure for SIOCADDRT/SIOCDELRT.

Reviewed by:	emaste, dim

MFC r314152 (by jkim):

Remove an assembler flag, which is redundant since r309124.  The upstream
took care of it by introducing a macro NO_EXEC_STACK_DIRECTIVE.

http://llvm.org/viewvc/llvm-project?rev=273500&view=rev

Reviewed by:	dim

MFC r314564:

Upgrade our copies of clang, llvm, lld, lldb, compiler-rt and libc++ to
4.0.0 (branches/release_40 296509).  The release will follow soon.

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

Also note that as of 4.0.0, lld should be able to link the base system
on amd64 and aarch64.  See the WITH_LLD_IS_LLD setting in src.conf(5).
Though please be aware that this is work in progress.

Release notes for llvm, clang and lld will be available here:
<http://releases.llvm.org/4.0.0/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/clang/docs/ReleaseNotes.html>
<http://releases.llvm.org/4.0.0/tools/lld/docs/ReleaseNotes.html>

Thanks to Ed Maste, Jan Beich, Antoine Brodin and Eric Fiselier for
their help.

Relnotes:	yes
Exp-run:	antoine
PR:		215969, 216008

MFC r314708:

For now, revert r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

This commit is the cause of excessive compile times on skein_block.c
(and possibly other files) during kernel builds on amd64.

We never saw the problematic behavior described in this upstream commit,
so for now it is better to revert it.  An upstream bug has been filed
here: https://bugs.llvm.org/show_bug.cgi?id=32142

Reported by:	mjg

MFC r314795:

Reapply r287232 from upstream llvm trunk (by Daniil Fukalov):

  [SCEV] limit recursion depth of CompareSCEVComplexity

  Summary:
  CompareSCEVComplexity goes too deep (50+ on a quite a big unrolled
  loop) and runs almost infinite time.

  Added cache of "equal" SCEV pairs to earlier cutoff of further
  estimation. Recursion depth limit was also introduced as a parameter.

  Reviewers: sanjoy

  Subscribers: mzolotukhin, tstellarAMD, llvm-commits

  Differential Revision: https://reviews.llvm.org/D26389

Pull in r296992 from upstream llvm trunk (by Sanjoy Das):

  [SCEV] Decrease the recursion threshold for CompareValueComplexity

  Fixes PR32142.

  r287232 accidentally increased the recursion threshold for
  CompareValueComplexity from 2 to 32.  This change reverses that
  change by introducing a separate flag for CompareValueComplexity's
  threshold.

The latter revision fixes the excessive compile times for skein_block.c.

MFC r314907 | mmel | 2017-03-08 12:40:27 +0100 (Wed, 08 Mar 2017) | 7 lines

Unbreak ARMv6 world.

The new compiler_rt library imported with clang 4.0.0 have several fatal
issues (non-functional __udivsi3 for example) with ARM specific instrict
functions. As temporary workaround, until upstream solve these problems,
disable all thumb[1][2] related feature.

MFC r315016:

Update clang, llvm, lld, lldb, compiler-rt and libc++ to 4.0.0 release.
We were already very close to the last release candidate, so this is a
pretty minor update.

Relnotes:	yes

MFC r316005:

Revert r314907, and pull in r298713 from upstream compiler-rt trunk (by
Weiming Zhao):

  builtins: Select correct code fragments when compiling for Thumb1/Thum2/ARM ISA.

  Summary:
  Value of __ARM_ARCH_ISA_THUMB isn't based on the actual compilation
  mode (-mthumb, -marm), it reflect's capability of given CPU.

  Due to this:
   - use  __tbumb__ and __thumb2__ insteand of __ARM_ARCH_ISA_THUMB
   - use '.thumb' directive consistently  in all affected files
   - decorate all thumb functions using
     DEFINE_COMPILERRT_THUMB_FUNCTION()

  ---------
  Note: This patch doesn't fix broken Thumb1 variant of __udivsi3 !

  Reviewers: weimingz, rengolin, compnerd

  Subscribers: aemerson, dim

  Differential Revision: https://reviews.llvm.org/D30938

Discussed with:	mmel

1 files changed, 167 insertions, 141 deletions

diff --git a/contrib/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp b/contrib/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp
index 9501675..5349151 100644
--- a/contrib/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp
+++ b/contrib/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp
@@ -7,68 +7,84 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/DebugInfo/PDB/Raw/PDBFile.h"
-
 #include "llvm/ADT/ArrayRef.h"
-#include "llvm/DebugInfo/CodeView/StreamArray.h"
-#include "llvm/DebugInfo/CodeView/StreamInterface.h"
-#include "llvm/DebugInfo/CodeView/StreamReader.h"
-#include "llvm/DebugInfo/CodeView/StreamWriter.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/DebugInfo/MSF/MappedBlockStream.h"
+#include "llvm/DebugInfo/MSF/MSFCommon.h"
+#include "llvm/DebugInfo/MSF/StreamArray.h"
+#include "llvm/DebugInfo/MSF/StreamInterface.h"
+#include "llvm/DebugInfo/MSF/StreamReader.h"
 #include "llvm/DebugInfo/PDB/Raw/DbiStream.h"
-#include "llvm/DebugInfo/PDB/Raw/DirectoryStreamData.h"
-#include "llvm/DebugInfo/PDB/Raw/IndexedStreamData.h"
+#include "llvm/DebugInfo/PDB/Raw/GlobalsStream.h"
 #include "llvm/DebugInfo/PDB/Raw/InfoStream.h"
 #include "llvm/DebugInfo/PDB/Raw/NameHashTable.h"
+#include "llvm/DebugInfo/PDB/Raw/PDBFile.h"
 #include "llvm/DebugInfo/PDB/Raw/PublicsStream.h"
 #include "llvm/DebugInfo/PDB/Raw/RawError.h"
 #include "llvm/DebugInfo/PDB/Raw/SymbolStream.h"
 #include "llvm/DebugInfo/PDB/Raw/TpiStream.h"
 #include "llvm/Support/Endian.h"
-#include "llvm/Support/FileOutputBuffer.h"
-#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/Error.h"
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
 
 using namespace llvm;
 using namespace llvm::codeview;
+using namespace llvm::msf;
 using namespace llvm::pdb;
 
 namespace {
 typedef FixedStreamArray<support::ulittle32_t> ulittle_array;
-}
+} // end anonymous namespace
 
-PDBFile::PDBFile(std::unique_ptr<StreamInterface> PdbFileBuffer)
-    : Buffer(std::move(PdbFileBuffer)), SB(nullptr) {}
+PDBFile::PDBFile(std::unique_ptr<ReadableStream> PdbFileBuffer,
+                 BumpPtrAllocator &Allocator)
+    : Allocator(Allocator), Buffer(std::move(PdbFileBuffer)) {}
 
-PDBFile::~PDBFile() {}
+PDBFile::~PDBFile() = default;
 
-uint32_t PDBFile::getBlockSize() const { return SB->BlockSize; }
+uint32_t PDBFile::getBlockSize() const { return ContainerLayout.SB->BlockSize; }
 
-uint32_t PDBFile::getFreeBlockMapBlock() const { return SB->FreeBlockMapBlock; }
+uint32_t PDBFile::getFreeBlockMapBlock() const {
+  return ContainerLayout.SB->FreeBlockMapBlock;
+}
 
-uint32_t PDBFile::getBlockCount() const { return SB->NumBlocks; }
+uint32_t PDBFile::getBlockCount() const {
+  return ContainerLayout.SB->NumBlocks;
+}
 
-uint32_t PDBFile::getNumDirectoryBytes() const { return SB->NumDirectoryBytes; }
+uint32_t PDBFile::getNumDirectoryBytes() const {
+  return ContainerLayout.SB->NumDirectoryBytes;
+}
 
-uint32_t PDBFile::getBlockMapIndex() const { return SB->BlockMapAddr; }
+uint32_t PDBFile::getBlockMapIndex() const {
+  return ContainerLayout.SB->BlockMapAddr;
+}
 
-uint32_t PDBFile::getUnknown1() const { return SB->Unknown1; }
+uint32_t PDBFile::getUnknown1() const { return ContainerLayout.SB->Unknown1; }
 
 uint32_t PDBFile::getNumDirectoryBlocks() const {
-  return msf::bytesToBlocks(SB->NumDirectoryBytes, SB->BlockSize);
+  return msf::bytesToBlocks(ContainerLayout.SB->NumDirectoryBytes,
+                            ContainerLayout.SB->BlockSize);
 }
 
 uint64_t PDBFile::getBlockMapOffset() const {
-  return (uint64_t)SB->BlockMapAddr * SB->BlockSize;
+  return (uint64_t)ContainerLayout.SB->BlockMapAddr *
+         ContainerLayout.SB->BlockSize;
 }
 
-uint32_t PDBFile::getNumStreams() const { return StreamSizes.size(); }
+uint32_t PDBFile::getNumStreams() const {
+  return ContainerLayout.StreamSizes.size();
+}
 
 uint32_t PDBFile::getStreamByteSize(uint32_t StreamIndex) const {
-  return StreamSizes[StreamIndex];
+  return ContainerLayout.StreamSizes[StreamIndex];
 }
 
 ArrayRef<support::ulittle32_t>
 PDBFile::getStreamBlockList(uint32_t StreamIndex) const {
-  return StreamMap[StreamIndex];
+  return ContainerLayout.StreamMap[StreamIndex];
 }
 
 uint32_t PDBFile::getFileSize() const { return Buffer->getLength(); }
@@ -85,41 +101,72 @@ Expected<ArrayRef<uint8_t>> PDBFile::getBlockData(uint32_t BlockIndex,
 
 Error PDBFile::setBlockData(uint32_t BlockIndex, uint32_t Offset,
                             ArrayRef<uint8_t> Data) const {
-  if (Offset >= getBlockSize())
-    return make_error<RawError>(
-        raw_error_code::invalid_block_address,
-        "setBlockData attempted to write out of block bounds.");
-  if (Data.size() > getBlockSize() - Offset)
-    return make_error<RawError>(
-        raw_error_code::invalid_block_address,
-        "setBlockData attempted to write out of block bounds.");
-
-  uint64_t StreamBlockOffset = msf::blockToOffset(BlockIndex, getBlockSize());
-  StreamBlockOffset += Offset;
-  return Buffer->writeBytes(StreamBlockOffset, Data);
+  return make_error<RawError>(raw_error_code::not_writable,
+                              "PDBFile is immutable");
 }
 
 Error PDBFile::parseFileHeaders() {
   StreamReader Reader(*Buffer);
 
+  // Initialize SB.
+  const msf::SuperBlock *SB = nullptr;
   if (auto EC = Reader.readObject(SB)) {
     consumeError(std::move(EC));
     return make_error<RawError>(raw_error_code::corrupt_file,
                                 "Does not contain superblock");
   }
 
-  if (auto EC = setSuperBlock(SB))
+  if (auto EC = msf::validateSuperBlock(*SB))
+    return EC;
+
+  if (Buffer->getLength() % SB->BlockSize != 0)
+    return make_error<RawError>(raw_error_code::corrupt_file,
+                                "File size is not a multiple of block size");
+  ContainerLayout.SB = SB;
+
+  // Initialize Free Page Map.
+  ContainerLayout.FreePageMap.resize(SB->NumBlocks);
+  // The Fpm exists either at block 1 or block 2 of the MSF.  However, this
+  // allows for a maximum of getBlockSize() * 8 blocks bits in the Fpm, and
+  // thusly an equal number of total blocks in the file.  For a block size
+  // of 4KiB (very common), this would yield 32KiB total blocks in file, for a
+  // maximum file size of 32KiB * 4KiB = 128MiB.  Obviously this won't do, so
+  // the Fpm is split across the file at `getBlockSize()` intervals.  As a
+  // result, every block whose index is of the form |{1,2} + getBlockSize() * k|
+  // for any non-negative integer k is an Fpm block.  In theory, we only really
+  // need to reserve blocks of the form |{1,2} + getBlockSize() * 8 * k|, but
+  // current versions of the MSF format already expect the Fpm to be arranged
+  // at getBlockSize() intervals, so we have to be compatible.
+  // See the function fpmPn() for more information:
+  // https://github.com/Microsoft/microsoft-pdb/blob/master/PDB/msf/msf.cpp#L489
+  auto FpmStream = MappedBlockStream::createFpmStream(ContainerLayout, *Buffer);
+  StreamReader FpmReader(*FpmStream);
+  ArrayRef<uint8_t> FpmBytes;
+  if (auto EC = FpmReader.readBytes(FpmBytes,
+                                    msf::getFullFpmByteSize(ContainerLayout)))
     return EC;
+  uint32_t BlocksRemaining = getBlockCount();
+  uint32_t BI = 0;
+  for (auto Byte : FpmBytes) {
+    uint32_t BlocksThisByte = std::min(BlocksRemaining, 8U);
+    for (uint32_t I = 0; I < BlocksThisByte; ++I) {
+      if (Byte & (1 << I))
+        ContainerLayout.FreePageMap[BI] = true;
+      --BlocksRemaining;
+      ++BI;
+    }
+  }
 
   Reader.setOffset(getBlockMapOffset());
-  if (auto EC = Reader.readArray(DirectoryBlocks, getNumDirectoryBlocks()))
+  if (auto EC = Reader.readArray(ContainerLayout.DirectoryBlocks,
+                                 getNumDirectoryBlocks()))
     return EC;
 
   return Error::success();
 }
 
 Error PDBFile::parseStreamData() {
-  assert(SB);
+  assert(ContainerLayout.SB);
   if (DirectoryStream)
     return Error::success();
 
@@ -130,21 +177,20 @@ Error PDBFile::parseStreamData() {
   // is exactly what we are attempting to parse.  By specifying a custom
   // subclass of IPDBStreamData which only accesses the fields that have already
   // been parsed, we can avoid this and reuse MappedBlockStream.
-  auto DS = MappedBlockStream::createDirectoryStream(*this);
-  if (!DS)
-    return DS.takeError();
-  StreamReader Reader(**DS);
+  auto DS = MappedBlockStream::createDirectoryStream(ContainerLayout, *Buffer);
+  StreamReader Reader(*DS);
   if (auto EC = Reader.readInteger(NumStreams))
     return EC;
 
-  if (auto EC = Reader.readArray(StreamSizes, NumStreams))
+  if (auto EC = Reader.readArray(ContainerLayout.StreamSizes, NumStreams))
     return EC;
   for (uint32_t I = 0; I < NumStreams; ++I) {
     uint32_t StreamSize = getStreamByteSize(I);
     // FIXME: What does StreamSize ~0U mean?
     uint64_t NumExpectedStreamBlocks =
-        StreamSize == UINT32_MAX ? 0 : msf::bytesToBlocks(StreamSize,
-                                                          SB->BlockSize);
+        StreamSize == UINT32_MAX
+            ? 0
+            : msf::bytesToBlocks(StreamSize, ContainerLayout.SB->BlockSize);
 
     // For convenience, we store the block array contiguously.  This is because
     // if someone calls setStreamMap(), it is more convenient to be able to call
@@ -156,29 +202,46 @@ Error PDBFile::parseStreamData() {
     if (auto EC = Reader.readArray(Blocks, NumExpectedStreamBlocks))
       return EC;
     for (uint32_t Block : Blocks) {
-      uint64_t BlockEndOffset = (uint64_t)(Block + 1) * SB->BlockSize;
+      uint64_t BlockEndOffset =
+          (uint64_t)(Block + 1) * ContainerLayout.SB->BlockSize;
       if (BlockEndOffset > getFileSize())
         return make_error<RawError>(raw_error_code::corrupt_file,
                                     "Stream block map is corrupt.");
     }
-    StreamMap.push_back(Blocks);
+    ContainerLayout.StreamMap.push_back(Blocks);
   }
 
   // We should have read exactly SB->NumDirectoryBytes bytes.
   assert(Reader.bytesRemaining() == 0);
-  DirectoryStream = std::move(*DS);
+  DirectoryStream = std::move(DS);
   return Error::success();
 }
 
-llvm::ArrayRef<support::ulittle32_t> PDBFile::getDirectoryBlockArray() const {
-  return DirectoryBlocks;
+ArrayRef<support::ulittle32_t> PDBFile::getDirectoryBlockArray() const {
+  return ContainerLayout.DirectoryBlocks;
+}
+
+Expected<GlobalsStream &> PDBFile::getPDBGlobalsStream() {
+  if (!Globals) {
+    auto DbiS = getPDBDbiStream();
+    if (!DbiS)
+      return DbiS.takeError();
+
+    auto GlobalS = safelyCreateIndexedStream(
+        ContainerLayout, *Buffer, DbiS->getGlobalSymbolStreamIndex());
+    if (!GlobalS) return GlobalS.takeError();
+    auto TempGlobals = llvm::make_unique<GlobalsStream>(std::move(*GlobalS));
+    if (auto EC = TempGlobals->reload())
+      return std::move(EC);
+    Globals = std::move(TempGlobals);
+  }
+  return *Globals;
 }
 
 Expected<InfoStream &> PDBFile::getPDBInfoStream() {
   if (!Info) {
-    auto InfoS = MappedBlockStream::createIndexedStream(StreamPDB, *this);
-    if (!InfoS)
-      return InfoS.takeError();
+    auto InfoS = safelyCreateIndexedStream(ContainerLayout, *Buffer, StreamPDB);
+    if (!InfoS) return InfoS.takeError();
     auto TempInfo = llvm::make_unique<InfoStream>(std::move(*InfoS));
     if (auto EC = TempInfo->reload())
       return std::move(EC);
@@ -189,9 +252,8 @@ Expected<InfoStream &> PDBFile::getPDBInfoStream() {
 
 Expected<DbiStream &> PDBFile::getPDBDbiStream() {
   if (!Dbi) {
-    auto DbiS = MappedBlockStream::createIndexedStream(StreamDBI, *this);
-    if (!DbiS)
-      return DbiS.takeError();
+    auto DbiS = safelyCreateIndexedStream(ContainerLayout, *Buffer, StreamDBI);
+    if (!DbiS) return DbiS.takeError();
     auto TempDbi = llvm::make_unique<DbiStream>(*this, std::move(*DbiS));
     if (auto EC = TempDbi->reload())
       return std::move(EC);
@@ -202,9 +264,8 @@ Expected<DbiStream &> PDBFile::getPDBDbiStream() {
 
 Expected<TpiStream &> PDBFile::getPDBTpiStream() {
   if (!Tpi) {
-    auto TpiS = MappedBlockStream::createIndexedStream(StreamTPI, *this);
-    if (!TpiS)
-      return TpiS.takeError();
+    auto TpiS = safelyCreateIndexedStream(ContainerLayout, *Buffer, StreamTPI);
+    if (!TpiS) return TpiS.takeError();
     auto TempTpi = llvm::make_unique<TpiStream>(*this, std::move(*TpiS));
     if (auto EC = TempTpi->reload())
       return std::move(EC);
@@ -215,9 +276,8 @@ Expected<TpiStream &> PDBFile::getPDBTpiStream() {
 
 Expected<TpiStream &> PDBFile::getPDBIpiStream() {
   if (!Ipi) {
-    auto IpiS = MappedBlockStream::createIndexedStream(StreamIPI, *this);
-    if (!IpiS)
-      return IpiS.takeError();
+    auto IpiS = safelyCreateIndexedStream(ContainerLayout, *Buffer, StreamIPI);
+    if (!IpiS) return IpiS.takeError();
     auto TempIpi = llvm::make_unique<TpiStream>(*this, std::move(*IpiS));
     if (auto EC = TempIpi->reload())
       return std::move(EC);
@@ -232,12 +292,9 @@ Expected<PublicsStream &> PDBFile::getPDBPublicsStream() {
     if (!DbiS)
       return DbiS.takeError();
 
-    uint32_t PublicsStreamNum = DbiS->getPublicSymbolStreamIndex();
-
-    auto PublicS =
-        MappedBlockStream::createIndexedStream(PublicsStreamNum, *this);
-    if (!PublicS)
-      return PublicS.takeError();
+    auto PublicS = safelyCreateIndexedStream(
+        ContainerLayout, *Buffer, DbiS->getPublicSymbolStreamIndex());
+    if (!PublicS) return PublicS.takeError();
     auto TempPublics =
         llvm::make_unique<PublicsStream>(*this, std::move(*PublicS));
     if (auto EC = TempPublics->reload())
@@ -254,11 +311,10 @@ Expected<SymbolStream &> PDBFile::getPDBSymbolStream() {
       return DbiS.takeError();
 
     uint32_t SymbolStreamNum = DbiS->getSymRecordStreamIndex();
-
     auto SymbolS =
-        MappedBlockStream::createIndexedStream(SymbolStreamNum, *this);
-    if (!SymbolS)
-      return SymbolS.takeError();
+        safelyCreateIndexedStream(ContainerLayout, *Buffer, SymbolStreamNum);
+    if (!SymbolS) return SymbolS.takeError();
+
     auto TempSymbols = llvm::make_unique<SymbolStream>(std::move(*SymbolS));
     if (auto EC = TempSymbols->reload())
       return std::move(EC);
@@ -275,14 +331,9 @@ Expected<NameHashTable &> PDBFile::getStringTable() {
 
     uint32_t NameStreamIndex = IS->getNamedStreamIndex("/names");
 
-    if (NameStreamIndex == 0)
-      return make_error<RawError>(raw_error_code::no_stream);
-    if (NameStreamIndex >= getNumStreams())
-      return make_error<RawError>(raw_error_code::no_stream);
-
-    auto NS = MappedBlockStream::createIndexedStream(NameStreamIndex, *this);
-    if (!NS)
-      return NS.takeError();
+    auto NS =
+        safelyCreateIndexedStream(ContainerLayout, *Buffer, NameStreamIndex);
+    if (!NS) return NS.takeError();
 
     StreamReader Reader(**NS);
     auto N = llvm::make_unique<NameHashTable>();
@@ -294,72 +345,47 @@ Expected<NameHashTable &> PDBFile::getStringTable() {
   return *StringTable;
 }
 
-Error PDBFile::setSuperBlock(const msf::SuperBlock *Block) {
-  if (auto EC = msf::validateSuperBlock(*Block))
-    return EC;
-
-  if (Buffer->getLength() % SB->BlockSize != 0)
-    return make_error<RawError>(raw_error_code::corrupt_file,
-                                "File size is not a multiple of block size");
+bool PDBFile::hasPDBDbiStream() const { return StreamDBI < getNumStreams(); }
 
-  SB = Block;
-  return Error::success();
+bool PDBFile::hasPDBGlobalsStream() {
+  auto DbiS = getPDBDbiStream();
+  if (!DbiS) return false;
+  return DbiS->getGlobalSymbolStreamIndex() < getNumStreams();
 }
 
-Error PDBFile::commit() {
-  StreamWriter Writer(*Buffer);
-
-  if (auto EC = Writer.writeObject(*SB))
-    return EC;
-  Writer.setOffset(getBlockMapOffset());
-  if (auto EC = Writer.writeArray(DirectoryBlocks))
-    return EC;
-
-  auto DS = MappedBlockStream::createDirectoryStream(*this);
-  if (!DS)
-    return DS.takeError();
-  auto DirStream = std::move(*DS);
-  StreamWriter DW(*DirStream);
-  if (auto EC = DW.writeInteger(this->getNumStreams()))
-    return EC;
-
-  if (auto EC = DW.writeArray(StreamSizes))
-    return EC;
-
-  for (const auto &Blocks : StreamMap) {
-    if (auto EC = DW.writeArray(Blocks))
-      return EC;
-  }
-
-  if (Info) {
-    if (auto EC = Info->commit())
-      return EC;
-  }
+bool PDBFile::hasPDBInfoStream() { return StreamPDB < getNumStreams(); }
 
-  if (Dbi) {
-    if (auto EC = Dbi->commit())
-      return EC;
-  }
+bool PDBFile::hasPDBIpiStream() const { return StreamIPI < getNumStreams(); }
 
-  if (Symbols) {
-    if (auto EC = Symbols->commit())
-      return EC;
-  }
+bool PDBFile::hasPDBPublicsStream() {
+  auto DbiS = getPDBDbiStream();
+  if (!DbiS) return false;
+  return DbiS->getPublicSymbolStreamIndex() < getNumStreams();
+}
 
-  if (Publics) {
-    if (auto EC = Publics->commit())
-      return EC;
-  }
+bool PDBFile::hasPDBSymbolStream() {
+  auto DbiS = getPDBDbiStream();
+  if (!DbiS) return false;
+  return DbiS->getSymRecordStreamIndex() < getNumStreams();
+}
 
-  if (Tpi) {
-    if (auto EC = Tpi->commit())
-      return EC;
-  }
+bool PDBFile::hasPDBTpiStream() const { return StreamTPI < getNumStreams(); }
 
-  if (Ipi) {
-    if (auto EC = Ipi->commit())
-      return EC;
-  }
+bool PDBFile::hasStringTable() {
+  auto IS = getPDBInfoStream();
+  if (!IS) return false;
+  return IS->getNamedStreamIndex("/names") < getNumStreams();
+}
 
-  return Buffer->commit();
+/// Wrapper around MappedBlockStream::createIndexedStream()
+/// that checks if a stream with that index actually exists.
+/// If it does not, the return value will have an MSFError with
+/// code msf_error_code::no_stream. Else, the return value will
+/// contain the stream returned by createIndexedStream().
+Expected<std::unique_ptr<MappedBlockStream>> PDBFile::safelyCreateIndexedStream(
+    const MSFLayout &Layout, const ReadableStream &MsfData,
+    uint32_t StreamIndex) const {
+  if (StreamIndex >= getNumStreams())
+    return make_error<RawError>(raw_error_code::no_stream);
+  return MappedBlockStream::createIndexedStream(Layout, MsfData, StreamIndex);
 }