vendor/llvm/llvm-trunk-r375505vendor/llvm

8 files changed, 1295 insertions, 9 deletions

diff --git a/lib/DebugInfo/GSYM/FileWriter.cpp b/lib/DebugInfo/GSYM/FileWriter.cpp
new file mode 100644
index 000000000000..4b30dcb60a7b
--- /dev/null
+++ b/lib/DebugInfo/GSYM/FileWriter.cpp
@@ -0,0 +1,78 @@
+//===- FileWriter.cpp -------------------------------------------*- 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/GSYM/FileWriter.h"
+#include "llvm/Support/LEB128.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+
+using namespace llvm;
+using namespace gsym;
+
+FileWriter::~FileWriter() { OS.flush(); }
+
+void FileWriter::writeSLEB(int64_t S) {
+  uint8_t Bytes[32];
+  auto Length = encodeSLEB128(S, Bytes);
+  assert(Length < sizeof(Bytes));
+  OS.write(reinterpret_cast<const char *>(Bytes), Length);
+}
+
+void FileWriter::writeULEB(uint64_t U) {
+  uint8_t Bytes[32];
+  auto Length = encodeULEB128(U, Bytes);
+  assert(Length < sizeof(Bytes));
+  OS.write(reinterpret_cast<const char *>(Bytes), Length);
+}
+
+void FileWriter::writeU8(uint8_t U) {
+  OS.write(reinterpret_cast<const char *>(&U), sizeof(U));
+}
+
+void FileWriter::writeU16(uint16_t U) {
+  const uint16_t Swapped = support::endian::byte_swap(U, ByteOrder);
+  OS.write(reinterpret_cast<const char *>(&Swapped), sizeof(Swapped));
+}
+
+void FileWriter::writeU32(uint32_t U) {
+  const uint32_t Swapped = support::endian::byte_swap(U, ByteOrder);
+  OS.write(reinterpret_cast<const char *>(&Swapped), sizeof(Swapped));
+}
+
+void FileWriter::writeU64(uint64_t U) {
+  const uint64_t Swapped = support::endian::byte_swap(U, ByteOrder);
+  OS.write(reinterpret_cast<const char *>(&Swapped), sizeof(Swapped));
+}
+
+void FileWriter::fixup32(uint32_t U, uint64_t Offset) {
+  const uint32_t Swapped = support::endian::byte_swap(U, ByteOrder);
+  OS.pwrite(reinterpret_cast<const char *>(&Swapped), sizeof(Swapped),
+            Offset);
+}
+
+void FileWriter::writeData(llvm::ArrayRef<uint8_t> Data) {
+  OS.write(reinterpret_cast<const char *>(Data.data()), Data.size());
+}
+
+void FileWriter::writeNullTerminated(llvm::StringRef Str) {
+  OS << Str << '\0';
+}
+
+uint64_t FileWriter::tell() {
+  return OS.tell();
+}
+
+void FileWriter::alignTo(size_t Align) {
+  off_t Offset = OS.tell();
+  off_t AlignedOffset = (Offset + Align - 1) / Align * Align;
+  if (AlignedOffset == Offset)
+    return;
+  off_t PadCount = AlignedOffset - Offset;
+  OS.write_zeros(PadCount);
+}
diff --git a/lib/DebugInfo/GSYM/FunctionInfo.cpp b/lib/DebugInfo/GSYM/FunctionInfo.cpp
index 55c36a55b4be..ad022fec9e32 100644
--- a/lib/DebugInfo/GSYM/FunctionInfo.cpp
+++ b/lib/DebugInfo/GSYM/FunctionInfo.cpp
@@ -1,22 +1,147 @@
-//===- FunctionInfo.cpp -----------------------------------------*- C++ -*-===//
+//===- FunctionInfo.cpp ---------------------------------------------------===//
 //
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/GSYM/FunctionInfo.h"
+#include "llvm/DebugInfo/GSYM/FileWriter.h"
+#include "llvm/DebugInfo/GSYM/LineTable.h"
+#include "llvm/DebugInfo/GSYM/InlineInfo.h"
+#include "llvm/Support/DataExtractor.h"
 
 using namespace llvm;
 using namespace gsym;
 
+/// FunctionInfo information type that is used to encode the optional data
+/// that is associated with a FunctionInfo object.
+enum InfoType : uint32_t {
+  EndOfList = 0u,
+  LineTableInfo = 1u,
+  InlineInfo = 2u
+};
+
 raw_ostream &llvm::gsym::operator<<(raw_ostream &OS, const FunctionInfo &FI) {
   OS << '[' << HEX64(FI.Range.Start) << '-' << HEX64(FI.Range.End) << "): "
-     << "Name=" << HEX32(FI.Name) << '\n';
-  for (const auto &Line : FI.Lines)
-    OS << Line << '\n';
-  OS << FI.Inline;
+     << "Name=" << HEX32(FI.Name) << '\n' << FI.OptLineTable << FI.Inline;
   return OS;
 }
+
+llvm::Expected<FunctionInfo> FunctionInfo::decode(DataExtractor &Data,
+                                                  uint64_t BaseAddr) {
+  FunctionInfo FI;
+  FI.Range.Start = BaseAddr;
+  uint64_t Offset = 0;
+  if (!Data.isValidOffsetForDataOfSize(Offset, 4))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing FunctionInfo Size", Offset);
+  FI.Range.End = FI.Range.Start + Data.getU32(&Offset);
+  if (!Data.isValidOffsetForDataOfSize(Offset, 4))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing FunctionInfo Name", Offset);
+  FI.Name = Data.getU32(&Offset);
+  if (FI.Name == 0)
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": invalid FunctionInfo Name value 0x%8.8x",
+        Offset - 4, FI.Name);
+  bool Done = false;
+  while (!Done) {
+    if (!Data.isValidOffsetForDataOfSize(Offset, 4))
+      return createStringError(std::errc::io_error,
+          "0x%8.8" PRIx64 ": missing FunctionInfo InfoType value", Offset);
+    const uint32_t IT = Data.getU32(&Offset);
+    if (!Data.isValidOffsetForDataOfSize(Offset, 4))
+      return createStringError(std::errc::io_error,
+          "0x%8.8" PRIx64 ": missing FunctionInfo InfoType length", Offset);
+    const uint32_t InfoLength = Data.getU32(&Offset);
+    if (!Data.isValidOffsetForDataOfSize(Offset, InfoLength))
+      return createStringError(std::errc::io_error,
+          "0x%8.8" PRIx64 ": missing FunctionInfo data for InfoType %u",
+          Offset, IT);
+    DataExtractor InfoData(Data.getData().substr(Offset, InfoLength),
+                           Data.isLittleEndian(),
+                           Data.getAddressSize());
+    switch (IT) {
+      case InfoType::EndOfList:
+        Done = true;
+        break;
+
+      case InfoType::LineTableInfo:
+        if (Expected<LineTable> LT = LineTable::decode(InfoData, BaseAddr))
+          FI.OptLineTable = std::move(LT.get());
+        else
+          return LT.takeError();
+        break;
+
+      case InfoType::InlineInfo:
+        if (Expected<InlineInfo> II = InlineInfo::decode(InfoData, BaseAddr))
+          FI.Inline = std::move(II.get());
+        else
+          return II.takeError();
+        break;
+
+      default:
+        return createStringError(std::errc::io_error,
+                                 "0x%8.8" PRIx64 ": unsupported InfoType %u",
+                                 Offset-8, IT);
+    }
+    Offset += InfoLength;
+  }
+  return std::move(FI);
+}
+
+llvm::Expected<uint64_t> FunctionInfo::encode(FileWriter &O) const {
+  if (!isValid())
+    return createStringError(std::errc::invalid_argument,
+        "attempted to encode invalid FunctionInfo object");
+  // Align FunctionInfo data to a 4 byte alignment.
+  O.alignTo(4);
+  const uint64_t FuncInfoOffset = O.tell();
+  // Write the size in bytes of this function as a uint32_t. This can be zero
+  // if we just have a symbol from a symbol table and that symbol has no size.
+  O.writeU32(size());
+  // Write the name of this function as a uint32_t string table offset.
+  O.writeU32(Name);
+
+  if (OptLineTable.hasValue()) {
+    O.writeU32(InfoType::LineTableInfo);
+    // Write a uint32_t length as zero for now, we will fix this up after
+    // writing the LineTable out with the number of bytes that were written.
+    O.writeU32(0);
+    const auto StartOffset = O.tell();
+    llvm::Error err = OptLineTable->encode(O, Range.Start);
+    if (err)
+      return std::move(err);
+    const off_t Length = O.tell() - StartOffset;
+    if (Length > UINT32_MAX)
+        return createStringError(std::errc::invalid_argument,
+            "LineTable length is greater than UINT32_MAX");
+    // Fixup the size of the LineTable data with the correct size.
+    O.fixup32(static_cast<uint32_t>(Length), StartOffset - 4);
+  }
+
+  // Write out the inline function info if we have any and if it is valid.
+  if (Inline.hasValue()) {
+    O.writeU32(InfoType::InlineInfo);
+    // Write a uint32_t length as zero for now, we will fix this up after
+    // writing the LineTable out with the number of bytes that were written.
+    O.writeU32(0);
+    const auto StartOffset = O.tell();
+    llvm::Error err = Inline->encode(O, Range.Start);
+    if (err)
+      return std::move(err);
+    const off_t Length = O.tell() - StartOffset;
+    if (Length > UINT32_MAX)
+        return createStringError(std::errc::invalid_argument,
+            "InlineInfo length is greater than UINT32_MAX");
+    // Fixup the size of the InlineInfo data with the correct size.
+    O.fixup32(static_cast<uint32_t>(Length), StartOffset - 4);
+  }
+
+  // Terminate the data chunks with and end of list with zero size
+  O.writeU32(InfoType::EndOfList);
+  O.writeU32(0);
+  return FuncInfoOffset;
+}
diff --git a/lib/DebugInfo/GSYM/GsymCreator.cpp b/lib/DebugInfo/GSYM/GsymCreator.cpp
new file mode 100644
index 000000000000..f371426f2010
--- /dev/null
+++ b/lib/DebugInfo/GSYM/GsymCreator.cpp
@@ -0,0 +1,275 @@
+//===- GsymCreator.cpp ----------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/GSYM/GsymCreator.h"
+#include "llvm/DebugInfo/GSYM/FileWriter.h"
+#include "llvm/DebugInfo/GSYM/Header.h"
+#include "llvm/DebugInfo/GSYM/LineTable.h"
+#include "llvm/MC/StringTableBuilder.h"
+#include "llvm/Support/raw_ostream.h"
+
+#include <algorithm>
+#include <cassert>
+#include <functional>
+#include <vector>
+
+using namespace llvm;
+using namespace gsym;
+
+
+GsymCreator::GsymCreator() : StrTab(StringTableBuilder::ELF) {
+  insertFile(StringRef());
+}
+
+uint32_t GsymCreator::insertFile(StringRef Path,
+                                 llvm::sys::path::Style Style) {
+  llvm::StringRef directory = llvm::sys::path::parent_path(Path, Style);
+  llvm::StringRef filename = llvm::sys::path::filename(Path, Style);
+  FileEntry FE(insertString(directory), insertString(filename));
+
+  std::lock_guard<std::recursive_mutex> Guard(Mutex);
+  const auto NextIndex = Files.size();
+  // Find FE in hash map and insert if not present.
+  auto R = FileEntryToIndex.insert(std::make_pair(FE, NextIndex));
+  if (R.second)
+    Files.emplace_back(FE);
+  return R.first->second;
+}
+
+llvm::Error GsymCreator::save(StringRef Path,
+                              llvm::support::endianness ByteOrder) const {
+  std::error_code EC;
+  raw_fd_ostream OutStrm(Path, EC);
+  if (EC)
+    return llvm::errorCodeToError(EC);
+  FileWriter O(OutStrm, ByteOrder);
+  return encode(O);
+}
+
+llvm::Error GsymCreator::encode(FileWriter &O) const {
+  std::lock_guard<std::recursive_mutex> Guard(Mutex);
+  if (Funcs.empty())
+    return createStringError(std::errc::invalid_argument,
+                             "no functions to encode");
+  if (!Finalized)
+    return createStringError(std::errc::invalid_argument,
+                             "GsymCreator wasn't finalized prior to encoding");
+
+  if (Funcs.size() > UINT32_MAX)
+    return createStringError(std::errc::invalid_argument,
+                             "too many FunctionInfos");
+  const uint64_t MinAddr = Funcs.front().startAddress();
+  const uint64_t MaxAddr = Funcs.back().startAddress();
+  const uint64_t AddrDelta = MaxAddr - MinAddr;
+  Header Hdr;
+  Hdr.Magic = GSYM_MAGIC;
+  Hdr.Version = GSYM_VERSION;
+  Hdr.AddrOffSize = 0;
+  Hdr.UUIDSize = static_cast<uint8_t>(UUID.size());
+  Hdr.BaseAddress = MinAddr;
+  Hdr.NumAddresses = static_cast<uint32_t>(Funcs.size());
+  Hdr.StrtabOffset = 0; // We will fix this up later.
+  Hdr.StrtabOffset = 0; // We will fix this up later.
+  memset(Hdr.UUID, 0, sizeof(Hdr.UUID));
+  if (UUID.size() > sizeof(Hdr.UUID))
+    return createStringError(std::errc::invalid_argument,
+                             "invalid UUID size %u", (uint32_t)UUID.size());
+  // Set the address offset size correctly in the GSYM header.
+  if (AddrDelta <= UINT8_MAX)
+    Hdr.AddrOffSize = 1;
+  else if (AddrDelta <= UINT16_MAX)
+    Hdr.AddrOffSize = 2;
+  else if (AddrDelta <= UINT32_MAX)
+    Hdr.AddrOffSize = 4;
+  else
+    Hdr.AddrOffSize = 8;
+  // Copy the UUID value if we have one.
+  if (UUID.size() > 0)
+    memcpy(Hdr.UUID, UUID.data(), UUID.size());
+  // Write out the header.
+  llvm::Error Err = Hdr.encode(O);
+  if (Err)
+    return Err;
+
+  // Write out the address offsets.
+  O.alignTo(Hdr.AddrOffSize);
+  for (const auto &FuncInfo : Funcs) {
+    uint64_t AddrOffset = FuncInfo.startAddress() - Hdr.BaseAddress;
+    switch(Hdr.AddrOffSize) {
+      case 1: O.writeU8(static_cast<uint8_t>(AddrOffset)); break;
+      case 2: O.writeU16(static_cast<uint16_t>(AddrOffset)); break;
+      case 4: O.writeU32(static_cast<uint32_t>(AddrOffset)); break;
+      case 8: O.writeU64(AddrOffset); break;
+    }
+  }
+
+  // Write out all zeros for the AddrInfoOffsets.
+  O.alignTo(4);
+  const off_t AddrInfoOffsetsOffset = O.tell();
+  for (size_t i = 0, n = Funcs.size(); i < n; ++i)
+    O.writeU32(0);
+
+  // Write out the file table
+  O.alignTo(4);
+  assert(!Files.empty());
+  assert(Files[0].Dir == 0);
+  assert(Files[0].Base == 0);
+  size_t NumFiles = Files.size();
+  if (NumFiles > UINT32_MAX)
+    return createStringError(std::errc::invalid_argument,
+                             "too many files");
+  O.writeU32(static_cast<uint32_t>(NumFiles));
+  for (auto File: Files) {
+      O.writeU32(File.Dir);
+      O.writeU32(File.Base);
+  }
+
+  // Write out the sting table.
+  const off_t StrtabOffset = O.tell();
+  StrTab.write(O.get_stream());
+  const off_t StrtabSize = O.tell() - StrtabOffset;
+  std::vector<uint32_t> AddrInfoOffsets;
+
+  // Write out the address infos for each function info.
+  for (const auto &FuncInfo : Funcs) {
+    if (Expected<uint64_t> OffsetOrErr = FuncInfo.encode(O))
+        AddrInfoOffsets.push_back(OffsetOrErr.get());
+    else
+        return OffsetOrErr.takeError();
+  }
+  // Fixup the string table offset and size in the header
+  O.fixup32((uint32_t)StrtabOffset, offsetof(Header, StrtabOffset));
+  O.fixup32((uint32_t)StrtabSize, offsetof(Header, StrtabSize));
+
+  // Fixup all address info offsets
+  uint64_t Offset = 0;
+  for (auto AddrInfoOffset: AddrInfoOffsets) {
+    O.fixup32(AddrInfoOffset, AddrInfoOffsetsOffset + Offset);
+    Offset += 4;
+  }
+  return ErrorSuccess();
+}
+
+llvm::Error GsymCreator::finalize(llvm::raw_ostream &OS) {
+  std::lock_guard<std::recursive_mutex> Guard(Mutex);
+  if (Finalized)
+    return createStringError(std::errc::invalid_argument,
+                             "already finalized");
+  Finalized = true;
+
+  // Sort function infos so we can emit sorted functions.
+  llvm::sort(Funcs.begin(), Funcs.end());
+
+  // Don't let the string table indexes change by finalizing in order.
+  StrTab.finalizeInOrder();
+
+  // Remove duplicates function infos that have both entries from debug info
+  // (DWARF or Breakpad) and entries from the SymbolTable.
+  //
+  // Also handle overlapping function. Usually there shouldn't be any, but they
+  // can and do happen in some rare cases.
+  //
+  // (a)          (b)         (c)
+  //     ^  ^       ^            ^
+  //     |X |Y      |X ^         |X
+  //     |  |       |  |Y        |  ^
+  //     |  |       |  v         v  |Y
+  //     v  v       v               v
+  //
+  // In (a) and (b), Y is ignored and X will be reported for the full range.
+  // In (c), both functions will be included in the result and lookups for an
+  // address in the intersection will return Y because of binary search.
+  //
+  // Note that in case of (b), we cannot include Y in the result because then
+  // we wouldn't find any function for range (end of Y, end of X)
+  // with binary search
+  auto NumBefore = Funcs.size();
+  auto Curr = Funcs.begin();
+  auto Prev = Funcs.end();
+  while (Curr != Funcs.end()) {
+    // Can't check for overlaps or same address ranges if we don't have a
+    // previous entry
+    if (Prev != Funcs.end()) {
+      if (Prev->Range.intersects(Curr->Range)) {
+        // Overlapping address ranges.
+        if (Prev->Range == Curr->Range) {
+          // Same address range. Check if one is from debug info and the other
+          // is from a symbol table. If so, then keep the one with debug info.
+          // Our sorting guarantees that entries with matching address ranges
+          // that have debug info are last in the sort.
+          if (*Prev == *Curr) {
+            // FunctionInfo entries match exactly (range, lines, inlines)
+            OS << "warning: duplicate function info entries, removing "
+                  "duplicate:\n"
+               << *Curr << '\n';
+            Curr = Funcs.erase(Prev);
+          } else {
+            if (!Prev->hasRichInfo() && Curr->hasRichInfo()) {
+              // Same address range, one with no debug info (symbol) and the
+              // next with debug info. Keep the latter.
+              Curr = Funcs.erase(Prev);
+            } else {
+              OS << "warning: same address range contains different debug "
+                 << "info. Removing:\n"
+                 << *Prev << "\nIn favor of this one:\n"
+                 << *Curr << "\n";
+              Curr = Funcs.erase(Prev);
+            }
+          }
+        } else {
+          // print warnings about overlaps
+          OS << "warning: function ranges overlap:\n"
+             << *Prev << "\n"
+             << *Curr << "\n";
+        }
+      } else if (Prev->Range.size() == 0 &&
+                 Curr->Range.contains(Prev->Range.Start)) {
+        OS << "warning: removing symbol:\n"
+           << *Prev << "\nKeeping:\n"
+           << *Curr << "\n";
+        Curr = Funcs.erase(Prev);
+      }
+    }
+    if (Curr == Funcs.end())
+      break;
+    Prev = Curr++;
+  }
+
+  OS << "Pruned " << NumBefore - Funcs.size() << " functions, ended with "
+     << Funcs.size() << " total\n";
+  return Error::success();
+}
+
+uint32_t GsymCreator::insertString(StringRef S) {
+  std::lock_guard<std::recursive_mutex> Guard(Mutex);
+  if (S.empty())
+    return 0;
+  return StrTab.add(S);
+}
+
+void GsymCreator::addFunctionInfo(FunctionInfo &&FI) {
+  std::lock_guard<std::recursive_mutex> Guard(Mutex);
+  Funcs.emplace_back(FI);
+}
+
+void GsymCreator::forEachFunctionInfo(
+    std::function<bool(FunctionInfo &)> const &Callback) {
+  std::lock_guard<std::recursive_mutex> Guard(Mutex);
+  for (auto &FI : Funcs) {
+    if (!Callback(FI))
+      break;
+  }
+}
+
+void GsymCreator::forEachFunctionInfo(
+    std::function<bool(const FunctionInfo &)> const &Callback) const {
+  std::lock_guard<std::recursive_mutex> Guard(Mutex);
+  for (const auto &FI : Funcs) {
+    if (!Callback(FI))
+      break;
+  }
+}
diff --git a/lib/DebugInfo/GSYM/GsymReader.cpp b/lib/DebugInfo/GSYM/GsymReader.cpp
new file mode 100644
index 000000000000..1b448cf80b70
--- /dev/null
+++ b/lib/DebugInfo/GSYM/GsymReader.cpp
@@ -0,0 +1,265 @@
+//===- GsymReader.cpp -----------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/GSYM/GsymReader.h"
+
+#include <assert.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "llvm/DebugInfo/GSYM/GsymCreator.h"
+#include "llvm/DebugInfo/GSYM/InlineInfo.h"
+#include "llvm/DebugInfo/GSYM/LineTable.h"
+#include "llvm/Support/BinaryStreamReader.h"
+#include "llvm/Support/DataExtractor.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+using namespace llvm;
+using namespace gsym;
+
+GsymReader::GsymReader(std::unique_ptr<MemoryBuffer> Buffer) :
+    MemBuffer(std::move(Buffer)),
+    Endian(support::endian::system_endianness()) {}
+
+  GsymReader::GsymReader(GsymReader &&RHS) = default;
+
+GsymReader::~GsymReader() = default;
+
+llvm::Expected<GsymReader> GsymReader::openFile(StringRef Filename) {
+  // Open the input file and return an appropriate error if needed.
+  ErrorOr<std::unique_ptr<MemoryBuffer>> BuffOrErr =
+      MemoryBuffer::getFileOrSTDIN(Filename);
+  auto Err = BuffOrErr.getError();
+  if (Err)
+    return llvm::errorCodeToError(Err);
+  return create(BuffOrErr.get());
+}
+
+llvm::Expected<GsymReader> GsymReader::copyBuffer(StringRef Bytes) {
+  auto MemBuffer = MemoryBuffer::getMemBufferCopy(Bytes, "GSYM bytes");
+  return create(MemBuffer);
+}
+
+llvm::Expected<llvm::gsym::GsymReader>
+GsymReader::create(std::unique_ptr<MemoryBuffer> &MemBuffer) {
+  if (!MemBuffer.get())
+    return createStringError(std::errc::invalid_argument,
+                             "invalid memory buffer");
+  GsymReader GR(std::move(MemBuffer));
+  llvm::Error Err = GR.parse();
+  if (Err)
+    return std::move(Err);
+  return std::move(GR);
+}
+
+llvm::Error
+GsymReader::parse() {
+  BinaryStreamReader FileData(MemBuffer->getBuffer(),
+                              support::endian::system_endianness());
+  // Check for the magic bytes. This file format is designed to be mmap'ed
+  // into a process and accessed as read only. This is done for performance
+  // and efficiency for symbolicating and parsing GSYM data.
+  if (FileData.readObject(Hdr))
+    return createStringError(std::errc::invalid_argument,
+                             "not enough data for a GSYM header");
+
+  const auto HostByteOrder = support::endian::system_endianness();
+  switch (Hdr->Magic) {
+    case GSYM_MAGIC:
+      Endian = HostByteOrder;
+      break;
+    case GSYM_CIGAM:
+      // This is a GSYM file, but not native endianness.
+      Endian = sys::IsBigEndianHost ? support::little : support::big;
+      Swap.reset(new SwappedData);
+      break;
+    default:
+      return createStringError(std::errc::invalid_argument,
+                               "not a GSYM file");
+  }
+
+  bool DataIsLittleEndian = HostByteOrder != support::little;
+  // Read a correctly byte swapped header if we need to.
+  if (Swap) {
+    DataExtractor Data(MemBuffer->getBuffer(), DataIsLittleEndian, 4);
+    if (auto ExpectedHdr = Header::decode(Data))
+      Swap->Hdr = ExpectedHdr.get();
+    else
+      return ExpectedHdr.takeError();
+    Hdr = &Swap->Hdr;
+  }
+
+  // Detect errors in the header and report any that are found. If we make it
+  // past this without errors, we know we have a good magic value, a supported
+  // version number, verified address offset size and a valid UUID size.
+  if (Error Err = Hdr->checkForError())
+    return Err;
+
+  if (!Swap) {
+    // This is the native endianness case that is most common and optimized for
+    // efficient lookups. Here we just grab pointers to the native data and
+    // use ArrayRef objects to allow efficient read only access.
+
+    // Read the address offsets.
+    if (FileData.padToAlignment(Hdr->AddrOffSize) ||
+        FileData.readArray(AddrOffsets,
+                           Hdr->NumAddresses * Hdr->AddrOffSize))
+      return createStringError(std::errc::invalid_argument,
+                              "failed to read address table");
+
+    // Read the address info offsets.
+    if (FileData.padToAlignment(4) ||
+        FileData.readArray(AddrInfoOffsets, Hdr->NumAddresses))
+      return createStringError(std::errc::invalid_argument,
+                              "failed to read address info offsets table");
+
+    // Read the file table.
+    uint32_t NumFiles = 0;
+    if (FileData.readInteger(NumFiles) || FileData.readArray(Files, NumFiles))
+      return createStringError(std::errc::invalid_argument,
+                              "failed to read file table");
+
+    // Get the string table.
+    FileData.setOffset(Hdr->StrtabOffset);
+    if (FileData.readFixedString(StrTab.Data, Hdr->StrtabSize))
+      return createStringError(std::errc::invalid_argument,
+                              "failed to read string table");
+} else {
+  // This is the non native endianness case that is not common and not
+  // optimized for lookups. Here we decode the important tables into local
+  // storage and then set the ArrayRef objects to point to these swapped
+  // copies of the read only data so lookups can be as efficient as possible.
+  DataExtractor Data(MemBuffer->getBuffer(), DataIsLittleEndian, 4);
+
+  // Read the address offsets.
+  uint64_t Offset = alignTo(sizeof(Header), Hdr->AddrOffSize);
+  Swap->AddrOffsets.resize(Hdr->NumAddresses * Hdr->AddrOffSize);
+  switch (Hdr->AddrOffSize) {
+    case 1:
+      if (!Data.getU8(&Offset, Swap->AddrOffsets.data(), Hdr->NumAddresses))
+        return createStringError(std::errc::invalid_argument,
+                                  "failed to read address table");
+      break;
+    case 2:
+      if (!Data.getU16(&Offset,
+                        reinterpret_cast<uint16_t *>(Swap->AddrOffsets.data()),
+                        Hdr->NumAddresses))
+        return createStringError(std::errc::invalid_argument,
+                                  "failed to read address table");
+      break;
+    case 4:
+      if (!Data.getU32(&Offset,
+                        reinterpret_cast<uint32_t *>(Swap->AddrOffsets.data()),
+                        Hdr->NumAddresses))
+        return createStringError(std::errc::invalid_argument,
+                                  "failed to read address table");
+      break;
+    case 8:
+      if (!Data.getU64(&Offset,
+                        reinterpret_cast<uint64_t *>(Swap->AddrOffsets.data()),
+                        Hdr->NumAddresses))
+        return createStringError(std::errc::invalid_argument,
+                                  "failed to read address table");
+    }
+    AddrOffsets = ArrayRef<uint8_t>(Swap->AddrOffsets);
+
+    // Read the address info offsets.
+    Offset = alignTo(Offset, 4);
+    Swap->AddrInfoOffsets.resize(Hdr->NumAddresses);
+    if (Data.getU32(&Offset, Swap->AddrInfoOffsets.data(), Hdr->NumAddresses))
+      AddrInfoOffsets = ArrayRef<uint32_t>(Swap->AddrInfoOffsets);
+    else
+      return createStringError(std::errc::invalid_argument,
+                               "failed to read address table");
+    // Read the file table.
+    const uint32_t NumFiles = Data.getU32(&Offset);
+    if (NumFiles > 0) {
+      Swap->Files.resize(NumFiles);
+      if (Data.getU32(&Offset, &Swap->Files[0].Dir, NumFiles*2))
+        Files = ArrayRef<FileEntry>(Swap->Files);
+      else
+        return createStringError(std::errc::invalid_argument,
+                                 "failed to read file table");
+    }
+    // Get the string table.
+    StrTab.Data = MemBuffer->getBuffer().substr(Hdr->StrtabOffset,
+                                                Hdr->StrtabSize);
+    if (StrTab.Data.empty())
+      return createStringError(std::errc::invalid_argument,
+                               "failed to read string table");
+  }
+  return Error::success();
+
+}
+
+const Header &GsymReader::getHeader() const {
+  // The only way to get a GsymReader is from GsymReader::openFile(...) or
+  // GsymReader::copyBuffer() and the header must be valid and initialized to
+  // a valid pointer value, so the assert below should not trigger.
+  assert(Hdr);
+  return *Hdr;
+}
+
+Optional<uint64_t> GsymReader::getAddress(size_t Index) const {
+  switch (Hdr->AddrOffSize) {
+  case 1: return addressForIndex<uint8_t>(Index);
+  case 2: return addressForIndex<uint16_t>(Index);
+  case 4: return addressForIndex<uint32_t>(Index);
+  case 8: return addressForIndex<uint64_t>(Index);
+  }
+  return llvm::None;
+}
+
+Optional<uint64_t> GsymReader::getAddressInfoOffset(size_t Index) const {
+  const auto NumAddrInfoOffsets = AddrInfoOffsets.size();
+  if (Index < NumAddrInfoOffsets)
+    return AddrInfoOffsets[Index];
+  return llvm::None;
+}
+
+Expected<uint64_t>
+GsymReader::getAddressIndex(const uint64_t Addr) const {
+  if (Addr < Hdr->BaseAddress)
+    return createStringError(std::errc::invalid_argument,
+                             "address 0x%" PRIx64 " not in GSYM", Addr);
+  const uint64_t AddrOffset = Addr - Hdr->BaseAddress;
+  switch (Hdr->AddrOffSize) {
+  case 1: return getAddressOffsetIndex<uint8_t>(AddrOffset);
+  case 2: return getAddressOffsetIndex<uint16_t>(AddrOffset);
+  case 4: return getAddressOffsetIndex<uint32_t>(AddrOffset);
+  case 8: return getAddressOffsetIndex<uint64_t>(AddrOffset);
+  default: break;
+  }
+  return createStringError(std::errc::invalid_argument,
+                           "unsupported address offset size %u",
+                           Hdr->AddrOffSize);
+}
+
+llvm::Expected<FunctionInfo> GsymReader::getFunctionInfo(uint64_t Addr) const {
+  Expected<uint64_t> AddressIndex = getAddressIndex(Addr);
+  if (!AddressIndex)
+    return AddressIndex.takeError();
+  // Address info offsets size should have been checked in parse().
+  assert(*AddressIndex < AddrInfoOffsets.size());
+  auto AddrInfoOffset = AddrInfoOffsets[*AddressIndex];
+  DataExtractor Data(MemBuffer->getBuffer().substr(AddrInfoOffset), Endian, 4);
+  if (Optional<uint64_t> OptAddr = getAddress(*AddressIndex)) {
+    auto ExpectedFI = FunctionInfo::decode(Data, *OptAddr);
+    if (ExpectedFI) {
+      if (ExpectedFI->Range.contains(Addr) || ExpectedFI->Range.size() == 0)
+        return ExpectedFI;
+      return createStringError(std::errc::invalid_argument,
+                                "address 0x%" PRIx64 " not in GSYM", Addr);
+    }
+  }
+  return createStringError(std::errc::invalid_argument,
+                           "failed to extract address[%" PRIu64 "]",
+                           *AddressIndex);
+}
diff --git a/lib/DebugInfo/GSYM/Header.cpp b/lib/DebugInfo/GSYM/Header.cpp
new file mode 100644
index 000000000000..0b3fb9c49894
--- /dev/null
+++ b/lib/DebugInfo/GSYM/Header.cpp
@@ -0,0 +1,109 @@
+//===- Header.cpp -----------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/GSYM/Header.h"
+#include "llvm/DebugInfo/GSYM/FileWriter.h"
+#include "llvm/Support/DataExtractor.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+
+#define HEX8(v) llvm::format_hex(v, 4)
+#define HEX16(v) llvm::format_hex(v, 6)
+#define HEX32(v) llvm::format_hex(v, 10)
+#define HEX64(v) llvm::format_hex(v, 18)
+
+using namespace llvm;
+using namespace gsym;
+
+raw_ostream &llvm::gsym::operator<<(raw_ostream &OS, const Header &H) {
+  OS << "Header:\n";
+  OS << "  Magic        = " << HEX32(H.Magic) << "\n";
+  OS << "  Version      = " << HEX16(H.Version) << '\n';
+  OS << "  AddrOffSize  = " << HEX8(H.AddrOffSize) << '\n';
+  OS << "  UUIDSize     = " << HEX8(H.UUIDSize) << '\n';
+  OS << "  BaseAddress  = " << HEX64(H.BaseAddress) << '\n';
+  OS << "  NumAddresses = " << HEX32(H.NumAddresses) << '\n';
+  OS << "  StrtabOffset = " << HEX32(H.StrtabOffset) << '\n';
+  OS << "  StrtabSize   = " << HEX32(H.StrtabSize) << '\n';
+  OS << "  UUID         = ";
+  for (uint8_t I = 0; I < H.UUIDSize; ++I)
+    OS << format_hex_no_prefix(H.UUID[I], 2);
+  OS << '\n';
+  return OS;
+}
+
+/// Check the header and detect any errors.
+llvm::Error Header::checkForError() const {
+  if (Magic != GSYM_MAGIC)
+    return createStringError(std::errc::invalid_argument,
+                             "invalid GSYM magic 0x%8.8x", Magic);
+  if (Version != GSYM_VERSION)
+    return createStringError(std::errc::invalid_argument,
+                             "unsupported GSYM version %u", Version);
+  switch (AddrOffSize) {
+    case 1: break;
+    case 2: break;
+    case 4: break;
+    case 8: break;
+    default:
+        return createStringError(std::errc::invalid_argument,
+                                 "invalid address offset size %u",
+                                 AddrOffSize);
+  }
+  if (UUIDSize > GSYM_MAX_UUID_SIZE)
+    return createStringError(std::errc::invalid_argument,
+                             "invalid UUID size %u", UUIDSize);
+  return Error::success();
+}
+
+llvm::Expected<Header> Header::decode(DataExtractor &Data) {
+  uint64_t Offset = 0;
+  // The header is stored as a single blob of data that has a fixed byte size.
+  if (!Data.isValidOffsetForDataOfSize(Offset, sizeof(Header)))
+    return createStringError(std::errc::invalid_argument,
+                             "not enough data for a gsym::Header");
+  Header H;
+  H.Magic = Data.getU32(&Offset);
+  H.Version = Data.getU16(&Offset);
+  H.AddrOffSize = Data.getU8(&Offset);
+  H.UUIDSize = Data.getU8(&Offset);
+  H.BaseAddress = Data.getU64(&Offset);
+  H.NumAddresses = Data.getU32(&Offset);
+  H.StrtabOffset = Data.getU32(&Offset);
+  H.StrtabSize = Data.getU32(&Offset);
+  Data.getU8(&Offset, H.UUID, GSYM_MAX_UUID_SIZE);
+  if (llvm::Error Err = H.checkForError())
+    return std::move(Err);
+  return H;
+}
+
+llvm::Error Header::encode(FileWriter &O) const {
+  // Users must verify the Header is valid prior to calling this funtion.
+  if (llvm::Error Err = checkForError())
+    return Err;
+  O.writeU32(Magic);
+  O.writeU16(Version);
+  O.writeU8(AddrOffSize);
+  O.writeU8(UUIDSize);
+  O.writeU64(BaseAddress);
+  O.writeU32(NumAddresses);
+  O.writeU32(StrtabOffset);
+  O.writeU32(StrtabSize);
+  O.writeData(llvm::ArrayRef<uint8_t>(UUID));
+  return Error::success();
+}
+
+bool llvm::gsym::operator==(const Header &LHS, const Header &RHS) {
+  return LHS.Magic == RHS.Magic && LHS.Version == RHS.Version &&
+      LHS.AddrOffSize == RHS.AddrOffSize && LHS.UUIDSize == RHS.UUIDSize &&
+      LHS.BaseAddress == RHS.BaseAddress &&
+      LHS.NumAddresses == RHS.NumAddresses &&
+      LHS.StrtabOffset == RHS.StrtabOffset &&
+      LHS.StrtabSize == RHS.StrtabSize &&
+      memcmp(LHS.UUID, RHS.UUID, LHS.UUIDSize) == 0;
+}
diff --git a/lib/DebugInfo/GSYM/InlineInfo.cpp b/lib/DebugInfo/GSYM/InlineInfo.cpp
index 781c1755241d..32ed2c709575 100644
--- a/lib/DebugInfo/GSYM/InlineInfo.cpp
+++ b/lib/DebugInfo/GSYM/InlineInfo.cpp
@@ -8,7 +8,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/GSYM/FileEntry.h"
+#include "llvm/DebugInfo/GSYM/FileWriter.h"
 #include "llvm/DebugInfo/GSYM/InlineInfo.h"
+#include "llvm/Support/DataExtractor.h"
 #include <algorithm>
 #include <inttypes.h>
 
@@ -57,3 +59,101 @@ llvm::Optional<InlineInfo::InlineArray> InlineInfo::getInlineStack(uint64_t Addr
     return Result;
   return llvm::None;
 }
+
+/// Decode an InlineInfo in Data at the specified offset.
+///
+/// A local helper function to decode InlineInfo objects. This function is
+/// called recursively when parsing child InlineInfo objects.
+///
+/// \param Data The data extractor to decode from.
+/// \param Offset The offset within \a Data to decode from.
+/// \param BaseAddr The base address to use when decoding address ranges.
+/// \returns An InlineInfo or an error describing the issue that was
+/// encountered during decoding.
+static llvm::Expected<InlineInfo> decode(DataExtractor &Data, uint64_t &Offset,
+                                         uint64_t BaseAddr) {
+  InlineInfo Inline;
+  if (!Data.isValidOffset(Offset))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing InlineInfo address ranges data", Offset);
+  Inline.Ranges.decode(Data, BaseAddr, Offset);
+  if (Inline.Ranges.empty())
+    return Inline;
+  if (!Data.isValidOffsetForDataOfSize(Offset, 1))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing InlineInfo uint8_t indicating children",
+        Offset);
+  bool HasChildren = Data.getU8(&Offset) != 0;
+  if (!Data.isValidOffsetForDataOfSize(Offset, 4))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing InlineInfo uint32_t for name", Offset);
+  Inline.Name = Data.getU32(&Offset);
+  if (!Data.isValidOffset(Offset))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing ULEB128 for InlineInfo call file", Offset);
+  Inline.CallFile = (uint32_t)Data.getULEB128(&Offset);
+  if (!Data.isValidOffset(Offset))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing ULEB128 for InlineInfo call line", Offset);
+  Inline.CallLine = (uint32_t)Data.getULEB128(&Offset);
+  if (HasChildren) {
+    // Child address ranges are encoded relative to the first address in the
+    // parent InlineInfo object.
+    const auto ChildBaseAddr = Inline.Ranges[0].Start;
+    while (true) {
+      llvm::Expected<InlineInfo> Child = decode(Data, Offset, ChildBaseAddr);
+      if (!Child)
+        return Child.takeError();
+      // InlineInfo with empty Ranges termintes a child sibling chain.
+      if (Child.get().Ranges.empty())
+        break;
+      Inline.Children.emplace_back(std::move(*Child));
+    }
+  }
+  return Inline;
+}
+
+llvm::Expected<InlineInfo> InlineInfo::decode(DataExtractor &Data,
+                                              uint64_t BaseAddr) {
+  uint64_t Offset = 0;
+  return ::decode(Data, Offset, BaseAddr);
+}
+
+llvm::Error InlineInfo::encode(FileWriter &O, uint64_t BaseAddr) const {
+  // Users must verify the InlineInfo is valid prior to calling this funtion.
+  // We don't want to emit any InlineInfo objects if they are not valid since
+  // it will waste space in the GSYM file.
+  if (!isValid())
+    return createStringError(std::errc::invalid_argument,
+                             "attempted to encode invalid InlineInfo object");
+  Ranges.encode(O, BaseAddr);
+  bool HasChildren = !Children.empty();
+  O.writeU8(HasChildren);
+  O.writeU32(Name);
+  O.writeULEB(CallFile);
+  O.writeULEB(CallLine);
+  if (HasChildren) {
+    // Child address ranges are encoded as relative to the first
+    // address in the Ranges for this object. This keeps the offsets
+    // small and allows for efficient encoding using ULEB offsets.
+    const uint64_t ChildBaseAddr = Ranges[0].Start;
+    for (const auto &Child : Children) {
+      // Make sure all child address ranges are contained in the parent address
+      // ranges.
+      for (const auto &ChildRange: Child.Ranges) {
+        if (!Ranges.contains(ChildRange))
+          return createStringError(std::errc::invalid_argument,
+                                   "child range not contained in parent");
+      }
+      llvm::Error Err = Child.encode(O, ChildBaseAddr);
+      if (Err)
+        return Err;
+    }
+
+    // Terminate child sibling chain by emitting a zero. This zero will cause
+    // the decodeAll() function above to return false and stop the decoding
+    // of child InlineInfo objects that are siblings.
+    O.writeULEB(0);
+  }
+  return Error::success();
+}
diff --git a/lib/DebugInfo/GSYM/LineTable.cpp b/lib/DebugInfo/GSYM/LineTable.cpp
new file mode 100644
index 000000000000..824c0041be9f
--- /dev/null
+++ b/lib/DebugInfo/GSYM/LineTable.cpp
@@ -0,0 +1,287 @@
+//===- LineTable.cpp --------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/GSYM/LineTable.h"
+#include "llvm/DebugInfo/GSYM/FileWriter.h"
+#include "llvm/Support/DataExtractor.h"
+
+using namespace llvm;
+using namespace gsym;
+
+enum LineTableOpCode {
+  EndSequence = 0x00,  ///< End of the line table.
+  SetFile = 0x01,      ///< Set LineTableRow.file_idx, don't push a row.
+  AdvancePC = 0x02,    ///< Increment LineTableRow.address, and push a row.
+  AdvanceLine = 0x03,  ///< Set LineTableRow.file_line, don't push a row.
+  FirstSpecial = 0x04, ///< All special opcodes push a row.
+};
+
+struct DeltaInfo {
+  int64_t Delta;
+  uint32_t Count;
+  DeltaInfo(int64_t D, uint32_t C) : Delta(D), Count(C) {}
+};
+
+inline bool operator<(const DeltaInfo &LHS, int64_t Delta) {
+  return LHS.Delta < Delta;
+}
+
+static bool encodeSpecial(int64_t MinLineDelta, int64_t MaxLineDelta,
+                          int64_t LineDelta, uint64_t AddrDelta,
+                          uint8_t &SpecialOp) {
+  if (LineDelta < MinLineDelta)
+    return false;
+  if (LineDelta > MaxLineDelta)
+    return false;
+  int64_t LineRange = MaxLineDelta - MinLineDelta + 1;
+  int64_t AdjustedOp = ((LineDelta - MinLineDelta) + AddrDelta * LineRange);
+  int64_t Op = AdjustedOp + FirstSpecial;
+  if (Op < 0)
+    return false;
+  if (Op > 255)
+    return false;
+  SpecialOp = (uint8_t)Op;
+  return true;
+}
+
+typedef std::function<bool(const LineEntry &Row)> LineEntryCallback;
+
+static llvm::Error parse(DataExtractor &Data, uint64_t BaseAddr,
+                         LineEntryCallback const &Callback) {
+  uint64_t Offset = 0;
+  if (!Data.isValidOffset(Offset))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing LineTable MinDelta", Offset);
+  int64_t MinDelta = Data.getSLEB128(&Offset);
+  if (!Data.isValidOffset(Offset))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing LineTable MaxDelta", Offset);
+  int64_t MaxDelta = Data.getSLEB128(&Offset);
+  int64_t LineRange = MaxDelta - MinDelta + 1;
+  if (!Data.isValidOffset(Offset))
+    return createStringError(std::errc::io_error,
+        "0x%8.8" PRIx64 ": missing LineTable FirstLine", Offset);
+  const uint32_t FirstLine = (uint32_t)Data.getULEB128(&Offset);
+  LineEntry Row(BaseAddr, 1, FirstLine);
+  bool Done = false;
+  while (!Done) {
+    if (!Data.isValidOffset(Offset))
+      return createStringError(std::errc::io_error,
+          "0x%8.8" PRIx64 ": EOF found before EndSequence", Offset);
+    uint8_t Op = Data.getU8(&Offset);
+    switch (Op) {
+    case EndSequence:
+      Done = true;
+      break;
+    case SetFile:
+      if (!Data.isValidOffset(Offset))
+        return createStringError(std::errc::io_error,
+            "0x%8.8" PRIx64 ": EOF found before SetFile value",
+            Offset);
+      Row.File = (uint32_t)Data.getULEB128(&Offset);
+      break;
+    case AdvancePC:
+      if (!Data.isValidOffset(Offset))
+        return createStringError(std::errc::io_error,
+            "0x%8.8" PRIx64 ": EOF found before AdvancePC value",
+            Offset);
+      Row.Addr += Data.getULEB128(&Offset);
+      // If the function callback returns false, we stop parsing.
+      if (Callback(Row) == false)
+        return Error::success();
+      break;
+    case AdvanceLine:
+      if (!Data.isValidOffset(Offset))
+        return createStringError(std::errc::io_error,
+            "0x%8.8" PRIx64 ": EOF found before AdvanceLine value",
+            Offset);
+      Row.Line += Data.getSLEB128(&Offset);
+      break;
+    default: {
+        // A byte that contains both address and line increment.
+        uint8_t AdjustedOp = Op - FirstSpecial;
+        int64_t LineDelta = MinDelta + (AdjustedOp % LineRange);
+        uint64_t AddrDelta = (AdjustedOp / LineRange);
+        Row.Line += LineDelta;
+        Row.Addr += AddrDelta;
+        // If the function callback returns false, we stop parsing.
+        if (Callback(Row) == false)
+          return Error::success();
+        break;
+      }
+    }
+  }
+  return Error::success();
+}
+
+llvm::Error LineTable::encode(FileWriter &Out, uint64_t BaseAddr) const {
+  // Users must verify the LineTable is valid prior to calling this funtion.
+  // We don't want to emit any LineTable objects if they are not valid since
+  // it will waste space in the GSYM file.
+  if (!isValid())
+    return createStringError(std::errc::invalid_argument,
+                             "attempted to encode invalid LineTable object");
+
+  int64_t MinLineDelta = INT64_MAX;
+  int64_t MaxLineDelta = INT64_MIN;
+  std::vector<DeltaInfo> DeltaInfos;
+  if (Lines.size() == 1) {
+    MinLineDelta = 0;
+    MaxLineDelta = 0;
+  } else {
+    int64_t PrevLine = 1;
+    bool First = true;
+    for (const auto &line_entry : Lines) {
+      if (First)
+        First = false;
+      else {
+        int64_t LineDelta = (int64_t)line_entry.Line - PrevLine;
+        auto End = DeltaInfos.end();
+        auto Pos = std::lower_bound(DeltaInfos.begin(), End, LineDelta);
+        if (Pos != End && Pos->Delta == LineDelta)
+          ++Pos->Count;
+        else
+          DeltaInfos.insert(Pos, DeltaInfo(LineDelta, 1));
+        if (LineDelta < MinLineDelta)
+          MinLineDelta = LineDelta;
+        if (LineDelta > MaxLineDelta)
+          MaxLineDelta = LineDelta;
+      }
+      PrevLine = (int64_t)line_entry.Line;
+    }
+    assert(MinLineDelta <= MaxLineDelta);
+  }
+  // Set the min and max line delta intelligently based on the counts of
+  // the line deltas. if our range is too large.
+  const int64_t MaxLineRange = 14;
+  if (MaxLineDelta - MinLineDelta > MaxLineRange) {
+    uint32_t BestIndex = 0;
+    uint32_t BestEndIndex = 0;
+    uint32_t BestCount = 0;
+    const size_t NumDeltaInfos = DeltaInfos.size();
+    for (uint32_t I = 0; I < NumDeltaInfos; ++I) {
+      const int64_t FirstDelta = DeltaInfos[I].Delta;
+      uint32_t CurrCount = 0;
+      uint32_t J;
+      for (J = I; J < NumDeltaInfos; ++J) {
+        auto LineRange = DeltaInfos[J].Delta - FirstDelta;
+        if (LineRange > MaxLineRange)
+          break;
+        CurrCount += DeltaInfos[J].Count;
+      }
+      if (CurrCount > BestCount) {
+        BestIndex = I;
+        BestEndIndex = J - 1;
+        BestCount = CurrCount;
+      }
+    }
+    MinLineDelta = DeltaInfos[BestIndex].Delta;
+    MaxLineDelta = DeltaInfos[BestEndIndex].Delta;
+  }
+  if (MinLineDelta == MaxLineDelta && MinLineDelta > 0 &&
+      MinLineDelta < MaxLineRange)
+    MinLineDelta = 0;
+  assert(MinLineDelta <= MaxLineDelta);
+
+  // Initialize the line entry state as a starting point. All line entries
+  // will be deltas from this.
+  LineEntry Prev(BaseAddr, 1, Lines.front().Line);
+
+  // Write out the min and max line delta as signed LEB128.
+  Out.writeSLEB(MinLineDelta);
+  Out.writeSLEB(MaxLineDelta);
+  // Write out the starting line number as a unsigned LEB128.
+  Out.writeULEB(Prev.Line);
+
+  for (const auto &Curr : Lines) {
+    if (Curr.Addr < BaseAddr)
+      return createStringError(std::errc::invalid_argument,
+                               "LineEntry has address 0x%" PRIx64 " which is "
+                               "less than the function start address 0x%"
+                               PRIx64, Curr.Addr, BaseAddr);
+    if (Curr.Addr < Prev.Addr)
+      return createStringError(std::errc::invalid_argument,
+                               "LineEntry in LineTable not in ascending order");
+    const uint64_t AddrDelta = Curr.Addr - Prev.Addr;
+    int64_t LineDelta = 0;
+    if (Curr.Line > Prev.Line)
+      LineDelta = Curr.Line - Prev.Line;
+    else if (Prev.Line > Curr.Line)
+      LineDelta = -((int32_t)(Prev.Line - Curr.Line));
+
+    // Set the file if it doesn't match the current one.
+    if (Curr.File != Prev.File) {
+      Out.writeU8(SetFile);
+      Out.writeULEB(Curr.File);
+    }
+
+    uint8_t SpecialOp;
+    if (encodeSpecial(MinLineDelta, MaxLineDelta, LineDelta, AddrDelta,
+                      SpecialOp)) {
+      // Advance the PC and line and push a row.
+      Out.writeU8(SpecialOp);
+    } else {
+      // We can't encode the address delta and line delta into
+      // a single special opcode, we must do them separately.
+
+      // Advance the line.
+      if (LineDelta != 0) {
+        Out.writeU8(AdvanceLine);
+        Out.writeSLEB(LineDelta);
+      }
+
+      // Advance the PC and push a row.
+      Out.writeU8(AdvancePC);
+      Out.writeULEB(AddrDelta);
+    }
+    Prev = Curr;
+  }
+  Out.writeU8(EndSequence);
+  return Error::success();
+}
+
+// Parse all line table entries into the "LineTable" vector. We can
+// cache the results of this if needed, or we can call LineTable::lookup()
+// below.
+llvm::Expected<LineTable> LineTable::decode(DataExtractor &Data,
+                                            uint64_t BaseAddr) {
+  LineTable LT;
+  llvm::Error Err = parse(Data, BaseAddr, [&](const LineEntry &Row) -> bool {
+    LT.Lines.push_back(Row);
+    return true; // Keep parsing by returning true.
+  });
+  if (Err)
+    return std::move(Err);
+  return LT;
+}
+// Parse the line table on the fly and find the row we are looking for.
+// We will need to determine if we need to cache the line table by calling
+// LineTable::parseAllEntries(...) or just call this function each time.
+// There is a CPU vs memory tradeoff we will need to determine.
+LineEntry LineTable::lookup(DataExtractor &Data, uint64_t BaseAddr, uint64_t Addr) {
+  LineEntry Result;
+  llvm::Error Err = parse(Data, BaseAddr,
+                          [Addr, &Result](const LineEntry &Row) -> bool {
+    if (Addr < Row.Addr)
+      return false; // Stop parsing, result contains the line table row!
+    Result = Row;
+    if (Addr == Row.Addr) {
+      // Stop parsing, this is the row we are looking for since the address
+      // matches.
+      return false;
+    }
+    return true; // Keep parsing till we find the right row.
+  });
+  return Result;
+}
+
+raw_ostream &llvm::gsym::operator<<(raw_ostream &OS, const LineTable &LT) {
+  for (const auto &LineEntry : LT)
+    OS << LineEntry << '\n';
+  return OS;
+}
diff --git a/lib/DebugInfo/GSYM/Range.cpp b/lib/DebugInfo/GSYM/Range.cpp
index ca61984dacbd..19ab700fdd57 100644
--- a/lib/DebugInfo/GSYM/Range.cpp
+++ b/lib/DebugInfo/GSYM/Range.cpp
@@ -8,6 +8,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/GSYM/Range.h"
+#include "llvm/DebugInfo/GSYM/FileWriter.h"
+#include "llvm/Support/DataExtractor.h"
 #include <algorithm>
 #include <inttypes.h>
 
@@ -40,6 +42,17 @@ bool AddressRanges::contains(uint64_t Addr) const {
   return It != Ranges.begin() && Addr < It[-1].End;
 }
 
+bool AddressRanges::contains(AddressRange Range) const {
+  if (Range.size() == 0)
+    return false;
+  auto It = std::partition_point(
+      Ranges.begin(), Ranges.end(),
+      [=](const AddressRange &R) { return R.Start <= Range.Start; });
+  if (It == Ranges.begin())
+    return false;
+  return Range.End <= It[-1].End;
+}
+
 raw_ostream &llvm::gsym::operator<<(raw_ostream &OS, const AddressRange &R) {
   return OS << '[' << HEX64(R.Start) << " - " << HEX64(R.End) << ")";
 }
@@ -53,3 +66,37 @@ raw_ostream &llvm::gsym::operator<<(raw_ostream &OS, const AddressRanges &AR) {
   }
   return OS;
 }
+
+void AddressRange::encode(FileWriter &O, uint64_t BaseAddr) const {
+  assert(Start >= BaseAddr);
+  O.writeULEB(Start - BaseAddr);
+  O.writeULEB(size());
+}
+
+void AddressRange::decode(DataExtractor &Data, uint64_t BaseAddr,
+                          uint64_t &Offset) {
+  const uint64_t AddrOffset = Data.getULEB128(&Offset);
+  const uint64_t Size = Data.getULEB128(&Offset);
+  const uint64_t StartAddr = BaseAddr + AddrOffset;
+  Start = StartAddr;
+  End = StartAddr + Size;
+}
+
+void AddressRanges::encode(FileWriter &O, uint64_t BaseAddr) const {
+  O.writeULEB(Ranges.size());
+  if (Ranges.empty())
+    return;
+  for (auto Range : Ranges)
+    Range.encode(O, BaseAddr);
+}
+
+void AddressRanges::decode(DataExtractor &Data, uint64_t BaseAddr,
+                           uint64_t &Offset) {
+  clear();
+  uint64_t NumRanges = Data.getULEB128(&Offset);
+  if (NumRanges == 0)
+    return;
+  Ranges.resize(NumRanges);
+  for (auto &Range : Ranges)
+    Range.decode(Data, BaseAddr, Offset);
+}