Sketch out a DWARF parser.

This introduces a new library to LLVM: libDebugInfo. It will provide debug information
parsing to LLVM. Much of the design and some of the code is taken from the LLDB project.

It also contains an llvm-dwarfdump tool that can dump the abbrevs and DIEs from an
object file. It can be used to write tests for DWARF input and output easily.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@139627 91177308-0d34-0410-b5e6-96231b3b80d8

16 files changed, 1882 insertions, 0 deletions

diff --git a/lib/DebugInfo/CMakeLists.txt b/lib/DebugInfo/CMakeLists.txt
new file mode 100644
index 0000000000..446b8d6b15
--- /dev/null
+++ b/lib/DebugInfo/CMakeLists.txt
@@ -0,0 +1,13 @@
+add_llvm_library(LLVMMC
+  DIContext.cpp
+  DWARFAbbreviationDeclaration.cpp
+  DWARFCompileUnit.cpp
+  DWARFContext.cpp
+  DWARFDebugAbbrev.cpp
+  DWARFDebugInfoEntry.cpp
+  DWARFFormValue.cpp
+  )
+
+add_llvm_library_dependencies(LLVMDebugInfo
+  LLVMSupport
+  )
diff --git a/lib/DebugInfo/DIContext.cpp b/lib/DebugInfo/DIContext.cpp
new file mode 100644
index 0000000000..e2fd55fd6e
--- /dev/null
+++ b/lib/DebugInfo/DIContext.cpp
@@ -0,0 +1,24 @@
+//===-- DIContext.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/DIContext.h"
+#include "DWARFContext.h"
+using namespace llvm;
+
+DIContext::~DIContext() {}
+
+DIContext *DIContext::getDWARFContext(bool isLittleEndian,
+                                      StringRef infoSection,
+                                      StringRef abbrevSection,
+                                      StringRef aRangeSection,
+                                      StringRef lineSection,
+                                      StringRef stringSection) {
+  return new DWARFContextInMemory(isLittleEndian, infoSection, abbrevSection,
+                                  aRangeSection, lineSection, stringSection);
+}
diff --git a/lib/DebugInfo/DWARFAbbreviationDeclaration.cpp b/lib/DebugInfo/DWARFAbbreviationDeclaration.cpp
new file mode 100644
index 0000000000..00913a3bc0
--- /dev/null
+++ b/lib/DebugInfo/DWARFAbbreviationDeclaration.cpp
@@ -0,0 +1,66 @@
+//===-- DWARFAbbreviationDeclaration.cpp ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DWARFAbbreviationDeclaration.h"
+#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+using namespace dwarf;
+
+bool
+DWARFAbbreviationDeclaration::extract(DataExtractor data, uint32_t* offset_ptr){
+  return extract(data, offset_ptr, data.getULEB128(offset_ptr));
+}
+
+bool
+DWARFAbbreviationDeclaration::extract(DataExtractor data, uint32_t* offset_ptr,
+                                      uint32_t code) {
+  Code = code;
+  Attributes.clear();
+  if (Code) {
+    Tag = data.getULEB128(offset_ptr);
+    HasChildren = data.getU8(offset_ptr);
+
+    while (data.isValidOffset(*offset_ptr)) {
+      uint16_t attr = data.getULEB128(offset_ptr);
+      uint16_t form = data.getULEB128(offset_ptr);
+
+      if (attr && form)
+        Attributes.push_back(DWARFAttribute(attr, form));
+      else
+        break;
+    }
+
+    return Tag != 0;
+  }
+  else {
+    Tag = 0;
+    HasChildren = false;
+  }
+
+  return false;
+}
+
+void DWARFAbbreviationDeclaration::dump(raw_ostream &OS) const {
+  OS << '[' << getCode() << "] " << TagString(getTag()) << "\tDW_CHILDREN_"
+     << (hasChildren() ? "yes" : "no") << '\n';
+  for (unsigned i = 0, e = Attributes.size(); i != e; ++i)
+    OS << '\t' << AttributeString(Attributes[i].getAttribute())
+       << '\t' << FormEncodingString(Attributes[i].getForm()) << '\n';
+  OS << '\n';
+}
+
+uint32_t
+DWARFAbbreviationDeclaration::findAttributeIndex(uint16_t attr) const {
+  for (uint32_t i = 0, e = Attributes.size(); i != e; ++i) {
+    if (Attributes[i].getAttribute() == attr)
+      return i;
+  }
+  return -1U;
+}
diff --git a/lib/DebugInfo/DWARFAbbreviationDeclaration.h b/lib/DebugInfo/DWARFAbbreviationDeclaration.h
new file mode 100644
index 0000000000..2463a3cc04
--- /dev/null
+++ b/lib/DebugInfo/DWARFAbbreviationDeclaration.h
@@ -0,0 +1,54 @@
+//===-- DWARFAbbreviationDeclaration.h --------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H
+#define LLVM_DEBUGINFO_DWARFABBREVIATIONDECLARATION_H
+
+#include "DWARFAttribute.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/Support/DataExtractor.h"
+
+namespace llvm {
+
+class raw_ostream;
+
+class DWARFAbbreviationDeclaration {
+  uint32_t Code;
+  uint32_t Tag;
+  bool HasChildren;
+  SmallVector<DWARFAttribute, 8> Attributes;
+public:
+  enum { InvalidCode = 0 };
+  DWARFAbbreviationDeclaration()
+    : Code(InvalidCode), Tag(0), HasChildren(0) {}
+
+  uint32_t getCode() const { return Code; }
+  uint32_t getTag() const { return Tag; }
+  bool hasChildren() const { return HasChildren; }
+  uint32_t getNumAttributes() const { return Attributes.size(); }
+  uint16_t getAttrByIndex(uint32_t idx) const {
+    return Attributes.size() > idx ? Attributes[idx].getAttribute() : 0;
+  }
+  uint16_t getFormByIndex(uint32_t idx) const {
+    return Attributes.size() > idx ? Attributes[idx].getForm() : 0;
+  }
+
+  uint32_t findAttributeIndex(uint16_t attr) const;
+  bool extract(DataExtractor data, uint32_t* offset_ptr);
+  bool extract(DataExtractor data, uint32_t* offset_ptr, uint32_t code);
+  bool isValid() const { return Code != 0 && Tag != 0; }
+  void dump(raw_ostream &OS) const;
+  const SmallVectorImpl<DWARFAttribute> &getAttributes() const {
+    return Attributes;
+  }
+};
+
+}
+
+#endif
diff --git a/lib/DebugInfo/DWARFAttribute.h b/lib/DebugInfo/DWARFAttribute.h
new file mode 100644
index 0000000000..6f49b637c6
--- /dev/null
+++ b/lib/DebugInfo/DWARFAttribute.h
@@ -0,0 +1,30 @@
+//===-- DWARFAttribute.h ----------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_DWARFATTRIBUTE_H
+#define LLVM_DEBUGINFO_DWARFATTRIBUTE_H
+
+#include "llvm/Support/DataTypes.h"
+
+namespace llvm {
+
+class DWARFAttribute {
+  uint16_t Attribute;
+  uint16_t Form;
+  public:
+  DWARFAttribute(uint16_t attr, uint16_t form)
+    : Attribute(attr), Form(form) {}
+
+  uint16_t getAttribute() const { return Attribute; }
+  uint16_t getForm() const { return Form; }
+};
+
+}
+
+#endif
diff --git a/lib/DebugInfo/DWARFCompileUnit.cpp b/lib/DebugInfo/DWARFCompileUnit.cpp
new file mode 100644
index 0000000000..389de9d4e1
--- /dev/null
+++ b/lib/DebugInfo/DWARFCompileUnit.cpp
@@ -0,0 +1,203 @@
+//===-- DWARFCompileUnit.cpp ----------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DWARFCompileUnit.h"
+#include "DWARFContext.h"
+#include "DWARFFormValue.h"
+#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+using namespace dwarf;
+
+DataExtractor DWARFCompileUnit::getDebugInfoExtractor() const {
+  return DataExtractor(Context.getInfoSection(),
+                       Context.isLittleEndian(), getAddressByteSize());
+}
+
+bool DWARFCompileUnit::extract(DataExtractor debug_info, uint32_t *offset_ptr) {
+  clear();
+
+  Offset = *offset_ptr;
+
+  if (debug_info.isValidOffset(*offset_ptr)) {
+    uint64_t abbrOffset;
+    const DWARFDebugAbbrev *abbr = Context.getDebugAbbrev();
+    Length = debug_info.getU32(offset_ptr);
+    Version = debug_info.getU16(offset_ptr);
+    abbrOffset = debug_info.getU32(offset_ptr);
+    AddrSize = debug_info.getU8(offset_ptr);
+
+    bool lengthOK = debug_info.isValidOffset(getNextCompileUnitOffset()-1);
+    bool versionOK = DWARFContext::isSupportedVersion(Version);
+    bool abbrOffsetOK = Context.getAbbrevSection().size() > abbrOffset;
+    bool addrSizeOK = AddrSize == 4 || AddrSize == 8;
+
+    if (lengthOK && versionOK && addrSizeOK && abbrOffsetOK && abbr != NULL) {
+      Abbrevs = abbr->getAbbreviationDeclarationSet(abbrOffset);
+      return true;
+    }
+
+    // reset the offset to where we tried to parse from if anything went wrong
+    *offset_ptr = Offset;
+  }
+
+  return false;
+}
+
+uint32_t
+DWARFCompileUnit::extract(uint32_t offset, DataExtractor debug_info_data,
+                          const DWARFAbbreviationDeclarationSet *abbrevs) {
+  clear();
+
+  Offset = offset;
+
+  if (debug_info_data.isValidOffset(offset)) {
+    Length = debug_info_data.getU32(&offset);
+    Version = debug_info_data.getU16(&offset);
+    bool abbrevsOK = debug_info_data.getU32(&offset) == abbrevs->getOffset();
+    Abbrevs = abbrevs;
+    AddrSize = debug_info_data.getU8 (&offset);
+
+    bool versionOK = DWARFContext::isSupportedVersion(Version);
+    bool addrSizeOK = AddrSize == 4 || AddrSize == 8;
+
+    if (versionOK && addrSizeOK && abbrevsOK &&
+        debug_info_data.isValidOffset(offset))
+      return offset;
+  }
+  return 0;
+}
+
+void DWARFCompileUnit::clear() {
+  Offset = 0;
+  Length = 0;
+  Version = 0;
+  Abbrevs = 0;
+  AddrSize = 0;
+  BaseAddr = 0;
+  DieArray.clear();
+}
+
+void DWARFCompileUnit::dump(raw_ostream &OS) {
+  OS << format("0x%08x", Offset) << ": Compile Unit:"
+     << " length = " << format("0x%08x", Length)
+     << " version = " << format("0x%04x", Version)
+     << " abbr_offset = " << format("0x%04x", Abbrevs->getOffset())
+     << " addr_size = " << format("0x%02x", AddrSize)
+     << " (next CU at " << format("0x%08x", getNextCompileUnitOffset())
+     << ")\n";
+
+  extractDIEsIfNeeded(false);
+  for (unsigned i = 0, e = DieArray.size(); i != e; ++i)
+    DieArray[i].dump(OS, this, 10);
+}
+
+void DWARFCompileUnit::setDIERelations() {
+  if (DieArray.empty())
+    return;
+  DWARFDebugInfoEntryMinimal *die_array_begin = &DieArray.front();
+  DWARFDebugInfoEntryMinimal *die_array_end = &DieArray.back();
+  DWARFDebugInfoEntryMinimal *curr_die;
+  // We purposely are skipping the last element in the array in the loop below
+  // so that we can always have a valid next item
+  for (curr_die = die_array_begin; curr_die < die_array_end; ++curr_die) {
+    // Since our loop doesn't include the last element, we can always
+    // safely access the next die in the array.
+    DWARFDebugInfoEntryMinimal *next_die = curr_die + 1;
+
+    const DWARFAbbreviationDeclaration *curr_die_abbrev =
+      curr_die->getAbbreviationDeclarationPtr();
+
+    if (curr_die_abbrev) {
+      // Normal DIE
+      if (curr_die_abbrev->hasChildren())
+        next_die->setParent(curr_die);
+      else
+        curr_die->setSibling(next_die);
+    } else {
+      // NULL DIE that terminates a sibling chain
+      DWARFDebugInfoEntryMinimal *parent = curr_die->getParent();
+      if (parent)
+        parent->setSibling(next_die);
+    }
+  }
+
+  // Since we skipped the last element, we need to fix it up!
+  if (die_array_begin < die_array_end)
+    curr_die->setParent(die_array_begin);
+}
+
+size_t DWARFCompileUnit::extractDIEsIfNeeded(bool cu_die_only) {
+  const size_t initial_die_array_size = DieArray.size();
+  if ((cu_die_only && initial_die_array_size > 0) ||
+      initial_die_array_size > 1)
+    return 0; // Already parsed
+
+  // Set the offset to that of the first DIE and calculate the start of the
+  // next compilation unit header.
+  uint32_t offset = getFirstDIEOffset();
+  uint32_t next_cu_offset = getNextCompileUnitOffset();
+
+  DWARFDebugInfoEntryMinimal die;
+  // Keep a flat array of the DIE for binary lookup by DIE offset
+  uint32_t depth = 0;
+  // We are in our compile unit, parse starting at the offset
+  // we were told to parse
+
+  const uint8_t *fixed_form_sizes =
+    DWARFFormValue::getFixedFormSizesForAddressSize(getAddressByteSize());
+
+  while (offset < next_cu_offset &&
+         die.extractFast(this, fixed_form_sizes, &offset)) {
+
+    if (depth == 0) {
+      uint64_t base_addr =
+        die.getAttributeValueAsUnsigned(this, DW_AT_low_pc, -1U);
+      if (base_addr == -1U)
+        base_addr = die.getAttributeValueAsUnsigned(this, DW_AT_entry_pc, 0);
+      setBaseAddress(base_addr);
+    }
+
+    if (cu_die_only) {
+      addDIE(die);
+      return 1;
+    }
+    else if (depth == 0 && initial_die_array_size == 1) {
+      // Don't append the CU die as we already did that
+    } else {
+      addDIE (die);
+    }
+
+    const DWARFAbbreviationDeclaration *abbrDecl =
+      die.getAbbreviationDeclarationPtr();
+    if (abbrDecl) {
+      // Normal DIE
+      if (abbrDecl->hasChildren())
+        ++depth;
+    } else {
+      // NULL DIE.
+      if (depth > 0)
+        --depth;
+      if (depth == 0)
+        break;  // We are done with this compile unit!
+    }
+
+  }
+
+  // Give a little bit of info if we encounter corrupt DWARF (our offset
+  // should always terminate at or before the start of the next compilation
+  // unit header).
+  if (offset > next_cu_offset) {
+    fprintf (stderr, "warning: DWARF compile unit extends beyond its bounds cu 0x%8.8x at 0x%8.8x'\n", getOffset(), offset);
+  }
+
+  setDIERelations();
+  return DieArray.size();
+}
diff --git a/lib/DebugInfo/DWARFCompileUnit.h b/lib/DebugInfo/DWARFCompileUnit.h
new file mode 100644
index 0000000000..0c082ad337
--- /dev/null
+++ b/lib/DebugInfo/DWARFCompileUnit.h
@@ -0,0 +1,98 @@
+//===-- DWARFCompileUnit.h --------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_DWARFCOMPILEUNIT_H
+#define LLVM_DEBUGINFO_DWARFCOMPILEUNIT_H
+
+#include "DWARFDebugAbbrev.h"
+#include "DWARFDebugInfoEntry.h"
+#include <vector>
+
+namespace llvm {
+
+class DWARFContext;
+class raw_ostream;
+
+class DWARFCompileUnit {
+  DWARFContext &Context;
+
+  uint32_t Offset;
+  uint32_t Length;
+  uint16_t Version;
+  const DWARFAbbreviationDeclarationSet *Abbrevs;
+  uint8_t AddrSize;
+  uint64_t BaseAddr;
+  // The compile unit debug information entry item.
+  std::vector<DWARFDebugInfoEntryMinimal> DieArray;
+public:
+  DWARFCompileUnit(DWARFContext &context) : Context(context) {
+    clear();
+  }
+
+  DWARFContext &getContext() const { return Context; }
+  DataExtractor getDebugInfoExtractor() const;
+
+  bool extract(DataExtractor debug_info, uint32_t* offset_ptr);
+  uint32_t extract(uint32_t offset, DataExtractor debug_info_data,
+                   const DWARFAbbreviationDeclarationSet *abbrevs);
+
+  /// extractDIEsIfNeeded - Parses a compile unit and indexes its DIEs if it
+  /// hasn't already been done.
+  size_t extractDIEsIfNeeded(bool cu_die_only);
+  void clear();
+  void dump(raw_ostream &OS);
+  uint32_t getOffset() const { return Offset; }
+  /// Size in bytes of the compile unit header.
+  uint32_t getSize() const { return 11; }
+  bool containsDIEOffset(uint32_t die_offset) const {
+    return die_offset >= getFirstDIEOffset() &&
+      die_offset < getNextCompileUnitOffset();
+  }
+  uint32_t getFirstDIEOffset() const { return Offset + getSize(); }
+  uint32_t getNextCompileUnitOffset() const { return Offset + Length + 4; }
+  /// Size in bytes of the .debug_info data associated with this compile unit.
+  size_t getDebugInfoSize() const { return Length + 4 - getSize(); }
+  uint32_t getLength() const { return Length; }
+  uint16_t getVersion() const { return Version; }
+  const DWARFAbbreviationDeclarationSet *getAbbreviations() const {
+    return Abbrevs;
+  }
+  uint8_t getAddressByteSize() const { return AddrSize; }
+  uint64_t getBaseAddress() const { return BaseAddr; }
+
+  void setBaseAddress(uint64_t base_addr) {
+    BaseAddr = base_addr;
+  }
+
+  /// setDIERelations - We read in all of the DIE entries into our flat list
+  /// of DIE entries and now we need to go back through all of them and set the
+  /// parent, sibling and child pointers for quick DIE navigation.
+  void setDIERelations();
+
+  void addDIE(DWARFDebugInfoEntryMinimal &die) {
+    // The average bytes per DIE entry has been seen to be
+    // around 14-20 so lets pre-reserve the needed memory for
+    // our DIE entries accordingly. Search forward for "Compute
+    // average bytes per DIE" to see #if'ed out code that does
+    // that determination.
+
+    // Only reserve the memory if we are adding children of
+    // the main compile unit DIE. The compile unit DIE is always
+    // the first entry, so if our size is 1, then we are adding
+    // the first compile unit child DIE and should reserve
+    // the memory.
+    if (DieArray.empty())
+      DieArray.reserve(getDebugInfoSize() / 14);
+    DieArray.push_back(die);
+  }
+};
+
+}
+
+#endif
diff --git a/lib/DebugInfo/DWARFContext.cpp b/lib/DebugInfo/DWARFContext.cpp
new file mode 100644
index 0000000000..513e415fa5
--- /dev/null
+++ b/lib/DebugInfo/DWARFContext.cpp
@@ -0,0 +1,43 @@
+//===-- DWARFContext.cpp --------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DWARFContext.h"
+using namespace llvm;
+
+void DWARFContext::dump(raw_ostream &OS) {
+  getDebugAbbrev()->dump(OS);
+  for (unsigned i = 0, e = getNumCompileUnits(); i != e; ++i)
+    getCompileUnitAtIndex(i)->dump(OS);
+}
+
+const DWARFDebugAbbrev *DWARFContext::getDebugAbbrev() {
+  if (Abbrev)
+    return Abbrev.get();
+
+  DataExtractor abbrData(getAbbrevSection(), isLittleEndian(), 0);
+
+  Abbrev.reset(new DWARFDebugAbbrev());
+  Abbrev->parse(abbrData);
+  return Abbrev.get();
+}
+
+void DWARFContext::parseCompileUnits() {
+  uint32_t offset = 0;
+  const DataExtractor &debug_info_data = DataExtractor(getInfoSection(),
+                                                       isLittleEndian(), 0);
+  while (debug_info_data.isValidOffset(offset)) {
+    CUs.push_back(DWARFCompileUnit(*this));
+    if (!CUs.back().extract(debug_info_data, &offset)) {
+      CUs.pop_back();
+      break;
+    }
+
+    offset = CUs.back().getNextCompileUnitOffset();
+  }
+}
diff --git a/lib/DebugInfo/DWARFContext.h b/lib/DebugInfo/DWARFContext.h
new file mode 100644
index 0000000000..1a70f3feef
--- /dev/null
+++ b/lib/DebugInfo/DWARFContext.h
@@ -0,0 +1,104 @@
+//===-- DWARFContext.h ------------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===/
+
+#ifndef LLVM_DEBUGINFO_DWARFCONTEXT_H
+#define LLVM_DEBUGINFO_DWARFCONTEXT_H
+
+#include "DWARFCompileUnit.h"
+#include "llvm/DebugInfo/DIContext.h"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/SmallVector.h"
+
+namespace llvm {
+
+class DWARFDebugAbbrev;
+
+/// DWARFContext
+/// This data structure is the top level entity that deals with dwarf debug
+/// information parsing. The actual data is supplied through pure virtual
+/// methods that a concrete implementation provides.
+class DWARFContext : public DIContext {
+  bool IsLittleEndian;
+
+  SmallVector<DWARFCompileUnit, 1> CUs;
+  OwningPtr<DWARFDebugAbbrev> Abbrev;
+
+  DWARFContext(DWARFContext &); // = delete
+  DWARFContext &operator=(DWARFContext &); // = delete
+
+  /// Read compile units from the debug_info section and store them in CUs.
+  void parseCompileUnits();
+protected:
+  DWARFContext(bool isLittleEndian) : IsLittleEndian(isLittleEndian) {}
+public:
+  virtual void dump(raw_ostream &OS);
+  /// Get the number of compile units in this context.
+  unsigned getNumCompileUnits() {
+    if (CUs.empty())
+      parseCompileUnits();
+    return CUs.size();
+  }
+  /// Get the compile unit at the specified index for this compile unit.
+  DWARFCompileUnit *getCompileUnitAtIndex(unsigned index) {
+    if (CUs.empty())
+      parseCompileUnits();
+    return &CUs[index];
+  }
+
+  /// Get a pointer to the parsed DebugAbbrev object.
+  const DWARFDebugAbbrev *getDebugAbbrev();
+
+  bool isLittleEndian() const { return IsLittleEndian; }
+
+  virtual StringRef getInfoSection() = 0;
+  virtual StringRef getAbbrevSection() = 0;
+  virtual StringRef getARangeSection() = 0;
+  virtual StringRef getLineSection() = 0;
+  virtual StringRef getStringSection() = 0;
+
+  static bool isSupportedVersion(unsigned version) {
+    return version == 2 || version == 3;
+  }
+};
+
+
+/// DWARFContextInMemory is the simplest possible implementation of a
+/// DWARFContext. It assumes all content is available in memory and stores
+/// pointers to it.
+class DWARFContextInMemory : public DWARFContext {
+  StringRef InfoSection;
+  StringRef AbbrevSection;
+  StringRef ARangeSection;
+  StringRef LineSection;
+  StringRef StringSection;
+public:
+  DWARFContextInMemory(bool isLittleEndian,
+                       StringRef infoSection,
+                       StringRef abbrevSection,
+                       StringRef aRangeSection,
+                       StringRef lineSection,
+                       StringRef stringSection)
+    : DWARFContext(isLittleEndian),
+      InfoSection(infoSection),
+      AbbrevSection(abbrevSection),
+      ARangeSection(aRangeSection),
+      LineSection(lineSection),
+      StringSection(stringSection)
+    {}
+
+  virtual StringRef getInfoSection() { return InfoSection; }
+  virtual StringRef getAbbrevSection() { return AbbrevSection; }
+  virtual StringRef getARangeSection() { return ARangeSection; }
+  virtual StringRef getLineSection() { return LineSection; }
+  virtual StringRef getStringSection() { return StringSection; }
+};
+
+}
+
+#endif
diff --git a/lib/DebugInfo/DWARFDebugAbbrev.cpp b/lib/DebugInfo/DWARFDebugAbbrev.cpp
new file mode 100644
index 0000000000..68769f05cd
--- /dev/null
+++ b/lib/DebugInfo/DWARFDebugAbbrev.cpp
@@ -0,0 +1,108 @@
+//===-- DWARFDebugAbbrev.cpp ----------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DWARFDebugAbbrev.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+bool DWARFAbbreviationDeclarationSet::extract(DataExtractor data,
+                                              uint32_t* offset_ptr) {
+  const uint32_t beginOffset = *offset_ptr;
+  Offset = beginOffset;
+  clear();
+  DWARFAbbreviationDeclaration abbrevDeclaration;
+  uint32_t prevAbbrAode = 0;
+  while (abbrevDeclaration.extract(data, offset_ptr)) {
+    Decls.push_back(abbrevDeclaration);
+    if (IdxOffset == 0) {
+      IdxOffset = abbrevDeclaration.getCode();
+    } else {
+      if (prevAbbrAode + 1 != abbrevDeclaration.getCode())
+        IdxOffset = UINT32_MAX;// Out of order indexes, we can't do O(1) lookups
+    }
+    prevAbbrAode = abbrevDeclaration.getCode();
+  }
+  return beginOffset != *offset_ptr;
+}
+
+
+void DWARFAbbreviationDeclarationSet::dump(raw_ostream &OS) const {
+  for (unsigned i = 0, e = Decls.size(); i != e; ++i)
+    Decls[i].dump(OS);
+}
+
+
+const DWARFAbbreviationDeclaration*
+DWARFAbbreviationDeclarationSet::getAbbreviationDeclaration(uint32_t abbrCode)
+  const {
+  if (IdxOffset == UINT32_MAX) {
+    DWARFAbbreviationDeclarationCollConstIter pos;
+    DWARFAbbreviationDeclarationCollConstIter end = Decls.end();
+    for (pos = Decls.begin(); pos != end; ++pos) {
+      if (pos->getCode() == abbrCode)
+        return &(*pos);
+    }
+  } else {
+    uint32_t idx = abbrCode - IdxOffset;
+    if (idx < Decls.size())
+      return &Decls[idx];
+  }
+  return NULL;
+}
+
+DWARFDebugAbbrev::DWARFDebugAbbrev() :
+  m_abbrevCollMap(),
+  m_prev_abbr_offset_pos(m_abbrevCollMap.end()) {}
+
+
+void DWARFDebugAbbrev::parse(DataExtractor data) {
+  uint32_t offset = 0;
+
+  while (data.isValidOffset(offset)) {
+    uint32_t initial_cu_offset = offset;
+    DWARFAbbreviationDeclarationSet abbrevDeclSet;
+
+    if (abbrevDeclSet.extract(data, &offset))
+      m_abbrevCollMap[initial_cu_offset] = abbrevDeclSet;
+    else
+      break;
+  }
+  m_prev_abbr_offset_pos = m_abbrevCollMap.end();
+}
+
+void DWARFDebugAbbrev::dump(raw_ostream &OS) const {
+  if (m_abbrevCollMap.empty()) {
+    OS << "< EMPTY >\n";
+    return;
+  }
+
+  DWARFAbbreviationDeclarationCollMapConstIter pos;
+  for (pos = m_abbrevCollMap.begin(); pos != m_abbrevCollMap.end(); ++pos) {
+    OS << format("Abbrev table for offset: 0x%8.8x\n", pos->first);
+    pos->second.dump(OS);
+  }
+}
+
+const DWARFAbbreviationDeclarationSet*
+DWARFDebugAbbrev::getAbbreviationDeclarationSet(uint64_t cu_abbr_offset) const {
+  DWARFAbbreviationDeclarationCollMapConstIter end = m_abbrevCollMap.end();
+  DWARFAbbreviationDeclarationCollMapConstIter pos;
+  if (m_prev_abbr_offset_pos != end &&
+      m_prev_abbr_offset_pos->first == cu_abbr_offset) {
+    return &(m_prev_abbr_offset_pos->second);
+  } else {
+    pos = m_abbrevCollMap.find(cu_abbr_offset);
+    m_prev_abbr_offset_pos = pos;
+  }
+
+  if (pos != m_abbrevCollMap.end())
+    return &(pos->second);
+  return NULL;
+}
diff --git a/lib/DebugInfo/DWARFDebugAbbrev.h b/lib/DebugInfo/DWARFDebugAbbrev.h
new file mode 100644
index 0000000000..eaa79a1014
--- /dev/null
+++ b/lib/DebugInfo/DWARFDebugAbbrev.h
@@ -0,0 +1,71 @@
+//===-- DWARFDebugAbbrev.h --------------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_DWARFDEBUGABBREV_H
+#define LLVM_DEBUGINFO_DWARFDEBUGABBREV_H
+
+#include "DWARFAbbreviationDeclaration.h"
+#include <list>
+#include <map>
+#include <vector>
+
+namespace llvm {
+
+typedef std::vector<DWARFAbbreviationDeclaration>
+  DWARFAbbreviationDeclarationColl;
+typedef DWARFAbbreviationDeclarationColl::iterator
+  DWARFAbbreviationDeclarationCollIter;
+typedef DWARFAbbreviationDeclarationColl::const_iterator
+  DWARFAbbreviationDeclarationCollConstIter;
+
+class DWARFAbbreviationDeclarationSet {
+  uint64_t Offset;
+  uint32_t IdxOffset;
+  std::vector<DWARFAbbreviationDeclaration> Decls;
+  public:
+  DWARFAbbreviationDeclarationSet()
+    : Offset(0), IdxOffset(0) {}
+
+  DWARFAbbreviationDeclarationSet(uint64_t offset, uint32_t idxOffset)
+    : Offset(offset), IdxOffset(idxOffset) {}
+
+  void clear() {
+    IdxOffset = 0;
+    Decls.clear();
+  }
+  uint64_t getOffset() const { return Offset; }
+  void dump(raw_ostream &OS) const;
+  bool extract(DataExtractor data, uint32_t* offset_ptr);
+
+  const DWARFAbbreviationDeclaration *
+    getAbbreviationDeclaration(uint32_t abbrCode) const;
+};
+
+typedef std::map<uint64_t, DWARFAbbreviationDeclarationSet>
+  DWARFAbbreviationDeclarationCollMap;
+typedef DWARFAbbreviationDeclarationCollMap::iterator
+  DWARFAbbreviationDeclarationCollMapIter;
+typedef DWARFAbbreviationDeclarationCollMap::const_iterator
+  DWARFAbbreviationDeclarationCollMapConstIter;
+
+class DWARFDebugAbbrev {
+public:
+  DWARFDebugAbbrev();
+  const DWARFAbbreviationDeclarationSet *
+    getAbbreviationDeclarationSet(uint64_t cu_abbr_offset) const;
+  void dump(raw_ostream &OS) const;
+  void parse(DataExtractor data);
+protected:
+  DWARFAbbreviationDeclarationCollMap m_abbrevCollMap;
+  mutable DWARFAbbreviationDeclarationCollMapConstIter m_prev_abbr_offset_pos;
+};
+
+}
+
+#endif
diff --git a/lib/DebugInfo/DWARFDebugInfoEntry.cpp b/lib/DebugInfo/DWARFDebugInfoEntry.cpp
new file mode 100644
index 0000000000..5813a55f2f
--- /dev/null
+++ b/lib/DebugInfo/DWARFDebugInfoEntry.cpp
@@ -0,0 +1,410 @@
+//===-- DWARFDebugInfoEntry.cpp --------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DWARFDebugInfoEntry.h"
+#include "DWARFCompileUnit.h"
+#include "DWARFContext.h"
+#include "DWARFDebugAbbrev.h"
+#include "DWARFFormValue.h"
+#include "llvm/Support/Dwarf.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+using namespace dwarf;
+
+v