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

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