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.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();
+  }
+}