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/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;
+}