dwarfdump: Use the index to find the right abbrev offset in DWP files

llvm-svn: 253277
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
index 348476d..169acee 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -14,7 +14,7 @@
 #include "llvm/Support/Path.h"
 #include <cstdio>
 
-using namespace llvm;
+namespace llvm {
 using namespace dwarf;
 
 void DWARFUnitSectionBase::parse(DWARFContext &C, const DWARFSection &Section) {
@@ -24,7 +24,8 @@
 }
 
 void DWARFUnitSectionBase::parseDWO(DWARFContext &C,
-                                    const DWARFSection &DWOSection) {
+                                    const DWARFSection &DWOSection,
+                                    DWARFUnitIndex *Index) {
   parseImpl(C, DWOSection, C.getDebugAbbrevDWO(), C.getRangeDWOSection(),
             C.getStringDWOSection(), C.getStringOffsetDWOSection(),
             C.getAddrSection(), C.isLittleEndian());
@@ -33,10 +34,11 @@
 DWARFUnit::DWARFUnit(DWARFContext &DC, const DWARFSection &Section,
                      const DWARFDebugAbbrev *DA, StringRef RS, StringRef SS,
                      StringRef SOS, StringRef AOS, bool LE,
-                     const DWARFUnitSectionBase &UnitSection)
+                     const DWARFUnitSectionBase &UnitSection,
+                     const DWARFUnitIndex::Entry *IndexEntry)
     : Context(DC), InfoSection(Section), Abbrev(DA), RangeSection(RS),
       StringSection(SS), StringOffsetSection(SOS), AddrOffsetSection(AOS),
-      isLittleEndian(LE), UnitSection(UnitSection) {
+      isLittleEndian(LE), UnitSection(UnitSection), IndexEntry(IndexEntry) {
   clear();
 }
 
@@ -69,6 +71,17 @@
   Length = debug_info.getU32(offset_ptr);
   Version = debug_info.getU16(offset_ptr);
   uint64_t AbbrOffset = debug_info.getU32(offset_ptr);
+  if (IndexEntry) {
+    if (AbbrOffset)
+      return false;
+    auto *UnitContrib = IndexEntry->getOffset();
+    if (!UnitContrib || UnitContrib->Length != (Length + 4))
+      return false;
+    auto *AbbrEntry = IndexEntry->getOffset(DW_SECT_ABBREV);
+    if (!AbbrEntry)
+      return false;
+    AbbrOffset = AbbrEntry->Offset;
+  }
   AddrSize = debug_info.getU8(offset_ptr);
 
   bool LengthOK = debug_info.isValidOffset(getNextUnitOffset() - 1);
@@ -375,3 +388,12 @@
     return DWARFDebugInfoEntryInlinedChain();
   return SubprogramDIE->getInlinedChainForAddress(ChainCU, Address);
 }
+
+const DWARFUnitIndex &getDWARFUnitIndex(DWARFContext &Context,
+                                        DWARFSectionKind Kind) {
+  if (Kind == DW_SECT_INFO)
+    return Context.getCUIndex();
+  assert(Kind == DW_SECT_TYPES);
+  return Context.getTUIndex();
+}
+}