Index: include/llvm/DebugInfo/DWARFDebugInfoEntry.h
===================================================================
--- include/llvm/DebugInfo/DWARFDebugInfoEntry.h
+++ include/llvm/DebugInfo/DWARFDebugInfoEntry.h
@@ -30,13 +30,16 @@
   /// Offset within the .debug_info of the start of this entry.
   uint32_t Offset;
 
+  /// How many to substract to "this" to get the parent.
+  uint32_t ParentIdx;
+
   /// How many to add to "this" to get the sibling.
   uint32_t SiblingIdx;
 
   const DWARFAbbreviationDeclaration *AbbrevDecl;
 public:
   DWARFDebugInfoEntryMinimal()
-    : Offset(0), SiblingIdx(0), AbbrevDecl(nullptr) {}
+    : Offset(0), ParentIdx(0), SiblingIdx(0), AbbrevDecl(nullptr) {}
 
   void dump(raw_ostream &OS, DWARFUnit *u, unsigned recurseDepth,
             unsigned indent = 0) const;
@@ -66,6 +69,11 @@
     return SiblingIdx > 0 ? this + SiblingIdx : nullptr;
   }
 
+  // Returns the parent DIE or null if this is the root DIE.
+  const DWARFDebugInfoEntryMinimal *getParent() const {
+    return ParentIdx ? this - ParentIdx : nullptr;
+  }
+
   // We know we are kept in a vector of contiguous entries, so we know
   // we don't need to store our child pointer, if we have a child it will
   // be the next entry in the list...
@@ -82,6 +90,15 @@
       SiblingIdx = 0;
   }
 
+  void setParent(const DWARFDebugInfoEntryMinimal *Parent) {
+    if (Parent) {
+      // We know we are kept in a vector of contiguous entries, so we know
+      // our parent will be soewhere before "this".
+      ParentIdx = this - Parent;
+    } else
+      ParentIdx = 0;
+  }
+
   const DWARFAbbreviationDeclaration *getAbbreviationDeclarationPtr() const {
     return AbbrevDecl;
   }
Index: lib/DebugInfo/DWARFUnit.cpp
===================================================================
--- lib/DebugInfo/DWARFUnit.cpp
+++ lib/DebugInfo/DWARFUnit.cpp
@@ -143,12 +143,18 @@
   if (DieArray.size() <= 1)
     return;
 
-  std::vector<DWARFDebugInfoEntryMinimal *> ParentChain;
+  // Make sure the vector is never empty so that we don't have to
+  // check for emptyness inside the loop bellow.
+  std::vector<DWARFDebugInfoEntryMinimal *> ParentChain(1,&DieArray[0]);
   DWARFDebugInfoEntryMinimal *SiblingChain = nullptr;
   for (auto &DIE : DieArray) {
     if (SiblingChain) {
       SiblingChain->setSibling(&DIE);
     }
+    // Note that this will call setParent with itself on the root
+    // node. This will result in a null offset which is handled as 'no
+    // parent'.
+    DIE.setParent(ParentChain.back());
     if (const DWARFAbbreviationDeclaration *AbbrDecl =
             DIE.getAbbreviationDeclarationPtr()) {
       // Normal DIE.
@@ -165,7 +171,7 @@
     }
   }
   assert(SiblingChain == nullptr || SiblingChain == &DieArray[0]);
-  assert(ParentChain.empty());
+  assert(ParentChain.size() == 1 && ParentChain[0] == &DieArray[0]);
 }
 
 void DWARFUnit::extractDIEsToVector(