diff --git a/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h b/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
--- a/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
+++ b/llvm/include/llvm/DebugInfo/DWARF/DWARFUnit.h
@@ -252,13 +252,36 @@
 
   std::shared_ptr<DWARFUnit> DWO;
 
-  uint32_t getDIEIndex(const DWARFDebugInfoEntry *Die) {
+protected:
+  /// Return the index of a \p Die entry inside the unit's DIE vector.
+  ///
+  /// It is illegal to call this method with a DIE that hasn't be
+  /// created by this unit. In other word, it's illegal to call this
+  /// method on a DIE that isn't accessible by following
+  /// children/sibling links starting from this unit's getUnitDIE().
+  uint32_t getDIEIndex(const DWARFDebugInfoEntry *Die) const {
     auto First = DieArray.data();
     assert(Die >= First && Die < First + DieArray.size());
     return Die - First;
   }
 
-protected:
+  /// Return DWARFDebugInfoEntry for the specified index \p Index.
+  const DWARFDebugInfoEntry *getDebugInfoEntry(unsigned Index) const {
+    assert(Index < DieArray.size());
+    return &DieArray[Index];
+  }
+
+  const DWARFDebugInfoEntry *
+  getParentEntry(const DWARFDebugInfoEntry *Die) const;
+  const DWARFDebugInfoEntry *
+  getSiblingEntry(const DWARFDebugInfoEntry *Die) const;
+  const DWARFDebugInfoEntry *
+  getPreviousSiblingEntry(const DWARFDebugInfoEntry *Die) const;
+  const DWARFDebugInfoEntry *
+  getFirstChildEntry(const DWARFDebugInfoEntry *Die) const;
+  const DWARFDebugInfoEntry *
+  getLastChildEntry(const DWARFDebugInfoEntry *Die) const;
+
   const DWARFUnitHeader &getHeader() const { return Header; }
 
   /// Find the unit's contribution to the string offsets table and determine its
@@ -472,14 +495,13 @@
   /// created by this unit. In other word, it's illegal to call this
   /// method on a DIE that isn't accessible by following
   /// children/sibling links starting from this unit's getUnitDIE().
-  uint32_t getDIEIndex(const DWARFDie &D) {
+  uint32_t getDIEIndex(const DWARFDie &D) const {
     return getDIEIndex(D.getDebugInfoEntry());
   }
 
-  /// Return the DIE object at the given index.
+  /// Return the DIE object at the given index \p Index.
   DWARFDie getDIEAtIndex(unsigned Index) {
-    assert(Index < DieArray.size());
-    return DWARFDie(this, &DieArray[Index]);
+    return DWARFDie(this, getDebugInfoEntry(Index));
   }
 
   DWARFDie getParent(const DWARFDebugInfoEntry *Die);
@@ -488,19 +510,26 @@
   DWARFDie getFirstChild(const DWARFDebugInfoEntry *Die);
   DWARFDie getLastChild(const DWARFDebugInfoEntry *Die);
 
-  /// Return the DIE object for a given offset inside the
+  /// Return the DIE object for a given offset \p Offset inside the
   /// unit's DIE vector.
-  ///
-  /// The unit needs to have its DIEs extracted for this method to work.
   DWARFDie getDIEForOffset(uint64_t Offset) {
+    if (Optional<uint32_t> DieIdx = getDIEIndexForOffset(Offset))
+      return DWARFDie(this, &DieArray[*DieIdx]);
+
+    return DWARFDie();
+  }
+
+  /// Return the DIE index for a given offset \p Offset inside the
+  /// unit's DIE vector.
+  Optional<uint32_t> getDIEIndexForOffset(uint64_t Offset) {
     extractDIEsIfNeeded(false);
     auto It =
         llvm::partition_point(DieArray, [=](const DWARFDebugInfoEntry &DIE) {
           return DIE.getOffset() < Offset;
         });
     if (It != DieArray.end() && It->getOffset() == Offset)
-      return DWARFDie(this, &*It);
-    return DWARFDie();
+      return It - DieArray.begin();
+    return None;
   }
 
   uint32_t getLineTableOffset() const {
diff --git a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
--- a/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFUnit.cpp
@@ -877,39 +877,66 @@
 }
 
 DWARFDie DWARFUnit::getParent(const DWARFDebugInfoEntry *Die) {
+  if (const DWARFDebugInfoEntry *Entry = getParentEntry(Die))
+    return DWARFDie(this, Entry);
+
+  return DWARFDie();
+}
+
+const DWARFDebugInfoEntry *
+DWARFUnit::getParentEntry(const DWARFDebugInfoEntry *Die) const {
   if (!Die)
-    return DWARFDie();
+    return nullptr;
+  assert(Die >= DieArray.data() && Die < DieArray.data() + DieArray.size());
 
   if (Optional<uint32_t> ParentIdx = Die->getParentIdx()) {
     assert(*ParentIdx < DieArray.size() &&
            "ParentIdx is out of DieArray boundaries");
-    return DWARFDie(this, &DieArray[*ParentIdx]);
+    return getDebugInfoEntry(*ParentIdx);
   }
 
-  return DWARFDie();
+  return nullptr;
 }
 
 DWARFDie DWARFUnit::getSibling(const DWARFDebugInfoEntry *Die) {
+  if (const DWARFDebugInfoEntry *Sibling = getSiblingEntry(Die))
+    return DWARFDie(this, Sibling);
+
+  return DWARFDie();
+}
+
+const DWARFDebugInfoEntry *
+DWARFUnit::getSiblingEntry(const DWARFDebugInfoEntry *Die) const {
   if (!Die)
-    return DWARFDie();
+    return nullptr;
+  assert(Die >= DieArray.data() && Die < DieArray.data() + DieArray.size());
 
   if (Optional<uint32_t> SiblingIdx = Die->getSiblingIdx()) {
     assert(*SiblingIdx < DieArray.size() &&
            "SiblingIdx is out of DieArray boundaries");
-    return DWARFDie(this, &DieArray[*SiblingIdx]);
+    return &DieArray[*SiblingIdx];
   }
 
-  return DWARFDie();
+  return nullptr;
 }
 
 DWARFDie DWARFUnit::getPreviousSibling(const DWARFDebugInfoEntry *Die) {
+  if (const DWARFDebugInfoEntry *Sibling = getPreviousSiblingEntry(Die))
+    return DWARFDie(this, Sibling);
+
+  return DWARFDie();
+}
+
+const DWARFDebugInfoEntry *
+DWARFUnit::getPreviousSiblingEntry(const DWARFDebugInfoEntry *Die) const {
   if (!Die)
-    return DWARFDie();
+    return nullptr;
+  assert(Die >= DieArray.data() && Die < DieArray.data() + DieArray.size());
 
   Optional<uint32_t> ParentIdx = Die->getParentIdx();
   if (!ParentIdx)
     // Die is a root die, there is no previous sibling.
-    return DWARFDie();
+    return nullptr;
 
   assert(*ParentIdx < DieArray.size() &&
          "ParentIdx is out of DieArray boundaries");
@@ -918,7 +945,7 @@
   uint32_t PrevDieIdx = getDIEIndex(Die) - 1;
   if (PrevDieIdx == *ParentIdx)
     // Immediately previous node is parent, there is no previous sibling.
-    return DWARFDie();
+    return nullptr;
 
   while (DieArray[PrevDieIdx].getParentIdx() != *ParentIdx) {
     PrevDieIdx = *DieArray[PrevDieIdx].getParentIdx();
@@ -929,32 +956,56 @@
            "PrevDieIdx is not a child of parent of Die");
   }
 
-  return DWARFDie(this, &DieArray[PrevDieIdx]);
+  return &DieArray[PrevDieIdx];
 }
 
 DWARFDie DWARFUnit::getFirstChild(const DWARFDebugInfoEntry *Die) {
+  if (const DWARFDebugInfoEntry *Child = getFirstChildEntry(Die))
+    return DWARFDie(this, Child);
+
+  return DWARFDie();
+}
+
+const DWARFDebugInfoEntry *
+DWARFUnit::getFirstChildEntry(const DWARFDebugInfoEntry *Die) const {
+  if (!Die)
+    return nullptr;
+  assert(Die >= DieArray.data() && Die < DieArray.data() + DieArray.size());
+
   if (!Die->hasChildren())
-    return DWARFDie();
+    return nullptr;
 
   // TODO: Instead of checking here for invalid die we might reject
   // invalid dies at parsing stage(DWARFUnit::extractDIEsToVector).
   // We do not want access out of bounds when parsing corrupted debug data.
   size_t I = getDIEIndex(Die) + 1;
   if (I >= DieArray.size())
-    return DWARFDie();
-  return DWARFDie(this, &DieArray[I]);
+    return nullptr;
+  return &DieArray[I];
 }
 
 DWARFDie DWARFUnit::getLastChild(const DWARFDebugInfoEntry *Die) {
+  if (const DWARFDebugInfoEntry *Child = getLastChildEntry(Die))
+    return DWARFDie(this, Child);
+
+  return DWARFDie();
+}
+
+const DWARFDebugInfoEntry *
+DWARFUnit::getLastChildEntry(const DWARFDebugInfoEntry *Die) const {
+  if (!Die)
+    return nullptr;
+  assert(Die >= DieArray.data() && Die < DieArray.data() + DieArray.size());
+
   if (!Die->hasChildren())
-    return DWARFDie();
+    return nullptr;
 
   if (Optional<uint32_t> SiblingIdx = Die->getSiblingIdx()) {
     assert(*SiblingIdx < DieArray.size() &&
            "SiblingIdx is out of DieArray boundaries");
     assert(DieArray[*SiblingIdx - 1].getTag() == dwarf::DW_TAG_null &&
            "Bad end of children marker");
-    return DWARFDie(this, &DieArray[*SiblingIdx - 1]);
+    return &DieArray[*SiblingIdx - 1];
   }
 
   // If SiblingIdx is set for non-root dies we could be sure that DWARF is
@@ -969,11 +1020,13 @@
   if (getDIEIndex(Die) == 0 && DieArray.size() > 1 &&
       DieArray.back().getTag() == dwarf::DW_TAG_null) {
     // For the unit die we might take last item from DieArray.
-    assert(getDIEIndex(Die) == getDIEIndex(getUnitDIE()) && "Bad unit die");
-    return DWARFDie(this, &DieArray.back());
+    assert(getDIEIndex(Die) ==
+               getDIEIndex(const_cast<DWARFUnit *>(this)->getUnitDIE()) &&
+           "Bad unit die");
+    return &DieArray.back();
   }
 
-  return DWARFDie();
+  return nullptr;
 }
 
 const DWARFAbbreviationDeclarationSet *DWARFUnit::getAbbreviations() const {