diff --git a/llvm/include/llvm/IR/Attributes.h b/llvm/include/llvm/IR/Attributes.h
index 3871db9a200ed..c8d6db66c36a2 100644
--- a/llvm/include/llvm/IR/Attributes.h
+++ b/llvm/include/llvm/IR/Attributes.h
@@ -73,7 +73,9 @@ class Attribute {
     #define GET_ATTR_NAMES
     #define ATTRIBUTE_ENUM(ENUM_NAME, OTHER) ENUM_NAME,
     #include "llvm/IR/Attributes.inc"
-    EndAttrKinds           ///< Sentinal value useful for loops
+    EndAttrKinds,          ///< Sentinal value useful for loops
+    EmptyKey,              ///< Use as Empty key for DenseMap of AttrKind
+    TombstoneKey,          ///< Use as Tombstone key for DenseMap of AttrKind
   };
 
 private:
diff --git a/llvm/include/llvm/Transforms/Utils/KnowledgeRetention.h b/llvm/include/llvm/Transforms/Utils/KnowledgeRetention.h
index c3baf8a43c0d8..fcc0dae76fe1e 100644
--- a/llvm/include/llvm/Transforms/Utils/KnowledgeRetention.h
+++ b/llvm/include/llvm/Transforms/Utils/KnowledgeRetention.h
@@ -60,13 +60,11 @@ inline bool hasAttributeInAssume(CallInst &AssumeCI, Value *IsOn,
 }
 
 template<> struct DenseMapInfo<Attribute::AttrKind> {
-  static constexpr auto MaxValue = std::numeric_limits<
-      std::underlying_type<Attribute::AttrKind>::type>::max();
   static Attribute::AttrKind getEmptyKey() {
-    return static_cast<Attribute::AttrKind>(MaxValue);
+    return Attribute::EmptyKey;
   }
   static Attribute::AttrKind getTombstoneKey() {
-    return static_cast<Attribute::AttrKind>(MaxValue - 1);
+    return Attribute::TombstoneKey;
   }
   static unsigned getHashValue(Attribute::AttrKind AK) {
     return hash_combine(AK);
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 0d24359328888..de2a6b47e6e29 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1218,6 +1218,8 @@ StructType *BitcodeReader::createIdentifiedStructType(LLVMContext &Context) {
 static uint64_t getRawAttributeMask(Attribute::AttrKind Val) {
   switch (Val) {
   case Attribute::EndAttrKinds:
+  case Attribute::EmptyKey:
+  case Attribute::TombstoneKey:
     llvm_unreachable("Synthetic enumerators which should never get here");
 
   case Attribute::None:            return 0;
diff --git a/llvm/lib/Transforms/Utils/CodeExtractor.cpp b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
index e72e17f495afe..d026e4793b156 100644
--- a/llvm/lib/Transforms/Utils/CodeExtractor.cpp
+++ b/llvm/lib/Transforms/Utils/CodeExtractor.cpp
@@ -887,6 +887,8 @@ Function *CodeExtractor::constructFunction(const ValueSet &inputs,
       case Attribute::ZExt:
       case Attribute::ImmArg:
       case Attribute::EndAttrKinds:
+      case Attribute::EmptyKey:
+      case Attribute::TombstoneKey:
         continue;
       // Those attributes should be safe to propagate to the extracted function.
       case Attribute::AlwaysInline: