Index: llvm/include/llvm/ADT/APInt.h
===================================================================
--- llvm/include/llvm/ADT/APInt.h
+++ llvm/include/llvm/ADT/APInt.h
@@ -2267,13 +2267,13 @@
 template <> struct DenseMapInfo<APInt, void> {
   static inline APInt getEmptyKey() {
     APInt V(nullptr, 0);
-    V.U.VAL = 0;
+    V.U.VAL = ~0ULL;
     return V;
   }
 
   static inline APInt getTombstoneKey() {
     APInt V(nullptr, 0);
-    V.U.VAL = 1;
+    V.U.VAL = ~1ULL;
     return V;
   }
 
Index: llvm/unittests/ADT/APIntTest.cpp
===================================================================
--- llvm/unittests/ADT/APIntTest.cpp
+++ llvm/unittests/ADT/APIntTest.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/Twine.h"
 #include "gtest/gtest.h"
@@ -3126,4 +3127,11 @@
   EXPECT_EQ(APIntOps::ScaleBitMask(APInt(8, 0xE4), 4, true), APInt(4, 0x08));
 }
 
+TEST(APIntTest, DenseMap) {
+  DenseMap<APInt, int> Map;
+  APInt ZeroWidthInt(0, 0, false);
+  Map.insert({ZeroWidthInt, 0});
+  Map.find(ZeroWidthInt);
+}
+
 } // end anonymous namespace