1 files changed, 10 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/StackMaps.cpp b/llvm/lib/CodeGen/StackMaps.cpp
index 967cf751f36..d3791c3feb5 100644
--- a/llvm/lib/CodeGen/StackMaps.cpp
+++ b/llvm/lib/CodeGen/StackMaps.cpp
@@ -222,6 +222,16 @@ void StackMaps::recordStackMapOpers(const MachineInstr &MI, uint64_t ID,
     // -1 is directly encoded as .long 0xFFFFFFFF with no constant pool.
     if (I->LocType == Location::Constant && !isInt<32>(I->Offset)) {
       I->LocType = Location::ConstantIndex;
+      // ConstPool is intentionally a MapVector of 'uint64_t's (as
+      // opposed to 'int64_t's).  We should never be in a situation
+      // where we have to insert either the tombstone or the empty
+      // keys into a map, and for a DenseMap<uint64_t, T> these are
+      // (uint64_t)0 and (uint64_t)-1.  They can be and are
+      // represented using 32 bit integers.
+
+      assert((uint64_t)I->Offset != DenseMapInfo<uint64_t>::getEmptyKey() &&
+             (uint64_t)I->Offset != DenseMapInfo<uint64_t>::getTombstoneKey() &&
+             "empty and tombstone keys should fit in 32 bits!");
       auto Result = ConstPool.insert(std::make_pair(I->Offset, I->Offset));
       I->Offset = Result.first - ConstPool.begin();
     }