diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -271,6 +271,12 @@
       return false;
     };
 
+    // Short-circuit unnecessary preferred location map construction.
+    if (VLocs.empty()) {
+      flushDbgValues(MBB.begin(), &MBB);
+      return;
+    }
+
     // Map of the preferred location for each value.
     std::map<ValueIDNum, LocIdx> ValueToLoc;
     ActiveMLocs.reserve(VLocs.size());