diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
index 40537b7..377fd57 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.cpp
@@ -1657,9 +1657,10 @@
 /// fragments of that DILocalVariable which overlap. This reduces work during
 /// the data-flow stage from "Find any overlapping fragments" to "Check if the
 /// known-to-overlap fragments are present".
-/// \param MI A previously unprocessed DEBUG_VALUE instruction to analyze for
+/// \param MI A previously unprocessed debug instruction to analyze for
 ///           fragment usage.
 void InstrRefBasedLDV::accumulateFragmentMap(MachineInstr &MI) {
+  assert(MI.isDebugValue() || MI.isDebugRef());
   DebugVariable MIVar(MI.getDebugVariable(), MI.getDebugExpression(),
                       MI.getDebugLoc()->getInlinedAt());
   FragmentInfo ThisFragment = MIVar.getFragmentOrDefault();
@@ -1761,7 +1762,7 @@
     for (auto &MI : MBB) {
       process(MI);
       // Also accumulate fragment map.
-      if (MI.isDebugValue())
+      if (MI.isDebugValue() || MI.isDebugRef())
         accumulateFragmentMap(MI);
 
       // Create a map from the instruction number (if present) to the
@@ -2929,7 +2930,7 @@
   ++MaxNumBlocks;
 
   MLocTransfer.resize(MaxNumBlocks);
-  vlocs.resize(MaxNumBlocks);
+  vlocs.resize(MaxNumBlocks, VLocTracker(OverlapFragments, EmptyExpr));
   SavedLiveIns.resize(MaxNumBlocks);
 
   initialSetup(MF);
@@ -3074,6 +3075,8 @@
   BBNumToRPO.clear();
   DebugInstrNumToInstr.clear();
   DebugPHINumToValue.clear();
+  OverlapFragments.clear();
+  SeenFragments.clear();
 
   return Changed;
 }
diff --git a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
index 81005e2..13ef84d 100644
--- a/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
+++ b/llvm/lib/CodeGen/LiveDebugValues/InstrRefBasedImpl.h
@@ -655,6 +655,14 @@
                               const DbgValueProperties &Properties);
 };
 
+/// Types for recording sets of variable fragments that overlap. For a given
+/// local variable, we record all other fragments of that variable that could
+/// overlap it, to reduce search time.
+using FragmentOfVar =
+    std::pair<const DILocalVariable *, DIExpression::FragmentInfo>;
+using OverlapMap =
+    DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>;
+
 /// Collection of DBG_VALUEs observed when traversing a block. Records each
 /// variable and the value the DBG_VALUE refers to. Requires the machine value
 /// location dataflow algorithm to have run already, so that values can be
@@ -672,9 +680,12 @@
   MapVector<DebugVariable, DbgValue> Vars;
   DenseMap<DebugVariable, const DILocation *> Scopes;
   MachineBasicBlock *MBB = nullptr;
+  const OverlapMap &OverlappingFragments;
+  DbgValueProperties EmptyProperties;
 
 public:
-  VLocTracker() {}
+  VLocTracker(const OverlapMap &O, const DIExpression *EmptyExpr)
+      : OverlappingFragments(O), EmptyProperties(EmptyExpr, false) {}
 
   void defVar(const MachineInstr &MI, const DbgValueProperties &Properties,
               Optional<ValueIDNum> ID) {
@@ -689,6 +700,8 @@
     if (!Result.second)
       Result.first->second = Rec;
     Scopes[Var] = MI.getDebugLoc().get();
+
+    considerOverlaps(Var, MI.getDebugLoc().get());
   }
 
   void defVar(const MachineInstr &MI, const MachineOperand &MO) {
@@ -704,17 +717,38 @@
     if (!Result.second)
       Result.first->second = Rec;
     Scopes[Var] = MI.getDebugLoc().get();
+
+    considerOverlaps(Var, MI.getDebugLoc().get());
+  }
+
+  void considerOverlaps(const DebugVariable &Var, const DILocation *Loc) {
+    auto Overlaps = OverlappingFragments.find(
+        {Var.getVariable(), Var.getFragmentOrDefault()});
+    if (Overlaps == OverlappingFragments.end())
+      return;
+
+    // Otherwise: terminate any overlapped variable locations.
+    for (auto FragmentInfo : Overlaps->second) {
+      // The "empty" fragment is stored as DebugVariable::DefaultFragment, so
+      // that it overlaps with everything, however its cannonical representation
+      // in a DebugVariable is as "None".
+      Optional<DIExpression::FragmentInfo> OptFragmentInfo = FragmentInfo;
+      if (DebugVariable::isDefaultFragment(FragmentInfo))
+        OptFragmentInfo = None;
+
+      DebugVariable Overlapped(Var.getVariable(), OptFragmentInfo,
+                               Var.getInlinedAt());
+      DbgValue Rec = DbgValue(EmptyProperties, DbgValue::Undef);
+
+      // Attempt insertion; overwrite if it's already mapped.
+      auto Result = Vars.insert(std::make_pair(Overlapped, Rec));
+      if (!Result.second)
+        Result.first->second = Rec;
+      Scopes[Overlapped] = Loc;
+    }
   }
 };
 
-/// Types for recording sets of variable fragments that overlap. For a given
-/// local variable, we record all other fragments of that variable that could
-/// overlap it, to reduce search time.
-using FragmentOfVar =
-    std::pair<const DILocalVariable *, DIExpression::FragmentInfo>;
-using OverlapMap =
-    DenseMap<FragmentOfVar, SmallVector<DIExpression::FragmentInfo, 1>>;
-
 // XXX XXX docs
 class InstrRefBasedLDV : public LDVImpl {
 public:
diff --git a/llvm/test/DebugInfo/MIR/X86/live-debug-values-fragments.mir b/llvm/test/DebugInfo/MIR/X86/live-debug-values-fragments.mir
index 34317d7..eef53c0 100644
--- a/llvm/test/DebugInfo/MIR/X86/live-debug-values-fragments.mir
+++ b/llvm/test/DebugInfo/MIR/X86/live-debug-values-fragments.mir
@@ -1,4 +1,4 @@
-# RUN: llc %s -o - -run-pass=livedebugvalues -experimental-debug-variable-locations=false | FileCheck %s
+# RUN: llc %s -o - -run-pass=livedebugvalues -experimental-debug-variable-locations=true | FileCheck %s
 #
 # The first func tests that, for two independent variable fragments defined in
 # blocks 1 and 2, _both_ their locations are propagated into the exit block.
@@ -15,10 +15,10 @@
 #
 # CHECK-LABEL: foo
 # CHECK-LABEL: bb.3.bb3:
-# CHECK:      DBG_VALUE $ebx, $noreg, !{{[0-9]+}},
-# CHECK-SAME:                 !DIExpression(DW_OP_LLVM_fragment, 32, 32)
-# CHECK-NEXT: DBG_VALUE $eax, $noreg, !{{[0-9]+}},
+# CHECK:      DBG_VALUE $ecx, $noreg, !{{[0-9]+}},
 # CHECK-SAME:                 !DIExpression(DW_OP_LLVM_fragment, 0, 32)
+# CHECK-NEXT: DBG_VALUE $ebx, $noreg, !{{[0-9]+}},
+# CHECK-SAME:                 !DIExpression(DW_OP_LLVM_fragment, 32, 32)
 # CHECK-NEXT: XOR32rr
 # CHECK-NEXT: RET64
 #
@@ -37,7 +37,7 @@
 
 # CHECK-LABEL: bb.2.bb2:
 # CHECK-NOT:  DBG_VALUE
-# CHECK:      DBG_VALUE $ax, $noreg, !{{[0-9]+}},
+# CHECK:      DBG_VALUE $cx, $noreg, !{{[0-9]+}},
 # CHECK-SAME:                 !DIExpression(DW_OP_LLVM_fragment, 8, 16)
 # CHECK-NEXT: MOV32rr
 # CHECK-NEXT: ADD32ri8
@@ -46,10 +46,10 @@
 # CHECK-NEXT: JMP_1
 
 # CHECK-LABEL: bb.3.bb3:
-# CHECK:      DBG_VALUE $ebx, $noreg, !{{[0-9]+}},
-# CHECK-SAME:                 !DIExpression(DW_OP_LLVM_fragment, 32, 32)
-# CHECK-NEXT: DBG_VALUE $ax, $noreg, !{{[0-9]+}},
+# CHECK:      DBG_VALUE $cx, $noreg, !{{[0-9]+}},
 # CHECK-SAME:                 !DIExpression(DW_OP_LLVM_fragment, 8, 16)
+# CHECK-NEXT: DBG_VALUE $ebx, $noreg, !{{[0-9]+}},
+# CHECK-SAME:                 !DIExpression(DW_OP_LLVM_fragment, 32, 32)
 # CHECK-NEXT: XOR32rr
 # CHECK-NEXT: RET64
 
diff --git a/llvm/unittests/CodeGen/InstrRefLDVTest.cpp b/llvm/unittests/CodeGen/InstrRefLDVTest.cpp
index 866eef8..d093f28 100644
--- a/llvm/unittests/CodeGen/InstrRefLDVTest.cpp
+++ b/llvm/unittests/CodeGen/InstrRefLDVTest.cpp
@@ -49,6 +49,7 @@
   DILocalVariable *FuncVariable;
   DIBasicType *LongInt;
   DIExpression *EmptyExpr;
+  LiveDebugValues::OverlapMap Overlaps;
 
   DebugLoc OutermostLoc, InBlockLoc, NotNestedBlockLoc, InlinedLoc;
 
@@ -169,7 +170,7 @@
 
   void addVTracker() {
     ASSERT_TRUE(LDV);
-    VTracker = std::make_unique<VLocTracker>();
+    VTracker = std::make_unique<VLocTracker>(Overlaps, EmptyExpr);
     LDV->VTracker = &*VTracker;
   }
 
@@ -2515,7 +2516,7 @@
   AssignBlocks.insert(MBB0);
 
   SmallVector<VLocTracker, 1> VLocs;
-  VLocs.resize(1);
+  VLocs.resize(1, VLocTracker(Overlaps, EmptyExpr));
 
   InstrRefBasedLDV::LiveInsT Output;
 
@@ -2579,7 +2580,7 @@
   AssignBlocks.insert(MBB3);
 
   SmallVector<VLocTracker, 1> VLocs;
-  VLocs.resize(4);
+  VLocs.resize(4, VLocTracker(Overlaps, EmptyExpr));
 
   InstrRefBasedLDV::LiveInsT Output;
 
@@ -2792,7 +2793,7 @@
   AssignBlocks.insert(MBB2);
 
   SmallVector<VLocTracker, 3> VLocs;
-  VLocs.resize(3);
+  VLocs.resize(3, VLocTracker(Overlaps, EmptyExpr));
 
   InstrRefBasedLDV::LiveInsT Output;
 
@@ -3048,7 +3049,7 @@
   AssignBlocks.insert(MBB4);
 
   SmallVector<VLocTracker, 5> VLocs;
-  VLocs.resize(5);
+  VLocs.resize(5, VLocTracker(Overlaps, EmptyExpr));
 
   InstrRefBasedLDV::LiveInsT Output;