diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index f05f0be2..df6b101 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "SelectionDAGBuilder.h"
+#include "SDNodeDbgValue.h"
 #include "llvm/ADT/APFloat.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
@@ -1077,29 +1078,64 @@
   }
 }
 
+void SelectionDAGBuilder::dropDanglingDebugInfo(const DILocalVariable *Variable,
+                                                const DIExpression *Expr) {
+  SmallVector<const Value *, 4> ToRemove;
+  for (auto &DMI : DanglingDebugInfoMap) {
+    DanglingDebugInfo &DDI = DMI.second;
+    if (DDI.getDI()) {
+      const DbgValueInst *DI = DDI.getDI();
+      DIVariable *DanglingVariable = DI->getVariable();
+      DIExpression *DanglingExpr = DI->getExpression();
+      if (DanglingVariable == Variable &&
+          Expr->fragmentsOverlap(DanglingExpr)) {
+        DEBUG(dbgs() << "Dropping dangling debug info for " << *DI << "\n");
+        ToRemove.push_back(DMI.first);
+      }
+    }
+  }
+
+  for (auto V : ToRemove)
+    DanglingDebugInfoMap[V] = DanglingDebugInfo();
+}
+
 // resolveDanglingDebugInfo - if we saw an earlier dbg_value referring to V,
 // generate the debug data structures now that we've seen its definition.
 void SelectionDAGBuilder::resolveDanglingDebugInfo(const Value *V,
                                                    SDValue Val) {
   DanglingDebugInfo &DDI = DanglingDebugInfoMap[V];
-  if (DDI.getDI()) {
-    const DbgValueInst *DI = DDI.getDI();
-    DebugLoc dl = DDI.getdl();
-    unsigned DbgSDNodeOrder = DDI.getSDNodeOrder();
-    DILocalVariable *Variable = DI->getVariable();
-    DIExpression *Expr = DI->getExpression();
-    assert(Variable->isValidLocationForIntrinsic(dl) &&
-           "Expected inlined-at fields to agree");
-    SDDbgValue *SDV;
-    if (Val.getNode()) {
-      if (!EmitFuncArgumentDbgValue(V, Variable, Expr, dl, false, Val)) {
-        SDV = getDbgValue(Val, Variable, Expr, dl, DbgSDNodeOrder);
-        DAG.AddDbgValue(SDV, Val.getNode(), false);
-      }
+  if (!DDI.getDI())
+    return;
+  const DbgValueInst *DI = DDI.getDI();
+  DebugLoc dl = DDI.getdl();
+  unsigned ValSDNodeOrder = Val.getNode()->getIROrder();
+  unsigned DbgSDNodeOrder = DDI.getSDNodeOrder();
+  DILocalVariable *Variable = DI->getVariable();
+  DIExpression *Expr = DI->getExpression();
+  assert(Variable->isValidLocationForIntrinsic(dl) &&
+         "Expected inlined-at fields to agree");
+  SDDbgValue *SDV;
+  if (Val.getNode()) {
+    if (!EmitFuncArgumentDbgValue(V, Variable, Expr, dl, false, Val)) {
+      DEBUG(dbgs() << "Resolve dangling debug info [order=" << DbgSDNodeOrder
+            << "] for:\n  " << *DI << "\n");
+      DEBUG(dbgs() << "  By mapping to:\n    "; Val.dump());
+      // Increase the SDNodeOrder for the DbgValue here to make sure it is
+      // inserted after the definition of Val when emitting the instructions
+      // after ISel. An alternative could be to teach
+      // ScheduleDAGSDNodes::EmitSchedule to delay the insertion properly.
+      DEBUG(if (ValSDNodeOrder > DbgSDNodeOrder)
+              dbgs() << "changing SDNodeOrder from " << DbgSDNodeOrder
+                     << " to " << ValSDNodeOrder << "\n");
+      SDV = getDbgValue(Val, Variable, Expr, dl,
+                        std::max(DbgSDNodeOrder, ValSDNodeOrder));
+      DAG.AddDbgValue(SDV, Val.getNode(), false);
     } else
-      DEBUG(dbgs() << "Dropping debug info for " << *DI << "\n");
-    DanglingDebugInfoMap[V] = DanglingDebugInfo();
-  }
+      DEBUG(dbgs() << "Resolved dangling debug info for " << *DI
+            << "in EmitFuncArgumentDbgValue\n");
+  } else
+    DEBUG(dbgs() << "Dropping debug info for " << *DI << "\n");
+  DanglingDebugInfoMap[V] = DanglingDebugInfo();
 }
 
 /// getCopyFromRegs - If there was virtual register allocated for the value V
@@ -5178,6 +5214,7 @@
     const DbgInfoIntrinsic &DI = cast<DbgInfoIntrinsic>(I);
     DILocalVariable *Variable = DI.getVariable();
     DIExpression *Expression = DI.getExpression();
+    dropDanglingDebugInfo(Variable, Expression);
     assert(Variable && "Missing variable");
 
     // Check if address has undef value.
@@ -5209,10 +5246,11 @@
     // DBG_VALUE instructions. llvm.dbg.declare is handled as a frame index in
     // the MachineFunction variable table.
     if (FI != std::numeric_limits<int>::max()) {
-      if (Intrinsic == Intrinsic::dbg_addr)
-        DAG.AddDbgValue(DAG.getFrameIndexDbgValue(Variable, Expression, FI, dl,
-                                                  SDNodeOrder),
-                        getRoot().getNode(), isParameter);
+      if (Intrinsic == Intrinsic::dbg_addr) {
+         SDDbgValue *SDV = DAG.getFrameIndexDbgValue(Variable, Expression,
+                                                     FI, dl, SDNodeOrder);
+         DAG.AddDbgValue(SDV, getRoot().getNode(), isParameter);
+      }
       return nullptr;
     }
 
@@ -5256,6 +5294,7 @@
 
     DILocalVariable *Variable = DI.getVariable();
     DIExpression *Expression = DI.getExpression();
+    dropDanglingDebugInfo(Variable, Expression);
     const Value *V = DI.getValue();
     if (!V)
       return nullptr;
@@ -5280,6 +5319,12 @@
       return nullptr;
     }
 
+    // TODO: When we get here we will either drop the dbg.value completely, or
+    // we try to move it forward by letting it dangle for awhile. So we should
+    // probably add an extra DbgValue to the DAG here, with a reference to
+    // "noreg", to indicate that we have lost the debug location for the
+    // variable.
+
     if (!V->use_empty() ) {
       // Do not call getValue(V) yet, as we don't want to generate code.
       // Remember it for later.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 9e7c2bc..3d58a04 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -671,6 +671,12 @@
   /// emit CopyFromReg of the specified type Ty. Return empty SDValue() otherwise.
   SDValue getCopyFromRegs(const Value *V, Type *Ty);
 
+  /// If we have dangling debug info that describes \p Variable, or an
+  /// overlapping part of variable considering the \p Expr, then this method
+  /// weill drop that debug info as it isn't valid any longer.
+  void dropDanglingDebugInfo(const DILocalVariable *Variable,
+                             const DIExpression *Expr);
+
   // resolveDanglingDebugInfo - if we saw an earlier dbg_value referring to V,
   // generate the debug data structures now that we've seen its definition.
   void resolveDanglingDebugInfo(const Value *V, SDValue Val);