diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 6f011fe4978919..72f0f610c8dbc4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1352,6 +1352,7 @@ void DwarfDebug::ensureAbstractEntityIsCreatedIfScoped(DwarfCompileUnit &CU,
 void DwarfDebug::collectVariableInfoFromMFTable(
     DwarfCompileUnit &TheCU, DenseSet<InlinedEntity> &Processed) {
   SmallDenseMap<InlinedEntity, DbgVariable *> MFVars;
+  LLVM_DEBUG(dbgs() << "DwarfDebug: collecting variables from MF side table\n");
   for (const auto &VI : Asm->MF->getVariableDbgInfo()) {
     if (!VI.Var)
       continue;
@@ -1363,13 +1364,18 @@ void DwarfDebug::collectVariableInfoFromMFTable(
     LexicalScope *Scope = LScopes.findLexicalScope(VI.Loc);
 
     // If variable scope is not found then skip this variable.
-    if (!Scope)
+    if (!Scope) {
+      LLVM_DEBUG(dbgs() << "Dropping debug info for " << VI.Var->getName()
+                        << ", no variable scope found\n");
       continue;
+    }
 
     ensureAbstractEntityIsCreatedIfScoped(TheCU, Var.first, Scope->getScopeNode());
     auto RegVar = std::make_unique<DbgVariable>(
                     cast<DILocalVariable>(Var.first), Var.second);
     RegVar->initializeMMI(VI.Expr, VI.Slot);
+    LLVM_DEBUG(dbgs() << "Created DbgVariable for " << VI.Var->getName()
+                      << "\n");
     if (DbgVariable *DbgVar = MFVars.lookup(Var))
       DbgVar->addMMIEntry(*RegVar);
     else if (InfoHolder.addScopeVariable(Scope, RegVar.get())) {
diff --git a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
index 9f78a1b4ca9fdf..ada09092c4782d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -1350,13 +1350,15 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) {
     const DbgDeclareInst *DI = cast<DbgDeclareInst>(II);
     assert(DI->getVariable() && "Missing variable");
     if (!FuncInfo.MF->getMMI().hasDebugInfo()) {
-      LLVM_DEBUG(dbgs() << "Dropping debug info for " << *DI << "\n");
+      LLVM_DEBUG(dbgs() << "Dropping debug info for " << *DI
+                        << " (!hasDebugInfo)\n");
       return true;
     }
 
     const Value *Address = DI->getAddress();
     if (!Address || isa<UndefValue>(Address)) {
-      LLVM_DEBUG(dbgs() << "Dropping debug info for " << *DI << "\n");
+      LLVM_DEBUG(dbgs() << "Dropping debug info for " << *DI
+                        << " (bad/undef address)\n");
       return true;
     }
 
@@ -1399,7 +1401,8 @@ bool FastISel::selectIntrinsicCall(const IntrinsicInst *II) {
     } else {
       // We can't yet handle anything else here because it would require
       // generating code, thus altering codegen because of debug info.
-      LLVM_DEBUG(dbgs() << "Dropping debug info for " << *DI << "\n");
+      LLVM_DEBUG(dbgs() << "Dropping debug info for " << *DI
+                        << " (no materialized reg for address)\n");
     }
     return true;
   }
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index dab86375156680..aa3a848bb1c4b2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5945,12 +5945,14 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
     DIExpression *Expression = DI.getExpression();
     dropDanglingDebugInfo(Variable, Expression);
     assert(Variable && "Missing variable");
-
+    LLVM_DEBUG(dbgs() << "SelectionDAG visiting debug intrinsic: " << DI
+                      << "\n");
     // Check if address has undef value.
     const Value *Address = DI.getVariableLocation();
     if (!Address || isa<UndefValue>(Address) ||
         (Address->use_empty() && !isa<Argument>(Address))) {
-      LLVM_DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
+      LLVM_DEBUG(dbgs() << "Dropping debug info for " << DI
+                        << " (bad/undef/unused-arg address)\n");
       return;
     }
 
@@ -5979,6 +5981,9 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
         SDDbgValue *SDV = DAG.getFrameIndexDbgValue(
             Variable, Expression, FI, /*IsIndirect*/ true, dl, SDNodeOrder);
         DAG.AddDbgValue(SDV, getRoot().getNode(), isParameter);
+      } else {
+        LLVM_DEBUG(dbgs() << "Skipping " << DI
+                          << " (variable info stashed in MF side table)\n");
       }
       return;
     }
@@ -6013,7 +6018,8 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
       // virtual register info from the FuncInfo.ValueMap.
       if (!EmitFuncArgumentDbgValue(Address, Variable, Expression, dl, true,
                                     N)) {
-        LLVM_DEBUG(dbgs() << "Dropping debug info for " << DI << "\n");
+        LLVM_DEBUG(dbgs() << "Dropping debug info for " << DI
+                          << " (could not emit func-arg dbg_value)\n");
       }
     }
     return;
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index b83c9026427419..51b2439dddc3d0 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1321,8 +1321,11 @@ static void processDbgDeclares(FunctionLoweringInfo &FuncInfo) {
       assert(DI->getVariable() && "Missing variable");
       assert(DI->getDebugLoc() && "Missing location");
       const Value *Address = DI->getAddress();
-      if (!Address)
+      if (!Address) {
+        LLVM_DEBUG(dbgs() << "processDbgDeclares skipping " << *DI
+                          << " (bad address)\n");
         continue;
+      }
 
       // Look through casts and constant offset GEPs. These mostly come from
       // inalloca.
@@ -1347,6 +1350,8 @@ static void processDbgDeclares(FunctionLoweringInfo &FuncInfo) {
       if (Offset.getBoolValue())
         Expr = DIExpression::prepend(Expr, DIExpression::ApplyOffset,
                                      Offset.getZExtValue());
+      LLVM_DEBUG(dbgs() << "processDbgDeclares: setVariableDbgInfo FI=" << FI
+                        << ", " << *DI << "\n");
       MF->setVariableDbgInfo(DI->getVariable(), Expr, FI, DI->getDebugLoc());
     }
   }