Make DebugVariable class available in DebugInfoMetadata

[StephenTozer]

Summary

This review is a prerequisite to: https://reviews.llvm.org/D70318

This patch moves the DebugVariable class from LiveDebugValues.cpp to DebugInfoMetadata.h, making it available in a much broader scope. In the patch linked above, this class is used in SimplifyCFG as an identifier for variables which require setting as undefined.

[Orlando]

llvm/include/llvm/IR/DebugInfoMetadata.h

3284

Could this be const OptFragmentInfo &?

[aprantl]

How about adding a quick unit test in the metadata unit test file?

llvm/include/llvm/IR/DebugInfoMetadata.h

3266

thanks!

3284

FragmentInfo small and meant to be used as a value type. I would prefer

Optional<FragmentInfo> (literally, without the using to hide the Optional). It's easier to read.

3293

Again, let's just return this by value.

3296

This warrants a comment explaining what this function does.

Is this actually more readable than Fragment.getValueOr(DefaultFragment)?

3300

isDefaultFragment?

3320

///

3322

return DV(nullptr, {}, nullptr)

3325

/// ... .

3327

DV(nullptr, {0, 0}, nullptr);

[StephenTozer]

llvm/include/llvm/IR/DebugInfoMetadata.h

3296

Does getFragmentOrDefault() sound more descriptive? It seems like a useful helper to have, in no small part because just having a static const member isn't as clear to a user as there being an explicit "get-value-or-default" function.

[StephenTozer]

Clean up code, fix comments.

[StephenTozer]

Use NoneType() to call correct DebugVariable constructor

[StephenTozer]

Add unit test, allow nullptr for DIExpression in DebugVariable ctor

[StephenTozer]

Remove redundant assignment on test variable construction

[aprantl]

llvm/include/llvm/IR/DebugInfoMetadata.h

117

getVariable?

[StephenTozer]

Rebased on master, rename getVar -> getVariable

[StephenTozer]

Merged in commit: llvmorg-10-init-11043-g269a9afe25cb

llvm/include/llvm/IR/DebugInfoMetadata.h

public:
   iterator begin() const { return N ? iterator(N->op_begin()) : iterator(); }
   iterator end() const { return N ? iterator(N->op_end()) : iterator(); }
 };
 
 /// Tagged DWARF-like metadata node.
 ///
 /// A metadata node with a DWARF tag (i.e., a constant named \c DW_TAG_*,
 /// defined in llvm/BinaryFormat/Dwarf.h).  Called \a DINode because it's
 /// potentially used for non-DWARF output.
 class DINode : public MDNode {
   friend class LLVMContextImpl;
   friend class MDNode;
 
 protected:
   DINode(LLVMContext &C, unsigned ID, StorageType Storage, unsigned Tag,
          ArrayRef<Metadata *> Ops1, ArrayRef<Metadata *> Ops2 = None)
       : MDNode(C, ID, Storage, Ops1, Ops2) {
#endif
   Metadata *getRawFile() const { return getOperand(0); }
   Metadata *getRawElements() const { return getOperand(1); }
 
   static bool classof(const Metadata *MD) {
     return MD->getMetadataID() == DIMacroFileKind;
   }
 };
 
+/// Identifies a unique instance of a variable.
+///
+/// Storage for identifying a potentially inlined instance of a variable,
+/// or a fragment thereof. This guarantees that exactly one variable instance
+/// may be identified by this class, even when that variable is a fragment of
+/// an aggregate variable and/or there is another inlined instance of the same
+/// source code variable nearby.
+/// This class does not necessarily uniquely identify that variable: it is
+/// possible that a DebugVariable with different parameters may point to the
+/// same variable instance, but not that one DebugVariable points to multiple
+/// variable instances.
+class DebugVariable {
+  using FragmentInfo = DIExpression::FragmentInfo;
+
+  const DILocalVariable *Variable;
+  Optional<FragmentInfo> Fragment;
+  const DILocation *InlinedAt;
+
+  /// Fragment that will overlap all other fragments. Used as default when
+  /// caller demands a fragment.
+  static const FragmentInfo DefaultFragment;
+
+public:
+  DebugVariable(const DILocalVariable *Var, Optional<FragmentInfo> FragmentInfo,
+                const DILocation *InlinedAt)
+      : Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {}
+
+  DebugVariable(const DILocalVariable *Var, const DIExpression *DIExpr,
+                const DILocation *InlinedAt)
+      : Variable(Var),
+        Fragment(DIExpr ? DIExpr->getFragmentInfo() : NoneType()),
+        InlinedAt(InlinedAt) {}
+
+  const DILocalVariable *getVariable() const { return Variable; }
+  const Optional<FragmentInfo> getFragment() const { return Fragment; }
+  const DILocation *getInlinedAt() const { return InlinedAt; }
+
+  const FragmentInfo getFragmentOrDefault() const {
+    return Fragment.getValueOr(DefaultFragment);
+  }
+
+  static bool isDefaultFragment(const FragmentInfo F) {
+    return F == DefaultFragment;
+  }
+
+  bool operator==(const DebugVariable &Other) const {
+    return std::tie(Variable, Fragment, InlinedAt) ==
+           std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
+  }
+
+  bool operator<(const DebugVariable &Other) const {
+    return std::tie(Variable, Fragment, InlinedAt) <
+           std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
+  }
+};
+
+template <> struct DenseMapInfo<DebugVariable> {
+  using FragmentInfo = DIExpression::FragmentInfo;
+
+  /// Empty key: no key should be generated that has no DILocalVariable.
+  static inline DebugVariable getEmptyKey() {
+    return DebugVariable(nullptr, NoneType(), nullptr);
+  }
+
+  /// Difference in tombstone is that the Optional is meaningful.
+  static inline DebugVariable getTombstoneKey() {
+    return DebugVariable(nullptr, {{0, 0}}, nullptr);
+  }
+
+  static unsigned getHashValue(const DebugVariable &D) {
+    unsigned HV = 0;
+    const Optional<FragmentInfo> Fragment = D.getFragment();
+    if (Fragment)
+      HV = DenseMapInfo<FragmentInfo>::getHashValue(*Fragment);
+
+    return hash_combine(D.getVariable(), HV, D.getInlinedAt());
+  }
+
+  static bool isEqual(const DebugVariable &A, const DebugVariable &B) {
+    return A == B;
+  }
+};
+
 } // end namespace llvm
 
 #undef DEFINE_MDNODE_GET_UNPACK_IMPL
 #undef DEFINE_MDNODE_GET_UNPACK
 #undef DEFINE_MDNODE_GET
 
 #endif // LLVM_IR_DEBUGINFOMETADATA_H

llvm/lib/CodeGen/LiveDebugValues.cpp

bool dominates(MachineBasicBlock *MBB) {
         LS.getMachineBasicBlocks(DL, LBlocks);
       return LBlocks.count(MBB) != 0 || LS.dominates(DL, MBB);
     }
   };
 
   using FragmentInfo = DIExpression::FragmentInfo;
   using OptFragmentInfo = Optional<DIExpression::FragmentInfo>;
 
-  /// Storage for identifying a potentially inlined instance of a variable,
-  /// or a fragment thereof.
-  class DebugVariable {
-    const DILocalVariable *Variable;
-    OptFragmentInfo Fragment;
-    const DILocation *InlinedAt;
-
-    /// Fragment that will overlap all other fragments. Used as default when
-    /// caller demands a fragment.
-    static const FragmentInfo DefaultFragment;
-
-  public:
-    DebugVariable(const DILocalVariable *Var, OptFragmentInfo &&FragmentInfo,
-                  const DILocation *InlinedAt)
-        : Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {}
-
-    DebugVariable(const DILocalVariable *Var, OptFragmentInfo &FragmentInfo,
-                  const DILocation *InlinedAt)
-        : Variable(Var), Fragment(FragmentInfo), InlinedAt(InlinedAt) {}
-
-    DebugVariable(const DILocalVariable *Var, const DIExpression *DIExpr,
-                  const DILocation *InlinedAt)
-        : DebugVariable(Var, DIExpr->getFragmentInfo(), InlinedAt) {}
-
-    DebugVariable(const MachineInstr &MI)
-        : DebugVariable(MI.getDebugVariable(),
-                        MI.getDebugExpression()->getFragmentInfo(),
-                        MI.getDebugLoc()->getInlinedAt()) {}
-
-    const DILocalVariable *getVar() const { return Variable; }
-    const OptFragmentInfo &getFragment() const { return Fragment; }
-    const DILocation *getInlinedAt() const { return InlinedAt; }
-
-    const FragmentInfo getFragmentDefault() const {
-      return Fragment.getValueOr(DefaultFragment);
-    }
-
-    static bool isFragmentDefault(FragmentInfo &F) {
-      return F == DefaultFragment;
-    }
-
-    bool operator==(const DebugVariable &Other) const {
-      return std::tie(Variable, Fragment, InlinedAt) ==
-             std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
-    }
-
-    bool operator<(const DebugVariable &Other) const {
-      return std::tie(Variable, Fragment, InlinedAt) <
-             std::tie(Other.Variable, Other.Fragment, Other.InlinedAt);
-    }
-  };
-
-  friend struct llvm::DenseMapInfo<DebugVariable>;
-
   /// A pair of debug variable and value location.
   struct VarLoc {
     // The location at which a spilled variable resides. It consists of a
     // register and an offset.
     struct SpillLoc {
       unsigned SpillBase;
       int SpillOffset;
       bool operator==(const SpillLoc &Other) const {
union {
       SpillLoc SpillLocation;
       uint64_t Hash;
       int64_t Immediate;
       const ConstantFP *FPImm;
       const ConstantInt *CImm;
     } Loc;
 
     VarLoc(const MachineInstr &MI, LexicalScopes &LS)
-        : Var(MI), Expr(MI.getDebugExpression()), MI(MI),
-          UVS(MI.getDebugLoc(), LS) {
+        : Var(MI.getDebugVariable(), MI.getDebugExpression(),
+              MI.getDebugLoc()->getInlinedAt()),
+          Expr(MI.getDebugExpression()), MI(MI), UVS(MI.getDebugLoc(), LS) {
       static_assert((sizeof(Loc) == sizeof(uint64_t)),
                     "hash does not cover all members of Loc");
       assert(MI.isDebugValue() && "not a DBG_VALUE");
       assert(MI.getNumOperands() == 4 && "malformed DBG_VALUE");
       if (int RegNo = isDbgValueDescribedByReg(MI)) {
         Kind = MI.isDebugEntryValue() ? EntryValueKind : RegisterKind;
         Loc.RegNo = RegNo;
       } else if (MI.getOperand(0).isImm()) {
void dump(const TargetRegisterInfo *TRI, raw_ostream &Out = dbgs()) const {
         break;
       case ImmediateKind:
         dbgs() << Loc.Immediate;
         break;
       case InvalidKind:
         llvm_unreachable("Invalid VarLoc in dump method");
       }
 
-      dbgs() << ", \"" << Var.getVar()->getName() << "\", " << *Expr << ", ";
+      dbgs() << ", \"" << Var.getVariable()->getName() << "\", " << *Expr
+             << ", ";
       if (Var.getInlinedAt())
         dbgs() << "!" << Var.getInlinedAt()->getMetadataID() << ")\n";
       else
         dbgs() << "(null))\n";
     }
 #endif
 
     bool operator==(const VarLoc &Other) const {
void printVarLocInMBB(const MachineFunction &MF, const VarLocInMBB &V,
                         raw_ostream &Out) const;
 
   /// Calculate the liveness information for the given machine function.
   bool runOnMachineFunction(MachineFunction &MF) override;
 };
 
 } // end anonymous namespace
 
-namespace llvm {
-
-template <> struct DenseMapInfo<LiveDebugValues::DebugVariable> {
-  using DV = LiveDebugValues::DebugVariable;
-  using OptFragmentInfo = LiveDebugValues::OptFragmentInfo;
-  using FragmentInfo = LiveDebugValues::FragmentInfo;
-
-  // Empty key: no key should be generated that has no DILocalVariable.
-  static inline DV getEmptyKey() {
-    return DV(nullptr, OptFragmentInfo(), nullptr);
-  }
-
-  // Difference in tombstone is that the Optional is meaningful
-  static inline DV getTombstoneKey() {
-    return DV(nullptr, OptFragmentInfo({0, 0}), nullptr);
-  }
-
-  static unsigned getHashValue(const DV &D) {
-    unsigned HV = 0;
-    const OptFragmentInfo &Fragment = D.getFragment();
-    if (Fragment)
-      HV = DenseMapInfo<FragmentInfo>::getHashValue(*Fragment);
-
-    return hash_combine(D.getVar(), HV, D.getInlinedAt());
-  }
-
-  static bool isEqual(const DV &A, const DV &B) { return A == B; }
-};
-
-} // namespace llvm
-
 //===----------------------------------------------------------------------===//
 //            Implementation
 //===----------------------------------------------------------------------===//
 
-const DIExpression::FragmentInfo
-    LiveDebugValues::DebugVariable::DefaultFragment = {
-        std::numeric_limits<uint64_t>::max(),
-        std::numeric_limits<uint64_t>::min()};
-
 char LiveDebugValues::ID = 0;
 
 char &llvm::LiveDebugValuesID = LiveDebugValues::ID;
 
 INITIALIZE_PASS(LiveDebugValues, DEBUG_TYPE, "Live DEBUG_VALUE analysis",
                 false, false)
 
 /// Default construct and initialize the pass.
auto DoErase = [this](DebugVariable VarToErase) {
     }
   };
 
   // Erase the variable/fragment that ends here.
   DoErase(Var);
 
   // Extract the fragment. Interpret an empty fragment as one that covers all
   // possible bits.
-  FragmentInfo ThisFragment = Var.getFragmentDefault();
+  FragmentInfo ThisFragment = Var.getFragmentOrDefault();
 
   // There may be fragments that overlap the designated fragment. Look them up
   // in the pre-computed overlap map, and erase them too.
-  auto MapIt = OverlappingFragments.find({Var.getVar(), ThisFragment});
+  auto MapIt = OverlappingFragments.find({Var.getVariable(), ThisFragment});
   if (MapIt != OverlappingFragments.end()) {
     for (auto Fragment : MapIt->second) {
       LiveDebugValues::OptFragmentInfo FragmentHolder;
-      if (!DebugVariable::isFragmentDefault(Fragment))
+      if (!DebugVariable::isDefaultFragment(Fragment))
         FragmentHolder = LiveDebugValues::OptFragmentInfo(Fragment);
-      DoErase({Var.getVar(), FragmentHolder, Var.getInlinedAt()});
+      DoErase({Var.getVariable(), FragmentHolder, Var.getInlinedAt()});
     }
   }
 }
 
 //===----------------------------------------------------------------------===//
 //            Debug Range Extension Implementation
 //===----------------------------------------------------------------------===//
 
 #ifndef NDEBUG
 void LiveDebugValues::printVarLocInMBB(const MachineFunction &MF,
                                        const VarLocInMBB &V,
                                        const VarLocMap &VarLocIDs,
                                        const char *msg,
                                        raw_ostream &Out) const {
   Out << '\n' << msg << '\n';
   for (const MachineBasicBlock &BB : MF) {
     const VarLocSet &L = V.lookup(&BB);
     if (L.empty())
       continue;
     Out << "MBB: " << BB.getNumber() << ":\n";
     for (unsigned VLL : L) {
       const VarLoc &VL = VarLocIDs[VLL];
-      Out << " Var: " << VL.Var.getVar()->getName();
+      Out << " Var: " << VL.Var.getVariable()->getName();
       Out << " MI: ";
       VL.dump(TRI, Out);
     }
   }
   Out << "\n";
 }
 #endif
 

 
 void LiveDebugValues::emitEntryValues(MachineInstr &MI,
                                       OpenRangesSet &OpenRanges,
                                       VarLocMap &VarLocIDs,
                                       TransferMap &Transfers,
                                       DebugParamMap &DebugEntryVals,
                                       SparseBitVector<> &KillSet) {
   for (unsigned ID : KillSet) {
-    if (!VarLocIDs[ID].Var.getVar()->isParameter())
+    if (!VarLocIDs[ID].Var.getVariable()->isParameter())
       continue;
 
     const MachineInstr *CurrDebugInstr = &VarLocIDs[ID].MI;
 
     // If parameter's DBG_VALUE is not in the map that means we can't
     // generate parameter's entry value.
     if (!DebugEntryVals.count(CurrDebugInstr->getDebugVariable()))
       continue;
void LiveDebugValues::insertTransferDebugPair(
     unsigned NewReg) {
   const MachineInstr *DebugInstr = &VarLocIDs[OldVarID].MI;
 
   auto ProcessVarLoc = [&MI, &OpenRanges, &Transfers, &DebugInstr,
                         &VarLocIDs](VarLoc &VL) {
     unsigned LocId = VarLocIDs.insert(VL);
 
     // Close this variable's previous location range.
-    DebugVariable V(*DebugInstr);
+    DebugVariable V(DebugInstr->getDebugVariable(),
+                    DebugInstr->getDebugExpression(),
+                    DebugInstr->getDebugLoc()->getInlinedAt());
     OpenRanges.erase(V);
 
     // Record the new location as an open range, and a postponed transfer
     // inserting a DBG_VALUE for this location.
     OpenRanges.insert(LocId, VL.Var);
     TransferDebugPair MIP = {&MI, LocId};
     Transfers.push_back(MIP);
   };
if (isLocationSpill(MI, MF, Reg)) {
     LLVM_DEBUG(dbgs() << "Register: " << Reg << " " << printReg(Reg, TRI)
                       << "\n");
   }
   // Check if the register or spill location is the location of a debug value.
   for (unsigned ID : OpenRanges.getVarLocs()) {
     if (TKind == TransferKind::TransferSpill &&
         VarLocIDs[ID].isDescribedByReg() == Reg) {
       LLVM_DEBUG(dbgs() << "Spilling Register " << printReg(Reg, TRI) << '('
-                        << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
+                        << VarLocIDs[ID].Var.getVariable()->getName() << ")\n");
     } else if (TKind == TransferKind::TransferRestore &&
                VarLocIDs[ID].Kind == VarLoc::SpillLocKind &&
                VarLocIDs[ID].Loc.SpillLocation == *Loc) {
       LLVM_DEBUG(dbgs() << "Restoring Register " << printReg(Reg, TRI) << '('
-                        << VarLocIDs[ID].Var.getVar()->getName() << ")\n");
+                        << VarLocIDs[ID].Var.getVariable()->getName() << ")\n");
     } else
       continue;
     insertTransferDebugPair(MI, OpenRanges, Transfers, VarLocIDs, ID, TKind,
                             Reg);
     return;
   }
 }
 

 ///           fragment usage.
 /// \param SeenFragments Map from DILocalVariable to all fragments of that
 ///           Variable which are known to exist.
 /// \param OverlappingFragments The overlap map being constructed, from one
 ///           Var/Fragment pair to a vector of fragments known to overlap.
 void LiveDebugValues::accumulateFragmentMap(MachineInstr &MI,
                                             VarToFragments &SeenFragments,
                                             OverlapMap &OverlappingFragments) {
-  DebugVariable MIVar(MI);
-  FragmentInfo ThisFragment = MIVar.getFragmentDefault();
+  DebugVariable MIVar(MI.getDebugVariable(), MI.getDebugExpression(),
+                      MI.getDebugLoc()->getInlinedAt());
+  FragmentInfo ThisFragment = MIVar.getFragmentOrDefault();
 
   // If this is the first sighting of this variable, then we are guaranteed
   // there are currently no overlapping fragments either. Initialize the set
   // of seen fragments, record no overlaps for the current one, and return.
-  auto SeenIt = SeenFragments.find(MIVar.getVar());
+  auto SeenIt = SeenFragments.find(MIVar.getVariable());
   if (SeenIt == SeenFragments.end()) {
     SmallSet<FragmentInfo, 4> OneFragment;
     OneFragment.insert(ThisFragment);
-    SeenFragments.insert({MIVar.getVar(), OneFragment});
+    SeenFragments.insert({MIVar.getVariable(), OneFragment});
 
-    OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}});
+    OverlappingFragments.insert({{MIVar.getVariable(), ThisFragment}, {}});
     return;
   }
 
   // If this particular Variable/Fragment pair already exists in the overlap
   // map, it has already been accounted for.
   auto IsInOLapMap =
-      OverlappingFragments.insert({{MIVar.getVar(), ThisFragment}, {}});
+      OverlappingFragments.insert({{MIVar.getVariable(), ThisFragment}, {}});
   if (!IsInOLapMap.second)
     return;
 
   auto &ThisFragmentsOverlaps = IsInOLapMap.first->second;
   auto &AllSeenFragments = SeenIt->second;
 
   // Otherwise, examine all other seen fragments for this variable, with "this"
   // fragment being a previously unseen fragment. Record any pair of
   // overlapping fragments.
   for (auto &ASeenFragment : AllSeenFragments) {
     // Does this previously seen fragment overlap?
     if (DIExpression::fragmentsOverlap(ThisFragment, ASeenFragment)) {
       // Yes: Mark the current fragment as being overlapped.
       ThisFragmentsOverlaps.push_back(ASeenFragment);
       // Mark the previously seen fragment as being overlapped by the current
       // one.
       auto ASeenFragmentsOverlaps =
-          OverlappingFragments.find({MIVar.getVar(), ASeenFragment});
+          OverlappingFragments.find({MIVar.getVariable(), ASeenFragment});
       assert(ASeenFragmentsOverlaps != OverlappingFragments.end() &&
              "Previously seen var fragment has no vector of overlaps");
       ASeenFragmentsOverlaps->second.push_back(ThisFragment);
     }
   }
 
   AllSeenFragments.insert(ThisFragment);
 }
if (!NumVisited)
       InLocsT = OL->second;
     else
       InLocsT &= OL->second;
 
     LLVM_DEBUG({
       if (!InLocsT.empty()) {
         for (auto ID : InLocsT)
           dbgs() << "  gathered candidate incoming var: "
-                 << VarLocIDs[ID].Var.getVar()->getName() << "\n";
+                 << VarLocIDs[ID].Var.getVariable()->getName() << "\n";
       }
     });
 
     NumVisited++;
   }
 
   // Filter out DBG_VALUES that are out of scope.
   VarLocSet KillSet;
   bool IsArtificial = ArtificialBlocks.count(&MBB);
   if (!IsArtificial) {
     for (auto ID : InLocsT) {
       if (!VarLocIDs[ID].dominates(MBB)) {
         KillSet.set(ID);
         LLVM_DEBUG({
-          auto Name = VarLocIDs[ID].Var.getVar()->getName();
+          auto Name = VarLocIDs[ID].Var.getVariable()->getName();
           dbgs() << "  killing " << Name << ", it doesn't dominate MBB\n";
         });
       }
     }
   }
   InLocsT.intersectWithComplement(KillSet);
 
   // As we are processing blocks in reverse post-order we

llvm/lib/IR/DebugInfoMetadata.cpp

 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instructions.h"
 
 #include <numeric>
 
 using namespace llvm;
 
+const DIExpression::FragmentInfo DebugVariable::DefaultFragment = {
+    std::numeric_limits<uint64_t>::max(), std::numeric_limits<uint64_t>::min()};
+
 DILocation::DILocation(LLVMContext &C, StorageType Storage, unsigned Line,
                        unsigned Column, ArrayRef<Metadata *> MDs,
                        bool ImplicitCode)
     : MDNode(C, DILocationKind, Storage, MDs) {
   assert((MDs.size() == 1 || MDs.size() == 2) &&
          "Expected a scope and optional inlined-at");
 
   // Set line and column.

llvm/unittests/IR/MetadataTest.cpp

 //===- unittests/IR/MetadataTest.cpp - Metadata unit tests ----------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/IR/Metadata.h"
+#include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
// useful thing to do.)
     DistinctMDOperandPlaceholder PH(7);
     TrackingMDRef Ref(&PH);
     EXPECT_DEATH(MDTuple::getDistinct(Context, &PH),
                  "Placeholders can only be used once");
   }
 }
 #endif
 
+typedef MetadataTest DebugVariableTest;
+TEST_F(DebugVariableTest, DenseMap) {
+  DenseMap<DebugVariable, uint64_t> DebugVariableMap;
+
+  DILocalScope *Scope = getSubprogram();
+  DIFile *File = getFile();
+  DIType *Type = getDerivedType();
+  DINode::DIFlags Flags = static_cast<DINode::DIFlags>(7);
+
+  DILocation *InlinedLoc = DILocation::get(Context, 2, 7, Scope);
+
+  DILocalVariable *VarA =
+      DILocalVariable::get(Context, Scope, "A", File, 5, Type, 2, Flags, 8);
+  DILocalVariable *VarB =
+      DILocalVariable::get(Context, Scope, "B", File, 7, Type, 3, Flags, 8);
+
+  DebugVariable DebugVariableA(VarA, NoneType(), nullptr);
+  DebugVariable DebugVariableInlineA(VarA, NoneType(), InlinedLoc);
+  DebugVariable DebugVariableB(VarB, NoneType(), nullptr);
+  DebugVariable DebugVariableFragB(VarB, {{16, 16}}, nullptr);
+
+  DebugVariableMap.insert({DebugVariableA, 2});
+  DebugVariableMap.insert({DebugVariableInlineA, 3});
+  DebugVariableMap.insert({DebugVariableB, 6});
+  DebugVariableMap.insert({DebugVariableFragB, 12});
+
+  EXPECT_EQ(DebugVariableMap.count(DebugVariableA), 1);
+  EXPECT_EQ(DebugVariableMap.count(DebugVariableInlineA), 1);
+  EXPECT_EQ(DebugVariableMap.count(DebugVariableB), 1);
+  EXPECT_EQ(DebugVariableMap.count(DebugVariableFragB), 1);
+
+  EXPECT_EQ(DebugVariableMap.find(DebugVariableA)->second, 2);
+  EXPECT_EQ(DebugVariableMap.find(DebugVariableInlineA)->second, 3);
+  EXPECT_EQ(DebugVariableMap.find(DebugVariableB)->second, 6);
+  EXPECT_EQ(DebugVariableMap.find(DebugVariableFragB)->second, 12);
+}
+
 } // end namespace