Fix DenseMap iterator constness.

This patch forbids implicit conversion of DenseMap::const_iterator to
DenseMap::iterator which was possible because DenseMapIterator inherited
(publicly) from DenseMapConstIterator. Conversion the other way around is now
allowed as one may expect.

The template DenseMapConstIterator is removed and the template parameter
IsConst which specifies whether the iterator is constant is added to
DenseMapIterator.

Actually IsConst parameter is not necessary since the constness can be
determined from KeyT but this is not relevant to the fix and can be addressed
later.

Patch by Victor Zverovich!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@86636 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/DenseMap.h

@@ -14,8 +14,9 @@
 #ifndef LLVM_ADT_DENSEMAP_H
 #define LLVM_ADT_DENSEMAP_H
 
-#include "llvm/Support/PointerLikeTypeTraits.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Support/PointerLikeTypeTraits.h"
+#include "llvm/Support/type_traits.h"
 #include "llvm/ADT/DenseMapInfo.h"
 #include <iterator>
 #include <new>
@@ -27,12 +28,8 @@ namespace llvm {
 
 template<typename KeyT, typename ValueT,
          typename KeyInfoT = DenseMapInfo<KeyT>,
-         typename ValueInfoT = DenseMapInfo<ValueT> >
+         typename ValueInfoT = DenseMapInfo<ValueT>, bool IsConst = false>
 class DenseMapIterator;
-template<typename KeyT, typename ValueT,
-         typename KeyInfoT = DenseMapInfo<KeyT>,
-         typename ValueInfoT = DenseMapInfo<ValueT> >
-class DenseMapConstIterator;
 
 template<typename KeyT, typename ValueT,
          typename KeyInfoT = DenseMapInfo<KeyT>,
@@ -73,7 +70,8 @@ public:
   }
 
   typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
-  typedef DenseMapConstIterator<KeyT, ValueT, KeyInfoT> const_iterator;
+  typedef DenseMapIterator<KeyT, ValueT,
+                           KeyInfoT, ValueInfoT, true> const_iterator;
   inline iterator begin() {
      return iterator(Buckets, Buckets+NumBuckets);
   }
@@ -426,32 +424,47 @@ private:
   }
 };
 
-template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
-class DenseMapIterator : 
-      public std::iterator<std::forward_iterator_tag, std::pair<KeyT, ValueT>,
-                          ptrdiff_t> {
-  typedef std::pair<KeyT, ValueT> BucketT;
-protected:
-  const BucketT *Ptr, *End;
+template<typename KeyT, typename ValueT,
+         typename KeyInfoT, typename ValueInfoT, bool IsConst>
+class DenseMapIterator {
+  typedef std::pair<KeyT, ValueT> Bucket;
+  typedef DenseMapIterator<KeyT, ValueT,
+                           KeyInfoT, ValueInfoT, true> ConstIterator;
+  friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, ValueInfoT, true>;
+public:
+  typedef ptrdiff_t difference_type;
+  typedef typename conditional<IsConst, const Bucket, Bucket>::type value_type;
+  typedef value_type *pointer;
+  typedef value_type &reference;
+  typedef std::forward_iterator_tag iterator_category;
+private:
+  pointer Ptr, End;
 public:
   DenseMapIterator() : Ptr(0), End(0) {}
 
-  DenseMapIterator(const BucketT *Pos, const BucketT *E) : Ptr(Pos), End(E) {
+  DenseMapIterator(pointer Pos, pointer E) : Ptr(Pos), End(E) {
     AdvancePastEmptyBuckets();
   }
 
-  std::pair<KeyT, ValueT> &operator*() const {
-    return *const_cast<BucketT*>(Ptr);
+  // If IsConst is true this is a converting constructor from iterator to
+  // const_iterator and the default copy constructor is used.
+  // Otherwise this is a copy constructor for iterator.
+  DenseMapIterator(const DenseMapIterator<KeyT, ValueT,
+                                          KeyInfoT, ValueInfoT, false>& I)
+    : Ptr(I.Ptr), End(I.End) {}
+
+  reference operator*() const {
+    return *Ptr;
   }
-  std::pair<KeyT, ValueT> *operator->() const {
-    return const_cast<BucketT*>(Ptr);
+  pointer operator->() const {
+    return Ptr;
   }
 
-  bool operator==(const DenseMapIterator &RHS) const {
-    return Ptr == RHS.Ptr;
+  bool operator==(const ConstIterator &RHS) const {
+    return Ptr == RHS.operator->();
   }
-  bool operator!=(const DenseMapIterator &RHS) const {
-    return Ptr != RHS.Ptr;
+  bool operator!=(const ConstIterator &RHS) const {
+    return Ptr != RHS.operator->();
   }
 
   inline DenseMapIterator& operator++() {  // Preincrement
@@ -475,22 +488,6 @@ private:
   }
 };
 
-template<typename KeyT, typename ValueT, typename KeyInfoT, typename ValueInfoT>
-class DenseMapConstIterator : public DenseMapIterator<KeyT, ValueT, KeyInfoT> {
-public:
-  DenseMapConstIterator() : DenseMapIterator<KeyT, ValueT, KeyInfoT>() {}
-  DenseMapConstIterator(const std::pair<KeyT, ValueT> *Pos,
-                        const std::pair<KeyT, ValueT> *E)
-    : DenseMapIterator<KeyT, ValueT, KeyInfoT>(Pos, E) {
-  }
-  const std::pair<KeyT, ValueT> &operator*() const {
-    return *this->Ptr;
-  }
-  const std::pair<KeyT, ValueT> *operator->() const {
-    return this->Ptr;
-  }
-};
-
 } // end namespace llvm
 
 #endif

include/llvm/Analysis/SparsePropagation.h

@@ -153,7 +153,7 @@ public:
   /// value.  If an value is not in the map, it is returned as untracked,
   /// unlike the getOrInitValueState method.
   LatticeVal getLatticeState(Value *V) const {
-    DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
+    DenseMap<Value*, LatticeVal>::const_iterator I = ValueState.find(V);
     return I != ValueState.end() ? I->second : LatticeFunc->getUntrackedVal();
   }
   

include/llvm/Support/type_traits.h

@@ -96,6 +96,12 @@ template <typename T> struct remove_pointer<T*volatile> { typedef T type; };
 template <typename T> struct remove_pointer<T*const volatile> {
     typedef T type; };
 
+template <bool, typename T, typename F>
+struct conditional { typedef T type; };
+
+template <typename T, typename F>
+struct conditional<false, T, F> { typedef F type; };
+
 }
 
 #endif

lib/Analysis/IPA/Andersens.cpp

@@ -518,7 +518,7 @@ namespace {
     /// getObject - Return the node corresponding to the memory object for the
     /// specified global or allocation instruction.
     unsigned getObject(Value *V) const {
-      DenseMap<Value*, unsigned>::iterator I = ObjectNodes.find(V);
+      DenseMap<Value*, unsigned>::const_iterator I = ObjectNodes.find(V);
       assert(I != ObjectNodes.end() &&
              "Value does not have an object in the points-to graph!");
       return I->second;
@@ -527,7 +527,7 @@ namespace {
     /// getReturnNode - Return the node representing the return value for the
     /// specified function.
     unsigned getReturnNode(Function *F) const {
-      DenseMap<Function*, unsigned>::iterator I = ReturnNodes.find(F);
+      DenseMap<Function*, unsigned>::const_iterator I = ReturnNodes.find(F);
       assert(I != ReturnNodes.end() && "Function does not return a value!");
       return I->second;
     }
@@ -535,7 +535,7 @@ namespace {
     /// getVarargNode - Return the node representing the variable arguments
     /// formal for the specified function.
     unsigned getVarargNode(Function *F) const {
-      DenseMap<Function*, unsigned>::iterator I = VarargNodes.find(F);
+      DenseMap<Function*, unsigned>::const_iterator I = VarargNodes.find(F);
       assert(I != VarargNodes.end() && "Function does not take var args!");
       return I->second;
     }

lib/CodeGen/AsmPrinter/DwarfException.cpp

@@ -497,7 +497,7 @@ ComputeCallSiteTable(SmallVectorImpl<CallSiteEntry> &CallSites,
         SawPotentiallyThrowing = false;
 
       // Beginning of a new try-range?
-      RangeMapType::iterator L = PadMap.find(BeginLabel);
+      RangeMapType::const_iterator L = PadMap.find(BeginLabel);
       if (L == PadMap.end())
         // Nope, it was just some random label.
         continue;

lib/CodeGen/PreAllocSplitting.cpp

@@ -366,10 +366,10 @@ PreAllocSplitting::IsAvailableInStack(MachineBasicBlock *DefMBB,
   if (!DefMBB)
     return false;
 
-  DenseMap<unsigned, int>::iterator I = IntervalSSMap.find(Reg);
+  DenseMap<unsigned, int>::const_iterator I = IntervalSSMap.find(Reg);
   if (I == IntervalSSMap.end())
     return false;
-  DenseMap<SlotIndex, SlotIndex>::iterator
+  DenseMap<SlotIndex, SlotIndex>::const_iterator
     II = Def2SpillMap.find(DefIndex);
   if (II == Def2SpillMap.end())
     return false;

lib/CodeGen/SlotIndexes.cpp

@@ -201,7 +201,7 @@ void SlotIndexes::dump() const {
     }
   }
 
-  for (MBB2IdxMap::iterator itr = mbb2IdxMap.begin();
+  for (MBB2IdxMap::const_iterator itr = mbb2IdxMap.begin();
        itr != mbb2IdxMap.end(); ++itr) {
     errs() << "MBB " << itr->first->getNumber() << " (" << itr->first << ") - ["
            << itr->second.first << ", " << itr->second.second << "]\n";

lib/Target/MSP430/MSP430ISelDAGToDAG.cpp

@@ -364,7 +364,7 @@ bool MSP430DAGToDAGISel::IsLegalAndProfitableToFold(SDNode *N, SDNode *U,
   /// TokenFactor by PreprocessForRMW. Query the map Store => Load1 (created
   /// during preprocessing) to determine whether it's legal to introduce such
   /// "cycle" for a moment.
-  DenseMap<SDNode*, SDNode*>::iterator I = RMWStores.find(Root);
+  DenseMap<SDNode*, SDNode*>::const_iterator I = RMWStores.find(Root);
   if (I != RMWStores.end() && I->second == N)
     return true;
 

lib/Target/X86/X86InstrInfo.cpp

@@ -2170,7 +2170,7 @@ X86InstrInfo::foldMemoryOperandImpl(MachineFunction &MF,
   // If table selected...
   if (OpcodeTablePtr) {
     // Find the Opcode to fuse
-    DenseMap<unsigned*, std::pair<unsigned,unsigned> >::iterator I =
+    DenseMap<unsigned*, std::pair<unsigned,unsigned> >::const_iterator I =
       OpcodeTablePtr->find((unsigned*)MI->getOpcode());
     if (I != OpcodeTablePtr->end()) {
       unsigned Opcode = I->second.first;
@@ -2402,7 +2402,7 @@ bool X86InstrInfo::canFoldMemoryOperand(const MachineInstr *MI,
   
   if (OpcodeTablePtr) {
     // Find the Opcode to fuse
-    DenseMap<unsigned*, std::pair<unsigned,unsigned> >::iterator I =
+    DenseMap<unsigned*, std::pair<unsigned,unsigned> >::const_iterator I =
       OpcodeTablePtr->find((unsigned*)Opc);
     if (I != OpcodeTablePtr->end())
       return true;
@@ -2413,7 +2413,7 @@ bool X86InstrInfo::canFoldMemoryOperand(const MachineInstr *MI,
 bool X86InstrInfo::unfoldMemoryOperand(MachineFunction &MF, MachineInstr *MI,
                                 unsigned Reg, bool UnfoldLoad, bool UnfoldStore,
                                 SmallVectorImpl<MachineInstr*> &NewMIs) const {
-  DenseMap<unsigned*, std::pair<unsigned,unsigned> >::iterator I =
+  DenseMap<unsigned*, std::pair<unsigned,unsigned> >::const_iterator I =
     MemOp2RegOpTable.find((unsigned*)MI->getOpcode());
   if (I == MemOp2RegOpTable.end())
     return false;
@@ -2530,7 +2530,7 @@ X86InstrInfo::unfoldMemoryOperand(SelectionDAG &DAG, SDNode *N,
   if (!N->isMachineOpcode())
     return false;
 
-  DenseMap<unsigned*, std::pair<unsigned,unsigned> >::iterator I =
+  DenseMap<unsigned*, std::pair<unsigned,unsigned> >::const_iterator I =
     MemOp2RegOpTable.find((unsigned*)N->getMachineOpcode());
   if (I == MemOp2RegOpTable.end())
     return false;
@@ -2623,7 +2623,7 @@ X86InstrInfo::unfoldMemoryOperand(SelectionDAG &DAG, SDNode *N,
 unsigned X86InstrInfo::getOpcodeAfterMemoryUnfold(unsigned Opc,
                                       bool UnfoldLoad, bool UnfoldStore,
                                       unsigned *LoadRegIndex) const {
-  DenseMap<unsigned*, std::pair<unsigned,unsigned> >::iterator I =
+  DenseMap<unsigned*, std::pair<unsigned,unsigned> >::const_iterator I =
     MemOp2RegOpTable.find((unsigned*)Opc);
   if (I == MemOp2RegOpTable.end())
     return 0;

lib/Transforms/Scalar/ABCD.cpp

@@ -1049,7 +1049,7 @@ void ABCD::InequalityGraph::printHeader(raw_ostream &OS, Function &F) const {
 
 /// Prints the body of the dot file
 void ABCD::InequalityGraph::printBody(raw_ostream &OS) const {
-  DenseMap<Value *, SmallPtrSet<Edge *, 16> >::iterator begin =
+  DenseMap<Value *, SmallPtrSet<Edge *, 16> >::const_iterator begin =
       graph.begin(), end = graph.end();
 
   for (; begin != end ; ++begin) {

lib/Transforms/Scalar/GVN.cpp

@@ -624,7 +624,7 @@ uint32_t ValueTable::lookup_or_add(Value *V) {
 /// lookup - Returns the value number of the specified value. Fails if
 /// the value has not yet been numbered.
 uint32_t ValueTable::lookup(Value *V) const {
-  DenseMap<Value*, uint32_t>::iterator VI = valueNumbering.find(V);
+  DenseMap<Value*, uint32_t>::const_iterator VI = valueNumbering.find(V);
   assert(VI != valueNumbering.end() && "Value not numbered?");
   return VI->second;
 }
@@ -644,7 +644,7 @@ void ValueTable::erase(Value *V) {
 /// verifyRemoved - Verify that the value is removed from all internal data
 /// structures.
 void ValueTable::verifyRemoved(const Value *V) const {
-  for (DenseMap<Value*, uint32_t>::iterator
+  for (DenseMap<Value*, uint32_t>::const_iterator
          I = valueNumbering.begin(), E = valueNumbering.end(); I != E; ++I) {
     assert(I->first != V && "Inst still occurs in value numbering map!");
   }
@@ -2011,12 +2011,12 @@ void GVN::verifyRemoved(const Instruction *Inst) const {
 
   // Walk through the value number scope to make sure the instruction isn't
   // ferreted away in it.
-  for (DenseMap<BasicBlock*, ValueNumberScope*>::iterator
+  for (DenseMap<BasicBlock*, ValueNumberScope*>::const_iterator
          I = localAvail.begin(), E = localAvail.end(); I != E; ++I) {
     const ValueNumberScope *VNS = I->second;
 
     while (VNS) {
-      for (DenseMap<uint32_t, Value*>::iterator
+      for (DenseMap<uint32_t, Value*>::const_iterator
              II = VNS->table.begin(), IE = VNS->table.end(); II != IE; ++II) {
         assert(II->second != Inst && "Inst still in value numbering scope!");
       }

lib/Transforms/Scalar/SCCVN.cpp

@@ -507,7 +507,7 @@ void ValueTable::erase(Value *V) {
 /// verifyRemoved - Verify that the value is removed from all internal data
 /// structures.
 void ValueTable::verifyRemoved(const Value *V) const {
-  for (DenseMap<Value*, uint32_t>::iterator
+  for (DenseMap<Value*, uint32_t>::const_iterator
          I = valueNumbering.begin(), E = valueNumbering.end(); I != E; ++I) {
     assert(I->first != V && "Inst still occurs in value numbering map!");
   }

lib/VMCore/Metadata.cpp

@@ -341,11 +341,11 @@ MDNode *MetadataContextImpl::getMD(unsigned MDKind, const Instruction *Inst) {
 /// getMDs - Get the metadata attached to an Instruction.
 void MetadataContextImpl::
 getMDs(const Instruction *Inst, SmallVectorImpl<MDPairTy> &MDs) const {
-  MDStoreTy::iterator I = MetadataStore.find(Inst);
+  MDStoreTy::const_iterator I = MetadataStore.find(Inst);
   if (I == MetadataStore.end())
     return;
   MDs.resize(I->second.size());
-  for (MDMapTy::iterator MI = I->second.begin(), ME = I->second.end();
+  for (MDMapTy::const_iterator MI = I->second.begin(), ME = I->second.end();
        MI != ME; ++MI)
     // MD kinds are numbered from 1.
     MDs[MI->first - 1] = std::make_pair(MI->first, MI->second);

unittests/ADT/DenseMapTest.cpp

@@ -164,4 +164,16 @@ TEST_F(DenseMapTest, IterationTest) {
   }
 }
 
+// const_iterator test
+TEST_F(DenseMapTest, ConstIteratorTest) {
+  // Check conversion from iterator to const_iterator.
+  DenseMap<uint32_t, uint32_t>::iterator it = uintMap.begin();
+  DenseMap<uint32_t, uint32_t>::const_iterator cit(it);
+  EXPECT_TRUE(it == cit);
+
+  // Check copying of const_iterators.
+  DenseMap<uint32_t, uint32_t>::const_iterator cit2(cit);
+  EXPECT_TRUE(cit == cit2);
+}
+
 }