[IR] Redesign the case iterator in SwitchInst to actually be an iterator

and to expose a handle to represent the actual case rather than having
the iterator return a reference to itself.

All of this allows the iterator to be used with common STL facilities,
standard algorithms, etc.

Doing this exposed some missing facilities in the iterator facade that
I've fixed and required some work to the actual iterator to fully
support the necessary API.

Differential Revision: https://reviews.llvm.org/D31548

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300032 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/ADT/iterator.h

@@ -165,9 +165,15 @@ public:
     return !static_cast<const DerivedT *>(this)->operator<(RHS);
   }
 
+  PointerT operator->() { return &static_cast<DerivedT *>(this)->operator*(); }
   PointerT operator->() const {
     return &static_cast<const DerivedT *>(this)->operator*();
   }
+  ReferenceProxy operator[](DifferenceTypeT n) {
+    static_assert(IsRandomAccess,
+                  "Subscripting is only defined for random access iterators.");
+    return ReferenceProxy(static_cast<DerivedT *>(this)->operator+(n));
+  }
   ReferenceProxy operator[](DifferenceTypeT n) const {
     static_assert(IsRandomAccess,
                   "Subscripting is only defined for random access iterators.");

include/llvm/Analysis/CFGPrinter.h

@@ -140,8 +140,7 @@ struct DOTGraphTraits<const Function*> : public DefaultDOTGraphTraits {
 
       std::string Str;
       raw_string_ostream OS(Str);
-      SwitchInst::ConstCaseIt Case =
-          SwitchInst::ConstCaseIt::fromSuccessorIndex(SI, SuccNo);
+      auto Case = *SwitchInst::ConstCaseIt::fromSuccessorIndex(SI, SuccNo);
       OS << Case.getCaseValue()->getValue();
       return OS.str();
     }

include/llvm/IR/Instructions.h

@@ -3096,49 +3096,39 @@ public:
   // -2
   static const unsigned DefaultPseudoIndex = static_cast<unsigned>(~0L-1);
 
-  template <class SwitchInstT, class ConstantIntT, class BasicBlockT>
-  class CaseIteratorT
-      : public iterator_facade_base<
-            CaseIteratorT<SwitchInstT, ConstantIntT, BasicBlockT>,
-            std::random_access_iterator_tag,
-            CaseIteratorT<SwitchInstT, ConstantIntT, BasicBlockT>> {
+  template <typename CaseHandleT> class CaseIteratorT;
+
+  /// A handle to a particular switch case. It exposes a convenient interface
+  /// to both the case value and the successor block.
+  ///
+  /// We define this as a template and instantiate it to form both a const and
+  /// non-const handle.
+  template <typename SwitchInstT, typename ConstantIntT, typename BasicBlockT>
+  class CaseHandleT {
+    // Directly befriend both const and non-const iterators.
+    friend class SwitchInst::CaseIteratorT<
+        CaseHandleT<SwitchInstT, ConstantIntT, BasicBlockT>>;
+
   protected:
+    // Expose the switch type we're parameterized with to the iterator.
+    typedef SwitchInstT SwitchInstType;
+
     SwitchInstT *SI;
     ptrdiff_t Index;
 
-  public:
-    typedef CaseIteratorT<SwitchInstT, ConstantIntT, BasicBlockT> Self;
-
-    /// Default constructed iterator is in an invalid state until assigned to
-    /// a case for a particular switch.
-    CaseIteratorT() : SI(nullptr) {}
-
-    /// Initializes case iterator for given SwitchInst and for given
-    /// case number.
-    CaseIteratorT(SwitchInstT *SI, unsigned CaseNum) {
-      this->SI = SI;
-      Index = CaseNum;
-    }
-
-    /// Initializes case iterator for given SwitchInst and for given
-    /// TerminatorInst's successor index.
-    static Self fromSuccessorIndex(SwitchInstT *SI, unsigned SuccessorIndex) {
-      assert(SuccessorIndex < SI->getNumSuccessors() &&
-             "Successor index # out of range!");
-      return SuccessorIndex != 0 ?
-             Self(SI, SuccessorIndex - 1) :
-             Self(SI, DefaultPseudoIndex);
-    }
+    CaseHandleT() = default;
+    CaseHandleT(SwitchInstT *SI, ptrdiff_t Index) : SI(SI), Index(Index) {}
 
+  public:
     /// Resolves case value for current case.
-    ConstantIntT *getCaseValue() {
+    ConstantIntT *getCaseValue() const {
       assert((unsigned)Index < SI->getNumCases() &&
              "Index out the number of cases.");
       return reinterpret_cast<ConstantIntT *>(SI->getOperand(2 + Index * 2));
     }
 
     /// Resolves successor for current case.
-    BasicBlockT *getCaseSuccessor() {
+    BasicBlockT *getCaseSuccessor() const {
       assert(((unsigned)Index < SI->getNumCases() ||
               (unsigned)Index == DefaultPseudoIndex) &&
              "Index out the number of cases.");
@@ -3156,43 +3146,20 @@ public:
       return (unsigned)Index != DefaultPseudoIndex ? Index + 1 : 0;
     }
 
-    Self &operator+=(ptrdiff_t N) {
-      // Check index correctness after addition.
-      // Note: Index == getNumCases() means end().
-      assert(Index + N >= 0 && (unsigned)(Index + N) <= SI->getNumCases() &&
-             "Index out the number of cases.");
-      Index += N;
-      return *this;
-    }
-    Self &operator-=(ptrdiff_t N) {
-      // Check index correctness after subtraction.
-      // Note: Index == getNumCases() means end().
-      assert(Index - N >= 0 && (unsigned)(Index - N) <= SI->getNumCases() &&
-             "Index out the number of cases.");
-      Index -= N;
-      return *this;
-    }
-    bool operator==(const Self& RHS) const {
+    bool operator==(const CaseHandleT &RHS) const {
       assert(SI == RHS.SI && "Incompatible operators.");
       return Index == RHS.Index;
     }
-    bool operator<(const Self& RHS) const {
-      assert(SI == RHS.SI && "Incompatible operators.");
-      return Index < RHS.Index;
-    }
-    Self &operator*() { return *this; }
-    const Self &operator*() const { return *this; }
   };
 
-  typedef CaseIteratorT<const SwitchInst, const ConstantInt, const BasicBlock>
-    ConstCaseIt;
+  typedef CaseHandleT<const SwitchInst, const ConstantInt, const BasicBlock>
+      ConstCaseHandle;
 
-  class CaseIt : public CaseIteratorT<SwitchInst, ConstantInt, BasicBlock> {
-    typedef CaseIteratorT<SwitchInst, ConstantInt, BasicBlock> ParentTy;
+  class CaseHandle : public CaseHandleT<SwitchInst, ConstantInt, BasicBlock> {
+    friend class SwitchInst::CaseIteratorT<CaseHandle>;
 
   public:
-    CaseIt(const ParentTy &Src) : ParentTy(Src) {}
-    CaseIt(SwitchInst *SI, unsigned CaseNum) : ParentTy(SI, CaseNum) {}
+    CaseHandle(SwitchInst *SI, ptrdiff_t Index) : CaseHandleT(SI, Index) {}
 
     /// Sets the new value for current case.
     void setValue(ConstantInt *V) {
@@ -3207,6 +3174,74 @@ public:
     }
   };
 
+  template <typename CaseHandleT>
+  class CaseIteratorT
+      : public iterator_facade_base<CaseIteratorT<CaseHandleT>,
+                                    std::random_access_iterator_tag,
+                                    CaseHandleT> {
+    typedef typename CaseHandleT::SwitchInstType SwitchInstT;
+
+    CaseHandleT Case;
+
+  public:
+    /// Default constructed iterator is in an invalid state until assigned to
+    /// a case for a particular switch.
+    CaseIteratorT() = default;
+
+    /// Initializes case iterator for given SwitchInst and for given
+    /// case number.
+    CaseIteratorT(SwitchInstT *SI, unsigned CaseNum) : Case(SI, CaseNum) {}
+
+    /// Initializes case iterator for given SwitchInst and for given
+    /// TerminatorInst's successor index.
+    static CaseIteratorT fromSuccessorIndex(SwitchInstT *SI,
+                                            unsigned SuccessorIndex) {
+      assert(SuccessorIndex < SI->getNumSuccessors() &&
+             "Successor index # out of range!");
+      return SuccessorIndex != 0 ? CaseIteratorT(SI, SuccessorIndex - 1)
+                                 : CaseIteratorT(SI, DefaultPseudoIndex);
+    }
+
+    /// Support converting to the const variant. This will be a no-op for const
+    /// variant.
+    operator CaseIteratorT<ConstCaseHandle>() const {
+      return CaseIteratorT<ConstCaseHandle>(Case.SI, Case.Index);
+    }
+
+    CaseIteratorT &operator+=(ptrdiff_t N) {
+      // Check index correctness after addition.
+      // Note: Index == getNumCases() means end().
+      assert(Case.Index + N >= 0 &&
+             (unsigned)(Case.Index + N) <= Case.SI->getNumCases() &&
+             "Case.Index out the number of cases.");
+      Case.Index += N;
+      return *this;
+    }
+    CaseIteratorT &operator-=(ptrdiff_t N) {
+      // Check index correctness after subtraction.
+      // Note: Case.Index == getNumCases() means end().
+      assert(Case.Index - N >= 0 &&
+             (unsigned)(Case.Index - N) <= Case.SI->getNumCases() &&
+             "Case.Index out the number of cases.");
+      Case.Index -= N;
+      return *this;
+    }
+    ptrdiff_t operator-(const CaseIteratorT &RHS) const {
+      assert(Case.SI == RHS.Case.SI && "Incompatible operators.");
+      return Case.Index - RHS.Case.Index;
+    }
+    bool operator==(const CaseIteratorT &RHS) const { return Case == RHS.Case; }
+    bool operator<(const CaseIteratorT &RHS) const {
+      assert(Case.SI == RHS.Case.SI && "Incompatible operators.");
+      return Case.Index < RHS.Case.Index;
+    }
+    CaseHandleT &operator*() { return Case; }
+    const CaseHandleT &operator*() const { return Case; }
+  };
+
+  typedef CaseIteratorT<CaseHandle> CaseIt;
+  typedef CaseIteratorT<ConstCaseHandle> ConstCaseIt;
+
   static SwitchInst *Create(Value *Value, BasicBlock *Default,
                             unsigned NumCases,
                             Instruction *InsertBefore = nullptr) {
@@ -3290,30 +3325,40 @@ public:
   /// default case iterator to indicate that it is handled by the default
   /// handler.
   CaseIt findCaseValue(const ConstantInt *C) {
-    for (CaseIt i = case_begin(), e = case_end(); i != e; ++i)
-      if (i.getCaseValue() == C)
-        return i;
+    CaseIt I = llvm::find_if(
+        cases(), [C](CaseHandle &Case) { return Case.getCaseValue() == C; });
+    if (I != case_end())
+      return I;
+
     return case_default();
   }
   ConstCaseIt findCaseValue(const ConstantInt *C) const {
-    for (ConstCaseIt i = case_begin(), e = case_end(); i != e; ++i)
-      if (i.getCaseValue() == C)
-        return i;
+    ConstCaseIt I = llvm::find_if(cases(), [C](ConstCaseHandle &Case) {
+      return Case.getCaseValue() == C;
+    });
+    if (I != case_end())
+      return I;
+
     return case_default();
   }
 
   /// Finds the unique case value for a given successor. Returns null if the
   /// successor is not found, not unique, or is the default case.
   ConstantInt *findCaseDest(BasicBlock *BB) {
-    if (BB == getDefaultDest()) return nullptr;
+    if (BB == getDefaultDest())
+      return nullptr;
 
     ConstantInt *CI = nullptr;
-    for (CaseIt i = case_begin(), e = case_end(); i != e; ++i) {
-      if (i.getCaseSuccessor() == BB) {
-        if (CI) return nullptr;   // Multiple cases lead to BB.
-        else CI = i.getCaseValue();
-      }
+    for (auto Case : cases()) {
+      if (Case.getCaseSuccessor() != BB)
+        continue;
+
+      if (CI)
+        return nullptr; // Multiple cases lead to BB.
+
+      CI = Case.getCaseValue();
     }
+
     return CI;
   }
 
@@ -3330,7 +3375,7 @@ public:
   /// This action invalidates iterators for all cases following the one removed,
   /// including the case_end() iterator. It returns an iterator for the next
   /// case.
-  CaseIt removeCase(CaseIt i);
+  CaseIt removeCase(CaseIt I);
 
   unsigned getNumSuccessors() const { return getNumOperands()/2; }
   BasicBlock *getSuccessor(unsigned idx) const {

lib/Analysis/InlineCost.cpp

@@ -1014,8 +1014,8 @@ bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
   // does not (yet) fire.
   SmallPtrSet<BasicBlock *, 8> SuccessorBlocks;
   SuccessorBlocks.insert(SI.getDefaultDest());
-  for (auto I = SI.case_begin(), E = SI.case_end(); I != E; ++I)
-    SuccessorBlocks.insert(I.getCaseSuccessor());
+  for (auto Case : SI.cases())
+    SuccessorBlocks.insert(Case.getCaseSuccessor());
   // Add cost corresponding to the number of distinct destinations. The first
   // we model as free because of fallthrough.
   Cost += (SuccessorBlocks.size() - 1) * InlineConstants::InstrCost;
@@ -1379,7 +1379,7 @@ bool CallAnalyzer::analyzeCall(CallSite CS) {
       Value *Cond = SI->getCondition();
       if (ConstantInt *SimpleCond =
               dyn_cast_or_null<ConstantInt>(SimplifiedValues.lookup(Cond))) {
-        BBWorklist.insert(SI->findCaseValue(SimpleCond).getCaseSuccessor());
+        BBWorklist.insert(SI->findCaseValue(SimpleCond)->getCaseSuccessor());
         continue;
       }
     }

lib/Analysis/LazyValueInfo.cpp

@@ -1430,14 +1430,14 @@ static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
     unsigned BitWidth = Val->getType()->getIntegerBitWidth();
     ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
 
-    for (SwitchInst::CaseIt i : SI->cases()) {
-      ConstantRange EdgeVal(i.getCaseValue()->getValue());
+    for (auto Case : SI->cases()) {
+      ConstantRange EdgeVal(Case.getCaseValue()->getValue());
       if (DefaultCase) {
         // It is possible that the default destination is the destination of
         // some cases. There is no need to perform difference for those cases.
-        if (i.getCaseSuccessor() != BBTo)
+        if (Case.getCaseSuccessor() != BBTo)
           EdgesVals = EdgesVals.difference(EdgeVal);
-      } else if (i.getCaseSuccessor() == BBTo)
+      } else if (Case.getCaseSuccessor() == BBTo)
         EdgesVals = EdgesVals.unionWith(EdgeVal);
     }
     Result = LVILatticeVal::getRange(std::move(EdgesVals));

lib/Analysis/SparsePropagation.cpp

@@ -195,7 +195,7 @@ void SparseSolver::getFeasibleSuccessors(TerminatorInst &TI,
     Succs.assign(TI.getNumSuccessors(), true);
     return;
   }
-  SwitchInst::CaseIt Case = SI.findCaseValue(cast<ConstantInt>(C));
+  SwitchInst::CaseHandle Case = *SI.findCaseValue(cast<ConstantInt>(C));
   Succs[Case.getSuccessorIndex()] = true;
 }
 

lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -2578,7 +2578,7 @@ void ModuleBitcodeWriter::writeInstruction(const Instruction &I,
       Vals.push_back(VE.getTypeID(SI.getCondition()->getType()));
       pushValue(SI.getCondition(), InstID, Vals);
       Vals.push_back(VE.getValueID(SI.getDefaultDest()));
-      for (SwitchInst::ConstCaseIt Case : SI.cases()) {
+      for (auto Case : SI.cases()) {
         Vals.push_back(VE.getValueID(Case.getCaseValue()));
         Vals.push_back(VE.getValueID(Case.getCaseSuccessor()));
       }

lib/CodeGen/CodeGenPrepare.cpp

@@ -5457,7 +5457,7 @@ bool CodeGenPrepare::optimizeSwitchInst(SwitchInst *SI) {
   auto *ExtInst = CastInst::Create(ExtType, Cond, NewType);
   ExtInst->insertBefore(SI);
   SI->setCondition(ExtInst);
-  for (SwitchInst::CaseIt Case : SI->cases()) {
+  for (auto Case : SI->cases()) {
     APInt NarrowConst = Case.getCaseValue()->getValue();
     APInt WideConst = (ExtType == Instruction::ZExt) ?
                       NarrowConst.zext(RegWidth) : NarrowConst.sext(RegWidth);

lib/ExecutionEngine/Interpreter/Execution.cpp

@@ -899,10 +899,10 @@ void Interpreter::visitSwitchInst(SwitchInst &I) {
 
   // Check to see if any of the cases match...
   BasicBlock *Dest = nullptr;
-  for (SwitchInst::CaseIt i = I.case_begin(), e = I.case_end(); i != e; ++i) {
-    GenericValue CaseVal = getOperandValue(i.getCaseValue(), SF);
+  for (auto Case : I.cases()) {
+    GenericValue CaseVal = getOperandValue(Case.getCaseValue(), SF);
     if (executeICMP_EQ(CondVal, CaseVal, ElTy).IntVal != 0) {
-      Dest = cast<BasicBlock>(i.getCaseSuccessor());
+      Dest = cast<BasicBlock>(Case.getCaseSuccessor());
       break;
     }
   }

lib/IR/AsmWriter.cpp

@@ -2897,12 +2897,11 @@ void AssemblyWriter::printInstruction(const Instruction &I) {
     Out << ", ";
     writeOperand(SI.getDefaultDest(), true);
     Out << " [";
-    for (SwitchInst::ConstCaseIt i = SI.case_begin(), e = SI.case_end();
-         i != e; ++i) {
+    for (auto Case : SI.cases()) {
       Out << "\n    ";
-      writeOperand(i.getCaseValue(), true);
+      writeOperand(Case.getCaseValue(), true);
       Out << ", ";
-      writeOperand(i.getCaseSuccessor(), true);
+      writeOperand(Case.getCaseSuccessor(), true);
     }
     Out << "\n  ]";
   } else if (isa<IndirectBrInst>(I)) {

lib/IR/Instructions.cpp

@@ -3659,16 +3659,16 @@ void SwitchInst::addCase(ConstantInt *OnVal, BasicBlock *Dest) {
   // Initialize some new operands.
   assert(OpNo+1 < ReservedSpace && "Growing didn't work!");
   setNumHungOffUseOperands(OpNo+2);
-  CaseIt Case(this, NewCaseIdx);
+  CaseHandle Case(this, NewCaseIdx);
   Case.setValue(OnVal);
   Case.setSuccessor(Dest);
 }
 
 /// removeCase - This method removes the specified case and its successor
 /// from the switch instruction.
-SwitchInst::CaseIt SwitchInst::removeCase(CaseIt i) {
-  unsigned idx = i.getCaseIndex();
-  
+SwitchInst::CaseIt SwitchInst::removeCase(CaseIt I) {
+  unsigned idx = I->getCaseIndex();
+
   assert(2 + idx*2 < getNumOperands() && "Case index out of range!!!");
 
   unsigned NumOps = getNumOperands();

lib/Transforms/Coroutines/CoroSplit.cpp

@@ -185,9 +185,9 @@ static void handleFinalSuspend(IRBuilder<> &Builder, Value *FramePtr,
                                coro::Shape &Shape, SwitchInst *Switch,
                                bool IsDestroy) {
   assert(Shape.HasFinalSuspend);
-  auto FinalCase = --Switch->case_end();
-  BasicBlock *ResumeBB = FinalCase.getCaseSuccessor();
-  Switch->removeCase(FinalCase);
+  auto FinalCaseIt = std::prev(Switch->case_end());
+  BasicBlock *ResumeBB = FinalCaseIt->getCaseSuccessor();
+  Switch->removeCase(FinalCaseIt);
   if (IsDestroy) {
     BasicBlock *OldSwitchBB = Switch->getParent();
     auto *NewSwitchBB = OldSwitchBB->splitBasicBlock(Switch, "Switch");

lib/Transforms/InstCombine/InstructionCombining.cpp

@@ -2254,11 +2254,11 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
   ConstantInt *AddRHS;
   if (match(Cond, m_Add(m_Value(Op0), m_ConstantInt(AddRHS)))) {
     // Change 'switch (X+4) case 1:' into 'switch (X) case -3'.
-    for (SwitchInst::CaseIt CaseIter : SI.cases()) {
-      Constant *NewCase = ConstantExpr::getSub(CaseIter.getCaseValue(), AddRHS);
+    for (auto Case : SI.cases()) {
+      Constant *NewCase = ConstantExpr::getSub(Case.getCaseValue(), AddRHS);
       assert(isa<ConstantInt>(NewCase) &&
              "Result of expression should be constant");
-      CaseIter.setValue(cast<ConstantInt>(NewCase));
+      Case.setValue(cast<ConstantInt>(NewCase));
     }
     SI.setCondition(Op0);
     return &SI;
@@ -2290,9 +2290,9 @@ Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) {
     Value *NewCond = Builder->CreateTrunc(Cond, Ty, "trunc");
     SI.setCondition(NewCond);
 
-    for (SwitchInst::CaseIt CaseIter : SI.cases()) {
-      APInt TruncatedCase = CaseIter.getCaseValue()->getValue().trunc(NewWidth);
-      CaseIter.setValue(ConstantInt::get(SI.getContext(), TruncatedCase));
+    for (auto Case : SI.cases()) {
+      APInt TruncatedCase = Case.getCaseValue()->getValue().trunc(NewWidth);
+      Case.setValue(ConstantInt::get(SI.getContext(), TruncatedCase));
     }
     return &SI;
   }
@@ -3072,17 +3072,7 @@ static bool AddReachableCodeToWorklist(BasicBlock *BB, const DataLayout &DL,
       }
     } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
       if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) {
-        // See if this is an explicit destination.
-        for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
-             i != e; ++i)
-          if (i.getCaseValue() == Cond) {
-            BasicBlock *ReachableBB = i.getCaseSuccessor();
-            Worklist.push_back(ReachableBB);
-            continue;
-          }
-
-        // Otherwise it is the default destination.
-        Worklist.push_back(SI->getDefaultDest());
+        Worklist.push_back(SI->findCaseValue(Cond)->getCaseSuccessor());
         continue;
       }
     }

lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

@@ -236,7 +236,7 @@ static bool processSwitch(SwitchInst *SI, LazyValueInfo *LVI) {
   // removing a case doesn't cause trouble for the iteration.
   bool Changed = false;
   for (auto CI = SI->case_begin(), CE = SI->case_end(); CI != CE;) {
-    ConstantInt *Case = CI.getCaseValue();
+    ConstantInt *Case = CI->getCaseValue();
 
     // Check to see if the switch condition is equal to/not equal to the case
     // value on every incoming edge, equal/not equal being the same each time.
@@ -269,7 +269,7 @@ static bool processSwitch(SwitchInst *SI, LazyValueInfo *LVI) {
 
     if (State == LazyValueInfo::False) {
       // This case never fires - remove it.
-      CI.getCaseSuccessor()->removePredecessor(BB);
+      CI->getCaseSuccessor()->removePredecessor(BB);
       CI = SI->removeCase(CI);
       CE = SI->case_end();
 

lib/Transforms/Scalar/GVN.cpp

@@ -1761,11 +1761,11 @@ bool GVN::processInstruction(Instruction *I) {
 
     for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
          i != e; ++i) {
-      BasicBlock *Dst = i.getCaseSuccessor();
+      BasicBlock *Dst = i->getCaseSuccessor();
       // If there is only a single edge, propagate the case value into it.
       if (SwitchEdges.lookup(Dst) == 1) {
         BasicBlockEdge E(Parent, Dst);
-        Changed |= propagateEquality(SwitchCond, i.getCaseValue(), E, true);
+        Changed |= propagateEquality(SwitchCond, i->getCaseValue(), E, true);
       }
     }
     return Changed;

lib/Transforms/Scalar/JumpThreading.cpp

@@ -1269,7 +1269,7 @@ bool JumpThreadingPass::ProcessThreadableEdges(Value *Cond, BasicBlock *BB,
     else if (BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator()))
       DestBB = BI->getSuccessor(cast<ConstantInt>(Val)->isZero());
     else if (SwitchInst *SI = dyn_cast<SwitchInst>(BB->getTerminator())) {
-      DestBB = SI->findCaseValue(cast<ConstantInt>(Val)).getCaseSuccessor();
+      DestBB = SI->findCaseValue(cast<ConstantInt>(Val))->getCaseSuccessor();
     } else {
       assert(isa<IndirectBrInst>(BB->getTerminator())
               && "Unexpected terminator");

lib/Transforms/Scalar/LoopUnrollPass.cpp

@@ -509,7 +509,7 @@ analyzeLoopUnrollCost(const Loop *L, unsigned TripCount, DominatorTree &DT,
             KnownSucc = SI->getSuccessor(0);
           else if (ConstantInt *SimpleCondVal =
                        dyn_cast<ConstantInt>(SimpleCond))
-            KnownSucc = SI->findCaseValue(SimpleCondVal).getCaseSuccessor();
+            KnownSucc = SI->findCaseValue(SimpleCondVal)->getCaseSuccessor();
         }
       }
       if (KnownSucc) {

lib/Transforms/Scalar/LoopUnswitch.cpp

@@ -709,9 +709,8 @@ bool LoopUnswitch::processCurrentLoop() {
           // Do not process same value again and again.
           // At this point we have some cases already unswitched and
           // some not yet unswitched. Let's find the first not yet unswitched one.
-          for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
-               i != e; ++i) {
-            Constant *UnswitchValCandidate = i.getCaseValue();
+          for (auto Case : SI->cases()) {
+            Constant *UnswitchValCandidate = Case.getCaseValue();
             if (!BranchesInfo.isUnswitched(SI, UnswitchValCandidate)) {
               UnswitchVal = UnswitchValCandidate;
               break;
@@ -987,7 +986,7 @@ bool LoopUnswitch::TryTrivialLoopUnswitch(bool &Changed) {
       if (!Cond)
         break;
       // Find the target block we are definitely going to.
-      CurrentBB = SI->findCaseValue(Cond).getCaseSuccessor();
+      CurrentBB = SI->findCaseValue(Cond)->getCaseSuccessor();
     } else {
       // We do not understand these terminator instructions.
       break;
@@ -1051,13 +1050,12 @@ bool LoopUnswitch::TryTrivialLoopUnswitch(bool &Changed) {
     // this.
     // Note that we can't trivially unswitch on the default case or
     // on already unswitched cases.
-    for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end();
-         i != e; ++i) {
+    for (auto Case : SI->cases()) {
       BasicBlock *LoopExitCandidate;
-      if ((LoopExitCandidate = isTrivialLoopExitBlock(currentLoop,
-                                               i.getCaseSuccessor()))) {
+      if ((LoopExitCandidate =
+               isTrivialLoopExitBlock(currentLoop, Case.getCaseSuccessor()))) {
         // Okay, we found a trivial case, remember the value that is trivial.
-        ConstantInt *CaseVal = i.getCaseValue();
+        ConstantInt *CaseVal = Case.getCaseValue();
 
         // Check that it was not unswitched before, since already unswitched
         // trivial vals are looks trivial too.
@@ -1361,9 +1359,11 @@ void LoopUnswitch::RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
     // NOTE: if a case value for the switch is unswitched out, we record it
     // after the unswitch finishes. We can not record it here as the switch
     // is not a direct user of the partial LIV.
-    SwitchInst::CaseIt DeadCase = SI->findCaseValue(cast<ConstantInt>(Val));
+    SwitchInst::CaseHandle DeadCase =
+        *SI->findCaseValue(cast<ConstantInt>(Val));
     // Default case is live for multiple values.
-    if (DeadCase == SI->case_default()) continue;
+    if (DeadCase == *SI->case_default())
+      continue;
 
     // Found a dead case value.  Don't remove PHI nodes in the
     // successor if they become single-entry, those PHI nodes may

lib/Transforms/Scalar/LowerExpectIntrinsic.cpp

@@ -67,11 +67,11 @@ static bool handleSwitchExpect(SwitchInst &SI) {
   if (!ExpectedValue)
     return false;
 
-  SwitchInst::CaseIt Case = SI.findCaseValue(ExpectedValue);
+  SwitchInst::CaseHandle Case = *SI.findCaseValue(ExpectedValue);
   unsigned n = SI.getNumCases(); // +1 for default case.
   SmallVector<uint32_t, 16> Weights(n + 1, UnlikelyBranchWeight);
 
-  if (Case == SI.case_default())
+  if (Case == *SI.case_default())
     Weights[0] = LikelyBranchWeight;
   else
     Weights[Case.getCaseIndex() + 1] = LikelyBranchWeight;

lib/Transforms/Scalar/NewGVN.cpp

@@ -2054,8 +2054,8 @@ void NewGVN::processOutgoingEdges(TerminatorInst *TI, BasicBlock *B) {
     if (CondEvaluated && isa<ConstantInt>(CondEvaluated)) {
       auto *CondVal = cast<ConstantInt>(CondEvaluated);
       // We should be able to get case value for this.
-      auto CaseVal = SI->findCaseValue(CondVal);
-      if (CaseVal.getCaseSuccessor() == SI->getDefaultDest()) {
+      auto Case = *SI->findCaseValue(CondVal);
+      if (Case.getCaseSuccessor() == SI->getDefaultDest()) {
         // We proved the value is outside of the range of the case.
         // We can't do anything other than mark the default dest as reachable,
         // and go home.
@@ -2063,7 +2063,7 @@ void NewGVN::processOutgoingEdges(TerminatorInst *TI, BasicBlock *B) {
         return;
       }
       // Now get where it goes and mark it reachable.
-      BasicBlock *TargetBlock = CaseVal.getCaseSuccessor();
+      BasicBlock *TargetBlock = Case.getCaseSuccessor();
       updateReachableEdge(B, TargetBlock);
     } else {
       for (unsigned i = 0, e = SI->getNumSuccessors(); i != e; ++i) {

lib/Transforms/Scalar/SCCP.cpp

@@ -604,7 +604,7 @@ void SCCPSolver::getFeasibleSuccessors(TerminatorInst &TI,
       return;
     }
 
-    Succs[SI->findCaseValue(CI).getSuccessorIndex()] = true;
+    Succs[SI->findCaseValue(CI)->getSuccessorIndex()] = true;
     return;
   }
 
@@ -683,7 +683,7 @@ bool SCCPSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
     if (!CI)
       return !SCValue.isUnknown();
 
-    return SI->findCaseValue(CI).getCaseSuccessor() == To;
+    return SI->findCaseValue(CI)->getCaseSuccessor() == To;
   }
 
   // In case of indirect branch and its address is a blockaddress, we mark
@@ -1554,12 +1554,12 @@ bool SCCPSolver::ResolvedUndefsIn(Function &F) {
       // If the input to SCCP is actually switch on undef, fix the undef to
       // the first constant.
       if (isa<UndefValue>(SI->getCondition())) {
-        SI->setCondition(SI->case_begin().getCaseValue());
-        markEdgeExecutable(&BB, SI->case_begin().getCaseSuccessor());
+        SI->setCondition(SI->case_begin()->getCaseValue());
+        markEdgeExecutable(&BB, SI->case_begin()->getCaseSuccessor());
         return true;
       }
 
-      markForcedConstant(SI->getCondition(), SI->case_begin().getCaseValue());
+      markForcedConstant(SI->getCondition(), SI->case_begin()->getCaseValue());
       return true;
     }
   }

lib/Transforms/Utils/CloneFunction.cpp

@@ -354,7 +354,7 @@ void PruningFunctionCloner::CloneBlock(const BasicBlock *BB,
       Cond = dyn_cast_or_null<ConstantInt>(V);
     }
     if (Cond) {     // Constant fold to uncond branch!
-      SwitchInst::ConstCaseIt Case = SI->findCaseValue(Cond);
+      SwitchInst::ConstCaseHandle Case = *SI->findCaseValue(Cond);
       BasicBlock *Dest = const_cast<BasicBlock*>(Case.getCaseSuccessor());
       VMap[OldTI] = BranchInst::Create(Dest, NewBB);
       ToClone.push_back(Dest);

lib/Transforms/Utils/Evaluator.cpp

@@ -487,7 +487,7 @@ bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
         ConstantInt *Val =
           dyn_cast<ConstantInt>(getVal(SI->getCondition()));
         if (!Val) return false;  // Cannot determine.
-        NextBB = SI->findCaseValue(Val).getCaseSuccessor();
+        NextBB = SI->findCaseValue(Val)->getCaseSuccessor();
       } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
         Value *Val = getVal(IBI->getAddress())->stripPointerCasts();
         if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))

lib/Transforms/Utils/Local.cpp

@@ -126,20 +126,20 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
     // If the default is unreachable, ignore it when searching for TheOnlyDest.
     if (isa<UnreachableInst>(DefaultDest->getFirstNonPHIOrDbg()) &&
         SI->getNumCases() > 0) {
-      TheOnlyDest = SI->case_begin().getCaseSuccessor();
+      TheOnlyDest = SI->case_begin()->getCaseSuccessor();
     }
 
     // Figure out which case it goes to.
     for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) {
       // Found case matching a constant operand?
-      if (i.getCaseValue() == CI) {
-        TheOnlyDest = i.getCaseSuccessor();
+      if (i->getCaseValue() == CI) {
+        TheOnlyDest = i->getCaseSuccessor();
         break;
       }
 
       // Check to see if this branch is going to the same place as the default
       // dest.  If so, eliminate it as an explicit compare.
-      if (i.getCaseSuccessor() == DefaultDest) {
+      if (i->getCaseSuccessor() == DefaultDest) {
         MDNode *MD = SI->getMetadata(LLVMContext::MD_prof);
         unsigned NCases = SI->getNumCases();
         // Fold the case metadata into the default if there will be any branches
@@ -153,7 +153,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
             Weights.push_back(CI->getValue().getZExtValue());
           }
           // Merge weight of this case to the default weight.
-          unsigned idx = i.getCaseIndex();
+          unsigned idx = i->getCaseIndex();
           Weights[0] += Weights[idx+1];
           // Remove weight for this case.
           std::swap(Weights[idx+1], Weights.back());
@@ -172,7 +172,8 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
       // Otherwise, check to see if the switch only branches to one destination.
       // We do this by reseting "TheOnlyDest" to null when we find two non-equal
       // destinations.
-      if (i.getCaseSuccessor() != TheOnlyDest) TheOnlyDest = nullptr;
+      if (i->getCaseSuccessor() != TheOnlyDest)
+        TheOnlyDest = nullptr;
 
       // Increment this iterator as we haven't removed the case.
       ++i;
@@ -211,7 +212,7 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB, bool DeleteDeadConditions,
     if (SI->getNumCases() == 1) {
       // Otherwise, we can fold this switch into a conditional branch
       // instruction if it has only one non-default destination.
-      SwitchInst::CaseIt FirstCase = SI->case_begin();
+      auto FirstCase = *SI->case_begin();
       Value *Cond = Builder.CreateICmpEQ(SI->getCondition(),
           FirstCase.getCaseValue(), "cond");
 

lib/Transforms/Utils/LowerSwitch.cpp

@@ -356,10 +356,10 @@ unsigned LowerSwitch::Clusterify(CaseVector& Cases, SwitchInst *SI) {
   unsigned numCmps = 0;
 
   // Start with "simple" cases
-  for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e; ++i)
-    Cases.push_back(CaseRange(i.getCaseValue(), i.getCaseValue(),
-                              i.getCaseSuccessor()));
-  
+  for (auto Case : SI->cases())
+    Cases.push_back(CaseRange(Case.getCaseValue(), Case.getCaseValue(),
+                              Case.getCaseSuccessor()));
+
   std::sort(Cases.begin(), Cases.end(), CaseCmp());
 
   // Merge case into clusters

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -714,10 +714,9 @@ BasicBlock *SimplifyCFGOpt::GetValueEqualityComparisonCases(
     TerminatorInst *TI, std::vector<ValueEqualityComparisonCase> &Cases) {
   if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) {
     Cases.reserve(SI->getNumCases());
-    for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e;
-         ++i)
-      Cases.push_back(
-          ValueEqualityComparisonCase(i.getCaseValue(), i.getCaseSuccessor()));
+    for (auto Case : SI->cases())
+      Cases.push_back(ValueEqualityComparisonCase(Case.getCaseValue(),
+                                                  Case.getCaseSuccessor()));
     return SI->getDefaultDest();
   }
 
@@ -850,12 +849,12 @@ bool SimplifyCFGOpt::SimplifyEqualityComparisonWithOnlyPredecessor(
       }
     for (SwitchInst::CaseIt i = SI->case_end(), e = SI->case_begin(); i != e;) {
       --i;
-      if (DeadCases.count(i.getCaseValue())) {
+      if (DeadCases.count(i->getCaseValue())) {
         if (HasWeight) {
-          std::swap(Weights[i.getCaseIndex() + 1], Weights.back());
+          std::swap(Weights[i->getCaseIndex() + 1], Weights.back());
           Weights.pop_back();
         }
-        i.getCaseSuccessor()->removePredecessor(TI->getParent());
+        i->getCaseSuccessor()->removePredecessor(TI->getParent());
         SI->removeCase(i);
       }
     }
@@ -3444,8 +3443,8 @@ static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) {
 
   // Find the relevant condition and destinations.
   Value *Condition = Select->getCondition();
-  BasicBlock *TrueBB = SI->findCaseValue(TrueVal).getCaseSuccessor();
-  BasicBlock *FalseBB = SI->findCaseValue(FalseVal).getCaseSuccessor();
+  BasicBlock *TrueBB = SI->findCaseValue(TrueVal)->getCaseSuccessor();
+  BasicBlock *FalseBB = SI->findCaseValue(FalseVal)->getCaseSuccessor();
 
   // Get weight for TrueBB and FalseBB.
   uint32_t TrueWeight = 0, FalseWeight = 0;
@@ -3455,9 +3454,9 @@ static bool SimplifySwitchOnSelect(SwitchInst *SI, SelectInst *Select) {
     GetBranchWeights(SI, Weights);
     if (Weights.size() == 1 + SI->getNumCases()) {
       TrueWeight =
-          (uint32_t)Weights[SI->findCaseValue(TrueVal).getSuccessorIndex()];
+          (uint32_t)Weights[SI->findCaseValue(TrueVal)->getSuccessorIndex()];
       FalseWeight =
-          (uint32_t)Weights[SI->findCaseValue(FalseVal).getSuccessorIndex()];
+          (uint32_t)Weights[SI->findCaseValue(FalseVal)->getSuccessorIndex()];
     }
   }
 
@@ -4160,7 +4159,7 @@ bool SimplifyCFGOpt::SimplifyUnreachable(UnreachableInst *UI) {
       }
     } else if (auto *SI = dyn_cast<SwitchInst>(TI)) {
       for (auto i = SI->case_begin(), e = SI->case_end(); i != e;) {
-        if (i.getCaseSuccessor() != BB) {
+        if (i->getCaseSuccessor() != BB) {
           ++i;
           continue;
         }
@@ -4251,18 +4250,18 @@ static bool TurnSwitchRangeIntoICmp(SwitchInst *SI, IRBuilder<> &Builder) {
   SmallVector<ConstantInt *, 16> CasesA;
   SmallVector<ConstantInt *, 16> CasesB;
 
-  for (SwitchInst::CaseIt I : SI->cases()) {
-    BasicBlock *Dest = I.getCaseSuccessor();
+  for (auto Case : SI->cases()) {
+    BasicBlock *Dest = Case.getCaseSuccessor();
     if (!DestA)
       DestA = Dest;
     if (Dest == DestA) {
-      CasesA.push_back(I.getCaseValue());
+      CasesA.push_back(Case.getCaseValue());
       continue;
     }
     if (!DestB)
       DestB = Dest;
     if (Dest == DestB) {
-      CasesB.push_back(I.getCaseValue());
+      CasesB.push_back(Case.getCaseValue());
       continue;
     }
     return false; // More than two destinations.
@@ -4412,17 +4411,17 @@ static bool EliminateDeadSwitchCases(SwitchInst *SI, AssumptionCache *AC,
 
   // Remove dead cases from the switch.
   for (ConstantInt *DeadCase : DeadCases) {
-    SwitchInst::CaseIt Case = SI->findCaseValue(DeadCase);
-    assert(Case != SI->case_default() &&
+    SwitchInst::CaseIt CaseI = SI->findCaseValue(DeadCase);
+    assert(CaseI != SI->case_default() &&
            "Case was not found. Probably mistake in DeadCases forming.");
     if (HasWeight) {
-      std::swap(Weights[Case.getCaseIndex() + 1], Weights.back());
+      std::swap(Weights[CaseI->getCaseIndex() + 1], Weights.back());
       Weights.pop_back();
     }
 
     // Prune unused values from PHI nodes.
-    Case.getCaseSuccessor()->removePredecessor(SI->getParent());
-    SI->removeCase(Case);
+    CaseI->getCaseSuccessor()->removePredecessor(SI->getParent());
+    SI->removeCase(CaseI);
   }
   if (HasWeight && Weights.size() >= 2) {
     SmallVector<uint32_t, 8> MDWeights(Weights.begin(), Weights.end());
@@ -4476,10 +4475,9 @@ static bool ForwardSwitchConditionToPHI(SwitchInst *SI) {
   typedef DenseMap<PHINode *, SmallVector<int, 4>> ForwardingNodesMap;
   ForwardingNodesMap ForwardingNodes;
 
-  for (SwitchInst::CaseIt I = SI->case_begin(), E = SI->case_end(); I != E;
-       ++I) {
-    ConstantInt *CaseValue = I.getCaseValue();
-    BasicBlock *CaseDest = I.getCaseSuccessor();
+  for (auto Case : SI->cases()) {
+    ConstantInt *CaseValue = Case.getCaseValue();
+    BasicBlock *CaseDest = Case.getCaseSuccessor();
 
     int PhiIndex;
     PHINode *PHI =
@@ -5214,8 +5212,8 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
   // common destination, as well as the min and max case values.
   assert(SI->case_begin() != SI->case_end());
   SwitchInst::CaseIt CI = SI->case_begin();
-  ConstantInt *MinCaseVal = CI.getCaseValue();
-  ConstantInt *MaxCaseVal = CI.getCaseValue();
+  ConstantInt *MinCaseVal = CI->getCaseValue();
+  ConstantInt *MaxCaseVal = CI->getCaseValue();
 
   BasicBlock *CommonDest = nullptr;
   typedef SmallVector<std::pair<ConstantInt *, Constant *>, 4> ResultListTy;
@@ -5225,7 +5223,7 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
   SmallVector<PHINode *, 4> PHIs;
 
   for (SwitchInst::CaseIt E = SI->case_end(); CI != E; ++CI) {
-    ConstantInt *CaseVal = CI.getCaseValue();
+    ConstantInt *CaseVal = CI->getCaseValue();
     if (CaseVal->getValue().slt(MinCaseVal->getValue()))
       MinCaseVal = CaseVal;
     if (CaseVal->getValue().sgt(MaxCaseVal->getValue()))
@@ -5234,7 +5232,7 @@ static bool SwitchToLookupTable(SwitchInst *SI, IRBuilder<> &Builder,
     // Resulting value at phi nodes for this case value.
     typedef SmallVector<std::pair<PHINode *, Constant *>, 4> ResultsTy;
     ResultsTy Results;
-    if (!GetCaseResults(SI, CaseVal, CI.getCaseSuccessor(), &CommonDest,
+    if (!GetCaseResults(SI, CaseVal, CI->getCaseSuccessor(), &CommonDest,
                         Results, DL, TTI))
       return false;
 
@@ -5515,11 +5513,10 @@ static bool ReduceSwitchRange(SwitchInst *SI, IRBuilder<> &Builder,
   auto *Rot = Builder.CreateOr(LShr, Shl);
   SI->replaceUsesOfWith(SI->getCondition(), Rot);
 
-  for (SwitchInst::CaseIt C = SI->case_begin(), E = SI->case_end(); C != E;
-       ++C) {
-    auto *Orig = C.getCaseValue();
+  for (auto Case : SI->cases()) {
+    auto *Orig = Case.getCaseValue();
     auto Sub = Orig->getValue() - APInt(Ty->getBitWidth(), Base);
-    C.setValue(
+    Case.setValue(
         cast<ConstantInt>(ConstantInt::get(Ty, Sub.lshr(ShiftC->getValue()))));
   }
   return true;

tools/llvm-diff/DifferenceEngine.cpp

@@ -315,17 +315,15 @@ class FunctionDifferenceEngine {
       bool Difference = false;
 
       DenseMap<ConstantInt*,BasicBlock*> LCases;
-      
-      for (SwitchInst::CaseIt I = LI->case_begin(), E = LI->case_end();
-           I != E; ++I)
-        LCases[I.getCaseValue()] = I.getCaseSuccessor();
-        
-      for (SwitchInst::CaseIt I = RI->case_begin(), E = RI->case_end();
-           I != E; ++I) {
-        ConstantInt *CaseValue = I.getCaseValue();
+      for (auto Case : LI->cases())
+        LCases[Case.getCaseValue()] = Case.getCaseSuccessor();
+
+      for (auto Case : RI->cases()) {
+        ConstantInt *CaseValue = Case.getCaseValue();
         BasicBlock *LCase = LCases[CaseValue];
         if (LCase) {
-          if (TryUnify) tryUnify(LCase, I.getCaseSuccessor());
+          if (TryUnify)
+            tryUnify(LCase, Case.getCaseSuccessor());
           LCases.erase(CaseValue);
         } else if (Complain || !Difference) {
           if (Complain)

unittests/IR/InstructionsTest.cpp

@@ -677,5 +677,68 @@ TEST(InstructionsTest, GEPIndices) {
   delete GEPI;
 }
 
+TEST(InstructionsTest, SwitchInst) {
+  LLVMContext C;
+
+  std::unique_ptr<BasicBlock> BB1, BB2, BB3;
+  BB1.reset(BasicBlock::Create(C));
+  BB2.reset(BasicBlock::Create(C));
+  BB3.reset(BasicBlock::Create(C));
+
+  // We create block 0 after the others so that it gets destroyed first and
+  // clears the uses of the other basic blocks.
+  std::unique_ptr<BasicBlock> BB0(BasicBlock::Create(C));
+
+  auto *Int32Ty = Type::getInt32Ty(C);
+
+  SwitchInst *SI =
+      SwitchInst::Create(UndefValue::get(Int32Ty), BB0.get(), 3, BB0.get());
+  SI->addCase(ConstantInt::get(Int32Ty, 1), BB1.get());
+  SI->addCase(ConstantInt::get(Int32Ty, 2), BB2.get());
+  SI->addCase(ConstantInt::get(Int32Ty, 3), BB3.get());
+
+  auto CI = SI->case_begin();
+  ASSERT_NE(CI, SI->case_end());
+  EXPECT_EQ(1, CI->getCaseValue()->getSExtValue());
+  EXPECT_EQ(BB1.get(), CI->getCaseSuccessor());
+  EXPECT_EQ(2, (CI + 1)->getCaseValue()->getSExtValue());
+  EXPECT_EQ(BB2.get(), (CI + 1)->getCaseSuccessor());
+  EXPECT_EQ(3, (CI + 2)->getCaseValue()->getSExtValue());
+  EXPECT_EQ(BB3.get(), (CI + 2)->getCaseSuccessor());
+  EXPECT_EQ(CI + 1, std::next(CI));
+  EXPECT_EQ(CI + 2, std::next(CI, 2));
+  EXPECT_EQ(CI + 3, std::next(CI, 3));
+  EXPECT_EQ(SI->case_end(), CI + 3);
+  EXPECT_EQ(0, CI - CI);
+  EXPECT_EQ(1, (CI + 1) - CI);
+  EXPECT_EQ(2, (CI + 2) - CI);
+  EXPECT_EQ(3, SI->case_end() - CI);
+  EXPECT_EQ(3, std::distance(CI, SI->case_end()));
+
+  auto CCI = const_cast<const SwitchInst *>(SI)->case_begin();
+  SwitchInst::ConstCaseIt CCE = SI->case_end();
+  ASSERT_NE(CCI, SI->case_end());
+  EXPECT_EQ(1, CCI->getCaseValue()->getSExtValue());
+  EXPECT_EQ(BB1.get(), CCI->getCaseSuccessor());
+  EXPECT_EQ(2, (CCI + 1)->getCaseValue()->getSExtValue());
+  EXPECT_EQ(BB2.get(), (CCI + 1)->getCaseSuccessor());
+  EXPECT_EQ(3, (CCI + 2)->getCaseValue()->getSExtValue());
+  EXPECT_EQ(BB3.get(), (CCI + 2)->getCaseSuccessor());
+  EXPECT_EQ(CCI + 1, std::next(CCI));
+  EXPECT_EQ(CCI + 2, std::next(CCI, 2));
+  EXPECT_EQ(CCI + 3, std::next(CCI, 3));
+  EXPECT_EQ(CCE, CCI + 3);
+  EXPECT_EQ(0, CCI - CCI);
+  EXPECT_EQ(1, (CCI + 1) - CCI);
+  EXPECT_EQ(2, (CCI + 2) - CCI);
+  EXPECT_EQ(3, CCE - CCI);
+  EXPECT_EQ(3, std::distance(CCI, CCE));
+
+  // Make sure that the const iterator is compatible with a const auto ref.
+  const auto &Handle = *CCI;
+  EXPECT_EQ(1, Handle.getCaseValue()->getSExtValue());
+  EXPECT_EQ(BB1.get(), Handle.getCaseSuccessor());
+}
+
 } // end anonymous namespace
 } // end namespace llvm