[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

llvm-svn: 300032

1 files changed, 7 insertions, 17 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 99243b7444a..f8b930f5771 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/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;
       }
     }