[PATCH] D113788: IR: Fix const-correctness of SwitchInst::CaseIterator and CaseHandle

[Duncan P. N. Exon Smith via Phabricator via llvm-commits]

dexonsmith created this revision.
dexonsmith added a reviewer: dblaikie.
dexonsmith requested review of this revision.
Herald added a project: LLVM.

Fix some confusion between the two types of `const` a pointer/iterator
can have. Users of a SwitchInst::CaseIterator should not (and do not!)
manually mutate the SwitchInst::CaseHandle that tracks its internal
state. Change operator*() to return `const CaseHandle&`, remove the
non-const-qualified operator*(), and const-qualify
CaseHandle::setValue() and CaseHandle::setSuccessor().


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D113788

Files:
  llvm/include/llvm/IR/Instructions.h


Index: llvm/include/llvm/IR/Instructions.h
===================================================================
--- llvm/include/llvm/IR/Instructions.h
+++ llvm/include/llvm/IR/Instructions.h
@@ -3350,14 +3350,14 @@
     CaseHandle(SwitchInst *SI, ptrdiff_t Index) : CaseHandleImpl(SI, Index) {}
 
     /// Sets the new value for current case.
-    void setValue(ConstantInt *V) {
+    void setValue(ConstantInt *V) const {
       assert((unsigned)Index < SI->getNumCases() &&
              "Index out the number of cases.");
       SI->setOperand(2 + Index*2, reinterpret_cast<Value*>(V));
     }
 
     /// Sets the new successor for current case.
-    void setSuccessor(BasicBlock *S) {
+    void setSuccessor(BasicBlock *S) const {
       SI->setSuccessor(getSuccessorIndex(), S);
     }
   };
@@ -3366,7 +3366,7 @@
   class CaseIteratorImpl
       : public iterator_facade_base<CaseIteratorImpl<CaseHandleT>,
                                     std::random_access_iterator_tag,
-                                    CaseHandleT> {
+                                    const CaseHandleT> {
     using SwitchInstT = typename CaseHandleT::SwitchInstType;
 
     CaseHandleT Case;
@@ -3425,7 +3425,6 @@
       assert(Case.SI == RHS.Case.SI && "Incompatible operators.");
       return Case.Index < RHS.Case.Index;
     }
-    CaseHandleT &operator*() { return Case; }
     const CaseHandleT &operator*() const { return Case; }
   };
 
@@ -3515,15 +3514,16 @@
   /// default case iterator to indicate that it is handled by the default
   /// handler.
   CaseIt findCaseValue(const ConstantInt *C) {
-    CaseIt I = llvm::find_if(
-        cases(), [C](CaseHandle &Case) { return Case.getCaseValue() == C; });
+    CaseIt I = llvm::find_if(cases(), [C](const CaseHandle &Case) {
+      return Case.getCaseValue() == C;
+    });
     if (I != case_end())
       return I;
 
     return case_default();
   }
   ConstCaseIt findCaseValue(const ConstantInt *C) const {
-    ConstCaseIt I = llvm::find_if(cases(), [C](ConstCaseHandle &Case) {
+    ConstCaseIt I = llvm::find_if(cases(), [C](const ConstCaseHandle &Case) {
       return Case.getCaseValue() == C;
     });
     if (I != case_end())


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