DebugInfo: Make DWARFExpression::iterator a const iterator

3d1d8c767b made
DWARFExpression::iterator's Operation member `mutable`. After a few prep
commits, the iterator can instead be made a `const` iterator since no
caller can change the Operation.

Differential Revision: https://reviews.llvm.org/D113958

llvm/include/llvm/DebugInfo/DWARF/DWARFExpression.h

@@ -109,11 +109,11 @@ public:
   /// An iterator to go through the expression operations.
   class iterator
       : public iterator_facade_base<iterator, std::forward_iterator_tag,
-                                    Operation> {
+                                    const Operation> {
     friend class DWARFExpression;
     const DWARFExpression *Expr;
     uint64_t Offset;
-    mutable Operation Op;
+    Operation Op;
     iterator(const DWARFExpression *Expr, uint64_t Offset)
         : Expr(Expr), Offset(Offset) {
       Op.Error =
@@ -130,9 +130,7 @@ public:
       return *this;
     }
 
-    class Operation &operator*() const {
-      return Op;
-    }
+    const Operation &operator*() const { return Op; }
 
     iterator skipBytes(uint64_t Add) const {
       return iterator(Expr, Op.EndOffset + Add);

llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp

@@ -408,7 +408,7 @@ static bool printCompactDWARFExpr(raw_ostream &OS, DWARFExpression::iterator I,
   SmallVector<PrintedExpr, 4> Stack;
 
   while (I != E) {
-    DWARFExpression::Operation &Op = *I;
+    const DWARFExpression::Operation &Op = *I;
     uint8_t Opcode = Op.getCode();
     switch (Opcode) {
     case dwarf::DW_OP_regx: {

llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp

@@ -552,9 +552,10 @@ unsigned DWARFVerifier::verifyDebugInfoAttribute(const DWARFDie &Die,
         DataExtractor Data(toStringRef(Entry.Expr), DCtx.isLittleEndian(), 0);
         DWARFExpression Expression(Data, U->getAddressByteSize(),
                                    U->getFormParams().Format);
-        bool Error = any_of(Expression, [](DWARFExpression::Operation &Op) {
-          return Op.isError();
-        });
+        bool Error =
+            any_of(Expression, [](const DWARFExpression::Operation &Op) {
+              return Op.isError();
+            });
         if (Error || !Expression.verify(U))
           ReportError("DIE contains invalid DWARF expression:");
       }
@@ -1400,11 +1401,12 @@ static bool isVariableIndexable(const DWARFDie &Die, DWARFContext &DCtx) {
                        U->getAddressByteSize());
     DWARFExpression Expression(Data, U->getAddressByteSize(),
                                U->getFormParams().Format);
-    bool IsInteresting = any_of(Expression, [](DWARFExpression::Operation &Op) {
-      return !Op.isError() && (Op.getCode() == DW_OP_addr ||
-                               Op.getCode() == DW_OP_form_tls_address ||
-                               Op.getCode() == DW_OP_GNU_push_tls_address);
-    });
+    bool IsInteresting =
+        any_of(Expression, [](const DWARFExpression::Operation &Op) {
+          return !Op.isError() && (Op.getCode() == DW_OP_addr ||
+                                   Op.getCode() == DW_OP_form_tls_address ||
+                                   Op.getCode() == DW_OP_GNU_push_tls_address);
+        });
     if (IsInteresting)
       return true;
   }

llvm/tools/llvm-dwarfdump/Statistics.cpp

@@ -322,7 +322,7 @@ static void collectStatsForDie(DWARFDie Die, const std::string &FnPrefix,
                                U->getFormParams().Format);
     // Consider the expression containing the DW_OP_entry_value as
     // an entry value.
-    return llvm::any_of(Expression, [](DWARFExpression::Operation &Op) {
+    return llvm::any_of(Expression, [](const DWARFExpression::Operation &Op) {
       return Op.getCode() == dwarf::DW_OP_entry_value ||
              Op.getCode() == dwarf::DW_OP_GNU_entry_value;
     });