[DWARF] Simplify DWARFAttribute. NFC.

[ikudrin]

Summary

The first argument in the constructor was ignored, and the remaining arguments were always passed as their defaults.
This patch simplifies the class by moving all initializations to the members.

[Eugene.Zelenko]

lib/DebugInfo/DWARF/DWARFDie.cpp

666

You don't need to call default member constructor explicitly. Default member initialization could be used for Index too.

[ikudrin]

• Removed AttrValue from the member initializer list of the constructor of DWARFDie::attribute_iterator.

lib/DebugInfo/DWARF/DWARFDie.cpp

666

The main intent here was to remove the first unused argument in the constructor of DWARFAttribute because it is a bit of misleading. And other changes in that class were done because there was no reason not to do them when I was there.
As for Index, I believe it is out of the scope of this patch because it is a member of a different class.

[probinson]

include/llvm/DebugInfo/DWARF/DWARFAttribute.h

32

Form(0) is what the DWARFFormValue default ctor uses, you do not need to make this explicit here.

[dblaikie]

include/llvm/DebugInfo/DWARF/DWARFAttribute.h

33–34

Remove this ctor since it's the same as the implicit default ctor now.

44–45

Could you remove this function, and replace the one use (in DWARFDie.cpp) with "AttrValue = {};" instead, now that default construction has the desired effect.

[ikudrin]

• Adjusted the initializer for Value.
• Removed the constructor.
• Removed the method clear() and replaced the only usage with AttrValue = {}.

[dblaikie]

include/llvm/DebugInfo/DWARF/DWARFAttribute.h

33–34

This should be written as:

DWARFFormValue Value;

There's no need to explicitly default construct & then copy construct the object - the default constructor will be called implicitly.

[clayborg]

I agree with all comments. After those few things are fixed, this looks good.

[ikudrin]

• Removed explicit initialization of Value.

[ikudrin]

include/llvm/DebugInfo/DWARF/DWARFAttribute.h

33–34

Well, I usually prefer more explicit code because it is just simpler to understand, hoping that the optimizer will remove any redundancy. But let it be as you said.

[ikudrin]

Ping.

include/llvm/DebugInfo/DWARF/DWARFAttribute.h

 /// This class is designed to be used by clients that want to iterate across all
 /// attributes in a DWARFDie.
 struct DWARFAttribute {
   /// The debug info/types offset for this attribute.
   uint32_t Offset = 0;
   /// The debug info/types section byte size of the data for this attribute.
   uint32_t ByteSize = 0;
   /// The attribute enumeration of this attribute.
-  dwarf::Attribute Attr;
+  dwarf::Attribute Attr = dwarf::Attribute(0);
   /// The form and value for this attribute.
   DWARFFormValue Value;
 
-  DWARFAttribute(uint32_t O, dwarf::Attribute A = dwarf::Attribute(0),
-                 dwarf::Form F = dwarf::Form(0)) : Attr(A), Value(F) {}
-
   bool isValid() const {
     return Offset != 0 && Attr != dwarf::Attribute(0);
   }
 
   explicit operator bool() const {
     return isValid();
   }
 
   /// Identifies DWARF attributes that may contain a reference to a
   /// DWARF expression.
   static bool mayHaveLocationDescription(dwarf::Attribute Attr);
-
-  void clear() {
-    Offset = 0;
-    ByteSize = 0;
-    Attr = dwarf::Attribute(0);
-    Value = DWARFFormValue();
-  }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_DEBUGINFO_DWARFATTRIBUTE_H

lib/DebugInfo/DWARF/DWARFDie.cpp

 }
 
 iterator_range<DWARFDie::attribute_iterator> DWARFDie::attributes() const {
   return make_range(attribute_iterator(*this, false),
                     attribute_iterator(*this, true));
 }
 
 DWARFDie::attribute_iterator::attribute_iterator(DWARFDie D, bool End)
-    : Die(D), AttrValue(0), Index(0) {
+    : Die(D), Index(0) {
   auto AbbrDecl = Die.getAbbreviationDeclarationPtr();
   assert(AbbrDecl && "Must have abbreviation declaration");
   if (End) {
     // This is the end iterator so we set the index to the attribute count.
     Index = AbbrDecl->getNumAttributes();
   } else {
     // This is the begin iterator so we extract the value for this->Index.
     AttrValue.Offset = D.getOffset() + AbbrDecl->getCodeByteSize();
if (Index < NumAttrs) {
     uint32_t ParseOffset = AttrValue.Offset;
     auto U = Die.getDwarfUnit();
     assert(U && "Die must have valid DWARF unit");
     AttrValue.Value = DWARFFormValue::createFromUnit(
         AbbrDecl.getFormByIndex(Index), U, &ParseOffset);
     AttrValue.ByteSize = ParseOffset - AttrValue.Offset;
   } else {
     assert(Index == NumAttrs && "Indexes should be [0, NumAttrs) only");
-    AttrValue.clear();
+    AttrValue = {};
   }
 }
 
 DWARFDie::attribute_iterator &DWARFDie::attribute_iterator::operator++() {
   if (auto AbbrDecl = Die.getAbbreviationDeclarationPtr())
     updateForIndex(*AbbrDecl, Index + 1);
   return *this;
 }