[NFC] Add DebugVariableAggregate class

A DebugVariableAggregate is a DebugVariable that discards FragmentInfo; it
represents a whole variable instance.

Reviewed By: StephenTozer

Differential Revision: https://reviews.llvm.org/D146298

Author: OCHyams

llvm/include/llvm/IR/DebugInfoMetadata.h

@@ -3817,6 +3817,18 @@ template <> struct DenseMapInfo<DebugVariable> {
   }
 };
 
+/// Identifies a unique instance of a whole variable (discards/ignores fragment
+/// information).
+class DebugVariableAggregate : public DebugVariable {
+public:
+  DebugVariableAggregate(const DbgVariableIntrinsic *DVI);
+  DebugVariableAggregate(const DebugVariable &V)
+      : DebugVariable(V.getVariable(), std::nullopt, V.getInlinedAt()) {}
+};
+
+template <>
+struct DenseMapInfo<DebugVariableAggregate>
+    : public DenseMapInfo<DebugVariable> {};
 } // end namespace llvm
 
 #undef DEFINE_MDNODE_GET_UNPACK_IMPL

llvm/lib/IR/DebugInfoMetadata.cpp

@@ -42,6 +42,10 @@ DebugVariable::DebugVariable(const DbgVariableIntrinsic *DII)
       Fragment(DII->getExpression()->getFragmentInfo()),
       InlinedAt(DII->getDebugLoc().getInlinedAt()) {}
 
+DebugVariableAggregate::DebugVariableAggregate(const DbgVariableIntrinsic *DVI)
+    : DebugVariable(DVI->getVariable(), std::nullopt,
+                    DVI->getDebugLoc()->getInlinedAt()) {}
+
 DILocation::DILocation(LLVMContext &C, StorageType Storage, unsigned Line,
                        unsigned Column, ArrayRef<Metadata *> MDs,
                        bool ImplicitCode)