Change if() continue; to an assert if a DBG_VALUE or DBG_VALUE_LIST returns a null DILocalVariable

[rastogishubham]

Summary

A DBG_VALUE or DBG_VALUE_LIST must always return a non-null DILocalVariable, the ARMLoadStoreOptimizer code that move’s DBG_VALUE and DBG_VALUE_LIST instructions if their corresponding loads have been moved, currently just continues if it finds a DBG_VALUE or DBG_VALUE_LIST with a null DILocalVariable, change that to an assert

[rastogishubham]

clang-formatted the diff

llvm/lib/Target/ARM/ARMLoadStoreOptimizer.cpp

auto PopulateRegisterAndInstrMapForDebugInstr = [&](Register Reg) {
         return;
       auto &InstrVec = RegIt->getSecond();
       InstrVec.push_back(&MI);
       InstrMap[&MI].push_back(Reg);
     };
 
     if (MI.isDebugValue()) {
       auto *DILocalVar = MI.getDebugVariable();
-      // TODO: This should not happen, have to fix the MIR verifier to check for
-      // such instances and fix them.
-      if (!DILocalVar)
-        continue;
+      assert(DILocalVar &&
+             "DBG_VALUE or DBG_VALUE_LIST must contain a DILocalVariable");
+
       auto DbgVar = createDebugVariableFromMachineInstr(&MI);
       // If the first operand is a register and it exists in the RegisterMap, we
       // know this is a DBG_VALUE that uses the result of a load that was moved,
       // and is therefore a candidate to also be moved, add it to the
       // RegisterMap and InstrMap.
       forEachDbgRegOperand(&MI, [&](MachineOperand &Op) {
         PopulateRegisterAndInstrMapForDebugInstr(Op.getReg());
       });