change checking for auto-init metadata to use `equalsStr` instead of casing MDOperand nodes.

[zjaffal]

Summary

Since MD_annotation metadata now supports having mutliple strings in the annotation node. casing Operand to string directly will cause a crash. When checking if MDOperand equals str you can use equalsStr method.

llvm/lib/Transforms/Utils/MoveAutoInit.cpp

 
 static cl::opt<unsigned> MoveAutoInitThreshold(
     "move-auto-init-threshold", cl::Hidden, cl::init(128),
     cl::desc("Maximum instructions to analyze per moved initialization"));
 
 static bool hasAutoInitMetadata(const Instruction &I) {
   return I.hasMetadata(LLVMContext::MD_annotation) &&
          any_of(I.getMetadata(LLVMContext::MD_annotation)->operands(),
-                [](const MDOperand &Op) {
-                  return cast<MDString>(Op.get())->getString() == "auto-init";
-                });
+                [](const MDOperand &Op) { return Op.equalsStr("auto-init"); });
 }
 
 static std::optional<MemoryLocation> writeToAlloca(const Instruction &I) {
   MemoryLocation ML;
   if (auto *MI = dyn_cast<MemIntrinsic>(&I))
     ML = MemoryLocation::getForDest(MI);
   else if (auto *SI = dyn_cast<StoreInst>(&I))
     ML = MemoryLocation::get(SI);