SIL/SILOptimizer: Fix unused variable warnings.

Author: tshortli

include/swift/SIL/AddressWalker.h

@@ -314,12 +314,12 @@ TransitiveAddressWalker<Impl>::walk(SILValue projectedAddress) {
         callVisitUse(op);
         continue;
       }
-      if (auto *mdi = dyn_cast<MarkDependenceInst>(user)) {
+      if (isa<MarkDependenceInst>(user)) {
         // If we are the value use of a forwarding markdep, look through it.
         transitiveResultUses(op);
         continue;
       }
-      if (auto *mdi = dyn_cast<MarkDependenceAddrInst>(user)) {
+      if (isa<MarkDependenceAddrInst>(user)) {
         // The address operand is simply a leaf use.
         callVisitUse(op);
         continue;

lib/SILOptimizer/Mandatory/MoveOnlyObjectCheckerUtils.cpp

@@ -512,7 +512,7 @@ void MoveOnlyObjectCheckerPImpl::check(
           //   %1 = load_borrow %0
           //   %2 = copy_value %1
           //   %3 = mark_unresolved_non_copyable_value [no_consume_or_assign] %2
-          if (auto *lbi = dyn_cast<LoadBorrowInst>(orig)) {
+          if (isa<LoadBorrowInst>(orig)) {
             for (auto *use : markedInst->getConsumingUses()) {
               destroys.push_back(cast<DestroyValueInst>(use->getUser()));
             }