Fix two pessimizing moves.

[csigg]

Summary

See https://en.cppreference.com/w/cpp/language/return#Automatic_move_from_local_variables_and_parameters

llvm/include/llvm/Support/TaskQueue.h

std::future<ResultTy> F = T.P->get_future();
       // task immediately.
       if (IsTaskInFlight)
         Tasks.push_back(std::move(T));
       else {
         Scheduler.async(std::move(T));
         IsTaskInFlight = true;
       }
     }
-    return std::move(F);
+    return F;
   }
 
 private:
   void completeTask() {
     // We just completed a task.  If there are no more tasks in the queue,
     // update IsTaskInFlight to false and stop doing work.  Otherwise
     // schedule the next task (while not holding the lock).
     std::function<void()> Continuation;

mlir/include/mlir/Parser.h

inline OwningOpRef<ContainerOpT> constructContainerOpForParserIfNecessary(
   Block *opBlock = &op->getRegion(0).front();
   opBlock->getOperations().splice(opBlock->begin(),
                                   parsedBlock->getOperations());
 
   // After splicing, verify just this operation to ensure it can properly
   // contain the operations inside of it.
   if (failed(op.verify()))
     return OwningOpRef<ContainerOpT>();
-  return std::move(opRef);
+  return opRef;
 }
 } // end namespace detail
 
 /// This parses the file specified by the indicated SourceMgr and appends parsed
 /// operations to the given block. If the block is non-empty, the operations are
 /// placed before the current terminator. If parsing is successful, success is
 /// returned. Otherwise, an error message is emitted through the error handler
 /// registered in the context, and failure is returned. If `sourceFileLoc` is