Provided is a method of transforming program code written such that a plurality of work-items are allocated respectively to and concurrently executed on a plurality of processing elements included in a computing unit. A program code translator may identify, in the program code, two or more code regions, which are to be enclosed by work-item coalescing loops (WCLs), based on a synchronization barrier function contained in the program code, such that the work-items are serially executable on a smaller number of processing elements than a number of the processing elements, and may enclose the identified code regions with the WCLs, respectively.