An apparatus and method for executing code are provided. The apparatus includes a memory manager that allocates a stack in memory to store processed data that needs to be retained; a loop generator that divides program code programmed to be processed in parallel into regions based on a barrier function, transforms a region that includes the processed data that needs to be retained in the stack into a first coalescing loop, and transforms a region that uses the processed data stored in the stack into a second coalescing loop such that the transformed program code may be serially processed; and a loop changer that reverses a processing order of the second coalescing loop in comparison to a processing order of the first coalescing loop.