NDRnage Kernels Global Memory Write Pattern

The compile does NOT optimize out the computation (it actually isn't smart enough to do that), and it is indeed vectorizing your kernel; however, the compiler can easily tell that your computation does not depend on the work-item ID and hence, does NOT vectorize the computation, but it does vectorize the write to memory which depends on the work-item ID. In this case the compiler creates the logic in a way that the computation is only done once, but copied back SIMD times (in a single coalesced write). The reason why you don not see any difference in the logic utilization is that the difference is so small, it does not reflect in the "percentage" values. If you check the actual numbers in the HTML report, there are small differences in LUT and FF utilization. The difference is of course only caused by the line with the memory write, and the resource utilization for the rest of the lines is exactly the same. Furthermore, You can clearly see in the system viewer that the write port is getting wider.