Comment by ap4

I want to have 512 threads per block, each thread calculating simultaneously 128 values. That's 65536 values per block. I can't accumulate each of these values in registers, because the GPU has the limit of max 65536 registers per block, and some additional registers are needed in the kernel. But if I find a way to trick the first stages of the compiler that it has sufficient amount of free registers, then sometimes, like in the case of this kernel, the later stages of the compiler are sufficiently smart to give me what I want: 512 threads per block, each calculating 128 values.