Defensive guard: if SMEM cap computes max_threads_by_smem < 32 (or rounds to 0), floor at 32 (one warp). Prevents launching 0 threads which is undefined behavior.
Defensive guard: if SMEM cap computes max_threads_by_smem < 32 (or rounds to 0), floor at 32 (one warp). Prevents launching 0 threads which is undefined behavior.