Function calculate_occupancy 

pub fn calculate_occupancy(
    size: [u32; 3],
    hw: &WorkgroupHwParams,
    shared_mem_bytes: u32,
    regs_per_thread: u32,
) -> OccupancyResult

Calculate occupancy for a given workgroup size and resource usage.

Occupancy is the ratio of active warps to maximum warps, limited by:

• Total thread count
• Shared memory usage
• Register usage per thread