    1. store_src_rg                   coords = src.rg
    2. init_lane_masks                CondMask = LoopMask = RetMask = true
    3. copy_constant                  $0 = 0x3F800000 (1.0)
    4. copy_constant                  $1 = 0x40000000 (2.0)
    5. copy_constant                  $2 = 0x40400000 (3.0)
    6. copy_constant                  $3 = 0x40800000 (4.0)
    7. copy_4_slots_unmasked          [main].result = $0..3
    8. load_src                       src.rgba = [main].result