    1. store_src_rg                   coords = src.rg
    2. init_lane_masks                CondMask = LoopMask = RetMask = true
    3. zero_4_slots_unmasked          rgb[0], rgb[1], rgb[2], a = 0
    4. zero_slot_unmasked             $0 = 0
    5. copy_slot_unmasked             rgb[0] = $0
    6. copy_constant                  $0 = 0x3F800000 (1.0)
    7. copy_slot_unmasked             rgb[1] = $0
    8. zero_slot_unmasked             $0 = 0
    9. copy_slot_unmasked             rgb[2] = $0
   10. copy_constant                  $0 = 0x3F800000 (1.0)
   11. copy_slot_unmasked             a = $0
   12. copy_4_slots_unmasked          $0..3 = rgb[0], rgb[1], rgb[2], a
   13. load_src                       src.rgba = $0..3