    1. store_src_rg                   coords = src.rg
    2. init_lane_masks                CondMask = LoopMask = RetMask = true
    3. zero_2_slots_unmasked          r, g = 0
    4. zero_slot_unmasked             $0 = 0
    5. copy_slot_unmasked             r = $0
    6. copy_constant                  $0 = 0x3F800000 (1.0)
    7. copy_slot_unmasked             g = $0
    8. copy_2_slots_unmasked          $0..1 = r, g
    9. zero_slot_unmasked             $2 = 0
   10. copy_constant                  $3 = 0x3F800000 (1.0)
   11. load_src                       src.rgba = $0..3