    1. store_src_rg                   coords = src.rg
    2. init_lane_masks                CondMask = LoopMask = RetMask = true
    3. zero_4_slots_unmasked          $0..3 = 0
    4. copy_4_constants               $4..7 = colorGreen
    5. sub_4_floats                   $0..3 -= $4..7
    6. copy_4_slots_unmasked          x = $0..3
    7. zero_4_slots_unmasked          $0..3 = 0
    8. copy_4_slots_unmasked          $4..7 = x
    9. sub_4_floats                   $0..3 -= $4..7
   10. copy_4_slots_unmasked          [this_function_is_defined_before_use].result = $0..3
   11. copy_4_slots_unmasked          [main].result = $0..3
   12. load_src                       src.rgba = [main].result