test_vpkshss_1:
  #_ REGISTER_IN v3 [00000001, 00020003, 00040005, 00060007]
  #_ REGISTER_IN v4 [00080009, 000A000B, 000C000D, 000E000F]
  vpkshss v5, v3, v4
  blr
  #_ REGISTER_OUT v3 [00000001, 00020003, 00040005, 00060007]
  #_ REGISTER_OUT v4 [00080009, 000A000B, 000C000D, 000E000F]
  #_ REGISTER_OUT v5 [00010203, 04050607, 08090A0B, 0C0D0E0F]

test_vpkshss_2:
  #_ REGISTER_IN v3 [7FFF8000, 00020003, 00040005, 00060007]
  #_ REGISTER_IN v4 [7FFF8000, 000A000B, 000C000D, 000E000F]
  vpkshss v5, v3, v4
  blr
  #_ REGISTER_OUT v3 [7FFF8000, 00020003, 00040005, 00060007]
  #_ REGISTER_OUT v4 [7FFF8000, 000A000B, 000C000D, 000E000F]
  #_ REGISTER_OUT v5 [7F800203, 04050607, 7F800A0B, 0C0D0E0F]

test_vpkshss_3:
  # {-1, -128, 0, 127, -2, -129, 1, 128}
  #_ REGISTER_IN v3 [FFFFFF80, 0000007F, FFFEFF7F, 00010080]
  # {-3, -130, 2, 129, -4, -131, 3, 130}
  #_ REGISTER_IN v4 [FFFDFF7E, 00020081, FFFCFF7D, 00030082]
  vpkshss v5, v3, v4
  blr
  #_ REGISTER_OUT v3 [FFFFFF80, 0000007F, FFFEFF7F, 00010080]
  #_ REGISTER_OUT v4 [FFFDFF7E, 00020081, FFFCFF7D, 00030082]
  # {-1, -128, 0, 127, -2, -128, 1, 127,
  #  -3, -128, 2, 127, -4, -128, 3, 127}
  #_ REGISTER_OUT v5 [FF80007F, FE80017F, FD80027F, FC80037F]