Comment 3 for bug 1640518

Andrew, according to the valgrind community, the error

  Memcheck: mc_machine.c:329 (get_otrack_shadow_offset_wrk): the 'impossible' happened.

is probably due to the lock elision code accessing a hardware register that valgrind doesn't know about, so there isn't a shadow register to consult. Our valgrind guys will look into that aspect of things. In the meantime, they tell us that you can circumvent this problem by not using --track-origins. Could you please give this a try?