[Bug tree-optimization/68718] libgomp c.exp with -fipa-pta hang in sort-1.c

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68718

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
omp_set/unset_lock of course is a memory barrier.  All the problematic
variables (it is not just busy, but also global_stack.top) are only modified
when guarded with the lock, the problem is just read data races - those vars
are read outside of the lock occassionally.  libgomp itself (and other
libraries) had such code quite often in the past, that has been changed a few
years ago especially when ppc64 started to see issues, but also when
-fsanitize=thread has been added.
This testcase just needs the same treatment.