[Bug libgomp/59194] tsan detects race for real variables in an OMP reduction clause

["Joost.VandeVondele at mat dot ethz.ch" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59194

--- Comment #5 from Joost VandeVondele <Joost.VandeVondele at mat dot ethz.ch> ---
(In reply to Jakub Jelinek from comment #4)
> I bet tsan complains because the load is
> not atomic, but does it really matter?  

I think there are (at least) two possible answers to this.

1) No, it doesn't matter, because we get the right result. This actually is
great, already and your and other gcc-ers effort is much appreciated.

2) But yes, it does. For users, having a tool to help verify/debug an OMP
program is very valuable. tsan is pretty close to doing being exactly that, and
the gomp+tsan combination would be really a plus for gcc, increasing in
importance as OMP (or related variants) becomes more and more common. Such
false positives reduce the value of the gomp+tsan tool significantly.
Therefore, if these issues could be fixed easily without significant downside,
I think this should be done. I'd happy to try patches, and do some tsan+omp
testing.