[Bug fortran/80304] [7 Regression] do-concurrent dosn't work well with gfortran 7.

[dominiq at lps dot ens.fr]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80304

--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr> ---
Compiling the code with -O1 gives

   131076.000       6.00000000    
   10.0000000       6.00000000    
   131080.000       6.00000000    

and with -Os

   4.00000000       6.00000000    
   10.0000000       6.00000000    
   516.000000       6.00000000    

The change occurred between revisions r239317 (2016-08-10, OK) and r239423
(2016-08-12, wrong).

The compiled code works with -Og and with -O2 and above.