Poor performance with GNAT-GPL-2017

[Charly <carl.weierstrass@googlemail.com>]

Hi,

when I found the new GNAT-GPL-2017 this morning I was happy and installed it at once.
But I was rather disappointed about the poor performance.
To be more precise:

When I switch to new hard- or software I allways check the performance with my private tool:
It solves Rubics Tabgle https://www.jaapsch.net/puzzles/tangle.htm with an ada programm, using one task per core.

With GNAT-GPL-2016 (gcc 4.9.4) it took about 0,4 sec to find both solutions,
with GNAT-GPL-2017 (gcc 6.3.1) it takes about 0,8 sec to find both solutions,
which means the program is slower by a factor of 2.

In both cases I use the following options: 
-O3 -gnatA -gnatn -funroll-loops -fPIC -gnatp -g -gnatW8 -gnatVn -mtune=amdfam10 -gnat12

Any ideas??

Sincerly
Charly