[Bug other/68483] gcc 5.2: suboptimal code compared to 4.9

[lvqcl.mail at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68483

--- Comment #1 from lvqcl.mail at gmail dot com ---
(In reply to lvqcl.mail from comment #0)
"gcc version 6.0.0 20151121 (experimental)" from dongsheng-daily (mingw-w64)
generates the same code as 4.9.2. So this regression was fixed in 6.x branch.