gcc 6.1.0 emits call to __sync_synchronize

[fedor_qd]

In which cases gcc emits __sync_synchronize? This method described as obsolete in gcc docs. GCC 6.1.0 call this method but GCC 5.3.0 doesn't. Libstdc and libatomics not installed. I have preprocessed some .cpp file and object file after compilation always has __sync_synchronize. Also gcc once was emit call to __sync_synchronize in another files. But call to __sync_synchronize was gone after recompilation them.

Always yours, Strizhniou Fiodar
Всегда ваш, Стрижнёв Фёдор