poor performance of robin_map<int,void *> on insert using gcc

[loopless]

Following on from the recently found issue, I have noted that when using an "int" key on Linux the insert performance is terrible compared to Windows. A quick test shows that robin_map<int,void*> is 2x faster than unordered_map<int,void*> on insert on Windows (Visual Studio 2019) but on Linux GCC (4.9) robin_map is at least 10x slower than unordered_map<int,void *> Same for 'long' as the key.
Is this due to poor performance of the std::hash functions?

[loopless]

Yup it's the bad hashing functions in GCC. I replaced with a better hashing function and performance was restored.