some basic questions about clang /MinGW64

Hi all.
I am allmost new to clang and so, you guess it, there are many pitfalls.
i use MinGW64/gcc4.8.1 right now and try to compiled wxWidgets, wxLua, .. sucessfully.
I try to use clang instead of gcc. I compiled sucessfully llvm+clang and copied clang.exe to my mingw/bin folder.
Now i am able to compile simple c/c++ sources using clang. Anyway some questions remains:
- clang seems not to support the -mtreads option.
- clang does not support the intrinsics in \mingw32\lib\gcc\i686-w64-mingw32\4.8.1\include\c++\atomic
How can i deal with?

Is there any documentation how to install clang into mingw?
Is have read about clang is able to optimize code across object file boundaries. I assume this doesnt work in case clang uses the gnu linker?

Anyone compiled sucessfully wxwidgets using clang and can give some hints?

TIA.
Ulrich.