I totally agree. (with the presumption that the llvm backend needs to be tested too: many of the "winners" are in llvm, not in the project you are working on and I am testing. But llvm does not work on Windows yet.
To be sure: FPC-llvm does not use LLVM compilers, but compiles directly to llvm. That is a "small" difference: the llvm linker will resolve though.
It might be even the case we are chasing shadows, apart from the compiler defaults, that is.
Maybe contact Jonas, who wrote the llvm backend.?