Hi, I noticed while poking around CMake's compiler modules that the defaults for XL are kind of inconsistent. Specifically, If you look here:
https://github.com/Kitware/CMake/blob/master/Modules/Compiler/XL-C.cmake CMake adds -qalias=noansi by default, which prevents a bunch of optimizations. CMake does not add that for XL C++. It also doesn't tweak any default aliasing settings for other compilers. Why XLC? At LLNL, we don't like qalias=noansi because it prevents a lot of optimizations, so we typically recommend that users NOT use that flag. It's been surprising for us that CMake adds it by default when it's not a default for XL, which uses -qalias=ansi (type-based aliasing) by default. Is there some reason CMake adds it? Could it be removed in future versions for consistency with the C++ settings? I can push a feature branch if people agree that this is a good idea. -Todd
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