[clang] [Clang] `constexpr` builtin floating point classification / comparison functions (PR #94118)

[Timm Baeder via cfe-commits]

tbaederr wrote:

Yeah it's a well known problem.

> Is there a different file that these tests should be added for? Like AST/ByteCode/builtin-functions.cpp?

That should work. I have sanitizers enabled locally so I can test the changes if you want.

https://github.com/llvm/llvm-project/pull/94118