https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120720
--- Comment #4 from Simon H. <sh1.gccbug at tikouka dot nz> --- Indeed, not JUST constexpr. But I tried substituting in std::max() and had the same problem with the constexpr side of things -- that I cannot implement a constexpr function which relies on it. I'm sure folding works just fine in that case, but evidently it's not legal C++ (or maybe it's fixed in a version I didn't test). I suppose constexpr std::max() is a C++ standards body problem, not a GCC problem, but it is still a problem and by extension many builtins probably should also be elevated to constexpr whenever they're able to be folded. Is that a separate bug to be filed? I don't feel qualified to do so because it probably involves enumerating all sorts of builtins and contemplating which of them should be changed.
