[Bug target/78056] [7 Regression] build failure on Power7

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78056

--- Comment #5 from Segher Boessenkool <segher at gcc dot gnu.org> ---
So it seems rs6000_overloaded_builtin_p doesn't return true for
some builtin where it should?  Kelvin?