[Bug tree-optimization/123958] [16 regression] ice in useless_type_conversion_p, at gimple-expr.cc:85 since r16-7264-ga70bdd86984c0b6cd8520e30ec713e3101c5d45f

[roger at nextmovesoftware dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123958

--- Comment #6 from Roger Sayle <roger at nextmovesoftware dot com> ---
A detail I forgot to mention above.  Adding -fno-math-errno resolves/works
around the issue, so the problem is squarely with gimple_expand_builtin_pow
returning NULL_TREE with flag_errno_math, and not with the clean-up of
fold_const_pow.