[Bug c/69033] [6 regression] many internal compiler errors starting with r231928

[nathan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69033

--- Comment #1 from Nathan Sidwell <nathan at gcc dot gnu.org> ---
patch r231928 reverted.  Analysis at
https://gcc.gnu.org/ml/gcc-patches/2015-12/msg02100.html