[Bug bootstrap/90132] make bootstrap fails with -O3 (gcc9 snapshot 20190414)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90132

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
I guess the basic issue again that we warn for unreachable code.  Note
libdecnumber is barely maintained and quite a big mess...