https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49213
--- Comment #38 from Paul Thomas <pault at gcc dot gnu.org> --- This bug has fixed itself on mainline. I thought that it might be r14-4943-g8d2130a4e5ce369f5884c8522934dc027db6e9d8 but reversion didn't cause a recurrence. @Martin - as and when you have the time, could you please find the commit that fixed this PR. Paul