https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68763
--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Created attachment 37506 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=37506&action=edit gcc6-pr68763.patch Partial fix. With the testcase reduction, I gave up, got only 4.7% reduction after 6 hours of 16 processes creduction. With this patch, the testcase compiles fine, but there is still modification in place - DEFARG_INSTANTIATIONS points to the particular TREE_LIST node containing the DEFAULT_ARG, while what we'd really need is let it point to the FUNCTION_DECLs whose TREE_TYPE we should modify similarly. Thoughts on that? I'll bootstrap/regtest this partial fix anyway.
