https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83396
--- Comment #11 from Alexandre Oliva <aoliva at gcc dot gnu.org> --- the problem is that a concatn resulting from decomposing a reg is not unshared in a debug insn because it's between blocks. reverting the remove_forwarder_block part of the tree-cfgcleanup.c changes in r255566 avoids the problem. still investigating... feedback on whether your bootstrap failure is affected by reverting this hunk (aside from the original bug report; that one is covered) is welcome at least the ia64 failure mode is so different that it's not likely to be the same problem. as for the sparc one, I'd appreciate a preprocessed testcase to look into it as well. thanks!
