https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113616
--- Comment #2 from Alex Coplan <acoplan at gcc dot gnu.org> ---
I think the problem is this loop (and others that iterate over debug
uses in this way):
// Now that we've characterized the defs involved, go through the
// debug uses and determine how to update them (if needed).
for (auto use : set->debug_insn_uses ())
{
if (*pair_dst < *use->insn () && defs[1])
// We're re-ordering defs[1] above a previous use of the
// same resource.
update_debug_use (use, defs[1], writeback_pats[1]);
else if (*pair_dst >= *use->insn ())
// We're re-ordering defs[0] below its use.
update_debug_use (use, defs[0], writeback_pats[0]);
}
because `update_debug_use` can remove uses from the list of debug uses,
we can't use a for-range loop as the iterator will become invalidated
before getting advanced.
Should be fairly straightforward to fix, sorry for the oversight.
