[Bug debug/80025] [5/6/7 Regression] ICE w/ -O2 (-O3, -Ofast) -g -ftracer (infinite recursion in rtx_equal_for_cselib_1)

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80025

--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Bernd Schmidt from comment #12)
> That still doesn't seem to address the root cause though? Isn't the problem
> that this reversible mappings code can create cycles and we should avoid
> creating these in the first place?

They can create cycles, but we can't avoid creating them generally, they are
very important for the debug info quality; if there is no cycle, it isn't a
problem, and determining whether there is a cycle is hard, because the locs
lists aren't cast in stone, they actually can have further locs added or
removed as the cselib processing goes on; and rtx_equal_for_cselib_1 is used
while they are still in flux.  Furthermore, even if there is a cycle, the
comparison function might not run into the cycle.  With the cap the comparison
function might try to use some other location in another recursion level and be
successful.