[Bug middle-end/81832] [8 Regression] ICE in expand_LOOP_DIST_ALIAS, at internal-fn.c:2273

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81832

James Greenhalgh <jgreenhalgh at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |amker at gcc dot gnu.org

--- Comment #2 from James Greenhalgh <jgreenhalgh at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #1)
> Confirmed, started with r250619.

Interesting. That commit seems unlikely to have broken anything (if it does,
the bug would be latent and would have been possible to trigger using the
revision prior). My bisect points to r250959 , which seems much more likely,
given the backtrace.

What I imagine you've done with your bisect is continued back through the
revisions with -ftree-loop-distribute set, that does get you to r250619, but as
this is also really just a change to default "options", you should continue
going back with -ftree-vectorize to find the real culprit. For example, r250617
will also ICE with -O3 -ftree-loop-distribute -ftree-vectorize .

I think this is a general and latent problem with the interaction between the
copy-header pass, and the loop distribution pass. Tracing back further I see
this start with r249994 .