On 6/14/21 4:04 PM, Richard Biener wrote:
The same issue that arises in PR100934 can happen in the backward threader now (Aldy?) - we eventually run into mark_irreducible_loops for non-FSM thread paths checking for paths crossing irreducible region boundaries.
I haven't been following the above PR, so I may be missing something, but it seems like you would need to twiddle all users of the path registry, not just the backwards threader.
/* Try to thread each block with more than one successor. */thread_jumps threader (/*speed_p=*/false); diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c index a86302be18e..387994fd882 100644 --- a/gcc/tree-ssa-threadupdate.c +++ b/gcc/tree-ssa-threadupdate.c @@ -1917,6 +1917,8 @@ jump_thread_path_registry::mark_threaded_blocks (bitmap threaded_blocks) edge e; edge_iterator ei;+ gcc_assert (loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS));+ /* It is possible to have jump threads in which one is a subpath of the other. ie, (A, B), (B, C), (C, D) where B is a joiner block and (B, C), (C, D) where no joiner block exists.
If you're asserting this, don't you need to initialize DOM and VRP with LOOPS_MAY_HAVE_MARKED_IRREDUCIBLE_REGIONS as well? They may use the registry via their jump_threader.
Hmmm...tree-vrp seems fine: loop_optimizer_init (LOOPS_NORMAL | LOOPS_HAVE_RECORDED_EXITS); because LOOPS_NORMAL includes LOOPS_MAY_HAVE_MARKED_IRREDUCIBLE_REGIONS. But you may need some massaging in DOM: loop_optimizer_init (LOOPS_HAVE_PREHEADERS | LOOPS_HAVE_SIMPLE_LATCHES); Aldy
