[Bug tree-optimization/62079] [4.9/5 Regression] ICE: in calc_dfs_tree, at dominance.c:401 with -fnon-call-exceptions

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62079

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ok, so this is if-after-reload which calls loop_optimizer_init on a CFG
with an unreachable block.  Thus we miss a cfg-cleanup somewhere.

Note that regular ifcvt runs a cleanup_cfg (CLEANUP_EXPENSIVE), but
not if-after-combine or if-after-reload.

It's peephole2 that ends up with this bogus CFG.

Passes leaving dangling unreachable blocks should fix that up.