[Bug target/124136] [16 Regression] ICE in bitmap_first_set_bit_worker, at bitmap.cc:1233 since r16-3290

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124136

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
ix86_get_dominator_for_reg asks nearest_common_dominator_for_set for the
dominator on an empty set.  There is no definition for regno 17.  The
caller also does not expect there to be no such block.