[Bug rtl-optimization/91164] [10 Regression] ICE in verify_dominators, at dominance.c:1184 (error: dominator of 114 should be 112, not 16)

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91164

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
I think callers are expected to drop dominators if they do not keep them
up-to-date.  In fact elsewhere we assume there are no unreachable blocks iff
dominators
are present(?).

We've fixed quite a few places in the RTL pipeline already (I remember
mode-switching.c).

Checking what GIMPLE cfg-cleanup does it now is implemented as part of
cleanup_control_flow_pre ():

  /* Remove all now (and previously) unreachable blocks.  */
  for (int i = NUM_FIXED_BLOCKS; i < last_basic_block_for_fn (cfun); ++i)
    {
      basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i);
      if (bb && !bitmap_bit_p (visited, bb->index))
        {
          if (!retval)
            free_dominance_info (CDI_DOMINATORS);

so IMHO we could mimick that.   Note GIMPLE cleanup-cfg (re-)computes
dominators
(since it needs them itself) after that.

And no, there's no less expensive way in general.