[Bug rtl-optimization/106751] [10/11/12/13 Regression] internal compiler error: in purge_dead_edges with inline-asm goto

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106751

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hubicka at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org

--- Comment #9 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I'm afraid I don't know much about the RTL lim, but
1840          reorder_insns (inv->insn, inv->insn, BB_END (preheader));
with no check whether it is actually ok to append the statement at the end of
the preheader bb (at least no check that I can find) sounds wrong to me and I'm
just confused why it doesn't break stuff much more often.
From what I can see, loop-invariant.cc pass happens in between loop2_init and
loop2_done passes where the former calls loop_optimizer_init (LOOPS_NORMAL |
LOOPS_HAVE_RECORDED_EXITS);
which should ensure that loops have preheaders, but doesn't actually ask for
LOOPS_HAVE_FALLTHRU_PREHEADERS.
If the latter was on, then create_preheader would force splitting of the edge:
          /* If we want fallthru preheaders, also create forwarder block when
             preheader ends with a jump or has predecessors from loop.  */
          else if ((flags & CP_FALLTHRU_PREHEADERS)
                   && (JUMP_P (BB_END (single_entry->src))
                       || has_preds_from_loop (single_entry->src, loop)))
            need_forwarder_block = true;
So, should loop-invariant.cc split_edge the preheader edge if preheader block
ends with JUMP_P, or shall we somehow arrange for
LOOPS_HAVE_FALLTHRU_PREHEADERS?