https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103388
Aldy Hernandez <aldyh at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |law at gcc dot gnu.org
Resolution|DUPLICATE |---
Status|RESOLVED |NEW
Last reconfirmed| |2021-11-23
Ever confirmed|0 |1
--- Comment #2 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
(In reply to Aldy Hernandez from comment #1)
> By *.threadfull1 this is the path at 4->5->7. It looks like:
>
> PREHEADER
> |
> v
> HEADER--------+
> | |
> V
> UNREACHABLE |
> | /
> V /
> return 0 <-+
>
> This is more or less PR102981.
>
> Is there any way we can stop reporting the same thing over and over?
>
> *** This bug has been marked as a duplicate of bug 102981 ***
Errr, wait a minute, that's not a loop. My bad.
We're failing to thread 4->5->xxx because:
Checking profitability of path (backwards): bb:5 (10 insns) bb:4
Control statement insns: 2
Overall: 8 insns
FAIL: Did not thread around loop and would copy too many statements.
which is a limitation of the backward threader copier:
/* The generic copier used by the backthreader does not re-use an
existing threading path to reduce code duplication. So for that
case, drastically reduce the number of statements we are allowed
to copy. */
if (!(threaded_through_latch && threaded_multiway_branch)
&& (n_insns * param_fsm_scale_path_stmts
>= param_max_jump_thread_duplication_stmts))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
" FAIL: Did not thread around loop and would copy too "
"many statements.\n");
return false;
}
Confirmed.
