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From: "aldyh at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103388] [12 Regression] missed optimization for dead code elimination at -O3 (vs. -O2)
Date: Tue, 23 Nov 2021 19:31:03 +0000 [thread overview]
Message-ID: <bug-103388-4-U5lH7bl7FO@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-103388-4@http.gcc.gnu.org/bugzilla/>
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.
next prev parent reply other threads:[~2021-11-23 19:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-23 18:21 [Bug tree-optimization/103388] New: " theodort at inf dot ethz.ch
2021-11-23 19:19 ` [Bug tree-optimization/103388] " aldyh at gcc dot gnu.org
2021-11-23 19:31 ` aldyh at gcc dot gnu.org [this message]
2021-11-23 23:18 ` law at gcc dot gnu.org
2021-11-24 8:50 ` [Bug tree-optimization/103388] [12 Regression] missed optimization for dead code elimination at -O3 (trunk vs 11.2.0) rguenth at gcc dot gnu.org
2022-01-18 14:24 ` rguenth at gcc dot gnu.org
2022-01-18 15:28 ` law at gcc dot gnu.org
2022-05-06 8:31 ` [Bug tree-optimization/103388] [12/13 " jakub at gcc dot gnu.org
2022-07-26 13:09 ` rguenth at gcc dot gnu.org
2023-05-08 12:23 ` [Bug tree-optimization/103388] [12/13/14 " rguenth at gcc dot gnu.org
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