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* [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade
@ 2024-09-08 10:22 joern274 at googlemail dot com
2024-09-08 12:56 ` [Bug c++/116645] " joern274 at googlemail dot com
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: joern274 at googlemail dot com @ 2024-09-08 10:22 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
Bug ID: 116645
Summary: Huge performance loss after 13.2.0 compiler upgrade
Product: gcc
Version: 13.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: joern274 at googlemail dot com
Target Milestone: ---
After upgrading g++ compiler from version 11.4.0 (Ubuntu 22.04 LTS) to version
13.2.0 (Ubuntu 24.04 LTS) the compile time for auto-generated verilator code
increased by a factor of *five*.
According to -ftime-report this is mostly due to "reload CSE regs" but I don't
know what this means.
Using this line to compile:
g++ -Os -I. -MMD -I/usr/local/share/verilator/include
-I/usr/local/share/verilator/include/vltstd -DVM_COVERAGE=0 -DVM_SC=0
-DVM_TIMING=0 -DVM_TRACE=1 -DVM_TRACE_FST=0 -DVM_TRACE_VCD=1 -faligned-new
-fcf-protection=none -Wno-bool-operation -Wno-shadow -Wno-sign-compare
-Wno-tautological-compare -Wno-uninitialized -Wno-unused-but-set-parameter
-Wno-unused-but-set-variable -Wno-unused-parameter -Wno-unused-variable -O3
-I/usr/include -c -o Vanalytic_filter_h_a4__ALL.o
Vanalytic_filter_h_a4__ALL.cpp
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug c++/116645] Huge performance loss after 13.2.0 compiler upgrade
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
@ 2024-09-08 12:56 ` joern274 at googlemail dot com
2024-09-08 13:43 ` [Bug rtl-optimization/116645] [13/14/15 regression] " sjames at gcc dot gnu.org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: joern274 at googlemail dot com @ 2024-09-08 12:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
--- Comment #1 from Jörn Langheinrich <joern274 at googlemail dot com> ---
Created attachment 59077
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59077&action=edit
ii-file created by -save-temps
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
2024-09-08 12:56 ` [Bug c++/116645] " joern274 at googlemail dot com
@ 2024-09-08 13:43 ` sjames at gcc dot gnu.org
2024-09-08 13:48 ` joern274 at googlemail dot com
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: sjames at gcc dot gnu.org @ 2024-09-08 13:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
Sam James <sjames at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|Huge performance loss after |[13/14/15 regression] Huge
|13.2.0 compiler upgrade |performance loss after
| |13.2.0 compiler upgrade
Component|c++ |rtl-optimization
--- Comment #2 from Sam James <sjames at gcc dot gnu.org> ---
Please share the full -ftime-report output too.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
2024-09-08 12:56 ` [Bug c++/116645] " joern274 at googlemail dot com
2024-09-08 13:43 ` [Bug rtl-optimization/116645] [13/14/15 regression] " sjames at gcc dot gnu.org
@ 2024-09-08 13:48 ` joern274 at googlemail dot com
2024-09-08 18:59 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: joern274 at googlemail dot com @ 2024-09-08 13:48 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
--- Comment #3 from Jörn Langheinrich <joern274 at googlemail dot com> ---
Created attachment 59078
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59078&action=edit
Output from -ftime-report
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
` (2 preceding siblings ...)
2024-09-08 13:48 ` joern274 at googlemail dot com
@ 2024-09-08 18:59 ` pinskia at gcc dot gnu.org
2024-09-09 8:13 ` [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade; reload CSE regs has scalability issues rguenth at gcc dot gnu.org
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-09-08 18:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |13.4
Keywords| |needs-bisection,
| |needs-reduction
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade; reload CSE regs has scalability issues
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
` (3 preceding siblings ...)
2024-09-08 18:59 ` pinskia at gcc dot gnu.org
@ 2024-09-09 8:13 ` rguenth at gcc dot gnu.org
2024-09-09 8:13 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2024-09-09 8:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2024-09-09
Summary|[13/14/15 regression] Huge |[13/14/15 regression] Huge
|performance loss after |performance loss after
|13.2.0 compiler upgrade |13.2.0 compiler upgrade;
| |reload CSE regs has
| |scalability issues
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
I measure 41s with GCC 13.2, 57% spent in reload CSE regs, vs. 14s with GCC
11.4, 7% spent in reload CSE regs.
The compile-time with -O2 behaves similarly with GCC 13.2 but increases to 36s
with GCC 11.4, also showing the 63% reload CSE regs figure. So I'd probably
blame inliner heuristic changes for the observed difference but the problem
exposed looks latent.
With -O1, the suggested option for large auto-generated code when you
experience
compile-time or memory-usage issues, GCC 11.4 takes 20s, GCC 13.2 similar
(again both with 53% in reload CSE regs). Also confirmed with GCC 14.2 and
a somewhat old trunk (r15-2794).
So confirmed.
I don't think bisection will reveal anything interesting. Somebody needs
to sit down and look at postreload why it takes so long for this testcase.
A profile for GCC 14.2 shows
Samples: 89K of event 'cycles:Pu', Event count (approx.): 114469365450
Overhead Samples Command Shared Object Symbol
37.58% 33298 cc1plus cc1plus [.]
_ZN10hash_tableI13cselib_hasherLb0E11xcallocatorE19find_slot_with_hashERKPNS0_3keyEj13insert_option
14.25% 12619 cc1plus cc1plus [.]
_Z22rtx_equal_for_cselib_1P7rtx_defS0_12machine_modei
4.27% 3776 cc1plus cc1plus [.]
_Z14bitmap_set_bitP11bitmap_headi
so I'd say it's a bad hash (again).
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade; reload CSE regs has scalability issues
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
` (4 preceding siblings ...)
2024-09-09 8:13 ` [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade; reload CSE regs has scalability issues rguenth at gcc dot gnu.org
@ 2024-09-09 8:13 ` rguenth at gcc dot gnu.org
2024-09-09 8:17 ` rguenth at gcc dot gnu.org
2024-09-09 8:56 ` rguenth at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2024-09-09 8:13 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 59080
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=59080&action=edit
unincluded testcase
This testcase works with all GCCs from 11.4 to trunk.
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade; reload CSE regs has scalability issues
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
` (5 preceding siblings ...)
2024-09-09 8:13 ` rguenth at gcc dot gnu.org
@ 2024-09-09 8:17 ` rguenth at gcc dot gnu.org
2024-09-09 8:56 ` rguenth at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2024-09-09 8:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
I'm checking if it was fixed by r15-2218-g44e065a52fa606
^ permalink raw reply [flat|nested] 9+ messages in thread
* [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade; reload CSE regs has scalability issues
2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
` (6 preceding siblings ...)
2024-09-09 8:17 ` rguenth at gcc dot gnu.org
@ 2024-09-09 8:56 ` rguenth at gcc dot gnu.org
7 siblings, 0 replies; 9+ messages in thread
From: rguenth at gcc dot gnu.org @ 2024-09-09 8:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116645
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #6)
> I'm checking if it was fixed by r15-2218-g44e065a52fa606
Nope. The profile is still
Samples: 93K of event 'cycles:Pu', Event count (approx.): 122100166487
Overhead Samples Command Shared Object Symbol
37.71% 35113 cc1plus cc1plus [.]
_ZN10hash_tableI13cselib_hasherLb0E11xcallocatorE19find_slot_with_hashERKPNS0_3keyEj13insert_option
12.84% 11958 cc1plus cc1plus [.]
_Z22rtx_equal_for_cselib_1P7rtx_defS0_12machine_modei
5.75% 5359 cc1plus cc1plus [.]
_ZL13autoinc_splitP7rtx_defPS0_12machine_mode
what looks still dubious is the uses of new_cselib_val with 'next_uid' as
hash and how they are put into the hashtable (how we ever going to find those
again).
^ permalink raw reply [flat|nested] 9+ messages in thread
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2024-09-08 10:22 [Bug c++/116645] New: Huge performance loss after 13.2.0 compiler upgrade joern274 at googlemail dot com
2024-09-08 12:56 ` [Bug c++/116645] " joern274 at googlemail dot com
2024-09-08 13:43 ` [Bug rtl-optimization/116645] [13/14/15 regression] " sjames at gcc dot gnu.org
2024-09-08 13:48 ` joern274 at googlemail dot com
2024-09-08 18:59 ` pinskia at gcc dot gnu.org
2024-09-09 8:13 ` [Bug rtl-optimization/116645] [13/14/15 regression] Huge performance loss after 13.2.0 compiler upgrade; reload CSE regs has scalability issues rguenth at gcc dot gnu.org
2024-09-09 8:13 ` rguenth at gcc dot gnu.org
2024-09-09 8:17 ` rguenth at gcc dot gnu.org
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