[Bug c++/94781] version 9.3 g++ compilation time is slower by 20% or much more (closer to 50 % sometimes) in comparison to v7.

[ishikawa at yk dot rim.or.jp]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94781

--- Comment #10 from ishikawa,chiaki <ishikawa at yk dot rim.or.jp> ---
(In reply to Martin Liška from comment #9)
> Thanks.
> I've made a more permanent link here:
> https://drive.google.com/file/d/1s9i_l68CR8UGhqPfq0pdgQTH26G7YEFW/
> view?usp=sharing
> 
> I get these numbers for g++ UnifiedBindings23-v7.cpp -c -std=c++17 -O2
> -fno-checking -fmax-errors=1 -Wno-invalid-offsetof:
> 
>   7.4.0 (adafdb1e7212d53a)(06 Dec 2018 10:00): [took: 68.766s] result: OK
>   7.5.0 (b2d961e7342b5ba4)(14 Nov 2019 07:40): [took: 68.694s] result: OK
>   8.1.0 (406c2abec3f998e9)(02 May 2018 10:13): [took: 73.308s] result: OK
>   8.2.0 (ddeb81e76461fc00)(26 Jul 2018 09:47): [took: 72.738s] result: OK
>   8.3.0 (4c44b708f11eec6f)(22 Feb 2019 14:20): [took: 72.058s] result: OK
>   8.4.0 (8cd3bffead2ed1d1)(04 Mar 2020 08:30): [took: 71.730s] result: OK
>   9.1.0 (c8913260b0756f97)(03 May 2019 07:59): [took: 77.404s] result: OK
>   9.2.0 (a0c06cc27d2146b7)(12 Aug 2019 09:38): [took: 76.432s] result: OK
>   9.3.0 (4212a6a3e44f8704)(12 Mar 2020 11:08): [took: 76.636s] result: OK
> 
> current master:
>   438085cc66ed5801(05 May 2020 12:24)(Michael Meissner
> meissner@linux.ibm.com): [took: 78.698s] result: OK
> 
> Which is a regression of ~12% and one can't point to a single point where it
> jumped rapidly. Note that we do more inlining and more optimizations in
> general.

I will try to see if assigning more CPU cores to VirtualBox image I am using
locally can improve the situation. I am not sure how CPU cache is handled in
such a setting, but there may be some improvement.

Thank you again for your attention on this matter. I have been using GCC for
quite a long time on workstations and embedded systems. Thank you for making
the great package available to the wide developer community.

Chiaki