> From: Sam James <s...@gentoo.org> > Date: Sun, 17 Sep 2023 05:00:37 +0100
> Hans-Peter Nilsson via Gcc-patches <gcc-patches@gcc.gnu.org> writes: > > >> Date: Tue, 29 Aug 2023 15:42:27 -0400 > >> From: Marek Polacek via Gcc-patches <gcc-patches@gcc.gnu.org> > > > >> Surely, there must be no ABI impact, the option cannot cause > >> severe performance issues, > > > >> Currently, -fhardened enables: > > ... > >> -ftrivial-auto-var-init=zero > > > >> Thoughts? > > > > Regarding -ftrivial-auto-var-init=zero, I was consulted when > > colleagues investigating a performance regression > > pint-pointed it as *causing severe performance issues*; > > cf. https://github.com/systemd/systemd.git commit 1a4e392760 > > (TL;DR: adds "-ftrivial-auto-var-init=zero" to the systemd > > build). > > > > The situation was described as "we noticed that some test > > suites takes 35% percent longer time to finish. After > > further investigation it was noticed that running systemctl > > unmask x takes around 5s more time on [version including > > patch vs. before that patch]" (timing out some tests). > > Reverting that patch fixed the drop in performance. > > Did some bug ever get filed for this to see if we can do a bit > better here? Not that I know of; neither for systemd nor gcc. > Some slowdown doesn't mean it's of the expected magnitude. Can you please rephrase that? > > Just a data point, but I believe also exactly your intended > > use. IMO including -ftrivial-auto-var-init is worth extra > > consideration. > > > > Alternatively, strike the while "cannot cause severe > > performance issues". > > > > brgds, H-P >
