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* Re: [PATCH 0/2] Kconfig: -O3 enablement
@ 2022-06-24 18:29 Linus Torvalds
       [not found] ` <CA+55aFyugRmHNV1BbhB_YHf3mgaiU6ND_KL8bu0PPEaRVNwWHg@mail.gmail.com>
  2022-06-28 21:04 ` [PATCH] kbuild: drop support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 Nick Desaulniers
  0 siblings, 2 replies; 6+ messages in thread
From: Linus Torvalds @ 2022-06-24 18:29 UTC (permalink / raw)
  To: arnd
  Cc: bigeasy, chris, dmitry.torokhov, gustavoars, john.ogness,
	linux-kbuild, linux-kernel, masahiroy, mikoxyzzz, nathan,
	ndesaulniers, oleksandr, quic_eberman, seanjc, tglx, vbabka, x86

On Thu, Jun 23 at 7:27:29 PM  Arnd Bergmann <arnd@arndb.de> wrote:
>
> This probably also needs a dependency on !COMPILE_TEST so we don't
> report compile-time problems that are specific to -O3.

Honestly, let's just remove -O3 entirely.

Enabling it, and then not even build-testing the result, is just about
the *worst* possible case. That's just horrible.

The argument that "but ARC uses it" is not an argument. It was always
a bad argument, and ARC needs to just fix whatever it is that made it
an issue (likely already fixed with a compiler upgrade).

And there is no way I would ever accept this as a "let people try it" when

 - as mentioned, just use KCFLAGS=-O3 if you want to

 - -O3 has a *loong* history of generating worse code than -O2

so I will *not* be taking these kinds of patches without some very
serious explanations of why -O3 has suddenly become acceptable again.

Those explanations had better be more than "let people try". They
should have in-depth actual performance numbers for a real load, not
some made-up "bigger is better" logic.

                 Linus

^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2022-07-11  5:52 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-06-24 18:29 [PATCH 0/2] Kconfig: -O3 enablement Linus Torvalds
     [not found] ` <CA+55aFyugRmHNV1BbhB_YHf3mgaiU6ND_KL8bu0PPEaRVNwWHg@mail.gmail.com>
2022-06-24 18:38   ` Linus Torvalds
2022-06-28 21:04 ` [PATCH] kbuild: drop support for CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3 Nick Desaulniers
2022-06-29 10:48   ` Miko Larsson
2022-07-11  5:50     ` Masahiro Yamada
2022-07-11  5:05   ` Masahiro Yamada

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