linux-kernel - Re: subtle side effect of commit a1c48bb160f836

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Message-ID: <CAMuHMdXWHYF8hEEgeFxLTrhvmEDBVS2=VmKykfOtDkGjqODQbA@mail.gmail.com>
Date:	Thu, 18 Jun 2015 09:10:30 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:	Michal Marek <mmarek@...e.cz>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: subtle side effect of commit a1c48bb160f836

Hi Vineet,

On Thu, Jun 18, 2015 at 8:47 AM, Vineet Gupta
<Vineet.Gupta1@...opsys.com> wrote:
> commit a1c48bb160f8368 "Makefile: Fix unrecognized cross-compiler command line
> options" moved ARCH specific cc option handling before common -Os/O2 setup.
>
> For ARC this had a subtle effect that we can no longer over-ride generic -O2 with
> -O3, hence a performance regression observed going from 3.13 to 3.18 (the above
> commit went into 3.16)
>
> I want to understand how to properly fix this. Moving the include of arch makefile
> will bring back the old issue. I can introduce another option to set default optim
> level, but only arc/m32r care about it anyways.

Can we include $(srctree)/arch/$(SRCARCH)/Makefile twice?

Or perhaps we can not apply the extra -O* if there's already a -O* option?

Alternatively, as we already have CONFIG_CC_OPTIMIZE_FOR_SIZE,
a(nother) Kconfig option may make sense.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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