From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Anders Roxell <anders.roxell@linaro.org>,
Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
mpe@ellerman.id.au, stable@vger.kernel.org
Subject: Re: [PATCH 2/3] powerpc: fix build errors
Date: Fri, 25 Feb 2022 16:33:19 -0600 [thread overview]
Message-ID: <20220225223319.GT614@gate.crashing.org> (raw)
In-Reply-To: <1645748601.idp48wexp9.astroid@bobo.none>
On Fri, Feb 25, 2022 at 10:32:02AM +1000, Nicholas Piggin wrote:
> Excerpts from Segher Boessenkool's message of February 25, 2022 3:12 am:
> > On Thu, Feb 24, 2022 at 03:05:28PM +1000, Nicholas Piggin wrote:
> >> + * gcc 10 started to emit a .machine directive at the beginning of generated
> >> + * .s files, which overrides assembler -Wa,-m<cpu> options passed down.
> >> + * Unclear if this behaviour will be reverted.
> >
> > It will not be reverted. If you need a certain .machine for some asm
> > code, you should write just that!
>
> It should be reverted because it breaks old binutils which did not have
> the workaround patch for this broken gcc behaviour. And it is just
> unnecessary because -m option can already be used to do the same thing.
>
> Not that I expect gcc to revert it.
Nothing will happen if you do not file a bug report. And do read the
bug reporting instructions first please.
> >> +#ifdef CONFIG_CC_IS_GCC
> >> +#if (GCC_VERSION >= 100000)
> >> +#if (CONFIG_AS_VERSION == 23800)
> >> +asm(".machine any");
> >> +#endif
> >> +#endif
> >> +#endif
> >> +#endif /* __ASSEMBLY__ */
> >
> > Abusing toplevel asm like this is broken and you *will* end up with
> > unhappiness all around.
>
> It actually unbreaks things and reduces my unhappiness.
It is broken. You will need -fno-toplevel-reorder, and you really do
not want that, if you *can* use it in the kernel even.
> It's only done
> for broken compiler versions and only where as does not have the
> workaround for the breakage.
What compiler versions? Please file a PR.
Segher
next prev parent reply other threads:[~2022-02-25 22:38 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-23 13:58 [PATCH 1/3] powerpc: lib: sstep: fix 'sthcx' instruction Anders Roxell
2022-02-23 13:58 ` [PATCH 2/3] powerpc: fix build errors Anders Roxell
2022-02-23 15:21 ` Segher Boessenkool
2022-02-24 2:54 ` Nicholas Piggin
2022-02-24 5:05 ` Nicholas Piggin
2022-02-24 8:55 ` Arnd Bergmann
2022-02-24 10:11 ` Nicholas Piggin
2022-02-24 10:20 ` Arnd Bergmann
2022-02-24 11:13 ` Nicholas Piggin
2022-02-24 17:29 ` Segher Boessenkool
2022-02-25 0:23 ` Nicholas Piggin
2022-02-25 22:28 ` Segher Boessenkool
2022-02-26 0:07 ` Nicholas Piggin
2022-02-24 17:12 ` Segher Boessenkool
2022-02-25 0:32 ` Nicholas Piggin
2022-02-25 8:33 ` Arnd Bergmann
2022-02-25 10:51 ` Nicholas Piggin
2022-02-25 22:33 ` Segher Boessenkool [this message]
2022-02-24 12:39 ` Michael Ellerman
2022-02-24 16:12 ` Anders Roxell
2022-02-24 17:37 ` Segher Boessenkool
2022-02-23 13:58 ` [PATCH 3/3] powerpc: lib: sstep: " Anders Roxell
2022-02-23 15:27 ` Segher Boessenkool
2022-02-24 2:40 ` [PATCH 1/3] powerpc: lib: sstep: fix 'sthcx' instruction Nicholas Piggin
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