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
WARNING: multiple messages have this Message-ID (diff)
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, stable@vger.kernel.org, linuxppc-dev@lists.ozlabs.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: 48+ 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 ` Anders Roxell 2022-02-23 13:58 ` [PATCH 2/3] powerpc: fix build errors Anders Roxell 2022-02-23 13:58 ` Anders Roxell 2022-02-23 15:21 ` Segher Boessenkool 2022-02-23 15:21 ` Segher Boessenkool 2022-02-24 2:54 ` Nicholas Piggin 2022-02-24 2:54 ` Nicholas Piggin 2022-02-24 5:05 ` Nicholas Piggin 2022-02-24 5:05 ` Nicholas Piggin 2022-02-24 8:55 ` Arnd Bergmann 2022-02-24 8:55 ` Arnd Bergmann 2022-02-24 10:11 ` Nicholas Piggin 2022-02-24 10:11 ` Nicholas Piggin 2022-02-24 10:20 ` Arnd Bergmann 2022-02-24 10:20 ` Arnd Bergmann 2022-02-24 11:13 ` Nicholas Piggin 2022-02-24 11:13 ` Nicholas Piggin 2022-02-24 17:29 ` Segher Boessenkool 2022-02-24 17:29 ` Segher Boessenkool 2022-02-25 0:23 ` Nicholas Piggin 2022-02-25 0:23 ` Nicholas Piggin 2022-02-25 22:28 ` Segher Boessenkool 2022-02-25 22:28 ` Segher Boessenkool 2022-02-26 0:07 ` Nicholas Piggin 2022-02-26 0:07 ` Nicholas Piggin 2022-02-24 17:12 ` Segher Boessenkool 2022-02-24 17:12 ` Segher Boessenkool 2022-02-25 0:32 ` Nicholas Piggin 2022-02-25 0:32 ` Nicholas Piggin 2022-02-25 8:33 ` Arnd Bergmann 2022-02-25 8:33 ` Arnd Bergmann 2022-02-25 10:51 ` Nicholas Piggin 2022-02-25 10:51 ` Nicholas Piggin 2022-02-25 22:33 ` Segher Boessenkool [this message] 2022-02-25 22:33 ` Segher Boessenkool 2022-02-24 12:39 ` Michael Ellerman 2022-02-24 12:39 ` Michael Ellerman 2022-02-24 16:12 ` Anders Roxell 2022-02-24 16:12 ` Anders Roxell 2022-02-24 17:37 ` Segher Boessenkool 2022-02-24 17:37 ` Segher Boessenkool 2022-02-23 13:58 ` [PATCH 3/3] powerpc: lib: sstep: " Anders Roxell 2022-02-23 13:58 ` Anders Roxell 2022-02-23 15:27 ` Segher Boessenkool 2022-02-23 15:27 ` Segher Boessenkool 2022-02-24 2:40 ` [PATCH 1/3] powerpc: lib: sstep: fix 'sthcx' instruction Nicholas Piggin 2022-02-24 2:40 ` Nicholas Piggin
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