From: Arnd Bergmann <arnd@kernel.org>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Russell King <linux@armlinux.org.uk>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Arnd Bergmann <arnd@arndb.de>, Ard Biesheuvel <ardb@kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Nathan Chancellor <nathan@kernel.org>,
llvm@lists.linux.dev
Subject: Re: [PATCH 13/14] ARM: use .arch directives instead of assembler command line flags
Date: Tue, 28 Sep 2021 20:32:06 +0200 [thread overview]
Message-ID: <CAK8P3a2LezhdCczGsgWrrkShvowXMYSSdhfPJqSHwHEBRv4PvQ@mail.gmail.com> (raw)
In-Reply-To: <CAKwvOd=U1PpmHk0emq23FhQyAv5YyOr9SOMkQ8d-q=uL=uebhg@mail.gmail.com>
On Tue, Sep 28, 2021 at 7:10 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Tue, Sep 28, 2021 at 8:42 AM Arnd Bergmann <arnd@kernel.org> wrote:
> >
> > From: Nick Desaulniers <ndesaulniers@google.com>
> >
> > Similar to commit a6c30873ee4a ("ARM: 8989/1: use .fpu assembler
> > directives instead of assembler arguments").
> >
> > GCC and GNU binutils support setting the "sub arch" via -march=,
> > -Wa,-march, target function attribute, and .arch assembler directive.
> >
> > Clang's integrated assembler does not support -Wa,-march (and the logic
> > to overrule one when multiple of the above are used), and this can
> > cause annoying warnings such as:
> >
> > clang: warning: argument unused during compilation: '-march=armv6k' [-Wunused-command-line-argument]
> > clang: warning: argument unused during compilation: '-march=armv6k' [-Wunused-command-line-argument]
> > clang: warning: argument unused during compilation: '-march=armv6k' [-Wunused-command-line-argument]
>
> Note, the above lack of support was fixed in clang-13. That said, both
> Clang and GCC defer to -Wa,-march when -march is also present, so
> clang is still correct that -march is ignored. Thanks for resending;
> this is still helpful for earlier releases of clang that we still
> support.
The -Wunused-command-line-argument warning also caused a build
failure for me when building with 'make W=1', and I think there are
cases where the flags from the command line are contradictory.
Isn't the patch also needed for LTO? All I know is that with this
applied it all builds, but without it I run into link failures. I can dig
more into the specific failures, but overall I think this is the right
thing to do anyway.
Arnd
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next prev parent reply other threads:[~2021-09-28 18:36 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-28 15:41 [PATCH 00/14] ARM: randconfig build fixes Arnd Bergmann
2021-09-28 15:41 ` [PATCH 01/14] ARM: RiscPC needs older gcc version Arnd Bergmann
2021-09-28 16:03 ` Arnd Bergmann
2021-09-29 8:45 ` Arnd Bergmann
2021-09-28 15:41 ` [PATCH 02/14] ARM: patch: fix BE32 compilation Arnd Bergmann
2021-09-28 21:33 ` Linus Walleij
2021-09-28 15:41 ` [PATCH 03/14] ARM: remove duplicate memcpy() definition Arnd Bergmann
2021-09-28 21:39 ` Linus Walleij
2021-09-28 15:41 ` [PATCH 04/14] ARM: kprobes: address gcc -Wempty-body warning Arnd Bergmann
2021-09-28 15:41 ` [PATCH 05/14] ARM: ARMv7-M uses BE-8, not BE-32 Arnd Bergmann
2021-09-28 15:41 ` [PATCH 06/14] ARM: disallow CONFIG_THUMB with ARMv4 Arnd Bergmann
2021-09-29 18:52 ` Nick Desaulniers
2021-10-06 16:01 ` Ard Biesheuvel
2021-09-28 15:41 ` [PATCH 07/14] ARM: fix link warning with XIP + frame-pointer Arnd Bergmann
2021-09-28 15:41 ` [PATCH 08/14] ARM: kprobes: fix arch_init_kprobes() prototype Arnd Bergmann
2021-09-28 15:41 ` [PATCH 09/14] ARM: allow compile-testing without machine record Arnd Bergmann
2021-09-28 15:41 ` [PATCH 10/14] ARM: only warn about XIP address when not compile testing Arnd Bergmann
2021-09-28 15:41 ` [PATCH 11/14] ARM: kasan: work around LPAE build warning Arnd Bergmann
2021-09-28 15:41 ` [PATCH 12/14] ARM: add CONFIG_PHYS_OFFSET default values Arnd Bergmann
2021-09-28 16:02 ` Nicolas Pitre
2021-09-28 21:44 ` Linus Walleij
2021-09-28 15:41 ` [PATCH 13/14] ARM: use .arch directives instead of assembler command line flags Arnd Bergmann
2021-09-28 17:10 ` Nick Desaulniers
2021-09-28 18:32 ` Arnd Bergmann [this message]
2021-09-29 18:11 ` Nick Desaulniers
2022-01-21 22:17 ` Nathan Chancellor
2021-09-28 15:41 ` [PATCH 14/14] [RFC] ARM: forbid ftrace with clang and thumb2_kernel Arnd Bergmann
2021-09-28 17:20 ` Nick Desaulniers
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