Hi Arnd,

On Tue, Sep 28, 2021 at 05:41:42PM +0200, Arnd Bergmann 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]

Since most assembler is non-conditionally assembled with one sub arch
(modulo arch/arm/delay-loop.S which conditionally is assembled as armv4
based on CONFIG_ARCH_RPC, and arch/arm/mach-at91/pm-suspend.S which is
conditionally assembled as armv7-a based on CONFIG_CPU_V7), prefer the
.arch assembler directive.

Link: https://bugs.llvm.org/show_bug.cgi?id=48894
Link: https://github.com/ClangBuiltLinux/linux/issues/1195
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
[arnd] add a few more instances found in compile testing
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Did anything ever come of this patch (or series)? I would like to add
-Werror=unused-command-line-argument to CLANG_FLAGS so that invalid
flags will not cause cascading cc-option failures but we cannot not do
that until this is resolved.

Cheers,
Nathan

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