linux-kernel - Re: [PATCH v2] m68k: use kernel's generic muldi3 libgcc function

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Message-ID: <CAMuHMdVZh6-64hfx1jgOijBEG6cTftinqf+4fZvqjJtV1hO95g@mail.gmail.com>
Date: Tue, 5 Nov 2024 12:46:34 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Greg Ungerer <gerg@...ux-m68k.org>, arnd@...db.de
Cc: linux-m68k@...ts.linux-m68k.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] m68k: use kernel's generic muldi3 libgcc function

Hi Greg, Arnd,

On Mon, Nov 13, 2023 at 2:32 PM Greg Ungerer <gerg@...ux-m68k.org> wrote:
> Use the kernels own generic lib/muldi3.c implementation of muldi3 for
> 68K machines. Some 68K CPUs support 64bit multiplies so move the arch
> specific umul_ppmm() macro into a header file that is included by
> lib/muldi3.c. That way it can take advantage of the single instruction
> when available.
>
> There does not appear to be any existing mechanism for the generic
> lib/muldi3.c code to pick up an external arch definition of umul_ppmm().
> Create an arch specific libgcc.h that can optionally be included by
> the system include/linux/libgcc.h to allow for this.
>
> Somewhat oddly there is also a similar definition of umul_ppmm() in
> the non-architecture code in lib/crypto/mpi/longlong.h for a wide range
> or machines. Its presence ends up complicating the include setup and
> means not being able to use something like compiler.h instead. Actually
> there is a few other defines of umul_ppmm() macros spread around in
> various architectures, but not directly usable for the m68k case.
>
> Signed-off-by: Greg Ungerer <gerg@...ux-m68k.org>

Reviewed-by: Geert Uytterhoeven <geert@...ux-m68k.org>

>  arch/Kconfig                   |  8 +++
>  arch/m68k/Kconfig              |  2 +
>  arch/m68k/include/asm/libgcc.h | 20 +++++++
>  arch/m68k/lib/Makefile         |  2 +-
>  arch/m68k/lib/muldi3.c         | 97 ----------------------------------
>  include/linux/libgcc.h         |  4 ++
>  6 files changed, 35 insertions(+), 98 deletions(-)
>  create mode 100644 arch/m68k/include/asm/libgcc.h
>  delete mode 100644 arch/m68k/lib/muldi3.c

I had this in my local tree for about a year.
Is it fine to queue this in the m68k tree, or does this need a broader
coverage?

Thanks!

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