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

[Greg Ungerer]

Hi Geert,

On 5/11/24 21:46, Geert Uytterhoeven wrote:
> Hi Greg, Arnd,
>
> On Mon, Nov 13, 2023 at 2:32 PM Greg Ungerer <gerg@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
>
> Reviewed-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>
> >   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?

I am still in favor of it :-)
Would be good to get some feedback on the common code changes, like the change
to libgcc.h.

Regards
Greg