Re: Patches to fix building m68k with CPUFLAGS

[Jake Hamby <jake.hamby%gmail.com@localhost>]

Thanks for the very useful feedback, Rin. I'll modify my local tree
based on your comments and report the change to m68k.h to upstream.

On Mon, Jul 20, 2020 at 3:11 AM Rin Okuyama <rokuyama.rk%gmail.com@localhost> wrote:
>
> Hi,
>
> On 2020/07/20 12:14, Jake Hamby wrote:
> > After further testing, I found that GCC 8.4.0 generates bigger, and
> > very buggy code, for m68k. I've seen no freezes, uvm errors, or panics
> > on illegal instructions with the NetBSD-current build I made with
> > "-m68040" and my previous patch, minus the part to change HAVE_GCC
> > from 7 to 8.
>
> Yes, amiga kernel does not work correctly if compiled by GCC8. See more
> details in this thread:
>
> http://mail-index.netbsd.org/port-m68k/2020/06/04/msg000760.html
>
> On 2020/07/20 3:20, Jake Hamby wrote:
> > One more note on the "libgcc/config/m68k/lb1sf68.S" patches (to gcc
> > and gcc.old):
> ...
> > The reason you only see a failure
> > here with CPUFLAGS set is because, I suspect, "defined (__mcoldfire__)
> > && !defined (__mcfisab__)" must be defined in the default
> > configuration, and not if you use, e.g. "-m68040" or "-m68020-60"
> > (which should be the ideal default build flag for targets like Atari
> > ST and Amiga).
>
> This is not correct. __mcoldfire__ is not defined for our m68k ports.
> You can confirm this by:
>
> % m68k--netbsdelf-gcc -dM -E - < /dev/null | grep coldfire
>
> Also you can see braw is used for the library compiled without
> optimization flags as:
>
> % m68k--netbsdelf-objdump -d libgcc_s.so | grep _exception_handler
>
> I guess that libgcc_s can be compiled without -m68040 or -m68060, just
> because the generated code is small enough. In order to work this around,
> you can simply replace bra with bral in that file. Alternatively, you
> can build the library by skipping tsort and lorder:
>
> https://mail-index.netbsd.org/tech-toolchain/2020/06/15/msg003823.html
>
> On 2020/07/20 2:35, Jake Hamby wrote:
> > --- a/external/gpl3/binutils.old/usr.bin/gas/arch/m68k/config.h
> > +++ b/external/gpl3/binutils.old/usr.bin/gas/arch/m68k/config.h
> > @@ -298,7 +298,7 @@
> >   #define TARGET_ALIAS "m68k--netbsdelf"
> >
> >   /* Define as 1 if big endian. */
> > -/* #undef TARGET_BYTES_BIG_ENDIAN */
> > +#define TARGET_BYTES_BIG_ENDIAN 1
> >
> >   /* Canonical target. */
> >   #define TARGET_CANONICAL "m68k--netbsdelf"
>
> This patch is not necessary because m68k is purely big-endian platform,
> and TARGET_BYTES_BIG_ENDIAN is unconditionally defined in
> src/external/gpl3/binutils{,.old}/dist/gas/dist/config/tc-m68k.h.
>
> Your patch for external/gpl3/gcc/dist/gcc/config/m68k/m68k.h seems
> rational. I'd appreciate a lot if you could report this to upstream.
>
> As you pointed out, CPUFLAGS should be neglected in order kernel and
> some standalone programs to get compiled. However, I'm not sure whether
> share/mk/bsd.sys.mk is the best place to do this.
>
> Thanks,
> rin