[PATCH] gas: m68k M680LC040 F-LINE NOP insertion fixing emulation of fpu instructions

[Nathanial Sloss]

From what I've read historically on the issue it was fixed on later revisions 
of the lc040 from around late 1995.

Semiconductors marked with prefix MC as opposed to XC68lc040 should not have 
the bug and I beleive this is also true for coldfire which came in much later.

It's just that many manufactures (my suspect machine is a PowerBook 520) 
shipped with the earlier buggy revisions.


Best regards,

Nat

On Sun, 30 Mar 2025 16:30:05 Joel Sherrill wrote:
> Wow! The m68lc040 was on some mvme162 board variants. Over at RTEMS.org, we
> just recently cut the last release series with BSPs for m680x0 hardware. We
> did not remove basic CPU support for any m68k CPUs because we have Coldfire
> BSPs for at least one more release series. Removing cpu variant support was
> surgery we did not want to do.
> 
> Is there a way to know if the errata applies? I'm asking for posterity.
> 
> Thanks.
> 
> --joel sherrill
> 
> 
> 
> On Sat, Mar 29, 2025, 10:54 PM Nathanial Sloss
> <nathanialsloss@yahoo.com.au>
> 
> wrote:
> > Hi,
> > 
> > The m68k m68lc040 (early revisions) have an issue after executing f-line
> > (co
> > processor mmu/fpu) instructions and executing a trap in the case of fpu
> > emulation.
> > 
> > Unfornately due to time passed the processor errata as to how to address
> > the
> > issue has been lost.
> > 
> > Fortunately the issue was documented in a NetBSD PR:
> > 
> > http://gnats.netbsd.org/13078
> > 
> > Which proposes a solution to the problem which I have patched the GNU
> > assembler for.
> > 
> > As I have an affected machine with an lc040 processor I can confirm that
> > all
> > programmes compiled with the patched assember work as expected.
> > 
> > 
> > Best regards,
> > 
> > Nat