[PATCH] powerpc: Add gpr1 and fpu save/restore functions

[Timothy Pearson]

----- Original Message -----
> From: "Segher Boessenkool" <segher at kernel.crashing.org>
> To: "Timothy Pearson" <tpearson at raptorengineering.com>
> Cc: "linuxppc-dev" <linuxppc-dev at lists.ozlabs.org>
> Sent: Monday, February 12, 2024 11:30:43 AM
> Subject: Re: [PATCH] powerpc: Add gpr1 and fpu save/restore functions
> 
> Long long time ago, linux-0.11 or something, it was discovered that some
> programmiing mistakes resulted in double-length divisions (64x64->64 on
> 32-bit systems, say).  Most architectures have no hardware support for
> that, x86 is one of those; so you need very expensive support routines
> to do that (_udivdi3 or _divdi3 in that case, ...ti3 on 64-bit archs).
> 
> So it was decided to not link to libgcc to avoid this.  But that means
> that all the extremely many other suppoort routines, more for some other
> archs, are also not there.  While it would have been much easier to just
> link to something that provides the _{u,}divdi3 symbol and then causes a
> forced linking error from that!
> 
> 
> Segher

Interesting, that make sense.

How should we proceed from the current situation?  Bringing in libgcc seems
like a fairly invasive change, should we merge this to fix the current bug
(cannot build ppc64 kernel in size-optimized mode) and start discussion on
bringing in libgcc as the long-term fix across multiple architectures?

My goal here is to not have to carry a downstream patch in perpetuity for
our embedded Linux firmware, which needs to be compiled in size-optimized
mode due to hardware Flash limitations.

Thanks!