Re: [musl] Adding PowerPC SPE support

[Arnd Bergmann <arnd@kernel.org>]

On Sat, Jun 5, 2021 at 7:12 PM Rich Felker <dalias@libc.org> wrote:
>
> When the soft-float ABI for PowerPC was added in 2016 (commit
> 5a92dd95c77cee81755f1a441ae0b71e3ae2bcdb, mail thread "[PATCH v3] Add
> PowerPC soft-float support") with Freescale cpus having the
> alternative SPE FPU as the main use case, I noted that we could
> probably support hard float on them, but that it would involve
> determining some difficult ABI constraints. I'm now revisiting adding
> this support.

Note that regardless of the technical issues, there is a practical problem
in the long run, since gcc-8.5 was the last release with powerpcspe
support, and at some point in the future everyone will move to gcc-9
or higher.

The last e500/e500v2 based SoCs are now ten years old, and are
listed as available until 2025 but also "not recommended for new
designs". Linux kernel support for these has been marked as
"odd fixes" instead of "maintained" since early 2020, but in practice
this has been the case for much longer.

If I remember correctly, someone mentioned using musl on bare
metal e200 based microcontrollers, which is more interesting
for powerpcspe support than Linux user space, but this requires
additional patches already.

       Arnd