Re: [PATCH v2] Remove 32 bit sparc v8 support

[Romain Naour <romain dot naour at smile dot fr>]

Hi Adhemerval,

Le 12/11/2019 à 13:17, Adhemerval Zanella a écrit :
> Changes from previous version:
> 
>   - Remove sparc touch files in build-many-glibcs.py.
> 
> --
> 
> The pthread barrier has no support for sparc v8 since glibc 2.23
> (b02840bacdefd) and although there were some discussion to add
> support for LEON chips with CASA instruction [1] discussion has
> stalled since.
> 
> If LEON support is still a desirable feature, I would expect to work
> towards:
> 
>  - Enable USE_ATOMIC_COMPILER_BUILTINS for sparc32.
>  - Fix the possible instruction emulation code issue on kernel side
>    (as hinted by David Miller), so even a configuration targetting
>    LEON would work on sparc v9, although suboptimal.
>  - Move the generic *.S implementation to multiarch and add adapt
>    the ifunc selectors.
>  - Change the required multiarch to use generic implementation for
>    non v9 case.
>  - For the assembly specific implementation without ifunc support,
>    re-evaluate if sparcv9 is really a gain over generic implementation
>    with current compiler support.
> 
> The patch is straighforward, the sparc v9 is moved as the generic
> implementation, the sparc v8 implementations are removed, and a
> configure check is added to see if compiler sets __sparcv9__.
> 
> Checked on a sparcv9-linux-gnu.

One of my customer is still using sparc v8 LEON cpu on Gaisler's board [1].
Today, I asked him to forward this email to Gaisler in order to have some
feedback and maybe some support in upstream Glibc for LEON cpus.

For now, only old toolchains using Glibc 2.20 provided by Gaisler are available.

I know the sparc v8 support is stalled since glibc 2.23, can we wait before
merging this patch?

[1]
https://www.gaisler.com/index.php/products/operating-systems/linux?task=view&id=63

Best regards,
Romain

> 
> [1] https://sourceware.org/ml/libc-alpha/2016-11/msg00027.html
> ---