Re: [PATCH v2] powerpc64*: fix the order of implied sysdeps directories

["Tulio Magno Quites Machado Filho" <tuliom at linux dot vnet dot ibm dot com>]

"Gabriel F. T. Gomes" <gabriel@inconstante.eti.br> writes:

> This patch, initially intended in preparation for the transition of the
> long double format on powerpc64le, is now sent again regardless of any
> relevance it might have for the transition, because the changes are
> useful for other purposes as pointed out in
> https://sourceware.org/ml/libc-alpha/2017-12/msg00177.html
>
> Changes since v1:
>
>   - Rebased against current master and ran again with the same
>     generating script from v1 [1].
>   - Changed commit message.
>
> [1] https://sourceware.org/ml/libc-alpha/2017-12/msg00162.html
>
> -- 8< --
> The creation of the divergent sysdeps directory for powerpc64le
>
> commit 2f7f3cd8cd302bb10908c86f3f7b349df0a78e6a
> Author: Paul E. Murphy <murphyp@linux.vnet.ibm.com>
> Date:   Fri Jul 15 18:04:40 2016 -0500
>
>     powerpc64le: Create divergent sysdep directory for powerpc64le.
>
> allowed float128 to be enabled for powerpc64le (little-endian) and not
> for powerpc64 (big-endian).  Since the only intended difference between
> them was the presence or absence of the float128 interface, the sysdeps
> directory for powerpc64le explicitly reused the files from powerpc64
> (through the use of Implies files).
>
> Although this works, it also means that files under the powerpc64
> directory might be preferred over files under powerpc64le.  For
> instance, on a build for powerpc64le with target set to power9, a file
> from powerpc64/power5 might get built, even though a file with the same
> name exists in powerpc64le/power8.  That happens because the processor
> hierarchy was only defined in the sysdeps directory for powerpc64 (and
> borrowed by powerpc64le).
>
> This patch fixes this behavior, by moving sysdeps/powerpc/powerpc64 to
> sysdeps/powerpc/powerpc64-common and creating new Implies files to
> provide the hierarchy of processors for powerpc64 and powerpc64le
> separately.
>
> Builds for powerpc64le still use sysdeps/powerpc/powerpc64le, which now
> implies sysdeps/powerpc/powerpc64-common.  Likewise, builds for
> powerpc64 still use sysdeps/powerpc/powerpc64, which now has new Implies
> files to imply sysdeps/powerpc/powerpc64-common.  The hierarchy of
> processors is now implemented separately for powerpc64 and powerpc64le
> (each in its own subdirectory).  These changes have no effect on
> installed, stripped binaries (which remain unchanged).
>
> Tested that installed stripped binaries are unchanged and that there are
> no regressions on powerpc64 and powerpc64le.

The patch looks good to me in overall except for 2 issues:

 1. The Implies are listing non-existing directories, e.g.
    powerpc/powerpc64-common/power4/fpu.
    I agree it would be nice to prepare for the existence of some directories,
    but this causes a series of warnings when running configure.

 2. It is not preserving the order of directories for powerpc64le.  Current
    master code prefers files in the following order:
     fpu/multiarch
     fpu
     multiarch

    In order to fix this, it's necessary to:
    - sysdeps/powerpc/powerpc64le/power7/fpu/multiarch/Implies lists powerpc/powerpc64le/fpu/multiarch
    - sysdeps/powerpc/powerpc64le/power7/multiarch/Implies lists powerpc/powerpc64le/multiarch

-- 
Tulio Magno