Re: [PATCH v2 0/2] gcc: xtensa: allow dynamic configuration

[Max Filippov <jcmvbkbc@gmail.com>]

On Mon, Nov 28, 2022 at 4:46 PM Max Filippov <jcmvbkbc@gmail.com> wrote:
>
> Hello,
>
> this series addresses the long standing issue with xtensa configuration
> support by adding a way to configure toolchain for a specific xtensa
> core at runtime using the xtensa-dynconfig [1] library as a plugin.
> On a platform with shared library support single toolchain binary
> becomes capable of building code for arbitrary xtensa configuration.
> At the same time it fully preserves the traditional way of configuring
> the toolchain using the xtensa configuration overlay.
>
> Currently xtensa toolchain needs to be patched and rebuilt for every
> new xtensa processor configuration. This has a number of downsides:
> - toolchain builders need to change the toolchain source code, and
>   because xtensa configuration overlay is not a patch, this change is
>   special, embedding it into the toolchain build process gets
>   backpressure.
> - toolchain built for one configuration is usually not usable for any
>   other configuration. It's not possible for a distribution to provide
>   reusable prebuilt xtensa toolchain.
>
> This series allows building the toolchain (including target libraries)
> without its source code modification. Built toolchain takes configuration
> parameters from the shared object specified in the environment variable.
> That shared object may be built by the xtensa-dynconfig project [1].
>
> The same shared object is used for gcc, all binutils and for gdb.
> Xtensa core specific information needed to build that shared object is
> taken from the configuration overlay.
>
> Both gcc and binutils-gdb get new shared header file
> include/xtensa-dynconfig.h that provides definition of configuration
> data structure, initialization macros, redefines XCHAL_* macros to
> access this structure and declares function for loading configuration
> dynamically.
>
> This is not the first submission of this series, it was first
> submitted in 2017 [2]. This version has improved configuration
> versioning and GPL-compatibility check that was suggested in comments
> for the v1.
>
> [1] https://github.com/jcmvbkbc/xtensa-dynconfig
> [2] https://gcc.gnu.org/pipermail/gcc-patches/2017-May/475109.html
>
> Max Filippov (2):
>   gcc: xtensa: allow dynamic configuration
>   libgcc: xtensa: use built-in configuration
>
>  gcc/config.gcc                               |   1 +
>  gcc/config/xtensa/t-xtensa                   |   8 +-
>  gcc/config/xtensa/xtensa-dynconfig.c         | 170 +++++++
>  gcc/config/xtensa/xtensa-protos.h            |   1 +
>  gcc/config/xtensa/xtensa.h                   |  22 +-
>  include/xtensa-dynconfig.h                   | 442 +++++++++++++++++++
>  libgcc/config/xtensa/crti.S                  |   2 +-
>  libgcc/config/xtensa/crtn.S                  |   2 +-
>  libgcc/config/xtensa/lib1funcs.S             |   2 +-
>  libgcc/config/xtensa/lib2funcs.S             |   2 +-
>  libgcc/config/xtensa/xtensa-config-builtin.h | 198 +++++++++
>  11 files changed, 828 insertions(+), 22 deletions(-)
>  create mode 100644 gcc/config/xtensa/xtensa-dynconfig.c
>  create mode 100644 include/xtensa-dynconfig.h
>  create mode 100644 libgcc/config/xtensa/xtensa-config-builtin.h

Series regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.

-- 
Thanks.
-- Max