Re: [PATCH v2 0/2] Basic support for the Ventana VT1 w/ instruction fusion

[Philipp Tomsich <philipp.tomsich@vrull.eu>]

On Mon, 14 Nov 2022 at 21:58, Palmer Dabbelt <palmer@rivosinc.com> wrote:
>
> On Mon, 14 Nov 2022 12:03:38 PST (-0800), philipp.tomsich@vrull.eu wrote:
> > On Mon, 14 Nov 2022 at 21:00, Palmer Dabbelt <palmer@rivosinc.com> wrote:
> >>
> >> On Sun, 13 Nov 2022 12:48:22 PST (-0800), philipp.tomsich@vrull.eu wrote:
> >> >
> >> > This series provides support for the Ventana VT1 (a 4-way superscalar
> >> > rv64gc_zba_zbb_zbc_zbs_zifenci_xventanacondops core) including support
> >> > for the supported instruction fusion patterns.
> >> >
> >> > This includes the addition of the fusion-aware scheduling
> >> > infrastructure for RISC-V and implements idiom recognition for the
> >> > fusion patterns supported by VT1.
> >> >
> >> > Note that we don't signal support for XVentanaCondOps at this point,
> >> > as the XVentanaCondOps support is in-flight separately.  Changing the
> >> > defaults for VT1 can happen late in the cycle, so no need to link the
> >> > two different changesets.
> >> >
> >> > Changes in v2:
> >> > - Rebased and changed over to .rst-based documentation
> >> > - Updated to catch more fusion cases
> >> > - Signals support for Zifencei
> >> >
> >> > Philipp Tomsich (2):
> >> >   RISC-V: Add basic support for the Ventana-VT1 core
> >> >   RISC-V: Add instruction fusion (for ventana-vt1)
> >> >
> >> >  gcc/config/riscv/riscv-cores.def              |   3 +
> >> >  gcc/config/riscv/riscv-opts.h                 |   2 +-
> >> >  gcc/config/riscv/riscv.cc                     | 233 ++++++++++++++++++
> >> >  .../risc-v-options.rst                        |   5 +-
> >> >  4 files changed, 240 insertions(+), 3 deletions(-)
> >>
> >> I guess we never really properly talked about this on the GCC mailing
> >> lists, but IMO it's fine to start taking code for designs that have been
> >> announced under the assumption that if the hardware doesn't actually
> >> show up according to those timelines that it will be assumed to have
> >> never existed and thus be removed more quickly than usual.
> >>
> >> That said, I can't find anything describing that the VT-1 exists aside
> >> from these patches.  Is there anything that describes this design and
> >> when it's expected to be available?
> >
> > I have to defer to Jeff on this one.
>
> Looks like you already committed it, though:
>
> 991cfe5b30c ("RISC-V: Add instruction fusion (for ventana-vt1)")
> b4fca4fc70d ("RISC-V: Add basic support for the Ventana-VT1 core")
>
> We talked about this multiple times and I thought you were on board with
> the proposed "hardware needs to be announced" changes, did I
> misunderstand that?

Sorry — I had assumed that the "basic support" changes were agreed
upon between you and Jeff, given that Jeff had given the OK.

My position is still the same as discussed at LPC that "hardware needs
to be announced".

Thanks,
Philipp.