[libre-riscv-dev] PPC on Talos and Playstation 3

Luke Kenneth Casson Leighton lkcl at lkcl.net
Mon Mar 30 23:02:44 BST 2020

On Mon, Mar 30, 2020 at 8:35 PM Immanuel, Yehowshua U
<yimmanuel3 at gatech.edu> wrote:
> optional.  however we'll need to add our own modes: Khronos / Vulkan Compliance.
> Ah. Gotcha. So do we even NEED to test on ppc64?

yes absolutely.  otherwise, how will we know - for sure - that the HDL
is properly - and fully - ppc64 compliant?

> You can test 754 compliance on most anything.

except for PPC rounding modes and exception handling.  except that
IEEE754 compliance is *NOT* fully and exactly defined.  different
architectures have entirely different rules for rounding modes,
entirely different rules for NaN, and entirely different rules about
what and whether exceptions should be raised.

> If we opt out of the ppc mode -

ah no.  we absolutely have to have compliance with the requirements
set by the OpenPOWER Foundation.  otherwise we are not legally
permitted to use the name "POWER" associated with the project.

> then I imagine we don’t need PPC specific testing for the FPU.
> Is it possible to invoke PPC FPU mode through the instruction set?

it has to be enabled "by default".

we're negotiating with the OpenPOWER Foundation for the right to also
have a *Khronos* (Vulkan) Compliance Mode (as explained here:

the fact that the "non IEEE mode" exists at all on POWER is a good sign.


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