[Libre-soc-dev] planning next OPF ISA WG RFC: ls003, biginteger?
luke.leighton at gmail.com
Thu Mar 2 22:27:00 GMT 2023
On Thu, Mar 2, 2023 at 5:38 PM Jacob Lifshay <programmerjake at gmail.com> wrote:
> dsld/dsrd are no longer hard to use,
> however they still have the issue that they unnecessarily write to `overflow`,
no, they don't. it's conditional. Rc=1.
> making them much slower than necessary
no, they're not.
> because of having to read/write SO,
no, they don't. read the RFC.
> which means you can't run multiple instructions in parallel unless
> you have special dependency hardware for SO.
which is optional in the SFFS subset. and therefore not
> also, their overflow output is inconsistent with other powerisa shift instructions.
luckily we're not doing "other power isa shift instructions".
> i think we should just remove their overflow output, since that matches other powerisa unsigned shift instructions.
a large portion of the objections you raise are invalid, so i'm
leaving it in.
the ISA WG can always object and give reasons why it should
not be in.
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