By: Eric Fink (eric.delete@this.anon.com), June 2, 2022 10:11 pm
Room: Moderated Discussions
Heikki Kultala (heikk.i.kultal.a.delete@this.gmail.com) on June 2, 2022 12:04 pm wrote:
> But everything else is not equal. Simpler decoder typically means either
> 1) worse code density, worse cache hit rate, OR
> 2) less expressive instructions, more instructions needed to perform the same task.
>
> So the argument "RISC is always better because it allows simpler decoder" is just stupid.
I think though the argument might be (not sure, you guys are the expert) used for ARMv8. It does allow simpler decoding and it doesn't come with a code density disadvantage.
It would be very interesting indeed to get a good measure on how decode complexity actually impacts CPU performance. Not that we every will :)
> But everything else is not equal. Simpler decoder typically means either
> 1) worse code density, worse cache hit rate, OR
> 2) less expressive instructions, more instructions needed to perform the same task.
>
> So the argument "RISC is always better because it allows simpler decoder" is just stupid.
I think though the argument might be (not sure, you guys are the expert) used for ARMv8. It does allow simpler decoding and it doesn't come with a code density disadvantage.
It would be very interesting indeed to get a good measure on how decode complexity actually impacts CPU performance. Not that we every will :)
