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> It's a shame though that Zcmp extension didn't get into RVA23 even as an optional extension Zcmp is only for embedded applications without D support. You wo
by camel-cdr 10mo ago
> It's a shame though that Zcmp extension didn't get into RVA23 even as an optional extension
Zcmp is only for embedded applications without D support.
You wouldn't want an instruction with up to 13 destinations in high performance designs anyways.
If you want load/store pair, we already have that, you can just interpret two adjacent 16-bit load or stores as a single 32-bit instruction.
- Joker_vD 10mo ago> You wouldn't want an instruction with up to 13 destinations in high performance designs anyways. Why not? Code density matters even in high-performance designs although I guess the "millicode routines" can help with that somewhat. Still, the ordering of stores/loads is undefined, and they are allowed to be re-done however many times, so... it shouldn't be onerous to implement? Expanding it into μops during the decoding stages seems straightforward.
- camel-cdr 10mo ago> Expanding it into μops during the decoding stages seems straightforward. I wouldn't say so, because if you want to be able to crack an instruction into up to N uops, now the second instruction could be placed in any slot from the 2nd to the 1+Nth and you now have to create huge shuffle hardware tk support this. Apple for example can only crack instructions that generate up to 3 μops at decode (or before rename) anything beyond needs to be microcoded and stall decoding other instructions.