4 ms·
Hopefully B becomes ubiquitous in the next generation of SoC's, or RISC-V is going to look bad in any benchmarks that happen to have a popcnt in the hot path.
by gary_0 4y ago
Hopefully B becomes ubiquitous in the next generation of SoC's, or RISC-V is going to look bad in any benchmarks that happen to have a popcnt in the hot path.
- snvzz 4y agoAt least Zba, Zbb and Zbs are in RVA22 iirc. edit: Zbs.
- moloch-hai 4y agoZbc (carryless multiply) seems to be needed to implement AES-GCM
- snvzz 4y agoIt is required in Zkn (Scalar Crypto NIST Algorithms) and Zks (Scalar Crypto ShangMi Algorithms).
- gary_0 4y agoAh, you're right: https://github.com/riscv/riscv-profiles/blob/main/profiles.adoc#rva22-profiles https://github.com/riscv/riscv-profiles/blob/main/profiles.a... That's good to see. (Boy, it's really hard to find info about RISC-V profiles on Google. It just seems to ignore all the letters and numbers.)
- nullc 4y agoI worry a bit that B is too ambitious with many instructions that no one is using yet which are difficult to prove their value as a result, while regular RISC-V is essentially hobbled compared to ordinary cpus due to the absence of popcnt/clz.
- snvzz 4y agoMost implementations announced recently (e.g. in RISC-V Summit last December) have B. Even the newer revisions of cores that have been available for a while (like SiFive U74) have been updated with B support. As such, I believe it to be a non-issue. Hardware simply takes time. >which are difficult to prove their value as a result, As with any RISC-V extensions, each instruction had to meet many criteria to be allowed in there. Rationale accompany the instructions in the documentation.
- nullc 4y ago> Most implementations announced recently (e.g. in RISC-V Summit last December) have B. That's fantastic. > Rationale accompany the instructions in the documentation. I've read it-- I didn't personally need it to be convinced, but I'm surprised it convinced vendors. Glad to hear that it has.
- snvzz 4y ago>Hopefully B becomes ubiquitous in the next generation of SoC's Hopefully together with V.