[libre-riscv-dev] SV Prefix questions

Luke Kenneth Casson Leighton lkcl at lkcl.net
Sat Jun 22 18:08:19 BST 2019

I just realised that SVPrefix can actually operate standalone, as long as
VL is hardcoded  set to 1. None of the augmentation CSRs, VL, MVL, SUBVL
are needed, that in turn means STATE is not needed either.

svlen can then be viewed as a SIMD multiplier.

Only in the 64 bit case would STATE be needed, and then only if setting VL
is allowed.

Btw need to resolve how SVprefix interacts with or overrides register and
predication SV as well as the svlen CSR.


crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

More information about the libre-riscv-dev mailing list