riscv / riscv-cheri

This repository contains the CHERI extension specification, adding hardware capabilities to RISC-V ISA to enable fine-grained memory protection and scalable compartmentalization.
https://jira.riscv.org/browse/RVG-148
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better specification of opcode mappings #280

Closed tariqkurd-repo closed 4 months ago

tariqkurd-repo commented 4 months ago

this started out as a note about Zilsd but expanded rather to correctly address https://github.com/riscv/riscv-cheri/issues/274

there's no spec change here, but it clarifies the relationship between C.FSDSP, Zcmp, Zcmt and Zilsd, and for RV32 and RV64

plus some tidy up of instruction pages I spotted on the way

an important point is that Zcmp/Zcmt cannot exist in RV64 cap mode, as the same encodings are mapped to C.FSDSP. This shouldn't be a problem as the Zcm extensions are only really intended for RV32.