There is syntax for this already for fixed integer registers, which this is patterned after. Rather than prefixing the operand descriptor with a lower case "r", fixed segment registers are prefixed with a lower case "s". Change-Id: Ic08d323bef732a62de23f77ec805c8b7cd5e2303 Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55445 Reviewed-by: Matt Sinclair <mattdsinclair@gmail.com> Maintainer: Matt Sinclair <mattdsinclair@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com>