RISC-V ISA Explorer · System

Zimop: May-Be-Ops (NOP family)

Ratified 2024-03 · version 1.0.0

Reserves encodings that simply write zero today, letting later extensions redefine them without breaking old code.

Typical use: Reserved NOP encodings for future

Specification

Open Zimop in the explorer

Dependencies

Required by

Instructions (40)

Mnemonic	Name	Encoding	Match	Mask
`MOP.R.0`	May-be-operation 0 (1 source register)	`100000011100-----100-----1110011`	`0x81c04073`	`0xfff0707f`
`MOP.R.1`	May-be-operation 1 (1 source register)	`100000011101-----100-----1110011`	`0x81d04073`	`0xfff0707f`
`MOP.R.10`	May-be-operation 10 (1 source register)	`100010011110-----100-----1110011`	`0x89e04073`	`0xfff0707f`
`MOP.R.11`	May-be-operation 11 (1 source register)	`100010011111-----100-----1110011`	`0x89f04073`	`0xfff0707f`
`MOP.R.12`	May-be-operation 12 (1 source register)	`100011011100-----100-----1110011`	`0x8dc04073`	`0xfff0707f`
`MOP.R.13`	May-be-operation 13 (1 source register)	`100011011101-----100-----1110011`	`0x8dd04073`	`0xfff0707f`
`MOP.R.14`	May-be-operation 14 (1 source register)	`100011011110-----100-----1110011`	`0x8de04073`	`0xfff0707f`
`MOP.R.15`	May-be-operation 15 (1 source register)	`100011011111-----100-----1110011`	`0x8df04073`	`0xfff0707f`
`MOP.R.16`	May-be-operation 16 (1 source register)	`110000011100-----100-----1110011`	`0xc1c04073`	`0xfff0707f`
`MOP.R.17`	May-be-operation 17 (1 source register)	`110000011101-----100-----1110011`	`0xc1d04073`	`0xfff0707f`
`MOP.R.18`	May-be-operation 18 (1 source register)	`110000011110-----100-----1110011`	`0xc1e04073`	`0xfff0707f`
`MOP.R.19`	May-be-operation 19 (1 source register)	`110000011111-----100-----1110011`	`0xc1f04073`	`0xfff0707f`
`MOP.R.2`	May-be-operation 2 (1 source register)	`100000011110-----100-----1110011`	`0x81e04073`	`0xfff0707f`
`MOP.R.20`	May-be-operation 20 (1 source register)	`110001011100-----100-----1110011`	`0xc5c04073`	`0xfff0707f`
`MOP.R.21`	May-be-operation 21 (1 source register)	`110001011101-----100-----1110011`	`0xc5d04073`	`0xfff0707f`
`MOP.R.22`	May-be-operation 22 (1 source register)	`110001011110-----100-----1110011`	`0xc5e04073`	`0xfff0707f`
`MOP.R.23`	May-be-operation 23 (1 source register)	`110001011111-----100-----1110011`	`0xc5f04073`	`0xfff0707f`
`MOP.R.24`	May-be-operation 24 (1 source register)	`110010011100-----100-----1110011`	`0xc9c04073`	`0xfff0707f`
`MOP.R.25`	May-be-operation 25 (1 source register)	`110010011101-----100-----1110011`	`0xc9d04073`	`0xfff0707f`
`MOP.R.26`	May-be-operation 26 (1 source register)	`110010011110-----100-----1110011`	`0xc9e04073`	`0xfff0707f`
`MOP.R.27`	May-be-operation 27 (1 source register)	`110010011111-----100-----1110011`	`0xc9f04073`	`0xfff0707f`
`MOP.R.28`	May-be-operation 28 (1 source register)	`110011011100-----100-----1110011`	`0xcdc04073`	`0xfff0707f`
`MOP.R.29`	May-be-operation 29 (1 source register)	`110011011101-----100-----1110011`	`0xcdd04073`	`0xfff0707f`
`MOP.R.3`	May-be-operation 3 (1 source register)	`100000011111-----100-----1110011`	`0x81f04073`	`0xfff0707f`
`MOP.R.30`	May-be-operation 30 (1 source register)	`110011011110-----100-----1110011`	`0xcde04073`	`0xfff0707f`
`MOP.R.31`	May-be-operation 31 (1 source register)	`110011011111-----100-----1110011`	`0xcdf04073`	`0xfff0707f`
`MOP.R.4`	May-be-operation 4 (1 source register)	`100001011100-----100-----1110011`	`0x85c04073`	`0xfff0707f`
`MOP.R.5`	May-be-operation 5 (1 source register)	`100001011101-----100-----1110011`	`0x85d04073`	`0xfff0707f`
`MOP.R.6`	May-be-operation 6 (1 source register)	`100001011110-----100-----1110011`	`0x85e04073`	`0xfff0707f`
`MOP.R.7`	May-be-operation 7 (1 source register)	`100001011111-----100-----1110011`	`0x85f04073`	`0xfff0707f`
`MOP.R.8`	May-be-operation 8 (1 source register)	`100010011100-----100-----1110011`	`0x89c04073`	`0xfff0707f`
`MOP.R.9`	May-be-operation 9 (1 source register)	`100010011101-----100-----1110011`	`0x89d04073`	`0xfff0707f`
`MOP.RR.0`	May-be-operation 0 (2 source registers)	`1000001----------100-----1110011`	`0x82004073`	`0xfe00707f`
`MOP.RR.1`	May-be-operation 1 (2 source registers)	`1000011----------100-----1110011`	`0x86004073`	`0xfe00707f`
`MOP.RR.2`	May-be-operation 2 (2 source registers)	`1000101----------100-----1110011`	`0x8a004073`	`0xfe00707f`
`MOP.RR.3`	May-be-operation 3 (2 source registers)	`1000111----------100-----1110011`	`0x8e004073`	`0xfe00707f`
`MOP.RR.4`	May-be-operation 4 (2 source registers)	`1100001----------100-----1110011`	`0xc2004073`	`0xfe00707f`
`MOP.RR.5`	May-be-operation 5 (2 source registers)	`1100011----------100-----1110011`	`0xc6004073`	`0xfe00707f`
`MOP.RR.6`	May-be-operation 6 (2 source registers)	`1100101----------100-----1110011`	`0xca004073`	`0xfe00707f`
`MOP.RR.7`	May-be-operation 7 (2 source registers)	`1100111----------100-----1110011`	`0xce004073`	`0xfe00707f`