RISC-V ISA Explorer · Atomics (Za/Zic*)

Zaamo: Atomic Memory Operations

Ratified 2024-04 · version 1.0.0

Atomic read-modify-write operations on memory such as swap, add, logical, min and max, with no LR/SC pair.

Typical use: Lock-free counters and shared-memory updates

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Dependencies

Required by

Instructions (18)

Mnemonic	Name	Encoding	Match	Mask
`AMOADD.D`	Atomic fetch-and-add doubleword	`00000------------011-----0101111`	`0x302f`	`0xf800707f`
`AMOADD.W`	Atomic fetch-and-add word	`00000------------010-----0101111`	`0x202f`	`0xf800707f`
`AMOAND.D`	Atomic fetch-and-and doubleword	`01100------------011-----0101111`	`0x6000302f`	`0xf800707f`
`AMOAND.W`	Atomic fetch-and-and word	`01100------------010-----0101111`	`0x6000202f`	`0xf800707f`
`AMOMAX.D`	Atomic MAX doubleword	`10100------------011-----0101111`	`0xa000302f`	`0xf800707f`
`AMOMAX.W`	Atomic MAX word	`10100------------010-----0101111`	`0xa000202f`	`0xf800707f`
`AMOMAXU.D`	Atomic MAX unsigned doubleword	`11100------------011-----0101111`	`0xe000302f`	`0xf800707f`
`AMOMAXU.W`	Atomic MAX unsigned word	`11100------------010-----0101111`	`0xe000202f`	`0xf800707f`
`AMOMIN.D`	Atomic MIN doubleword	`10000------------011-----0101111`	`0x8000302f`	`0xf800707f`
`AMOMIN.W`	Atomic MIN word	`10000------------010-----0101111`	`0x8000202f`	`0xf800707f`
`AMOMINU.D`	Atomic MIN unsigned doubleword	`11000------------011-----0101111`	`0xc000302f`	`0xf800707f`
`AMOMINU.W`	Atomic MIN unsigned word	`11000------------010-----0101111`	`0xc000202f`	`0xf800707f`
`AMOOR.D`	Atomic fetch-and-or doubleword	`01000------------011-----0101111`	`0x4000302f`	`0xf800707f`
`AMOOR.W`	Atomic fetch-and-or word	`01000------------010-----0101111`	`0x4000202f`	`0xf800707f`
`AMOSWAP.D`	Atomic SWAP doubleword	`00001------------011-----0101111`	`0x800302f`	`0xf800707f`
`AMOSWAP.W`	Atomic SWAP word	`00001------------010-----0101111`	`0x800202f`	`0xf800707f`
`AMOXOR.D`	Atomic fetch-and-xor doubleword	`00100------------011-----0101111`	`0x2000302f`	`0xf800707f`
`AMOXOR.W`	Atomic fetch-and-xor word	`00100------------010-----0101111`	`0x2000202f`	`0xf800707f`