DMB -- A64

Data Memory Barrier is a memory barrier that ensures the ordering of observations of memory accesses, see Data Memory Barrier.

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1	1	0	1	0	1	0	1	0	0	0	0	0	0	1	1	0	0	1	1	CRm				1	0	1	1	1	1	1	1
																									opc		Rt

Assembler Symbols

Specifies the limitation on the barrier operation. Values are:

SY: Full system is the required shareability domain, reads and writes are the required access types, both before and after the barrier instruction. This option is referred to as the full system barrier. Encoded as CRm = 0b1111.
ST: Full system is the required shareability domain, writes are the required access type, both before and after the barrier instruction. Encoded as CRm = 0b1110.
LD: Full system is the required shareability domain, reads are the required access type before the barrier instruction, and reads and writes are the required access types after the barrier instruction. Encoded as CRm = 0b1101.
ISH: Inner Shareable is the required shareability domain, reads and writes are the required access types, both before and after the barrier instruction. Encoded as CRm = 0b1011.
ISHST: Inner Shareable is the required shareability domain, writes are the required access type, both before and after the barrier instruction. Encoded as CRm = 0b1010.
ISHLD: Inner Shareable is the required shareability domain, reads are the required access type before the barrier instruction, and reads and writes are the required access types after the barrier instruction. Encoded as CRm = 0b1001.
NSH: Non-shareable is the required shareability domain, reads and writes are the required access, both before and after the barrier instruction. Encoded as CRm = 0b0111.
NSHST: Non-shareable is the required shareability domain, writes are the required access type, both before and after the barrier instruction. Encoded as CRm = 0b0110.
NSHLD: Non-shareable is the required shareability domain, reads are the required access type before the barrier instruction, and reads and writes are the required access types after the barrier instruction. Encoded as CRm = 0b0101.
OSH: Outer Shareable is the required shareability domain, reads and writes are the required access types, both before and after the barrier instruction. Encoded as CRm = 0b0011.
OSHST: Outer Shareable is the required shareability domain, writes are the required access type, both before and after the barrier instruction. Encoded as CRm = 0b0010.
OSHLD: Outer Shareable is the required shareability domain, reads are the required access type before the barrier instruction, and reads and writes are the required access types after the barrier instruction. Encoded as CRm = 0b0001.

All other encodings of "CRm" that are not listed are reserved and can be encoded using the #<imm> syntax. All unsupported and reserved options must execute as a full system barrier operation, but software must not rely on this behavior. For more information on whether an access is before or after a barrier instruction, see Data Memory Barrier (DMB) or see Data Synchronization Barrier (DSB).

CRm	<option>
xx00	RESERVED
0001	OSHLD
0010	OSHST
0011	OSH
0101	NSHLD
0110	NSHST
0111	NSH
1001	ISHLD
1010	ISHST
1011	ISH
1101	LD
1110	ST
1111	SY

<imm>

Is a 4-bit unsigned immediate, in the range 0 to 15, encoded in the "CRm" field.

Operation

DataMemoryBarrier(domain, types);

Internal version only: aarchmrs v2024-03_relA, pseudocode v2024-03_rel, sve v2024-03_rel ; Build timestamp: 2024-03-26T09:45

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1	1	0	1	0	1	0	1	0	0	0	0	0	0	1	1	0	0	1	1	CRm				1	0	1	1	1	1	1	1
																									opc		Rt

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1	1	0	1	0	1	0	1	0	0	0	0	0	0	1	1	0	0	1	1	CRm				1	0	1	1	1	1	1	1
																									opc		Rt

DMB

DMB (<option>|#<imm>)

Assembler Symbols

Operation

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1	1	0	1	0	1	0	1	0	0	0	0	0	0	1	1	0	0	1	1	CRm				1	0	1	1	1	1	1	1
																									opc		Rt