Data Synchronization Barrier is a memory barrier that ensures the completion of memory accesses, see Data Synchronization Barrier (DSB).
It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
1 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | (1) | (1) | (1) | (1) | (1) | (1) | (1) | (1) | (0) | (0) | (0) | (0) | 0 | 1 | 0 | 0 | != 0x00 | |||
option |
// No additional decoding required
15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | (1) | (1) | (1) | (1) | 1 | 0 | (0) | 0 | (1) | (1) | (1) | (1) | 0 | 1 | 0 | 0 | != 0x00 | |||
option |
// No additional decoding required
For more information about the constrained unpredictable behavior, see Architectural Constraints on UNPREDICTABLE behaviors.
<c> |
For encoding A1: see Standard assembler syntax fields. Must be AL or omitted. |
For encoding T1: see Standard assembler syntax fields. |
<q> |
<option> |
Specifies an optional limitation on the barrier operation. Values are:
For more information on whether an access is before or after a barrier instruction, see Data Synchronization Barrier (DSB). All other encodings of option are reserved, other than the values 0b0000 and 0b0100. All unsupported and reserved options must execute as a full system DSB operation, but software must not rely on this behavior. The value 0b0000 is used to encode SSBB and the value 0b0100 is used to encode PSSBB. The instruction supports the following alternative <option> values, but Arm recommends that software does not use these alternative values:
|
if ConditionPassed() then EncodingSpecificOperations(); case option of when '0001' domain = MBReqDomain_OuterShareable; types = MBReqTypes_Reads; when '0010' domain = MBReqDomain_OuterShareable; types = MBReqTypes_Writes; when '0011' domain = MBReqDomain_OuterShareable; types = MBReqTypes_All; when '0101' domain = MBReqDomain_Nonshareable; types = MBReqTypes_Reads; when '0110' domain = MBReqDomain_Nonshareable; types = MBReqTypes_Writes; when '0111' domain = MBReqDomain_Nonshareable; types = MBReqTypes_All; when '1001' domain = MBReqDomain_InnerShareable; types = MBReqTypes_Reads; when '1010' domain = MBReqDomain_InnerShareable; types = MBReqTypes_Writes; when '1011' domain = MBReqDomain_InnerShareable; types = MBReqTypes_All; when '1101' domain = MBReqDomain_FullSystem; types = MBReqTypes_Reads; when '1110' domain = MBReqDomain_FullSystem; types = MBReqTypes_Writes; otherwise if option == '0000' then SEE "SSBB"; elsif option == '0100' then SEE "PSSBB"; else domain = MBReqDomain_FullSystem; types = MBReqTypes_All; if PSTATE.EL IN {EL0, EL1} && EL2Enabled() then if HCR.BSU == '11' then domain = MBReqDomain_FullSystem; if HCR.BSU == '10' && domain != MBReqDomain_FullSystem then domain = MBReqDomain_OuterShareable; if HCR.BSU == '01' && domain == MBReqDomain_Nonshareable then domain = MBReqDomain_InnerShareable; DataSynchronizationBarrier(domain, types);
Internal version only: isa v01_19, pseudocode v2020-09_xml, sve v2020-09_rc3 ; Build timestamp: 2020-09-30T21:35
Copyright © 2010-2020 Arm Limited or its affiliates. All rights reserved. This document is Non-Confidential.