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ISB

Instruction Synchronization Barrier flushes the pipeline in the PE and is a context synchronization event. For more information, see Instruction Synchronization Barrier (ISB).

313029282726252423222120191817161514131211109876543210
11010101000000110011CRm11011111
opc

System

ISB {<option>|#<imm>}

MemBarrierOp op; MBReqDomain domain; MBReqTypes types; case opc of when '00' op = MemBarrierOp_DSB; when '01' op = MemBarrierOp_DMB; when '10' op = MemBarrierOp_ISB; otherwise if HaveSBExt() && CRm<3:0> == '0000' then op = MemBarrierOp_SB; else UNDEFINED; case CRm<3:2> of when '00' domain = MBReqDomain_OuterShareable; when '01' domain = MBReqDomain_Nonshareable; when '10' domain = MBReqDomain_InnerShareable; when '11' domain = MBReqDomain_FullSystem; case CRm<1:0> of when '01' types = MBReqTypes_Reads; when '10' types = MBReqTypes_Writes; when '11' types = MBReqTypes_All; otherwise if CRm<3:2> == '01' then op = MemBarrierOp_PSSBB; elsif CRm<3:2> == '00' && opc == '00' then op = MemBarrierOp_SSBB; elsif HaveSBExt() && CRm<3:2> == '00' && opc == '11' then op = MemBarrierOp_SB; else types = MBReqTypes_All; domain = MBReqDomain_FullSystem// No additional decoding required;

Assembler Symbols

<option>

Specifies an optional limitation on the barrier operation. Values are:

SY
Full system barrier operation, encoded as CRm = 0b1111. Can be omitted.

All other encodings of CRm are reserved. The corresponding instructions execute as full system barrier operations, but must not be relied upon by software.

<imm>

Is an optional 4-bit unsigned immediate, in the range 0 to 15, defaulting to 15 and encoded in the "CRm" field.

Operation

case op of when MemBarrierOp_DSBDataSynchronizationBarrier(domain, types); when MemBarrierOp_DMBDataMemoryBarrier(domain, types); when MemBarrierOp_ISBInstructionSynchronizationBarrier(); when MemBarrierOp_SSBBSpeculativeStoreBypassBarrierToVA(); when MemBarrierOp_PSSBBSpeculativeStoreBypassBarrierToPA(); when MemBarrierOp_SBSpeculationBarrier();


Internal version only: isa v30.41v30.3, AdvSIMD v27.08v27.04, pseudocode r8p5_00bet2_rc5v85-xml-00bet9_rc1_1, sve v8.5-00bet10_rc5v8.5-00bet9_rc1 ; Build timestamp: 2019-03-28T062018-12-12T11:3450

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