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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).

It has encodings from the following instruction sets: A32 ( A1 ) and T32 ( T1 ) .

A1

313029282726252423222120191817161514131211109876543210
111101010111(1)(1)(1)(1)(1)(1)(1)(1)(0)(0)(0)(0)0110option

A1

ISB{<c>}{<q>} {<option>}

// No additional decoding required

T1

15141312111098765432101514131211109876543210
111100111011(1)(1)(1)(1)10(0)0(1)(1)(1)(1)0110option

T1

ISB{<c>}{<q>} {<option>}

// No additional decoding required

For more information about the constrained unpredictable behavior, see Architectural Constraints on UNPREDICTABLE behaviors.

Assembler Symbols

<c>

For encoding A1: see Standard assembler syntax fields. Must be AL or omitted.

For encoding T1: see Standard assembler syntax fields.

<q>

See Standard assembler syntax fields.

<option>

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

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

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

Operation

if ConditionPassed() then
    EncodingSpecificOperations();
    InstructionSynchronizationBarrier();
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