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<instructionsection id="ISB" title="ISB -- AArch32" type="instruction">
  <docvars>
    <docvar key="instr-class" value="general" />
    <docvar key="mnemonic" value="ISB" />
  </docvars>
  <heading>ISB</heading>
  <desc>
    <brief>
      <para>Instruction Synchronization Barrier</para>
    </brief>
    <authored>
      <para>Instruction Synchronization Barrier flushes the pipeline in the PE and is a context synchronization event. For more information, see <xref linkend="AA32CHDHFJFC">Instruction Synchronization Barrier (ISB)</xref>.</para>
    </authored>
    <encodingnotes>
      <para>For more information about the <arm-defined-word>constrained unpredictable</arm-defined-word> behavior, see <xref linkend="CJAEGDJC">Architectural Constraints on UNPREDICTABLE behaviors</xref>.</para>
    </encodingnotes>
  </desc>
  <alias_list howmany="0"></alias_list>
  <classes>
    <classesintro count="2">
      <txt>It has encodings from the following instruction sets:</txt>
      <txt> A32 (</txt>
      <a href="#iclass_a1">A1</a>
      <txt>)</txt>
      <txt> and </txt>
      <txt> T32 (</txt>
      <a href="#iclass_t1">T1</a>
      <txt>)</txt>
      <txt>.</txt>
    </classesintro>
    <iclass name="A1" oneof="2" id="iclass_a1" no_encodings="1" isa="A32">
      <docvars>
        <docvar key="armarmheading" value="A1" />
        <docvar key="instr-class" value="general" />
        <docvar key="isa" value="A32" />
        <docvar key="mnemonic" value="ISB" />
      </docvars>
      <iclassintro count="1"></iclassintro>
      <regdiagram form="32" psname="aarch32/instrs/ISB/A1_A.txt">
        <box hibit="31" width="12" settings="12">
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>0</c>
          <c>1</c>
          <c>0</c>
          <c>1</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
        </box>
        <box hibit="19" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="18" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="17" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="16" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="15" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="14" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="13" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="12" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="11" settings="1">
          <c>(0)</c>
        </box>
        <box hibit="10" settings="1">
          <c>(0)</c>
        </box>
        <box hibit="9" settings="1">
          <c>(0)</c>
        </box>
        <box hibit="8" settings="1">
          <c>(0)</c>
        </box>
        <box hibit="7" width="4" name="opcode" settings="4">
          <c>0</c>
          <c>1</c>
          <c>1</c>
          <c>0</c>
        </box>
        <box hibit="3" width="4" name="option" usename="1">
          <c colspan="4"></c>
        </box>
      </regdiagram>
      <encoding name="ISB_A1" oneofinclass="1" oneof="2" label="A1">
        <docvars>
          <docvar key="armarmheading" value="A1" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="A32" />
          <docvar key="mnemonic" value="ISB" />
        </docvars>
        <asmtemplate><text>ISB</text><text>{</text><a link="sa_c_1" hover="See {xref{ARMARM_Babbefhf}{Standard assembler syntax fields}}">&lt;c&gt;</a><text>}</text><text>{</text><a link="sa_q" hover="See {xref{ARMARM_Babbefhf}{Standard assembler syntax fields}}">&lt;q&gt;</a><text>}</text><text> </text><text>{</text><a link="sa_option" hover="Specifies an optional limitation on the barrier operation">&lt;option&gt;</a><text>}</text></asmtemplate>
      </encoding>
      <ps_section howmany="1">
        <ps name="aarch32/instrs/ISB/A1_A.txt" mylink="aarch32.instrs.ISB.A1_A.txt" enclabels="" sections="1" secttype="noheading">
          <pstext mayhavelinks="1" section="Decode" rep_section="decode">// No additional decoding required</pstext>
        </ps>
      </ps_section>
    </iclass>
    <iclass name="T1" oneof="2" id="iclass_t1" no_encodings="1" isa="T32">
      <docvars>
        <docvar key="armarmheading" value="T1" />
        <docvar key="instr-class" value="general" />
        <docvar key="isa" value="T32" />
        <docvar key="mnemonic" value="ISB" />
      </docvars>
      <iclassintro count="1"></iclassintro>
      <regdiagram form="16x2" psname="aarch32/instrs/ISB/T1_A.txt">
        <box hibit="31" width="12" settings="12">
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>0</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
        </box>
        <box hibit="19" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="18" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="17" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="16" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="15" width="2" settings="2">
          <c>1</c>
          <c>0</c>
        </box>
        <box hibit="13" settings="1">
          <c>(0)</c>
        </box>
        <box hibit="12" settings="1">
          <c>0</c>
        </box>
        <box hibit="11" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="10" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="9" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="8" settings="1">
          <c>(1)</c>
        </box>
        <box hibit="7" width="4" name="opc" settings="4">
          <c>0</c>
          <c>1</c>
          <c>1</c>
          <c>0</c>
        </box>
        <box hibit="3" width="4" name="option" usename="1">
          <c colspan="4"></c>
        </box>
      </regdiagram>
      <encoding name="ISB_T1" oneofinclass="1" oneof="2" label="T1">
        <docvars>
          <docvar key="armarmheading" value="T1" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="T32" />
          <docvar key="mnemonic" value="ISB" />
        </docvars>
        <asmtemplate><text>ISB</text><text>{</text><a link="sa_c" hover="See {xref{ARMARM_Babbefhf}{Standard assembler syntax fields}}">&lt;c&gt;</a><text>}</text><text>{</text><a link="sa_q" hover="See {xref{ARMARM_Babbefhf}{Standard assembler syntax fields}}">&lt;q&gt;</a><text>}</text><text> </text><text>{</text><a link="sa_option" hover="Specifies an optional limitation on the barrier operation">&lt;option&gt;</a><text>}</text></asmtemplate>
      </encoding>
      <ps_section howmany="1">
        <ps name="aarch32/instrs/ISB/T1_A.txt" mylink="aarch32.instrs.ISB.T1_A.txt" enclabels="" sections="1" secttype="noheading">
          <pstext mayhavelinks="1" section="Decode" rep_section="decode">// No additional decoding required</pstext>
        </ps>
      </ps_section>
    </iclass>
  </classes>
  <explanations scope="all">
    <explanation enclist="ISB_A1" symboldefcount="1">
      <symbol link="sa_c_1">&lt;c&gt;</symbol>
      <account encodedin="">
        <docvars>
          <docvar key="armarmheading" value="A1" />
          <docvar key="isa" value="A32" />
        </docvars>
        <intro>
          <para>For encoding A1: see <xref linkend="Babbefhf">Standard assembler syntax fields</xref>. Must be <value>AL</value> or omitted.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="ISB_T1" symboldefcount="2">
      <symbol link="sa_c">&lt;c&gt;</symbol>
      <account encodedin="">
        <docvars>
          <docvar key="armarmheading" value="T1" />
          <docvar key="isa" value="T32" />
        </docvars>
        <intro>
          <para>For encoding T1: see <xref linkend="Babbefhf">Standard assembler syntax fields</xref>.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="ISB_A1, ISB_T1" symboldefcount="1">
      <symbol link="sa_q">&lt;q&gt;</symbol>
      <account encodedin="">
        <intro>
          <para>See <xref linkend="Babbefhf">Standard assembler syntax fields</xref>.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="ISB_A1, ISB_T1" symboldefcount="1">
      <symbol link="sa_option">&lt;option&gt;</symbol>
      <account encodedin="option">
        <intro>
          <para>Specifies an optional limitation on the barrier operation. Values are:</para>
          <list type="param">
            <listitem>
              <param>SY</param><content>Full system barrier operation, encoded as option = <binarynumber>0b1111</binarynumber>. Can be omitted.</content>
            </listitem>
          </list>
          <para>All other encodings of option are reserved. The corresponding instructions execute as full system barrier operations, but must not be relied upon by software.</para>
        </intro>
      </account>
    </explanation>
  </explanations>
  <ps_section howmany="1">
    <ps name="aarch32/instrs/ISB/Op_A.txt" mylink="execute" enclabels="" sections="1" secttype="Operation">
      <pstext mayhavelinks="1" section="Execute" rep_section="execute">if <a link="impl-aarch32.ConditionPassed.0" file="shared_pseudocode.xml" hover="function: boolean ConditionPassed()">ConditionPassed</a>() then
    EncodingSpecificOperations();
    <a link="impl-shared.InstructionSynchronizationBarrier.0" file="shared_pseudocode.xml" hover="function: InstructionSynchronizationBarrier()">InstructionSynchronizationBarrier</a>();</pstext>
    </ps>
  </ps_section>
</instructionsection>
