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<instructionsection id="WFI" title="WFI -- AArch32" type="instruction">
  <docvars>
    <docvar key="instr-class" value="general" />
    <docvar key="mnemonic" value="WFI" />
  </docvars>
  <heading>WFI</heading>
  <desc>
    <brief>
      <para>Wait For Interrupt</para>
    </brief>
    <authored>
      <para>Wait For Interrupt is a hint instruction that indicates that the PE can enter a low-power state and remain there until a wakeup event occurs. For more information, see <xref linkend="CFIBBGJG">Wait For Interrupt</xref>.</para>
      <para>As described in <xref linkend="CFIBBGJG">Wait For Interrupt</xref>, the execution of a <instruction>WFI</instruction> instruction that would otherwise cause entry to a low-power state can be trapped to a higher Exception level, see:</para>
      <list type="unordered">
        <listitem><content><xref linkend="CHDJGAIC">Traps to Undefined mode of PL0 execution of WFE and WFI instructions</xref>.</content></listitem>
        <listitem><content><xref linkend="BEIBHJCJ">Traps to Hyp mode of Non-secure EL0 and EL1 execution of WFE and WFI instructions</xref>.</content></listitem>
        <listitem><content><xref linkend="CHDEGCIJ">Traps to Monitor mode of the execution of WFE and WFI instructions in modes other than Monitor mode</xref>.</content></listitem>
      </list>
    </authored>
    <encodingnotes>
      <para>For more information about the <arm-defined-word>constrained unpredictable</arm-defined-word> behavior of this instruction, see <xref linkend="CJAEGDJC">Architectural Constraints on UNPREDICTABLE behaviors</xref>.</para>
    </encodingnotes>
  </desc>
  <alias_list howmany="0"></alias_list>
  <classes>
    <classesintro count="3">
      <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> and </txt>
      <a href="#iclass_t2">T2</a>
      <txt>)</txt>
      <txt>.</txt>
    </classesintro>
    <iclass name="A1" oneof="3" 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="WFI" />
      </docvars>
      <iclassintro count="1"></iclassintro>
      <regdiagram form="32" psname="aarch32/instrs/WFI/A1_A.txt" tworows="1">
        <box hibit="31" width="4" name="cond" usename="1" settings="4" constraint="!= 1111">
          <c colspan="4">!= 1111</c>
        </box>
        <box hibit="27" width="5" settings="5">
          <c>0</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
          <c>0</c>
        </box>
        <box hibit="22" name="R" settings="1">
          <c>0</c>
        </box>
        <box hibit="21" width="2" settings="2">
          <c>1</c>
          <c>0</c>
        </box>
        <box hibit="19" width="2" name="imm4&lt;3:2&gt;" settings="2">
          <c>0</c>
          <c>0</c>
        </box>
        <box hibit="17" width="2" name="imm4&lt;1:0&gt;" settings="2">
          <c>0</c>
          <c>0</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" width="12" name="imm12" settings="12">
          <c>(0)</c>
          <c>(0)</c>
          <c>(0)</c>
          <c>(0)</c>
          <c>0</c>
          <c>0</c>
          <c>0</c>
          <c>0</c>
          <c>0</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
        </box>
      </regdiagram>
      <encoding name="WFI_A1" oneofinclass="1" oneof="3" label="A1">
        <docvars>
          <docvar key="armarmheading" value="A1" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="A32" />
          <docvar key="mnemonic" value="WFI" />
        </docvars>
        <asmtemplate><text>WFI</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></asmtemplate>
      </encoding>
      <ps_section howmany="1">
        <ps name="aarch32/instrs/WFI/A1_A.txt" mylink="aarch32.instrs.WFI.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="3" 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="WFI" />
      </docvars>
      <iclassintro count="1"></iclassintro>
      <regdiagram form="16" psname="aarch32/instrs/WFI/T1_A.txt">
        <box hibit="31" width="8" settings="8">
          <c>1</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
          <c>1</c>
        </box>
        <box hibit="23" width="4" name="hint" settings="4">
          <c>0</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
        </box>
        <box hibit="19" width="4" settings="4">
          <c>0</c>
          <c>0</c>
          <c>0</c>
          <c>0</c>
        </box>
      </regdiagram>
      <encoding name="WFI_T1" oneofinclass="1" oneof="3" label="T1">
        <docvars>
          <docvar key="armarmheading" value="T1" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="T32" />
          <docvar key="mnemonic" value="WFI" />
        </docvars>
        <asmtemplate><text>WFI</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></asmtemplate>
      </encoding>
      <ps_section howmany="1">
        <ps name="aarch32/instrs/WFI/T1_A.txt" mylink="aarch32.instrs.WFI.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>
    <iclass name="T2" oneof="3" id="iclass_t2" no_encodings="1" isa="T32">
      <docvars>
        <docvar key="armarmheading" value="T2" />
        <docvar key="instr-class" value="general" />
        <docvar key="isa" value="T32" />
        <docvar key="mnemonic" value="WFI" />
      </docvars>
      <iclassintro count="1"></iclassintro>
      <regdiagram form="16x2" psname="aarch32/instrs/WFI/T2_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>0</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>(0)</c>
        </box>
        <box hibit="10" width="3" settings="3">
          <c>0</c>
          <c>0</c>
          <c>0</c>
        </box>
        <box hibit="7" width="4" name="hint" settings="4">
          <c>0</c>
          <c>0</c>
          <c>0</c>
          <c>0</c>
        </box>
        <box hibit="3" width="4" name="option" settings="4">
          <c>0</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
        </box>
      </regdiagram>
      <encoding name="WFI_T2" oneofinclass="1" oneof="3" label="T2">
        <docvars>
          <docvar key="armarmheading" value="T2" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="T32" />
          <docvar key="mnemonic" value="WFI" />
        </docvars>
        <asmtemplate><text>WFI</text><text>{</text><a link="sa_c" hover="See {xref{ARMARM_Babbefhf}{Standard assembler syntax fields}}">&lt;c&gt;</a><text>}</text><text>.W</text></asmtemplate>
      </encoding>
      <ps_section howmany="1">
        <ps name="aarch32/instrs/WFI/T2_A.txt" mylink="aarch32.instrs.WFI.T2_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="WFI_A1, WFI_T1, WFI_T2" symboldefcount="1">
      <symbol link="sa_c">&lt;c&gt;</symbol>
      <account encodedin="">
        <intro>
          <para>See <xref linkend="Babbefhf">Standard assembler syntax fields</xref>.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="WFI_A1, WFI_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>
  </explanations>
  <ps_section howmany="1">
    <ps name="aarch32/instrs/WFI/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();
    if !<a link="impl-shared.InterruptPending.0" file="shared_pseudocode.xml" hover="function: boolean InterruptPending()">InterruptPending</a>() then
        if PSTATE.EL == <a link="EL0" file="shared_pseudocode.xml" hover="constant bits(2) EL0 = '00'">EL0</a> then
            // Check for traps described by the OS.
            <a link="AArch32.CheckForWFxTrap.2" file="shared_pseudocode.xml" hover="function: AArch32.CheckForWFxTrap(bits(2) target_el, WFxType wfxtype)">AArch32.CheckForWFxTrap</a>(<a link="EL1" file="shared_pseudocode.xml" hover="constant bits(2) EL1 = '01'">EL1</a>, <a link="WFxType_WFI" file="shared_pseudocode.xml" hover="enumeration WFxType {WFxType_WFE, WFxType_WFI, WFxType_WFET, WFxType_WFIT}">WFxType_WFI</a>);
        if PSTATE.EL IN {<a link="EL0" file="shared_pseudocode.xml" hover="constant bits(2) EL0 = '00'">EL0</a>, <a link="EL1" file="shared_pseudocode.xml" hover="constant bits(2) EL1 = '01'">EL1</a>} &amp;&amp; <a link="impl-shared.EL2Enabled.0" file="shared_pseudocode.xml" hover="function: boolean EL2Enabled()">EL2Enabled</a>() &amp;&amp; !<a link="impl-shared.IsInHost.0" file="shared_pseudocode.xml" hover="function: boolean IsInHost()">IsInHost</a>() then
            // Check for traps described by the Hypervisor.
            <a link="AArch32.CheckForWFxTrap.2" file="shared_pseudocode.xml" hover="function: AArch32.CheckForWFxTrap(bits(2) target_el, WFxType wfxtype)">AArch32.CheckForWFxTrap</a>(<a link="EL2" file="shared_pseudocode.xml" hover="constant bits(2) EL2 = '10'">EL2</a>, <a link="WFxType_WFI" file="shared_pseudocode.xml" hover="enumeration WFxType {WFxType_WFE, WFxType_WFI, WFxType_WFET, WFxType_WFIT}">WFxType_WFI</a>);
        if <a link="impl-shared.HaveEL.1" file="shared_pseudocode.xml" hover="function: boolean HaveEL(bits(2) el)">HaveEL</a>(<a link="EL3" file="shared_pseudocode.xml" hover="constant bits(2) EL3 = '11'">EL3</a>) &amp;&amp; PSTATE.M != <a link="M32_Monitor" file="shared_pseudocode.xml" hover="constant bits(5) M32_Monitor = '10110'">M32_Monitor</a> then
            // Check for traps described by the Secure Monitor.
            <a link="AArch32.CheckForWFxTrap.2" file="shared_pseudocode.xml" hover="function: AArch32.CheckForWFxTrap(bits(2) target_el, WFxType wfxtype)">AArch32.CheckForWFxTrap</a>(<a link="EL3" file="shared_pseudocode.xml" hover="constant bits(2) EL3 = '11'">EL3</a>, <a link="WFxType_WFI" file="shared_pseudocode.xml" hover="enumeration WFxType {WFxType_WFE, WFxType_WFI, WFxType_WFET, WFxType_WFIT}">WFxType_WFI</a>);
        integer localtimeout = 1 &lt;&lt; 64;  // No local timeout event is generated
        <a link="impl-shared.WaitForInterrupt.1" file="shared_pseudocode.xml" hover="function: WaitForInterrupt(integer localtimeout)">WaitForInterrupt</a>(localtimeout);</pstext>
    </ps>
  </ps_section>
</instructionsection>
