archived-ballistic/spec/arm64_xml/sub_addsub_imm.xml

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<instructionsection id="SUB_addsub_imm" title="SUB (immediate) -- A64" type="instruction">
  <docvars>
    <docvar key="cond-setting" value="no-s" />
    <docvar key="immediate-type" value="imm12u" />
    <docvar key="instr-class" value="general" />
    <docvar key="isa" value="A64" />
    <docvar key="mnemonic" value="SUB" />
  </docvars>
  <heading>SUB (immediate)</heading>
  <desc>
    <brief>
      <para>Subtract (immediate)</para>
    </brief>
    <authored>
      <para>Subtract (immediate) subtracts an optionally-shifted immediate value from a register value, and writes the result to the destination register.</para>
    </authored>
  </desc>
  <operationalnotes>
    <para>If PSTATE.DIT is 1:</para>
    <list type="unordered">
      <listitem><content>The execution time of this instruction is independent of:<list type="unordered"><listitem><content>The values of the data supplied in any of its registers.</content></listitem><listitem><content>The values of the NZCV flags.</content></listitem></list></content></listitem>
      <listitem><content>The response of this instruction to asynchronous exceptions does not vary based on:<list type="unordered"><listitem><content>The values of the data supplied in any of its registers.</content></listitem><listitem><content>The values of the NZCV flags.</content></listitem></list></content></listitem>
    </list>
  </operationalnotes>
  <alias_list howmany="0"></alias_list>
  <classes>
    <iclass name="Not setting the condition flags" oneof="1" id="iclass_no_s" no_encodings="2" isa="A64">
      <docvars>
        <docvar key="cond-setting" value="no-s" />
        <docvar key="immediate-type" value="imm12u" />
        <docvar key="instr-class" value="general" />
        <docvar key="isa" value="A64" />
        <docvar key="mnemonic" value="SUB" />
      </docvars>
      <iclassintro count="2"></iclassintro>
      <regdiagram form="32" psname="aarch64/instrs/integer/arithmetic/add-sub/immediate" tworows="1">
        <box hibit="31" name="sf" usename="1">
          <c></c>
        </box>
        <box hibit="30" name="op" usename="1" settings="1" psbits="x">
          <c>1</c>
        </box>
        <box hibit="29" name="S" usename="1" settings="1" psbits="x">
          <c>0</c>
        </box>
        <box hibit="28" width="6" settings="6">
          <c>1</c>
          <c>0</c>
          <c>0</c>
          <c>0</c>
          <c>1</c>
          <c>0</c>
        </box>
        <box hibit="22" name="sh" usename="1">
          <c></c>
        </box>
        <box hibit="21" width="12" name="imm12" usename="1">
          <c colspan="12"></c>
        </box>
        <box hibit="9" width="5" name="Rn" usename="1">
          <c colspan="5"></c>
        </box>
        <box hibit="4" width="5" name="Rd" usename="1">
          <c colspan="5"></c>
        </box>
      </regdiagram>
      <encoding name="SUB_32_addsub_imm" oneofinclass="2" oneof="2" label="32-bit" bitdiffs="sf == 0">
        <docvars>
          <docvar key="cond-setting" value="no-s" />
          <docvar key="datatype" value="32" />
          <docvar key="immediate-type" value="imm12u" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="A64" />
          <docvar key="mnemonic" value="SUB" />
        </docvars>
        <box hibit="31" width="1" name="sf">
          <c>0</c>
        </box>
        <asmtemplate><text>SUB  </text><a link="sa_wd_wsp" hover="32-bit destination general-purpose register or WSP (field &quot;Rd&quot;)">&lt;Wd|WSP&gt;</a><text>, </text><a link="sa_wn_wsp" hover="32-bit source general-purpose register or WSP (field &quot;Rn&quot;)">&lt;Wn|WSP&gt;</a><text>, #</text><a link="sa_imm" hover="Unsigned immediate [0-4095] (field &quot;imm12&quot;)">&lt;imm&gt;</a><text>{</text><text>, </text><a link="sa_shift" hover="Optional left shift to apply to the immediate, default LSL #0 (field &quot;sh&quot;) [LSL #0,LSL #12]">&lt;shift&gt;</a><text>}</text></asmtemplate>
      </encoding>
      <encoding name="SUB_64_addsub_imm" oneofinclass="2" oneof="2" label="64-bit" bitdiffs="sf == 1">
        <docvars>
          <docvar key="cond-setting" value="no-s" />
          <docvar key="datatype" value="64" />
          <docvar key="immediate-type" value="imm12u" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="A64" />
          <docvar key="mnemonic" value="SUB" />
        </docvars>
        <box hibit="31" width="1" name="sf">
          <c>1</c>
        </box>
        <asmtemplate><text>SUB  </text><a link="sa_xd_sp" hover="64-bit destination general-purpose register or SP (field &quot;Rd&quot;)">&lt;Xd|SP&gt;</a><text>, </text><a link="sa_xn_sp" hover="64-bit source general-purpose register or SP (field &quot;Rn&quot;)">&lt;Xn|SP&gt;</a><text>, #</text><a link="sa_imm" hover="Unsigned immediate [0-4095] (field &quot;imm12&quot;)">&lt;imm&gt;</a><text>{</text><text>, </text><a link="sa_shift" hover="Optional left shift to apply to the immediate, default LSL #0 (field &quot;sh&quot;) [LSL #0,LSL #12]">&lt;shift&gt;</a><text>}</text></asmtemplate>
      </encoding>
      <ps_section howmany="1">
        <ps name="aarch64/instrs/integer/arithmetic/add-sub/immediate" mylink="aarch64.instrs.integer.arithmetic.add-sub.immediate" enclabels="" sections="1" secttype="noheading">
          <pstext mayhavelinks="1" section="Decode" rep_section="decode">integer d = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(Rd);
integer n = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(Rn);
integer datasize = if sf == '1' then 64 else 32;
boolean sub_op = (op == '1');
boolean setflags = (S == '1');
bits(datasize) imm;

case sh of
    when '0' imm = <a link="impl-shared.ZeroExtend.2" file="shared_pseudocode.xml" hover="function: bits(N) ZeroExtend(bits(M) x, integer N)">ZeroExtend</a>(imm12, datasize);
    when '1' imm = <a link="impl-shared.ZeroExtend.2" file="shared_pseudocode.xml" hover="function: bits(N) ZeroExtend(bits(M) x, integer N)">ZeroExtend</a>(imm12 : <a link="impl-shared.Zeros.1" file="shared_pseudocode.xml" hover="function: bits(N) Zeros(integer N)">Zeros</a>(12), datasize);</pstext>
        </ps>
      </ps_section>
    </iclass>
  </classes>
  <explanations scope="all">
    <explanation enclist="SUB_32_addsub_imm" symboldefcount="1">
      <symbol link="sa_wd_wsp">&lt;Wd|WSP&gt;</symbol>
      <account encodedin="Rd">
        <intro>
          <para>Is the 32-bit name of the destination general-purpose register or stack pointer, encoded in the "Rd" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="SUB_32_addsub_imm" symboldefcount="1">
      <symbol link="sa_wn_wsp">&lt;Wn|WSP&gt;</symbol>
      <account encodedin="Rn">
        <intro>
          <para>Is the 32-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="SUB_64_addsub_imm" symboldefcount="1">
      <symbol link="sa_xd_sp">&lt;Xd|SP&gt;</symbol>
      <account encodedin="Rd">
        <intro>
          <para>Is the 64-bit name of the destination general-purpose register or stack pointer, encoded in the "Rd" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="SUB_64_addsub_imm" symboldefcount="1">
      <symbol link="sa_xn_sp">&lt;Xn|SP&gt;</symbol>
      <account encodedin="Rn">
        <intro>
          <para>Is the 64-bit name of the source general-purpose register or stack pointer, encoded in the "Rn" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="SUB_32_addsub_imm, SUB_64_addsub_imm" symboldefcount="1">
      <symbol link="sa_imm">&lt;imm&gt;</symbol>
      <account encodedin="imm12">
        <intro>
          <para>Is an unsigned immediate, in the range 0 to 4095, encoded in the "imm12" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="SUB_32_addsub_imm, SUB_64_addsub_imm" symboldefcount="1">
      <symbol link="sa_shift">&lt;shift&gt;</symbol>
      <definition encodedin="sh">
        <intro>Is the optional left shift to apply to the immediate, defaulting to LSL #0 and </intro>
        <table class="valuetable">
          <tgroup cols="2">
            <thead>
              <row>
                <entry class="bitfield">sh</entry>
                <entry class="symbol">&lt;shift&gt;</entry>
              </row>
            </thead>
            <tbody>
              <row>
                <entry class="bitfield">0</entry>
                <entry class="symbol">LSL #0</entry>
              </row>
              <row>
                <entry class="bitfield">1</entry>
                <entry class="symbol">LSL #12</entry>
              </row>
            </tbody>
          </tgroup>
        </table>
      </definition>
    </explanation>
  </explanations>
  <ps_section howmany="1">
    <ps name="aarch64/instrs/integer/arithmetic/add-sub/immediate" mylink="execute" enclabels="" sections="1" secttype="Operation">
      <pstext mayhavelinks="1" section="Execute" rep_section="execute">bits(datasize) result;
bits(datasize) operand1 = if n == 31 then <a link="impl-aarch64.SP.read.0" file="shared_pseudocode.xml" hover="accessor: bits(64) SP[]">SP</a>[]&lt;datasize-1:0&gt; else <a link="impl-aarch64.X.read.2" file="shared_pseudocode.xml" hover="accessor: bits(width) X[integer n, integer width]">X</a>[n, datasize];
bits(datasize) operand2 = imm;
bits(4) nzcv;
bit carry_in;

if sub_op then
    operand2 = NOT(operand2);
    carry_in = '1';
else
    carry_in = '0';

(result, nzcv) = <a link="impl-shared.AddWithCarry.3" file="shared_pseudocode.xml" hover="function: (bits(N), bits(4)) AddWithCarry(bits(N) x, bits(N) y, bit carry_in)">AddWithCarry</a>(operand1, operand2, carry_in);

if setflags then
    PSTATE.&lt;N,Z,C,V&gt; = nzcv;

if d == 31 &amp;&amp; !setflags then
    <a link="impl-aarch64.SP.write.0" file="shared_pseudocode.xml" hover="accessor: SP[] = bits(64) value">SP</a>[] = <a link="impl-shared.ZeroExtend.2" file="shared_pseudocode.xml" hover="function: bits(N) ZeroExtend(bits(M) x, integer N)">ZeroExtend</a>(result, 64);
else
    <a link="impl-aarch64.X.write.2" file="shared_pseudocode.xml" hover="accessor: X[integer n, integer width] = bits(width) value">X</a>[d, datasize] = result;</pstext>
    </ps>
  </ps_section>
</instructionsection>