archived-ballistic/spec/arm64_xml/msub.xml

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<instructionsection id="MSUB" title="MSUB -- A64" type="instruction">
  <docvars>
    <docvar key="instr-class" value="general" />
    <docvar key="isa" value="A64" />
    <docvar key="mnemonic" value="MSUB" />
  </docvars>
  <heading>MSUB</heading>
  <desc>
    <brief>
      <para>Multiply-Subtract</para>
    </brief>
    <authored>
      <para>Multiply-Subtract multiplies two register values, subtracts the product from a third 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="1">
    <alias_list_intro>This instruction is used by the alias </alias_list_intro>
    <aliasref aliaspageid="MNEG_MSUB" aliasfile="mneg_msub.xml" hover="Multiply-negate" punct=".">
      <text>MNEG</text>
      <aliaspref>Ra == '11111'</aliaspref>
    </aliasref>
    <alias_list_outro>
      <text>  See </text>
      <aliastablelink />
      <text> below for details of when the alias is preferred.</text>
    </alias_list_outro>
  </alias_list>
  <classes>
    <iclass name="Integer" oneof="1" id="iclass_general" no_encodings="2" isa="A64">
      <docvars>
        <docvar key="instr-class" value="general" />
        <docvar key="isa" value="A64" />
        <docvar key="mnemonic" value="MSUB" />
      </docvars>
      <iclassintro count="2"></iclassintro>
      <regdiagram form="32" psname="aarch64/instrs/integer/arithmetic/mul/uniform/add-sub" tworows="1">
        <box hibit="31" name="sf" usename="1">
          <c></c>
        </box>
        <box hibit="30" width="2" name="op54" settings="2">
          <c>0</c>
          <c>0</c>
        </box>
        <box hibit="28" width="5" settings="5">
          <c>1</c>
          <c>1</c>
          <c>0</c>
          <c>1</c>
          <c>1</c>
        </box>
        <box hibit="23" width="3" name="op31" settings="3">
          <c>0</c>
          <c>0</c>
          <c>0</c>
        </box>
        <box hibit="20" width="5" name="Rm" usename="1">
          <c colspan="5"></c>
        </box>
        <box hibit="15" name="o0" usename="1" settings="1" psbits="x">
          <c>1</c>
        </box>
        <box hibit="14" width="5" name="Ra" usename="1">
          <c colspan="5"></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="MSUB_32A_dp_3src" oneofinclass="2" oneof="2" label="32-bit" bitdiffs="sf == 0">
        <docvars>
          <docvar key="datatype" value="32" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="A64" />
          <docvar key="mnemonic" value="MSUB" />
        </docvars>
        <box hibit="31" width="1" name="sf">
          <c>0</c>
        </box>
        <asmtemplate><text>MSUB  </text><a link="sa_wd" hover="32-bit general-purpose destination register (field &quot;Rd&quot;)">&lt;Wd&gt;</a><text>, </text><a link="sa_wn" hover="First 32-bit general-purpose source register holding multiplicand (field &quot;Rn&quot;)">&lt;Wn&gt;</a><text>, </text><a link="sa_wm" hover="Second 32-bit general-purpose source register holding multiplier (field &quot;Rm&quot;)">&lt;Wm&gt;</a><text>, </text><a link="sa_wa" hover="Third 32-bit general-purpose source register holding minuend (field &quot;Ra&quot;)">&lt;Wa&gt;</a></asmtemplate>
      </encoding>
      <encoding name="MSUB_64A_dp_3src" oneofinclass="2" oneof="2" label="64-bit" bitdiffs="sf == 1">
        <docvars>
          <docvar key="datatype" value="64" />
          <docvar key="instr-class" value="general" />
          <docvar key="isa" value="A64" />
          <docvar key="mnemonic" value="MSUB" />
        </docvars>
        <box hibit="31" width="1" name="sf">
          <c>1</c>
        </box>
        <asmtemplate><text>MSUB  </text><a link="sa_xd" hover="64-bit general-purpose destination register (field &quot;Rd&quot;)">&lt;Xd&gt;</a><text>, </text><a link="sa_xn" hover="First 64-bit general-purpose source register holding multiplicand (field &quot;Rn&quot;)">&lt;Xn&gt;</a><text>, </text><a link="sa_xm" hover="Second 64-bit general-purpose source register holding multiplier (field &quot;Rm&quot;)">&lt;Xm&gt;</a><text>, </text><a link="sa_xa" hover="Third 64-bit general-purpose source register holding minuend (field &quot;Ra&quot;)">&lt;Xa&gt;</a></asmtemplate>
      </encoding>
      <ps_section howmany="1">
        <ps name="aarch64/instrs/integer/arithmetic/mul/uniform/add-sub" mylink="aarch64.instrs.integer.arithmetic.mul.uniform.add-sub" 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 m = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(Rm);
integer a = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(Ra);
integer destsize = if sf == '1' then 64 else 32;
integer datasize = destsize;
boolean sub_op = (o0 == '1');</pstext>
        </ps>
      </ps_section>
    </iclass>
  </classes>
  <explanations scope="all">
    <explanation enclist="MSUB_32A_dp_3src" symboldefcount="1">
      <symbol link="sa_wd">&lt;Wd&gt;</symbol>
      <account encodedin="Rd">
        <intro>
          <para>Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="MSUB_32A_dp_3src" symboldefcount="1">
      <symbol link="sa_wn">&lt;Wn&gt;</symbol>
      <account encodedin="Rn">
        <intro>
          <para>Is the 32-bit name of the first general-purpose source register holding the multiplicand, encoded in the "Rn" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="MSUB_32A_dp_3src" symboldefcount="1">
      <symbol link="sa_wm">&lt;Wm&gt;</symbol>
      <account encodedin="Rm">
        <intro>
          <para>Is the 32-bit name of the second general-purpose source register holding the multiplier, encoded in the "Rm" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="MSUB_32A_dp_3src" symboldefcount="1">
      <symbol link="sa_wa">&lt;Wa&gt;</symbol>
      <account encodedin="Ra">
        <intro>
          <para>Is the 32-bit name of the third general-purpose source register holding the minuend, encoded in the "Ra" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="MSUB_64A_dp_3src" symboldefcount="1">
      <symbol link="sa_xd">&lt;Xd&gt;</symbol>
      <account encodedin="Rd">
        <intro>
          <para>Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="MSUB_64A_dp_3src" symboldefcount="1">
      <symbol link="sa_xn">&lt;Xn&gt;</symbol>
      <account encodedin="Rn">
        <intro>
          <para>Is the 64-bit name of the first general-purpose source register holding the multiplicand, encoded in the "Rn" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="MSUB_64A_dp_3src" symboldefcount="1">
      <symbol link="sa_xm">&lt;Xm&gt;</symbol>
      <account encodedin="Rm">
        <intro>
          <para>Is the 64-bit name of the second general-purpose source register holding the multiplier, encoded in the "Rm" field.</para>
        </intro>
      </account>
    </explanation>
    <explanation enclist="MSUB_64A_dp_3src" symboldefcount="1">
      <symbol link="sa_xa">&lt;Xa&gt;</symbol>
      <account encodedin="Ra">
        <intro>
          <para>Is the 64-bit name of the third general-purpose source register holding the minuend, encoded in the "Ra" field.</para>
        </intro>
      </account>
    </explanation>
  </explanations>
  <aliastablehook anchor="aliasconditions">Alias Conditions</aliastablehook>
  <ps_section howmany="1">
    <ps name="aarch64/instrs/integer/arithmetic/mul/uniform/add-sub" mylink="execute" enclabels="" sections="1" secttype="Operation">
      <pstext mayhavelinks="1" section="Execute" rep_section="execute">bits(datasize) operand1 = <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 = <a link="impl-aarch64.X.read.2" file="shared_pseudocode.xml" hover="accessor: bits(width) X[integer n, integer width]">X</a>[m, datasize];
bits(destsize) operand3 = <a link="impl-aarch64.X.read.2" file="shared_pseudocode.xml" hover="accessor: bits(width) X[integer n, integer width]">X</a>[a, destsize];

integer result;

if sub_op then
    result = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(operand3) - (<a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(operand1) * <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(operand2));
else
    result = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(operand3) + (<a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(operand1) * <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(operand2));

<a link="impl-aarch64.X.write.2" file="shared_pseudocode.xml" hover="accessor: X[integer n, integer width] = bits(width) value">X</a>[d, destsize] = result&lt;destsize-1:0&gt;;</pstext>
    </ps>
  </ps_section>
</instructionsection>