source: clfs-embedded/BOOK/cross-tools/arm/abi.xml@ a040561

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<sect1 id="ch-system-abi">
  <?dbhtml filename="abi.html"?>

  <title>ABI Variables</title>

  <para os="a">On the ARM architecture, there are two major ABI types to choose
  from: EABI and OABI.  There is also a Thumb ABI and an Intel IWMMX specific
  ABI but these are generally not recommended for most uses.</para>

  <para os="b">The EABI (Embedded ABI) is newer and supports additional
  features, faster software floating point operations, and Thumb interworking,
  but is only compatible with ARMv4t and newer cores.  The EABI has
  sub-ABIs of: aapcs-linux and aapcs.  aapcs-linux has standard Linux 4 byte
  enums while aapcs has variable length enums.  aapcs-linux is recommended over
  aapcs.</para>

  <para os="c">The OABI (old ABI) is called apcs-gnu and supports ARMv4 and 
  older cores.  Generally the OABI is not used by modern ARM processors.</para>

  <xi:include xmlns:xi="http://www.w3.org/2003/XInclude"
  href="../common/abi.xml"
  xpointer="xpointer(//*[@os='a'])"/>

  <xi:include xmlns:xi="http://www.w3.org/2003/XInclude"
  href="../common/abi.xml"
  xpointer="xpointer(//*[@os='b'])"/>

  <xi:include xmlns:xi="http://www.w3.org/2003/XInclude"
  href="../common/abi.xml"
  xpointer="xpointer(//*[@os='c'])"/>

  <table>
    <title>List of Build Variables</title>
    <?dbfo table-width="3in" ?>

    <tgroup cols="2">

      <colspec colnum="1" colwidth="1.5in" colname="ABI to Select"/>
      <colspec colnum="2" colwidth="1.5in" colname="Variable Value"/>
      <colspec colnum="3" colwidth="2in" colname="Note"/>

      <thead>
        <row>
          <entry>ABI</entry>
          <entry>CLFS_ABI=Value</entry>
          <entry>Note</entry>
        </row>
      </thead>

      <tbody>
        <row>
          <entry>aapcs-linux</entry>
          <entry>aapcs-linux</entry>
          <entry>Recommended for EABI. Standard Linux 32 bit (int) enums</entry>
        </row>
        <row>
          <entry>apcs-gnu</entry>
          <entry>apcs-gnu</entry>
          <entry>Recommended for OABI</entry>
        </row>
        <row>
          <entry>atpcs</entry>
          <entry>atpcs</entry>
          <entry>Thumb ABI</entry>
        </row>
        <row>
          <entry>aapcs</entry>
          <entry>aapcs</entry>
          <entry>EABI w/ variable size enums</entry>
        </row>
        <row>
          <entry>iwmmxt</entry>
          <entry>iwmmxt</entry>
          <entry>Supports Intel XScale MMX extensions</entry>
        </row>
      </tbody>

    </tgroup>

  </table>

</sect1>