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| <title>Using as: Literal Directive</title> |
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| <a name="Literal-Directive"></a> |
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| Next: <a href="Literal-Position-Directive.html#Literal-Position-Directive" accesskey="n" rel="next">Literal Position Directive</a>, Previous: <a href="Transform-Directive.html#Transform-Directive" accesskey="p" rel="prev">Transform Directive</a>, Up: <a href="Xtensa-Directives.html#Xtensa-Directives" accesskey="u" rel="up">Xtensa Directives</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="literal"></a> |
| <h4 class="subsubsection">9.52.5.4 literal</h4> |
| <a name="index-literal-directive"></a> |
| |
| <p>The <code>.literal</code> directive is used to define literal pool data, i.e., |
| read-only 32-bit data accessed via <code>L32R</code> instructions. |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"> .literal <var>label</var>, <var>value</var>[, <var>value</var>…] |
| </pre></div> |
| |
| <p>This directive is similar to the standard <code>.word</code> directive, except |
| that the actual location of the literal data is determined by the |
| assembler and linker, not by the position of the <code>.literal</code> |
| directive. Using this directive gives the assembler freedom to locate |
| the literal data in the most appropriate place and possibly to combine |
| identical literals. For example, the code: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"> entry sp, 40 |
| .literal .L1, sym |
| l32r a4, .L1 |
| </pre></div> |
| |
| <p>can be used to load a pointer to the symbol <code>sym</code> into register |
| <code>a4</code>. The value of <code>sym</code> will not be placed between the |
| <code>ENTRY</code> and <code>L32R</code> instructions; instead, the assembler puts |
| the data in a literal pool. |
| </p> |
| <p>Literal pools are placed by default in separate literal sections; |
| however, when using the ‘<samp>--text-section-literals</samp>’ |
| option (see <a href="Xtensa-Options.html#Xtensa-Options">Command Line Options</a>), the literal |
| pools for PC-relative mode <code>L32R</code> instructions |
| are placed in the current section.<a name="DOCF3" href="#FOOT3"><sup>3</sup></a> |
| These text section literal |
| pools are created automatically before <code>ENTRY</code> instructions and |
| manually after ‘<samp>.literal_position</samp>’ directives (see <a href="Literal-Position-Directive.html#Literal-Position-Directive">literal_position</a>). If there are no preceding |
| <code>ENTRY</code> instructions, explicit <code>.literal_position</code> directives |
| must be used to place the text section literal pools; otherwise, |
| <code>as</code> will report an error. |
| </p> |
| <p>When literals are placed in separate sections, the literal section names |
| are derived from the names of the sections where the literals are |
| defined. The base literal section names are <code>.literal</code> for |
| PC-relative mode <code>L32R</code> instructions and <code>.lit4</code> for absolute |
| mode <code>L32R</code> instructions (see <a href="Absolute-Literals-Directive.html#Absolute-Literals-Directive">absolute-literals</a>). These base names are used for literals defined in |
| the default <code>.text</code> section. For literals defined in other |
| sections or within the scope of a <code>literal_prefix</code> directive |
| (see <a href="Literal-Prefix-Directive.html#Literal-Prefix-Directive">literal_prefix</a>), the following rules |
| determine the literal section name: |
| </p> |
| <ol> |
| <li> If the current section is a member of a section group, the literal |
| section name includes the group name as a suffix to the base |
| <code>.literal</code> or <code>.lit4</code> name, with a period to separate the base |
| name and group name. The literal section is also made a member of the |
| group. |
| |
| </li><li> If the current section name (or <code>literal_prefix</code> value) begins with |
| “<code>.gnu.linkonce.<var>kind</var>.</code>”, the literal section name is formed |
| by replacing “<code>.<var>kind</var></code>” with the base <code>.literal</code> or |
| <code>.lit4</code> name. For example, for literals defined in a section named |
| <code>.gnu.linkonce.t.func</code>, the literal section will be |
| <code>.gnu.linkonce.literal.func</code> or <code>.gnu.linkonce.lit4.func</code>. |
| |
| </li><li> If the current section name (or <code>literal_prefix</code> value) ends with |
| <code>.text</code>, the literal section name is formed by replacing that |
| suffix with the base <code>.literal</code> or <code>.lit4</code> name. For example, |
| for literals defined in a section named <code>.iram0.text</code>, the literal |
| section will be <code>.iram0.literal</code> or <code>.iram0.lit4</code>. |
| |
| </li><li> If none of the preceding conditions apply, the literal section name is |
| formed by adding the base <code>.literal</code> or <code>.lit4</code> name as a |
| suffix to the current section name (or <code>literal_prefix</code> value). |
| </li></ol> |
| |
| <div class="footnote"> |
| <hr> |
| <h4 class="footnotes-heading">Footnotes</h4> |
| |
| <h3><a name="FOOT3" href="#DOCF3">(3)</a></h3> |
| <p>Literals for the |
| <code>.init</code> and <code>.fini</code> sections are always placed in separate |
| sections, even when ‘<samp>--text-section-literals</samp>’ is enabled.</p> |
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