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| <h4 class="subsection">9.42.5 Directives</h4> |
| |
| <p><a name="index-Xtensa-directives-2043"></a><a name="index-directives_002c-Xtensa-2044"></a> |
| The Xtensa assembler supports a region-based directive syntax: |
| |
| <pre class="smallexample"> .begin <var>directive</var> [<var>options</var>] |
| ... |
| .end <var>directive</var> |
| </pre> |
| <p>All the Xtensa-specific directives that apply to a region of code use |
| this syntax. |
| |
| <p>The directive applies to code between the <code>.begin</code> and the |
| <code>.end</code>. The state of the option after the <code>.end</code> reverts to |
| what it was before the <code>.begin</code>. |
| A nested <code>.begin</code>/<code>.end</code> region can further |
| change the state of the directive without having to be aware of its |
| outer state. For example, consider: |
| |
| <pre class="smallexample"> .begin no-transform |
| L: add a0, a1, a2 |
| .begin transform |
| M: add a0, a1, a2 |
| .end transform |
| N: add a0, a1, a2 |
| .end no-transform |
| </pre> |
| <p>The <code>ADD</code> opcodes at <code>L</code> and <code>N</code> in the outer |
| <code>no-transform</code> region both result in <code>ADD</code> machine instructions, |
| but the assembler selects an <code>ADD.N</code> instruction for the |
| <code>ADD</code> at <code>M</code> in the inner <code>transform</code> region. |
| |
| <p>The advantage of this style is that it works well inside macros which can |
| preserve the context of their callers. |
| |
| <p>The following directives are available: |
| |
| <ul class="menu"> |
| <li><a accesskey="1" href="Schedule-Directive.html#Schedule-Directive">Schedule Directive</a>: Enable instruction scheduling. |
| <li><a accesskey="2" href="Longcalls-Directive.html#Longcalls-Directive">Longcalls Directive</a>: Use Indirect Calls for Greater Range. |
| <li><a accesskey="3" href="Transform-Directive.html#Transform-Directive">Transform Directive</a>: Disable All Assembler Transformations. |
| <li><a accesskey="4" href="Literal-Directive.html#Literal-Directive">Literal Directive</a>: Intermix Literals with Instructions. |
| <li><a accesskey="5" href="Literal-Position-Directive.html#Literal-Position-Directive">Literal Position Directive</a>: Specify Inline Literal Pool Locations. |
| <li><a accesskey="6" href="Literal-Prefix-Directive.html#Literal-Prefix-Directive">Literal Prefix Directive</a>: Specify Literal Section Name Prefix. |
| <li><a accesskey="7" href="Absolute-Literals-Directive.html#Absolute-Literals-Directive">Absolute Literals Directive</a>: Control PC-Relative vs. Absolute Literals. |
| </ul> |
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