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83 lines
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Next: <a rel="next" accesskey="n" href="RX_002dDirectives.html#RX_002dDirectives">RX-Directives</a>,
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Previous: <a rel="previous" accesskey="p" href="RX_002dOpts.html#RX_002dOpts">RX-Opts</a>,
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Up: <a rel="up" accesskey="u" href="RX_002dDependent.html#RX_002dDependent">RX-Dependent</a>
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<h4 class="subsection">9.40.2 Symbolic Operand Modifiers</h4>
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<p><a name="index-RX-modifiers-2030"></a><a name="index-syntax_002c-RX-2031"></a><a name="index-g_t_0025gp-2032"></a>
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The assembler supports one modifier when using symbol addresses
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in RX instruction operands. The general syntax is the following:
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<pre class="smallexample"> %gp(symbol)
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</pre>
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<p>The modifier returns the offset from the <var>__gp</var> symbol to the
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specified symbol as a 16-bit value. The intent is that this offset
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should be used in a register+offset move instruction when generating
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references to small data. Ie, like this:
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<pre class="smallexample"> mov.W %gp(_foo)[%gpreg], r1
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</pre>
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<p>The assembler also supports two meta register names which can be used
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to refer to registers whose values may not be known to the
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programmer. These meta register names are:
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<a name="index-g_t_0040samp_007b_0025gpreg_007d-2033"></a>
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<dl><dt><code>%gpreg</code><dd>The small data address register.
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<p><a name="index-g_t_0040samp_007b_0025pidreg_007d-2034"></a><br><dt><code>%pidreg</code><dd>The PID base address register.
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</dl>
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<p>Both registers normally have the value r13, but this can change if
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some registers have been reserved for use by interrupt handlers or if
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both the small data limit and position independent data features are
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being used at the same time.
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