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<title>Using as: Xtensa Immediate Relaxation</title>

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<a name="Xtensa-Immediate-Relaxation"></a>
<div class="header">
<p>
Previous: <a href="Xtensa-Jump-Relaxation.html#Xtensa-Jump-Relaxation" accesskey="p" rel="prev">Xtensa Jump Relaxation</a>, Up: <a href="Xtensa-Relaxation.html#Xtensa-Relaxation" accesskey="u" rel="up">Xtensa Relaxation</a> &nbsp; [<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>
</div>
<hr>
<a name="Other-Immediate-Field-Relaxation"></a>
<h4 class="subsubsection">9.53.4.4 Other Immediate Field Relaxation</h4>
<a name="index-immediate-fields_002c-relaxation"></a>
<a name="index-relaxation-of-immediate-fields"></a>

<p>The assembler normally performs the following other relaxations.  They
can be disabled by using underscore prefixes (see <a href="Xtensa-Opcodes.html#Xtensa-Opcodes">Opcode Names</a>), the &lsquo;<samp>--no-transform</samp>&rsquo; command-line option
(see <a href="Xtensa-Options.html#Xtensa-Options">Command Line Options</a>), or the
<code>no-transform</code> directive (see <a href="Transform-Directive.html#Transform-Directive">transform</a>).
</p>
<a name="index-MOVI-instructions_002c-relaxation"></a>
<a name="index-relaxation-of-MOVI-instructions"></a>
<p>The <code>MOVI</code> machine instruction can only materialize values in the
range from -2048 to 2047.  Values outside this range are best
materialized with <code>L32R</code> instructions.  Thus:
</p>
<div class="smallexample">
<pre class="smallexample">    movi a0, 100000
</pre></div>

<p>is assembled into the following machine code:
</p>
<div class="smallexample">
<pre class="smallexample">    .literal .L1, 100000
    l32r a0, .L1
</pre></div>

<a name="index-L8UI-instructions_002c-relaxation"></a>
<a name="index-L16SI-instructions_002c-relaxation"></a>
<a name="index-L16UI-instructions_002c-relaxation"></a>
<a name="index-L32I-instructions_002c-relaxation"></a>
<a name="index-relaxation-of-L8UI-instructions"></a>
<a name="index-relaxation-of-L16SI-instructions"></a>
<a name="index-relaxation-of-L16UI-instructions"></a>
<a name="index-relaxation-of-L32I-instructions"></a>
<p>The <code>L8UI</code> machine instruction can only be used with immediate
offsets in the range from 0 to 255. The <code>L16SI</code> and <code>L16UI</code>
machine instructions can only be used with offsets from 0 to 510.  The
<code>L32I</code> machine instruction can only be used with offsets from 0 to
1020.  A load offset outside these ranges can be materialized with
an <code>L32R</code> instruction if the destination register of the load
is different than the source address register.  For example:
</p>
<div class="smallexample">
<pre class="smallexample">    l32i a1, a0, 2040
</pre></div>

<p>is translated to:
</p>
<div class="smallexample">
<pre class="smallexample">    .literal .L1, 2040
    l32r a1, .L1
</pre><pre class="smallexample">    add a1, a0, a1
    l32i a1, a1, 0
</pre></div>

<p>If the load destination and source address register are the same, an
out-of-range offset causes an error.
</p>
<a name="index-ADDI-instructions_002c-relaxation"></a>
<a name="index-relaxation-of-ADDI-instructions"></a>
<p>The Xtensa <code>ADDI</code> instruction only allows immediate operands in the
range from -128 to 127.  There are a number of alternate instruction
sequences for the <code>ADDI</code> operation.  First, if the
immediate is 0, the <code>ADDI</code> will be turned into a <code>MOV.N</code>
instruction (or the equivalent <code>OR</code> instruction if the code density
option is not available).  If the <code>ADDI</code> immediate is outside of
the range -128 to 127, but inside the range -32896 to 32639, an
<code>ADDMI</code> instruction or <code>ADDMI</code>/<code>ADDI</code> sequence will be
used.  Finally, if the immediate is outside of this range and a free
register is available, an <code>L32R</code>/<code>ADD</code> sequence will be used
with a literal allocated from the literal pool.
</p>
<p>For example:
</p>
<div class="smallexample">
<pre class="smallexample">    addi    a5, a6, 0
    addi    a5, a6, 512
</pre><pre class="smallexample">    addi    a5, a6, 513
    addi    a5, a6, 50000
</pre></div>

<p>is assembled into the following:
</p>
<div class="smallexample">
<pre class="smallexample">    .literal .L1, 50000
    mov.n   a5, a6
</pre><pre class="smallexample">    addmi   a5, a6, 0x200
    addmi   a5, a6, 0x200
    addi    a5, a5, 1
</pre><pre class="smallexample">    l32r    a5, .L1
    add     a5, a6, a5
</pre></div>

<hr>
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