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240 lines
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<head>
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<title>Using as: Sparc-Relocs</title>
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<link href="AS-Index.html#AS-Index" rel="index" title="AS Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Sparc_002dSyntax.html#Sparc_002dSyntax" rel="up" title="Sparc-Syntax">
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<link href="Sparc_002dSize_002dTranslations.html#Sparc_002dSize_002dTranslations" rel="next" title="Sparc-Size-Translations">
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<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000">
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<a name="Sparc_002dRelocs"></a>
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<div class="header">
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<p>
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Next: <a href="Sparc_002dSize_002dTranslations.html#Sparc_002dSize_002dTranslations" accesskey="n" rel="next">Sparc-Size-Translations</a>, Previous: <a href="Sparc_002dConstants.html#Sparc_002dConstants" accesskey="p" rel="prev">Sparc-Constants</a>, Up: <a href="Sparc_002dSyntax.html#Sparc_002dSyntax" accesskey="u" rel="up">Sparc-Syntax</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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</div>
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<hr>
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<a name="Relocations-3"></a>
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<h4 class="subsubsection">9.42.3.4 Relocations</h4>
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<a name="index-Sparc-relocations"></a>
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<a name="index-relocations_002c-Sparc"></a>
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<p>ELF relocations are available as defined in the 32-bit and 64-bit
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Sparc ELF specifications.
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</p>
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<p><code>R_SPARC_HI22</code> is obtained using ‘<samp>%hi</samp>’ and <code>R_SPARC_LO10</code>
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is obtained using ‘<samp>%lo</samp>’. Likewise <code>R_SPARC_HIX22</code> is
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obtained from ‘<samp>%hix</samp>’ and <code>R_SPARC_LOX10</code> is obtained
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using ‘<samp>%lox</samp>’. For example:
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</p>
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<div class="example">
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<pre class="example">sethi %hi(symbol), %g1
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or %g1, %lo(symbol), %g1
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sethi %hix(symbol), %g1
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xor %g1, %lox(symbol), %g1
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</pre></div>
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<p>These “high” mnemonics extract bits 31:10 of their operand,
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and the “low” mnemonics extract bits 9:0 of their operand.
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</p>
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<p>V9 code model relocations can be requested as follows:
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</p>
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<ul>
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<li> <code>R_SPARC_HH22</code> is requested using ‘<samp>%hh</samp>’. It can
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also be generated using ‘<samp>%uhi</samp>’.
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</li><li> <code>R_SPARC_HM10</code> is requested using ‘<samp>%hm</samp>’. It can
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also be generated using ‘<samp>%ulo</samp>’.
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</li><li> <code>R_SPARC_LM22</code> is requested using ‘<samp>%lm</samp>’.
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</li><li> <code>R_SPARC_H44</code> is requested using ‘<samp>%h44</samp>’.
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</li><li> <code>R_SPARC_M44</code> is requested using ‘<samp>%m44</samp>’.
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</li><li> <code>R_SPARC_L44</code> is requested using ‘<samp>%l44</samp>’ or ‘<samp>%l34</samp>’.
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</li><li> <code>R_SPARC_H34</code> is requested using ‘<samp>%h34</samp>’.
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</li></ul>
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<p>The ‘<samp>%l34</samp>’ generates a <code>R_SPARC_L44</code> relocation because it
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calculates the necessary value, and therefore no explicit
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<code>R_SPARC_L34</code> relocation needed to be created for this purpose.
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</p>
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<p>The ‘<samp>%h34</samp>’ and ‘<samp>%l34</samp>’ relocations are used for the abs34 code
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model. Here is an example abs34 address generation sequence:
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</p>
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<div class="example">
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<pre class="example">sethi %h34(symbol), %g1
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sllx %g1, 2, %g1
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or %g1, %l34(symbol), %g1
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</pre></div>
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<p>The PC relative relocation <code>R_SPARC_PC22</code> can be obtained by
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enclosing an operand inside of ‘<samp>%pc22</samp>’. Likewise, the
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<code>R_SPARC_PC10</code> relocation can be obtained using ‘<samp>%pc10</samp>’.
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These are mostly used when assembling PIC code. For example, the
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standard PIC sequence on Sparc to get the base of the global offset
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table, PC relative, into a register, can be performed as:
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</p>
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<div class="example">
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<pre class="example">sethi %pc22(_GLOBAL_OFFSET_TABLE_-4), %l7
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add %l7, %pc10(_GLOBAL_OFFSET_TABLE_+4), %l7
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</pre></div>
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<p>Several relocations exist to allow the link editor to potentially
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optimize GOT data references. The <code>R_SPARC_GOTDATA_OP_HIX22</code>
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relocation can obtained by enclosing an operand inside of
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‘<samp>%gdop_hix22</samp>’. The <code>R_SPARC_GOTDATA_OP_LOX10</code>
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relocation can obtained by enclosing an operand inside of
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‘<samp>%gdop_lox10</samp>’. Likewise, <code>R_SPARC_GOTDATA_OP</code> can be
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obtained by enclosing an operand inside of ‘<samp>%gdop</samp>’.
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For example, assuming the GOT base is in register <code>%l7</code>:
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</p>
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<div class="example">
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<pre class="example">sethi %gdop_hix22(symbol), %l1
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xor %l1, %gdop_lox10(symbol), %l1
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ld [%l7 + %l1], %l2, %gdop(symbol)
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</pre></div>
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<p>There are many relocations that can be requested for access to
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thread local storage variables. All of the Sparc TLS mnemonics
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are supported:
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</p>
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<ul>
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<li> <code>R_SPARC_TLS_GD_HI22</code> is requested using ‘<samp>%tgd_hi22</samp>’.
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</li><li> <code>R_SPARC_TLS_GD_LO10</code> is requested using ‘<samp>%tgd_lo10</samp>’.
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</li><li> <code>R_SPARC_TLS_GD_ADD</code> is requested using ‘<samp>%tgd_add</samp>’.
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</li><li> <code>R_SPARC_TLS_GD_CALL</code> is requested using ‘<samp>%tgd_call</samp>’.
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</li><li> <code>R_SPARC_TLS_LDM_HI22</code> is requested using ‘<samp>%tldm_hi22</samp>’.
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</li><li> <code>R_SPARC_TLS_LDM_LO10</code> is requested using ‘<samp>%tldm_lo10</samp>’.
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</li><li> <code>R_SPARC_TLS_LDM_ADD</code> is requested using ‘<samp>%tldm_add</samp>’.
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</li><li> <code>R_SPARC_TLS_LDM_CALL</code> is requested using ‘<samp>%tldm_call</samp>’.
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</li><li> <code>R_SPARC_TLS_LDO_HIX22</code> is requested using ‘<samp>%tldo_hix22</samp>’.
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</li><li> <code>R_SPARC_TLS_LDO_LOX10</code> is requested using ‘<samp>%tldo_lox10</samp>’.
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</li><li> <code>R_SPARC_TLS_LDO_ADD</code> is requested using ‘<samp>%tldo_add</samp>’.
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</li><li> <code>R_SPARC_TLS_IE_HI22</code> is requested using ‘<samp>%tie_hi22</samp>’.
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</li><li> <code>R_SPARC_TLS_IE_LO10</code> is requested using ‘<samp>%tie_lo10</samp>’.
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</li><li> <code>R_SPARC_TLS_IE_LD</code> is requested using ‘<samp>%tie_ld</samp>’.
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</li><li> <code>R_SPARC_TLS_IE_LDX</code> is requested using ‘<samp>%tie_ldx</samp>’.
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</li><li> <code>R_SPARC_TLS_IE_ADD</code> is requested using ‘<samp>%tie_add</samp>’.
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</li><li> <code>R_SPARC_TLS_LE_HIX22</code> is requested using ‘<samp>%tle_hix22</samp>’.
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</li><li> <code>R_SPARC_TLS_LE_LOX10</code> is requested using ‘<samp>%tle_lox10</samp>’.
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</li></ul>
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<p>Here are some example TLS model sequences.
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</p>
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<p>First, General Dynamic:
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</p>
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<div class="example">
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<pre class="example">sethi %tgd_hi22(symbol), %l1
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add %l1, %tgd_lo10(symbol), %l1
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add %l7, %l1, %o0, %tgd_add(symbol)
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call __tls_get_addr, %tgd_call(symbol)
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nop
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</pre></div>
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<p>Local Dynamic:
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</p>
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<div class="example">
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<pre class="example">sethi %tldm_hi22(symbol), %l1
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add %l1, %tldm_lo10(symbol), %l1
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add %l7, %l1, %o0, %tldm_add(symbol)
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call __tls_get_addr, %tldm_call(symbol)
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nop
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sethi %tldo_hix22(symbol), %l1
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xor %l1, %tldo_lox10(symbol), %l1
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add %o0, %l1, %l1, %tldo_add(symbol)
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</pre></div>
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<p>Initial Exec:
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</p>
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<div class="example">
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<pre class="example">sethi %tie_hi22(symbol), %l1
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add %l1, %tie_lo10(symbol), %l1
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ld [%l7 + %l1], %o0, %tie_ld(symbol)
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add %g7, %o0, %o0, %tie_add(symbol)
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sethi %tie_hi22(symbol), %l1
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add %l1, %tie_lo10(symbol), %l1
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ldx [%l7 + %l1], %o0, %tie_ldx(symbol)
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add %g7, %o0, %o0, %tie_add(symbol)
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</pre></div>
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<p>And finally, Local Exec:
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</p>
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<div class="example">
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<pre class="example">sethi %tle_hix22(symbol), %l1
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add %l1, %tle_lox10(symbol), %l1
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add %g7, %l1, %l1
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</pre></div>
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<p>When assembling for 64-bit, and a secondary constant addend is
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specified in an address expression that would normally generate
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an <code>R_SPARC_LO10</code> relocation, the assembler will emit an
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<code>R_SPARC_OLO10</code> instead.
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</p>
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<hr>
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<div class="header">
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<p>
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Next: <a href="Sparc_002dSize_002dTranslations.html#Sparc_002dSize_002dTranslations" accesskey="n" rel="next">Sparc-Size-Translations</a>, Previous: <a href="Sparc_002dConstants.html#Sparc_002dConstants" accesskey="p" rel="prev">Sparc-Constants</a>, Up: <a href="Sparc_002dSyntax.html#Sparc_002dSyntax" accesskey="u" rel="up">Sparc-Syntax</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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