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194 lines
9.9 KiB
HTML
4 years ago
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<html lang="en">
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<head>
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<title>Sparc-Relocs - Using as</title>
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<meta http-equiv="Content-Type" content="text/html">
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<meta name="description" content="Using as">
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<meta name="generator" content="makeinfo 4.13">
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<link title="Top" rel="start" href="index.html#Top">
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<link rel="up" href="Sparc_002dSyntax.html#Sparc_002dSyntax" title="Sparc-Syntax">
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<link rel="prev" href="Sparc_002dConstants.html#Sparc_002dConstants" title="Sparc-Constants">
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<link rel="next" href="Sparc_002dSize_002dTranslations.html#Sparc_002dSize_002dTranslations" title="Sparc-Size-Translations">
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<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
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<!--
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This file documents the GNU Assembler "as".
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Copyright (C) 1991-2015 Free Software Foundation, Inc.
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3
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or any later version published by the Free Software Foundation;
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with no Invariant Sections, with no Front-Cover Texts, and with no
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Back-Cover Texts. A copy of the license is included in the
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section entitled ``GNU Free Documentation License''.
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-->
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<style type="text/css"><!--
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--></style>
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</head>
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<body>
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<div class="node">
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<a name="Sparc-Relocs"></a>
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<a name="Sparc_002dRelocs"></a>
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<p>
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Next: <a rel="next" accesskey="n" href="Sparc_002dSize_002dTranslations.html#Sparc_002dSize_002dTranslations">Sparc-Size-Translations</a>,
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Previous: <a rel="previous" accesskey="p" href="Sparc_002dConstants.html#Sparc_002dConstants">Sparc-Constants</a>,
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Up: <a rel="up" accesskey="u" href="Sparc_002dSyntax.html#Sparc_002dSyntax">Sparc-Syntax</a>
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<hr>
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</div>
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<h5 class="subsubsection">9.42.3.4 Relocations</h5>
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<p><a name="index-Sparc-relocations-2026"></a><a name="index-relocations_002c-Sparc-2027"></a>
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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><code>R_SPARC_HI22</code> is obtained using ‘<samp><span class="samp">%hi</span></samp>’ and <code>R_SPARC_LO10</code>
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is obtained using ‘<samp><span class="samp">%lo</span></samp>’. Likewise <code>R_SPARC_HIX22</code> is
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obtained from ‘<samp><span class="samp">%hix</span></samp>’ and <code>R_SPARC_LOX10</code> is obtained
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using ‘<samp><span class="samp">%lox</span></samp>’. For 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>
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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>V9 code model relocations can be requested as follows:
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<ul>
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<li><code>R_SPARC_HH22</code> is requested using ‘<samp><span class="samp">%hh</span></samp>’. It can
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also be generated using ‘<samp><span class="samp">%uhi</span></samp>’.
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<li><code>R_SPARC_HM10</code> is requested using ‘<samp><span class="samp">%hm</span></samp>’. It can
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also be generated using ‘<samp><span class="samp">%ulo</span></samp>’.
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<li><code>R_SPARC_LM22</code> is requested using ‘<samp><span class="samp">%lm</span></samp>’.
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<li><code>R_SPARC_H44</code> is requested using ‘<samp><span class="samp">%h44</span></samp>’.
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<li><code>R_SPARC_M44</code> is requested using ‘<samp><span class="samp">%m44</span></samp>’.
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<li><code>R_SPARC_L44</code> is requested using ‘<samp><span class="samp">%l44</span></samp>’ or ‘<samp><span class="samp">%l34</span></samp>’.
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<li><code>R_SPARC_H34</code> is requested using ‘<samp><span class="samp">%h34</span></samp>’.
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</ul>
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<p>The ‘<samp><span class="samp">%l34</span></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>The ‘<samp><span class="samp">%h34</span></samp>’ and ‘<samp><span class="samp">%l34</span></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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<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>
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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><span class="samp">%pc22</span></samp>’. Likewise, the
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<code>R_SPARC_PC10</code> relocation can be obtained using ‘<samp><span class="samp">%pc10</span></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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<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>
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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><span class="samp">%gdop_hix22</span></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><span class="samp">%gdop_lox10</span></samp>’. Likewise, <code>R_SPARC_GOTDATA_OP</code> can be
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obtained by enclosing an operand inside of ‘<samp><span class="samp">%gdop</span></samp>’.
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For example, assuming the GOT base is in register <code>%l7</code>:
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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>
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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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<ul>
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<li><code>R_SPARC_TLS_GD_HI22</code> is requested using ‘<samp><span class="samp">%tgd_hi22</span></samp>’.
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<li><code>R_SPARC_TLS_GD_LO10</code> is requested using ‘<samp><span class="samp">%tgd_lo10</span></samp>’.
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<li><code>R_SPARC_TLS_GD_ADD</code> is requested using ‘<samp><span class="samp">%tgd_add</span></samp>’.
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<li><code>R_SPARC_TLS_GD_CALL</code> is requested using ‘<samp><span class="samp">%tgd_call</span></samp>’.
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<li><code>R_SPARC_TLS_LDM_HI22</code> is requested using ‘<samp><span class="samp">%tldm_hi22</span></samp>’.
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<li><code>R_SPARC_TLS_LDM_LO10</code> is requested using ‘<samp><span class="samp">%tldm_lo10</span></samp>’.
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<li><code>R_SPARC_TLS_LDM_ADD</code> is requested using ‘<samp><span class="samp">%tldm_add</span></samp>’.
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<li><code>R_SPARC_TLS_LDM_CALL</code> is requested using ‘<samp><span class="samp">%tldm_call</span></samp>’.
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<li><code>R_SPARC_TLS_LDO_HIX22</code> is requested using ‘<samp><span class="samp">%tldo_hix22</span></samp>’.
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<li><code>R_SPARC_TLS_LDO_LOX10</code> is requested using ‘<samp><span class="samp">%tldo_lox10</span></samp>’.
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<li><code>R_SPARC_TLS_LDO_ADD</code> is requested using ‘<samp><span class="samp">%tldo_add</span></samp>’.
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<li><code>R_SPARC_TLS_IE_HI22</code> is requested using ‘<samp><span class="samp">%tie_hi22</span></samp>’.
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<li><code>R_SPARC_TLS_IE_LO10</code> is requested using ‘<samp><span class="samp">%tie_lo10</span></samp>’.
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<li><code>R_SPARC_TLS_IE_LD</code> is requested using ‘<samp><span class="samp">%tie_ld</span></samp>’.
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<li><code>R_SPARC_TLS_IE_LDX</code> is requested using ‘<samp><span class="samp">%tie_ldx</span></samp>’.
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<li><code>R_SPARC_TLS_IE_ADD</code> is requested using ‘<samp><span class="samp">%tie_add</span></samp>’.
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<li><code>R_SPARC_TLS_LE_HIX22</code> is requested using ‘<samp><span class="samp">%tle_hix22</span></samp>’.
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<li><code>R_SPARC_TLS_LE_LOX10</code> is requested using ‘<samp><span class="samp">%tle_lox10</span></samp>’.
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</ul>
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<p>Here are some example TLS model sequences.
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<p>First, General Dynamic:
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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>
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<p>Local Dynamic:
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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>
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<p>Initial Exec:
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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>
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<p>And finally, Local Exec:
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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>
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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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</body></html>
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