1<html lang="en"> 2<head> 3<title>PowerPC64 ELF64 - Untitled</title> 4<meta http-equiv="Content-Type" content="text/html"> 5<meta name="description" content="Untitled"> 6<meta name="generator" content="makeinfo 4.13"> 7<link title="Top" rel="start" href="index.html#Top"> 8<link rel="up" href="Machine-Dependent.html#Machine-Dependent" title="Machine Dependent"> 9<link rel="prev" href="PowerPC-ELF32.html#PowerPC-ELF32" title="PowerPC ELF32"> 10<link rel="next" href="SPU-ELF.html#SPU-ELF" title="SPU ELF"> 11<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> 12<!-- 13This file documents the GNU linker LD 14(Sourcery CodeBench Lite 2011.09-69) 15version 2.21.53. 16 17Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 182001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. 19 20Permission is granted to copy, distribute and/or modify this document 21under the terms of the GNU Free Documentation License, Version 1.3 22or any later version published by the Free Software Foundation; 23with no Invariant Sections, with no Front-Cover Texts, and with no 24Back-Cover Texts. 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Since branch offsets are signed, 60a stub section may serve two groups of input sections, one group before 61the stub section, and one group after it. However, when using 62conditional branches that require stubs, it may be better (for branch 63prediction) that stub sections only serve one group of input sections. 64A negative value for ‘<samp><span class="samp">N</span></samp>’ chooses this scheme, ensuring that 65branches to stubs always use a negative offset. Two special values of 66‘<samp><span class="samp">N</span></samp>’ are recognized, ‘<samp><span class="samp">1</span></samp>’ and ‘<samp><span class="samp">-1</span></samp>’. These both instruct 67<samp><span class="command">ld</span></samp> to automatically size input section groups for the branch types 68detected, with the same behaviour regarding stub placement as other 69positive or negative values of ‘<samp><span class="samp">N</span></samp>’ respectively. 70 71 <p>Note that ‘<samp><span class="samp">--stub-group-size</span></samp>’ does not split input sections. A 72single input section larger than the group size specified will of course 73create a larger group (of one section). If input sections are too 74large, it may not be possible for a branch to reach its stub. 75 76 <p><a name="index-PowerPC64-stub-symbols-645"></a><a name="index-g_t_002d_002demit_002dstub_002dsyms-646"></a><br><dt><samp><span class="option">--emit-stub-syms</span></samp><dd>This option causes <samp><span class="command">ld</span></samp> to label linker stubs with a local 77symbol that encodes the stub type and destination. 78 79 <p><a name="index-PowerPC64-dot-symbols-647"></a><a name="index-g_t_002d_002ddotsyms-648"></a><a name="index-g_t_002d_002dno_002ddotsyms-649"></a><br><dt><samp><span class="option">--dotsyms, --no-dotsyms</span></samp><dd>These two options control how <samp><span class="command">ld</span></samp> interprets version patterns 80in a version script. Older PowerPC64 compilers emitted both a 81function descriptor symbol with the same name as the function, and a 82code entry symbol with the name prefixed by a dot (‘<samp><span class="samp">.</span></samp>’). To 83properly version a function ‘<samp><span class="samp">foo</span></samp>’, the version script thus needs 84to control both ‘<samp><span class="samp">foo</span></samp>’ and ‘<samp><span class="samp">.foo</span></samp>’. The option 85‘<samp><span class="samp">--dotsyms</span></samp>’, on by default, automatically adds the required 86dot-prefixed patterns. Use ‘<samp><span class="samp">--no-dotsyms</span></samp>’ to disable this 87feature. 88 89 <p><a name="index-PowerPC64-TLS-optimization-650"></a><a name="index-g_t_002d_002dno_002dtls_002doptimize-651"></a><br><dt><samp><span class="option">--no-tls-optimize</span></samp><dd>PowerPC64 <samp><span class="command">ld</span></samp> normally performs some optimization of code 90sequences used to access Thread-Local Storage. Use this option to 91disable the optimization. 92 93 <p><a name="index-PowerPC64-OPD-optimization-652"></a><a name="index-g_t_002d_002dno_002dopd_002doptimize-653"></a><br><dt><samp><span class="option">--no-opd-optimize</span></samp><dd>PowerPC64 <samp><span class="command">ld</span></samp> normally removes <code>.opd</code> section entries 94corresponding to deleted link-once functions, or functions removed by 95the action of ‘<samp><span class="samp">--gc-sections</span></samp>’ or linker script <code>/DISCARD/</code>. 96Use this option to disable <code>.opd</code> optimization. 97 98 <p><a name="index-PowerPC64-OPD-spacing-654"></a><a name="index-g_t_002d_002dnon_002doverlapping_002dopd-655"></a><br><dt><samp><span class="option">--non-overlapping-opd</span></samp><dd>Some PowerPC64 compilers have an option to generate compressed 99<code>.opd</code> entries spaced 16 bytes apart, overlapping the third word, 100the static chain pointer (unused in C) with the first word of the next 101entry. This option expands such entries to the full 24 bytes. 102 103 <p><a name="index-PowerPC64-TOC-optimization-656"></a><a name="index-g_t_002d_002dno_002dtoc_002doptimize-657"></a><br><dt><samp><span class="option">--no-toc-optimize</span></samp><dd>PowerPC64 <samp><span class="command">ld</span></samp> normally removes unused <code>.toc</code> section 104entries. Such entries are detected by examining relocations that 105reference the TOC in code sections. A reloc in a deleted code section 106marks a TOC word as unneeded, while a reloc in a kept code section 107marks a TOC word as needed. Since the TOC may reference itself, TOC 108relocs are also examined. TOC words marked as both needed and 109unneeded will of course be kept. TOC words without any referencing 110reloc are assumed to be part of a multi-word entry, and are kept or 111discarded as per the nearest marked preceding word. This works 112reliably for compiler generated code, but may be incorrect if assembly 113code is used to insert TOC entries. Use this option to disable the 114optimization. 115 116 <p><a name="index-PowerPC64-multi_002dTOC-658"></a><a name="index-g_t_002d_002dno_002dmulti_002dtoc-659"></a><br><dt><samp><span class="option">--no-multi-toc</span></samp><dd>By default, PowerPC64 GCC generates code for a TOC model where TOC 117entries are accessed with a 16-bit offset from r2. This limits the 118total TOC size to 64K. PowerPC64 <samp><span class="command">ld</span></samp> extends this limit by 119grouping code sections such that each group uses less than 64K for its 120TOC entries, then inserts r2 adjusting stubs between inter-group 121calls. <samp><span class="command">ld</span></samp> does not split apart input sections, so cannot 122help if a single input file has a <code>.toc</code> section that exceeds 12364K, most likely from linking multiple files with <samp><span class="command">ld -r</span></samp>. 124Use this option to turn off this feature. 125</dl> 126 127 </body></html> 128 129