| <html lang="en"> |
| <head> |
| <title>PowerPC64 ELF64 - Untitled</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Untitled"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Machine-Dependent.html#Machine-Dependent" title="Machine Dependent"> |
| <link rel="prev" href="PowerPC-ELF32.html#PowerPC-ELF32" title="PowerPC ELF32"> |
| <link rel="next" href="SPU-ELF.html#SPU-ELF" title="SPU ELF"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| This file documents the GNU linker LD |
| (Sourcery G++ Lite 2011.03-41) |
| version 2.20.51. |
| |
| Copyright (C) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, |
| 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. |
| |
| Permission is granted to copy, distribute and/or modify this document |
| under the terms of the GNU Free Documentation License, Version 1.3 |
| or any later version published by the Free Software Foundation; |
| with no Invariant Sections, with no Front-Cover Texts, and with no |
| Back-Cover Texts. A copy of the license is included in the |
| section entitled ``GNU Free Documentation License''.--> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <style type="text/css"><!-- |
| pre.display { font-family:inherit } |
| pre.format { font-family:inherit } |
| pre.smalldisplay { font-family:inherit; font-size:smaller } |
| pre.smallformat { font-family:inherit; font-size:smaller } |
| pre.smallexample { font-size:smaller } |
| pre.smalllisp { font-size:smaller } |
| span.sc { font-variant:small-caps } |
| span.roman { font-family:serif; font-weight:normal; } |
| span.sansserif { font-family:sans-serif; font-weight:normal; } |
| --></style> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="PowerPC64-ELF64"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="SPU-ELF.html#SPU-ELF">SPU ELF</a>, |
| Previous: <a rel="previous" accesskey="p" href="PowerPC-ELF32.html#PowerPC-ELF32">PowerPC ELF32</a>, |
| Up: <a rel="up" accesskey="u" href="Machine-Dependent.html#Machine-Dependent">Machine Dependent</a> |
| <hr> |
| </div> |
| |
| <h3 class="section">4.10 <samp><span class="command">ld</span></samp> and PowerPC64 64-bit ELF Support</h3> |
| |
| <p><a name="index-PowerPC64-ELF64-options-626"></a> |
| |
| <a name="index-PowerPC64-stub-grouping-627"></a> |
| <a name="index-g_t_002d_002dstub_002dgroup_002dsize-628"></a> |
| <dl><dt><samp><span class="option">--stub-group-size</span></samp><dd>Long branch stubs, PLT call stubs and TOC adjusting stubs are placed |
| by <samp><span class="command">ld</span></samp> in stub sections located between groups of input sections. |
| ‘<samp><span class="samp">--stub-group-size</span></samp>’ specifies the maximum size of a group of input |
| sections handled by one stub section. Since branch offsets are signed, |
| a stub section may serve two groups of input sections, one group before |
| the stub section, and one group after it. However, when using |
| conditional branches that require stubs, it may be better (for branch |
| prediction) that stub sections only serve one group of input sections. |
| A negative value for ‘<samp><span class="samp">N</span></samp>’ chooses this scheme, ensuring that |
| branches to stubs always use a negative offset. Two special values of |
| ‘<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 |
| <samp><span class="command">ld</span></samp> to automatically size input section groups for the branch types |
| detected, with the same behaviour regarding stub placement as other |
| positive or negative values of ‘<samp><span class="samp">N</span></samp>’ respectively. |
| |
| <p>Note that ‘<samp><span class="samp">--stub-group-size</span></samp>’ does not split input sections. A |
| single input section larger than the group size specified will of course |
| create a larger group (of one section). If input sections are too |
| large, it may not be possible for a branch to reach its stub. |
| |
| <p><a name="index-PowerPC64-stub-symbols-629"></a><a name="index-g_t_002d_002demit_002dstub_002dsyms-630"></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 |
| symbol that encodes the stub type and destination. |
| |
| <p><a name="index-PowerPC64-dot-symbols-631"></a><a name="index-g_t_002d_002ddotsyms-632"></a><a name="index-g_t_002d_002dno_002ddotsyms-633"></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 |
| in a version script. Older PowerPC64 compilers emitted both a |
| function descriptor symbol with the same name as the function, and a |
| code entry symbol with the name prefixed by a dot (‘<samp><span class="samp">.</span></samp>’). To |
| properly version a function ‘<samp><span class="samp">foo</span></samp>’, the version script thus needs |
| to control both ‘<samp><span class="samp">foo</span></samp>’ and ‘<samp><span class="samp">.foo</span></samp>’. The option |
| ‘<samp><span class="samp">--dotsyms</span></samp>’, on by default, automatically adds the required |
| dot-prefixed patterns. Use ‘<samp><span class="samp">--no-dotsyms</span></samp>’ to disable this |
| feature. |
| |
| <p><a name="index-PowerPC64-TLS-optimization-634"></a><a name="index-g_t_002d_002dno_002dtls_002doptimize-635"></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 |
| sequences used to access Thread-Local Storage. Use this option to |
| disable the optimization. |
| |
| <p><a name="index-PowerPC64-OPD-optimization-636"></a><a name="index-g_t_002d_002dno_002dopd_002doptimize-637"></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 |
| corresponding to deleted link-once functions, or functions removed by |
| the action of ‘<samp><span class="samp">--gc-sections</span></samp>’ or linker script <code>/DISCARD/</code>. |
| Use this option to disable <code>.opd</code> optimization. |
| |
| <p><a name="index-PowerPC64-OPD-spacing-638"></a><a name="index-g_t_002d_002dnon_002doverlapping_002dopd-639"></a><br><dt><samp><span class="option">--non-overlapping-opd</span></samp><dd>Some PowerPC64 compilers have an option to generate compressed |
| <code>.opd</code> entries spaced 16 bytes apart, overlapping the third word, |
| the static chain pointer (unused in C) with the first word of the next |
| entry. This option expands such entries to the full 24 bytes. |
| |
| <p><a name="index-PowerPC64-TOC-optimization-640"></a><a name="index-g_t_002d_002dno_002dtoc_002doptimize-641"></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 |
| entries. Such entries are detected by examining relocations that |
| reference the TOC in code sections. A reloc in a deleted code section |
| marks a TOC word as unneeded, while a reloc in a kept code section |
| marks a TOC word as needed. Since the TOC may reference itself, TOC |
| relocs are also examined. TOC words marked as both needed and |
| unneeded will of course be kept. TOC words without any referencing |
| reloc are assumed to be part of a multi-word entry, and are kept or |
| discarded as per the nearest marked preceding word. This works |
| reliably for compiler generated code, but may be incorrect if assembly |
| code is used to insert TOC entries. Use this option to disable the |
| optimization. |
| |
| <p><a name="index-PowerPC64-multi_002dTOC-642"></a><a name="index-g_t_002d_002dno_002dmulti_002dtoc-643"></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 |
| entries are accessed with a 16-bit offset from r2. This limits the |
| total TOC size to 64K. PowerPC64 <samp><span class="command">ld</span></samp> extends this limit by |
| grouping code sections such that each group uses less than 64K for its |
| TOC entries, then inserts r2 adjusting stubs between inter-group |
| calls. <samp><span class="command">ld</span></samp> does not split apart input sections, so cannot |
| help if a single input file has a <code>.toc</code> section that exceeds |
| 64K, most likely from linking multiple files with <samp><span class="command">ld -r</span></samp>. |
| Use this option to turn off this feature. |
| </dl> |
| |
| </body></html> |
| |
