506 lines
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506 lines
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<title>Using the GNU Compiler Collection (GCC): M680x0 Options</title>
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<meta name="description" content="Using the GNU Compiler Collection (GCC): M680x0 Options">
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<link href="Option-Index.html#Option-Index" rel="index" title="Option Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="Submodel-Options.html#Submodel-Options" rel="up" title="Submodel Options">
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<link href="MCore-Options.html#MCore-Options" rel="next" title="MCore Options">
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<link href="M32R_002fD-Options.html#M32R_002fD-Options" rel="prev" title="M32R/D Options">
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<a name="M680x0-Options"></a>
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<div class="header">
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<p>
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Next: <a href="MCore-Options.html#MCore-Options" accesskey="n" rel="next">MCore Options</a>, Previous: <a href="M32R_002fD-Options.html#M32R_002fD-Options" accesskey="p" rel="prev">M32R/D Options</a>, Up: <a href="Submodel-Options.html#Submodel-Options" accesskey="u" rel="up">Submodel Options</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="M680x0-Options-1"></a>
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<h4 class="subsection">3.18.22 M680x0 Options</h4>
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<a name="index-M680x0-options"></a>
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<p>These are the ‘<samp>-m</samp>’ options defined for M680x0 and ColdFire processors.
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The default settings depend on which architecture was selected when
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the compiler was configured; the defaults for the most common choices
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are given below.
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</p>
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<dl compact="compact">
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<dt><code>-march=<var>arch</var></code></dt>
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<dd><a name="index-march-6"></a>
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<p>Generate code for a specific M680x0 or ColdFire instruction set
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architecture. Permissible values of <var>arch</var> for M680x0
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architectures are: ‘<samp>68000</samp>’, ‘<samp>68010</samp>’, ‘<samp>68020</samp>’,
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‘<samp>68030</samp>’, ‘<samp>68040</samp>’, ‘<samp>68060</samp>’ and ‘<samp>cpu32</samp>’. ColdFire
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architectures are selected according to Freescale’s ISA classification
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and the permissible values are: ‘<samp>isaa</samp>’, ‘<samp>isaaplus</samp>’,
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‘<samp>isab</samp>’ and ‘<samp>isac</samp>’.
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</p>
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<p>GCC defines a macro <code>__mcf<var>arch</var>__</code> whenever it is generating
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code for a ColdFire target. The <var>arch</var> in this macro is one of the
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<samp>-march</samp> arguments given above.
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</p>
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<p>When used together, <samp>-march</samp> and <samp>-mtune</samp> select code
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that runs on a family of similar processors but that is optimized
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for a particular microarchitecture.
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</p>
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</dd>
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<dt><code>-mcpu=<var>cpu</var></code></dt>
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<dd><a name="index-mcpu-6"></a>
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<p>Generate code for a specific M680x0 or ColdFire processor.
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The M680x0 <var>cpu</var>s are: ‘<samp>68000</samp>’, ‘<samp>68010</samp>’, ‘<samp>68020</samp>’,
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‘<samp>68030</samp>’, ‘<samp>68040</samp>’, ‘<samp>68060</samp>’, ‘<samp>68302</samp>’, ‘<samp>68332</samp>’
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and ‘<samp>cpu32</samp>’. The ColdFire <var>cpu</var>s are given by the table
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below, which also classifies the CPUs into families:
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</p>
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<table>
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<tr><td width="20%"><strong>Family</strong></td><td width="80%"><strong>‘<samp>-mcpu</samp>’ arguments</strong></td></tr>
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<tr><td width="20%">‘<samp>51</samp>’</td><td width="80%">‘<samp>51</samp>’ ‘<samp>51ac</samp>’ ‘<samp>51ag</samp>’ ‘<samp>51cn</samp>’ ‘<samp>51em</samp>’ ‘<samp>51je</samp>’ ‘<samp>51jf</samp>’ ‘<samp>51jg</samp>’ ‘<samp>51jm</samp>’ ‘<samp>51mm</samp>’ ‘<samp>51qe</samp>’ ‘<samp>51qm</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5206</samp>’</td><td width="80%">‘<samp>5202</samp>’ ‘<samp>5204</samp>’ ‘<samp>5206</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5206e</samp>’</td><td width="80%">‘<samp>5206e</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5208</samp>’</td><td width="80%">‘<samp>5207</samp>’ ‘<samp>5208</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5211a</samp>’</td><td width="80%">‘<samp>5210a</samp>’ ‘<samp>5211a</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5213</samp>’</td><td width="80%">‘<samp>5211</samp>’ ‘<samp>5212</samp>’ ‘<samp>5213</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5216</samp>’</td><td width="80%">‘<samp>5214</samp>’ ‘<samp>5216</samp>’</td></tr>
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<tr><td width="20%">‘<samp>52235</samp>’</td><td width="80%">‘<samp>52230</samp>’ ‘<samp>52231</samp>’ ‘<samp>52232</samp>’ ‘<samp>52233</samp>’ ‘<samp>52234</samp>’ ‘<samp>52235</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5225</samp>’</td><td width="80%">‘<samp>5224</samp>’ ‘<samp>5225</samp>’</td></tr>
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<tr><td width="20%">‘<samp>52259</samp>’</td><td width="80%">‘<samp>52252</samp>’ ‘<samp>52254</samp>’ ‘<samp>52255</samp>’ ‘<samp>52256</samp>’ ‘<samp>52258</samp>’ ‘<samp>52259</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5235</samp>’</td><td width="80%">‘<samp>5232</samp>’ ‘<samp>5233</samp>’ ‘<samp>5234</samp>’ ‘<samp>5235</samp>’ ‘<samp>523x</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5249</samp>’</td><td width="80%">‘<samp>5249</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5250</samp>’</td><td width="80%">‘<samp>5250</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5271</samp>’</td><td width="80%">‘<samp>5270</samp>’ ‘<samp>5271</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5272</samp>’</td><td width="80%">‘<samp>5272</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5275</samp>’</td><td width="80%">‘<samp>5274</samp>’ ‘<samp>5275</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5282</samp>’</td><td width="80%">‘<samp>5280</samp>’ ‘<samp>5281</samp>’ ‘<samp>5282</samp>’ ‘<samp>528x</samp>’</td></tr>
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<tr><td width="20%">‘<samp>53017</samp>’</td><td width="80%">‘<samp>53011</samp>’ ‘<samp>53012</samp>’ ‘<samp>53013</samp>’ ‘<samp>53014</samp>’ ‘<samp>53015</samp>’ ‘<samp>53016</samp>’ ‘<samp>53017</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5307</samp>’</td><td width="80%">‘<samp>5307</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5329</samp>’</td><td width="80%">‘<samp>5327</samp>’ ‘<samp>5328</samp>’ ‘<samp>5329</samp>’ ‘<samp>532x</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5373</samp>’</td><td width="80%">‘<samp>5372</samp>’ ‘<samp>5373</samp>’ ‘<samp>537x</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5407</samp>’</td><td width="80%">‘<samp>5407</samp>’</td></tr>
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<tr><td width="20%">‘<samp>5475</samp>’</td><td width="80%">‘<samp>5470</samp>’ ‘<samp>5471</samp>’ ‘<samp>5472</samp>’ ‘<samp>5473</samp>’ ‘<samp>5474</samp>’ ‘<samp>5475</samp>’ ‘<samp>547x</samp>’ ‘<samp>5480</samp>’ ‘<samp>5481</samp>’ ‘<samp>5482</samp>’ ‘<samp>5483</samp>’ ‘<samp>5484</samp>’ ‘<samp>5485</samp>’</td></tr>
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</table>
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<p><samp>-mcpu=<var>cpu</var></samp> overrides <samp>-march=<var>arch</var></samp> if
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<var>arch</var> is compatible with <var>cpu</var>. Other combinations of
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<samp>-mcpu</samp> and <samp>-march</samp> are rejected.
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</p>
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<p>GCC defines the macro <code>__mcf_cpu_<var>cpu</var></code> when ColdFire target
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<var>cpu</var> is selected. It also defines <code>__mcf_family_<var>family</var></code>,
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where the value of <var>family</var> is given by the table above.
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</p>
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</dd>
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<dt><code>-mtune=<var>tune</var></code></dt>
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<dd><a name="index-mtune-7"></a>
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<p>Tune the code for a particular microarchitecture within the
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constraints set by <samp>-march</samp> and <samp>-mcpu</samp>.
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The M680x0 microarchitectures are: ‘<samp>68000</samp>’, ‘<samp>68010</samp>’,
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‘<samp>68020</samp>’, ‘<samp>68030</samp>’, ‘<samp>68040</samp>’, ‘<samp>68060</samp>’
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and ‘<samp>cpu32</samp>’. The ColdFire microarchitectures
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are: ‘<samp>cfv1</samp>’, ‘<samp>cfv2</samp>’, ‘<samp>cfv3</samp>’, ‘<samp>cfv4</samp>’ and ‘<samp>cfv4e</samp>’.
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</p>
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<p>You can also use <samp>-mtune=68020-40</samp> for code that needs
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to run relatively well on 68020, 68030 and 68040 targets.
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<samp>-mtune=68020-60</samp> is similar but includes 68060 targets
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as well. These two options select the same tuning decisions as
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<samp>-m68020-40</samp> and <samp>-m68020-60</samp> respectively.
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</p>
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<p>GCC defines the macros <code>__mc<var>arch</var></code> and <code>__mc<var>arch</var>__</code>
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when tuning for 680x0 architecture <var>arch</var>. It also defines
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<code>mc<var>arch</var></code> unless either <samp>-ansi</samp> or a non-GNU <samp>-std</samp>
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option is used. If GCC is tuning for a range of architectures,
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as selected by <samp>-mtune=68020-40</samp> or <samp>-mtune=68020-60</samp>,
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it defines the macros for every architecture in the range.
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</p>
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<p>GCC also defines the macro <code>__m<var>uarch</var>__</code> when tuning for
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ColdFire microarchitecture <var>uarch</var>, where <var>uarch</var> is one
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of the arguments given above.
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</p>
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</dd>
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<dt><code>-m68000</code></dt>
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<dt><code>-mc68000</code></dt>
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<dd><a name="index-m68000"></a>
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<a name="index-mc68000"></a>
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<p>Generate output for a 68000. This is the default
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when the compiler is configured for 68000-based systems.
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It is equivalent to <samp>-march=68000</samp>.
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</p>
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<p>Use this option for microcontrollers with a 68000 or EC000 core,
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including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.
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</p>
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</dd>
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<dt><code>-m68010</code></dt>
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<dd><a name="index-m68010"></a>
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<p>Generate output for a 68010. This is the default
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when the compiler is configured for 68010-based systems.
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It is equivalent to <samp>-march=68010</samp>.
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</p>
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</dd>
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<dt><code>-m68020</code></dt>
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<dt><code>-mc68020</code></dt>
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<dd><a name="index-m68020"></a>
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<a name="index-mc68020"></a>
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<p>Generate output for a 68020. This is the default
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when the compiler is configured for 68020-based systems.
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It is equivalent to <samp>-march=68020</samp>.
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</p>
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</dd>
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<dt><code>-m68030</code></dt>
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<dd><a name="index-m68030"></a>
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<p>Generate output for a 68030. This is the default when the compiler is
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configured for 68030-based systems. It is equivalent to
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<samp>-march=68030</samp>.
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</p>
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</dd>
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<dt><code>-m68040</code></dt>
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<dd><a name="index-m68040"></a>
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<p>Generate output for a 68040. This is the default when the compiler is
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configured for 68040-based systems. It is equivalent to
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<samp>-march=68040</samp>.
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</p>
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<p>This option inhibits the use of 68881/68882 instructions that have to be
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emulated by software on the 68040. Use this option if your 68040 does not
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have code to emulate those instructions.
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</p>
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</dd>
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<dt><code>-m68060</code></dt>
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<dd><a name="index-m68060"></a>
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<p>Generate output for a 68060. This is the default when the compiler is
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configured for 68060-based systems. It is equivalent to
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<samp>-march=68060</samp>.
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</p>
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<p>This option inhibits the use of 68020 and 68881/68882 instructions that
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have to be emulated by software on the 68060. Use this option if your 68060
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does not have code to emulate those instructions.
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</p>
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</dd>
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<dt><code>-mcpu32</code></dt>
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<dd><a name="index-mcpu32"></a>
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<p>Generate output for a CPU32. This is the default
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when the compiler is configured for CPU32-based systems.
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It is equivalent to <samp>-march=cpu32</samp>.
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</p>
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<p>Use this option for microcontrollers with a
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CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334,
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68336, 68340, 68341, 68349 and 68360.
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</p>
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</dd>
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<dt><code>-m5200</code></dt>
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<dd><a name="index-m5200"></a>
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<p>Generate output for a 520X ColdFire CPU. This is the default
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when the compiler is configured for 520X-based systems.
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It is equivalent to <samp>-mcpu=5206</samp>, and is now deprecated
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in favor of that option.
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</p>
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<p>Use this option for microcontroller with a 5200 core, including
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the MCF5202, MCF5203, MCF5204 and MCF5206.
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</p>
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</dd>
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<dt><code>-m5206e</code></dt>
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<dd><a name="index-m5206e"></a>
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<p>Generate output for a 5206e ColdFire CPU. The option is now
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deprecated in favor of the equivalent <samp>-mcpu=5206e</samp>.
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</p>
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</dd>
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<dt><code>-m528x</code></dt>
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<dd><a name="index-m528x"></a>
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<p>Generate output for a member of the ColdFire 528X family.
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The option is now deprecated in favor of the equivalent
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<samp>-mcpu=528x</samp>.
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</p>
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</dd>
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<dt><code>-m5307</code></dt>
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<dd><a name="index-m5307"></a>
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<p>Generate output for a ColdFire 5307 CPU. The option is now deprecated
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in favor of the equivalent <samp>-mcpu=5307</samp>.
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</p>
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</dd>
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<dt><code>-m5407</code></dt>
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<dd><a name="index-m5407"></a>
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<p>Generate output for a ColdFire 5407 CPU. The option is now deprecated
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in favor of the equivalent <samp>-mcpu=5407</samp>.
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</p>
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</dd>
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<dt><code>-mcfv4e</code></dt>
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<dd><a name="index-mcfv4e"></a>
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<p>Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).
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This includes use of hardware floating-point instructions.
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The option is equivalent to <samp>-mcpu=547x</samp>, and is now
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deprecated in favor of that option.
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</p>
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</dd>
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<dt><code>-m68020-40</code></dt>
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<dd><a name="index-m68020_002d40"></a>
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<p>Generate output for a 68040, without using any of the new instructions.
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This results in code that can run relatively efficiently on either a
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68020/68881 or a 68030 or a 68040. The generated code does use the
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68881 instructions that are emulated on the 68040.
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</p>
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<p>The option is equivalent to <samp>-march=68020</samp> <samp>-mtune=68020-40</samp>.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-m68020-60</code></dt>
|
|
<dd><a name="index-m68020_002d60"></a>
|
|
<p>Generate output for a 68060, without using any of the new instructions.
|
|
This results in code that can run relatively efficiently on either a
|
|
68020/68881 or a 68030 or a 68040. The generated code does use the
|
|
68881 instructions that are emulated on the 68060.
|
|
</p>
|
|
<p>The option is equivalent to <samp>-march=68020</samp> <samp>-mtune=68020-60</samp>.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mhard-float</code></dt>
|
|
<dt><code>-m68881</code></dt>
|
|
<dd><a name="index-mhard_002dfloat-1"></a>
|
|
<a name="index-m68881"></a>
|
|
<p>Generate floating-point instructions. This is the default for 68020
|
|
and above, and for ColdFire devices that have an FPU. It defines the
|
|
macro <code>__HAVE_68881__</code> on M680x0 targets and <code>__mcffpu__</code>
|
|
on ColdFire targets.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-msoft-float</code></dt>
|
|
<dd><a name="index-msoft_002dfloat-4"></a>
|
|
<p>Do not generate floating-point instructions; use library calls instead.
|
|
This is the default for 68000, 68010, and 68832 targets. It is also
|
|
the default for ColdFire devices that have no FPU.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mdiv</code></dt>
|
|
<dt><code>-mno-div</code></dt>
|
|
<dd><a name="index-mdiv"></a>
|
|
<a name="index-mno_002ddiv"></a>
|
|
<p>Generate (do not generate) ColdFire hardware divide and remainder
|
|
instructions. If <samp>-march</samp> is used without <samp>-mcpu</samp>,
|
|
the default is “on” for ColdFire architectures and “off” for M680x0
|
|
architectures. Otherwise, the default is taken from the target CPU
|
|
(either the default CPU, or the one specified by <samp>-mcpu</samp>). For
|
|
example, the default is “off” for <samp>-mcpu=5206</samp> and “on” for
|
|
<samp>-mcpu=5206e</samp>.
|
|
</p>
|
|
<p>GCC defines the macro <code>__mcfhwdiv__</code> when this option is enabled.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mshort</code></dt>
|
|
<dd><a name="index-mshort"></a>
|
|
<p>Consider type <code>int</code> to be 16 bits wide, like <code>short int</code>.
|
|
Additionally, parameters passed on the stack are also aligned to a
|
|
16-bit boundary even on targets whose API mandates promotion to 32-bit.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mno-short</code></dt>
|
|
<dd><a name="index-mno_002dshort"></a>
|
|
<p>Do not consider type <code>int</code> to be 16 bits wide. This is the default.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mnobitfield</code></dt>
|
|
<dt><code>-mno-bitfield</code></dt>
|
|
<dd><a name="index-mnobitfield"></a>
|
|
<a name="index-mno_002dbitfield"></a>
|
|
<p>Do not use the bit-field instructions. The <samp>-m68000</samp>, <samp>-mcpu32</samp>
|
|
and <samp>-m5200</samp> options imply <samp><span class="nolinebreak">-mnobitfield</span></samp><!-- /@w -->.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mbitfield</code></dt>
|
|
<dd><a name="index-mbitfield"></a>
|
|
<p>Do use the bit-field instructions. The <samp>-m68020</samp> option implies
|
|
<samp>-mbitfield</samp>. This is the default if you use a configuration
|
|
designed for a 68020.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mrtd</code></dt>
|
|
<dd><a name="index-mrtd"></a>
|
|
<p>Use a different function-calling convention, in which functions
|
|
that take a fixed number of arguments return with the <code>rtd</code>
|
|
instruction, which pops their arguments while returning. This
|
|
saves one instruction in the caller since there is no need to pop
|
|
the arguments there.
|
|
</p>
|
|
<p>This calling convention is incompatible with the one normally
|
|
used on Unix, so you cannot use it if you need to call libraries
|
|
compiled with the Unix compiler.
|
|
</p>
|
|
<p>Also, you must provide function prototypes for all functions that
|
|
take variable numbers of arguments (including <code>printf</code>);
|
|
otherwise incorrect code is generated for calls to those
|
|
functions.
|
|
</p>
|
|
<p>In addition, seriously incorrect code results if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
</p>
|
|
<p>The <code>rtd</code> instruction is supported by the 68010, 68020, 68030,
|
|
68040, 68060 and CPU32 processors, but not by the 68000 or 5200.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mno-rtd</code></dt>
|
|
<dd><a name="index-mno_002drtd"></a>
|
|
<p>Do not use the calling conventions selected by <samp>-mrtd</samp>.
|
|
This is the default.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-malign-int</code></dt>
|
|
<dt><code>-mno-align-int</code></dt>
|
|
<dd><a name="index-malign_002dint"></a>
|
|
<a name="index-mno_002dalign_002dint"></a>
|
|
<p>Control whether GCC aligns <code>int</code>, <code>long</code>, <code>long long</code>,
|
|
<code>float</code>, <code>double</code>, and <code>long double</code> variables on a 32-bit
|
|
boundary (<samp>-malign-int</samp>) or a 16-bit boundary (<samp>-mno-align-int</samp>).
|
|
Aligning variables on 32-bit boundaries produces code that runs somewhat
|
|
faster on processors with 32-bit busses at the expense of more memory.
|
|
</p>
|
|
<p><strong>Warning:</strong> if you use the <samp>-malign-int</samp> switch, GCC
|
|
aligns structures containing the above types differently than
|
|
most published application binary interface specifications for the m68k.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mpcrel</code></dt>
|
|
<dd><a name="index-mpcrel"></a>
|
|
<p>Use the pc-relative addressing mode of the 68000 directly, instead of
|
|
using a global offset table. At present, this option implies <samp>-fpic</samp>,
|
|
allowing at most a 16-bit offset for pc-relative addressing. <samp>-fPIC</samp> is
|
|
not presently supported with <samp>-mpcrel</samp>, though this could be supported for
|
|
68020 and higher processors.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mno-strict-align</code></dt>
|
|
<dt><code>-mstrict-align</code></dt>
|
|
<dd><a name="index-mno_002dstrict_002dalign"></a>
|
|
<a name="index-mstrict_002dalign-1"></a>
|
|
<p>Do not (do) assume that unaligned memory references are handled by
|
|
the system.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-msep-data</code></dt>
|
|
<dd><p>Generate code that allows the data segment to be located in a different
|
|
area of memory from the text segment. This allows for execute-in-place in
|
|
an environment without virtual memory management. This option implies
|
|
<samp>-fPIC</samp>.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mno-sep-data</code></dt>
|
|
<dd><p>Generate code that assumes that the data segment follows the text segment.
|
|
This is the default.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mid-shared-library</code></dt>
|
|
<dd><p>Generate code that supports shared libraries via the library ID method.
|
|
This allows for execute-in-place and shared libraries in an environment
|
|
without virtual memory management. This option implies <samp>-fPIC</samp>.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mno-id-shared-library</code></dt>
|
|
<dd><p>Generate code that doesn’t assume ID-based shared libraries are being used.
|
|
This is the default.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mshared-library-id=n</code></dt>
|
|
<dd><p>Specifies the identification number of the ID-based shared library being
|
|
compiled. Specifying a value of 0 generates more compact code; specifying
|
|
other values forces the allocation of that number to the current
|
|
library, but is no more space- or time-efficient than omitting this option.
|
|
</p>
|
|
</dd>
|
|
<dt><code>-mxgot</code></dt>
|
|
<dt><code>-mno-xgot</code></dt>
|
|
<dd><a name="index-mxgot"></a>
|
|
<a name="index-mno_002dxgot"></a>
|
|
<p>When generating position-independent code for ColdFire, generate code
|
|
that works if the GOT has more than 8192 entries. This code is
|
|
larger and slower than code generated without this option. On M680x0
|
|
processors, this option is not needed; <samp>-fPIC</samp> suffices.
|
|
</p>
|
|
<p>GCC normally uses a single instruction to load values from the GOT.
|
|
While this is relatively efficient, it only works if the GOT
|
|
is smaller than about 64k. Anything larger causes the linker
|
|
to report an error such as:
|
|
</p>
|
|
<a name="index-relocation-truncated-to-fit-_0028ColdFire_0029"></a>
|
|
<div class="smallexample">
|
|
<pre class="smallexample">relocation truncated to fit: R_68K_GOT16O foobar
|
|
</pre></div>
|
|
|
|
<p>If this happens, you should recompile your code with <samp>-mxgot</samp>.
|
|
It should then work with very large GOTs. However, code generated with
|
|
<samp>-mxgot</samp> is less efficient, since it takes 4 instructions to fetch
|
|
the value of a global symbol.
|
|
</p>
|
|
<p>Note that some linkers, including newer versions of the GNU linker,
|
|
can create multiple GOTs and sort GOT entries. If you have such a linker,
|
|
you should only need to use <samp>-mxgot</samp> when compiling a single
|
|
object file that accesses more than 8192 GOT entries. Very few do.
|
|
</p>
|
|
<p>These options have no effect unless GCC is generating
|
|
position-independent code.
|
|
</p>
|
|
</dd>
|
|
</dl>
|
|
|
|
<hr>
|
|
<div class="header">
|
|
<p>
|
|
Next: <a href="MCore-Options.html#MCore-Options" accesskey="n" rel="next">MCore Options</a>, Previous: <a href="M32R_002fD-Options.html#M32R_002fD-Options" accesskey="p" rel="prev">M32R/D Options</a>, Up: <a href="Submodel-Options.html#Submodel-Options" accesskey="u" rel="up">Submodel Options</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
|
|
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|
|
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|
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|
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