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<h4 class="subsection">3.17.21 M680x0 Options</h4>
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<p><a name="index-M680x0-options-1816"></a>
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These are the ‘<samp><span class="samp">-m</span></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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<dl>
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<dt><code>-march=</code><var>arch</var><dd><a name="index-march-1817"></a>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><span class="samp">68000</span></samp>’, ‘<samp><span class="samp">68010</span></samp>’, ‘<samp><span class="samp">68020</span></samp>’,
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‘<samp><span class="samp">68030</span></samp>’, ‘<samp><span class="samp">68040</span></samp>’, ‘<samp><span class="samp">68060</span></samp>’ and ‘<samp><span class="samp">cpu32</span></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><span class="samp">isaa</span></samp>’, ‘<samp><span class="samp">isaaplus</span></samp>’,
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‘<samp><span class="samp">isab</span></samp>’ and ‘<samp><span class="samp">isac</span></samp>’.
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<p>GCC defines a macro <code>__mcf</code><var>arch</var><code>__</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><span class="option">-march</span></samp> arguments given above.
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<p>When used together, <samp><span class="option">-march</span></samp> and <samp><span class="option">-mtune</span></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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<br><dt><code>-mcpu=</code><var>cpu</var><dd><a name="index-mcpu-1818"></a>Generate code for a specific M680x0 or ColdFire processor.
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The M680x0 <var>cpu</var>s are: ‘<samp><span class="samp">68000</span></samp>’, ‘<samp><span class="samp">68010</span></samp>’, ‘<samp><span class="samp">68020</span></samp>’,
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‘<samp><span class="samp">68030</span></samp>’, ‘<samp><span class="samp">68040</span></samp>’, ‘<samp><span class="samp">68060</span></samp>’, ‘<samp><span class="samp">68302</span></samp>’, ‘<samp><span class="samp">68332</span></samp>’
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and ‘<samp><span class="samp">cpu32</span></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><table summary=""><tr align="left"><td valign="top" width="20%"><strong>Family</strong> </td><td valign="top" width="80%"><strong>‘</strong><samp><span class="samp">-mcpu</span></samp><strong>’ arguments</strong>
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">51</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">51</span></samp>’ ‘<samp><span class="samp">51ac</span></samp>’ ‘<samp><span class="samp">51ag</span></samp>’ ‘<samp><span class="samp">51cn</span></samp>’ ‘<samp><span class="samp">51em</span></samp>’ ‘<samp><span class="samp">51je</span></samp>’ ‘<samp><span class="samp">51jf</span></samp>’ ‘<samp><span class="samp">51jg</span></samp>’ ‘<samp><span class="samp">51jm</span></samp>’ ‘<samp><span class="samp">51mm</span></samp>’ ‘<samp><span class="samp">51qe</span></samp>’ ‘<samp><span class="samp">51qm</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5206</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5202</span></samp>’ ‘<samp><span class="samp">5204</span></samp>’ ‘<samp><span class="samp">5206</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5206e</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5206e</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5208</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5207</span></samp>’ ‘<samp><span class="samp">5208</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5211a</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5210a</span></samp>’ ‘<samp><span class="samp">5211a</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5213</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5211</span></samp>’ ‘<samp><span class="samp">5212</span></samp>’ ‘<samp><span class="samp">5213</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5216</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5214</span></samp>’ ‘<samp><span class="samp">5216</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">52235</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">52230</span></samp>’ ‘<samp><span class="samp">52231</span></samp>’ ‘<samp><span class="samp">52232</span></samp>’ ‘<samp><span class="samp">52233</span></samp>’ ‘<samp><span class="samp">52234</span></samp>’ ‘<samp><span class="samp">52235</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5225</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5224</span></samp>’ ‘<samp><span class="samp">5225</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">52259</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">52252</span></samp>’ ‘<samp><span class="samp">52254</span></samp>’ ‘<samp><span class="samp">52255</span></samp>’ ‘<samp><span class="samp">52256</span></samp>’ ‘<samp><span class="samp">52258</span></samp>’ ‘<samp><span class="samp">52259</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5235</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5232</span></samp>’ ‘<samp><span class="samp">5233</span></samp>’ ‘<samp><span class="samp">5234</span></samp>’ ‘<samp><span class="samp">5235</span></samp>’ ‘<samp><span class="samp">523x</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5249</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5249</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5250</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5250</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5271</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5270</span></samp>’ ‘<samp><span class="samp">5271</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5272</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5272</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5275</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5274</span></samp>’ ‘<samp><span class="samp">5275</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5282</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5280</span></samp>’ ‘<samp><span class="samp">5281</span></samp>’ ‘<samp><span class="samp">5282</span></samp>’ ‘<samp><span class="samp">528x</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">53017</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">53011</span></samp>’ ‘<samp><span class="samp">53012</span></samp>’ ‘<samp><span class="samp">53013</span></samp>’ ‘<samp><span class="samp">53014</span></samp>’ ‘<samp><span class="samp">53015</span></samp>’ ‘<samp><span class="samp">53016</span></samp>’ ‘<samp><span class="samp">53017</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5307</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5307</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5329</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5327</span></samp>’ ‘<samp><span class="samp">5328</span></samp>’ ‘<samp><span class="samp">5329</span></samp>’ ‘<samp><span class="samp">532x</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5373</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5372</span></samp>’ ‘<samp><span class="samp">5373</span></samp>’ ‘<samp><span class="samp">537x</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5407</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5407</span></samp>’
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<br></td></tr><tr align="left"><td valign="top" width="20%">‘<samp><span class="samp">5475</span></samp>’ </td><td valign="top" width="80%">‘<samp><span class="samp">5470</span></samp>’ ‘<samp><span class="samp">5471</span></samp>’ ‘<samp><span class="samp">5472</span></samp>’ ‘<samp><span class="samp">5473</span></samp>’ ‘<samp><span class="samp">5474</span></samp>’ ‘<samp><span class="samp">5475</span></samp>’ ‘<samp><span class="samp">547x</span></samp>’ ‘<samp><span class="samp">5480</span></samp>’ ‘<samp><span class="samp">5481</span></samp>’ ‘<samp><span class="samp">5482</span></samp>’ ‘<samp><span class="samp">5483</span></samp>’ ‘<samp><span class="samp">5484</span></samp>’ ‘<samp><span class="samp">5485</span></samp>’
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<br></td></tr></table>
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<p><samp><span class="option">-mcpu=</span><var>cpu</var></samp> overrides <samp><span class="option">-march=</span><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><span class="option">-mcpu</span></samp> and <samp><span class="option">-march</span></samp> are rejected.
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<p>GCC defines the macro <code>__mcf_cpu_</code><var>cpu</var> when ColdFire target
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<var>cpu</var> is selected. It also defines <code>__mcf_family_</code><var>family</var>,
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where the value of <var>family</var> is given by the table above.
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<br><dt><code>-mtune=</code><var>tune</var><dd><a name="index-mtune-1819"></a>Tune the code for a particular microarchitecture within the
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constraints set by <samp><span class="option">-march</span></samp> and <samp><span class="option">-mcpu</span></samp>.
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The M680x0 microarchitectures are: ‘<samp><span class="samp">68000</span></samp>’, ‘<samp><span class="samp">68010</span></samp>’,
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‘<samp><span class="samp">68020</span></samp>’, ‘<samp><span class="samp">68030</span></samp>’, ‘<samp><span class="samp">68040</span></samp>’, ‘<samp><span class="samp">68060</span></samp>’
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and ‘<samp><span class="samp">cpu32</span></samp>’. The ColdFire microarchitectures
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are: ‘<samp><span class="samp">cfv1</span></samp>’, ‘<samp><span class="samp">cfv2</span></samp>’, ‘<samp><span class="samp">cfv3</span></samp>’, ‘<samp><span class="samp">cfv4</span></samp>’ and ‘<samp><span class="samp">cfv4e</span></samp>’.
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<p>You can also use <samp><span class="option">-mtune=68020-40</span></samp> for code that needs
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to run relatively well on 68020, 68030 and 68040 targets.
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<samp><span class="option">-mtune=68020-60</span></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><span class="option">-m68020-40</span></samp> and <samp><span class="option">-m68020-60</span></samp> respectively.
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<p>GCC defines the macros <code>__mc</code><var>arch</var> and <code>__mc</code><var>arch</var><code>__</code>
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when tuning for 680x0 architecture <var>arch</var>. It also defines
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<code>mc</code><var>arch</var> unless either <samp><span class="option">-ansi</span></samp> or a non-GNU <samp><span class="option">-std</span></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><span class="option">-mtune=68020-40</span></samp> or <samp><span class="option">-mtune=68020-60</span></samp>,
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it defines the macros for every architecture in the range.
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<p>GCC also defines the macro <code>__m</code><var>uarch</var><code>__</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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<br><dt><code>-m68000</code><dt><code>-mc68000</code><dd><a name="index-m68000-1820"></a><a name="index-mc68000-1821"></a>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><span class="option">-march=68000</span></samp>.
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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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<br><dt><code>-m68010</code><dd><a name="index-m68010-1822"></a>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><span class="option">-march=68010</span></samp>.
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<br><dt><code>-m68020</code><dt><code>-mc68020</code><dd><a name="index-m68020-1823"></a><a name="index-mc68020-1824"></a>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><span class="option">-march=68020</span></samp>.
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<br><dt><code>-m68030</code><dd><a name="index-m68030-1825"></a>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><span class="option">-march=68030</span></samp>.
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<br><dt><code>-m68040</code><dd><a name="index-m68040-1826"></a>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><span class="option">-march=68040</span></samp>.
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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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<br><dt><code>-m68060</code><dd><a name="index-m68060-1827"></a>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><span class="option">-march=68060</span></samp>.
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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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<br><dt><code>-mcpu32</code><dd><a name="index-mcpu32-1828"></a>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><span class="option">-march=cpu32</span></samp>.
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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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<br><dt><code>-m5200</code><dd><a name="index-m5200-1829"></a>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><span class="option">-mcpu=5206</span></samp>, and is now deprecated
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in favor of that option.
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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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<br><dt><code>-m5206e</code><dd><a name="index-m5206e-1830"></a>Generate output for a 5206e ColdFire CPU. The option is now
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deprecated in favor of the equivalent <samp><span class="option">-mcpu=5206e</span></samp>.
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<br><dt><code>-m528x</code><dd><a name="index-m528x-1831"></a>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><span class="option">-mcpu=528x</span></samp>.
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<br><dt><code>-m5307</code><dd><a name="index-m5307-1832"></a>Generate output for a ColdFire 5307 CPU. The option is now deprecated
|
|
in favor of the equivalent <samp><span class="option">-mcpu=5307</span></samp>.
|
|
|
|
<br><dt><code>-m5407</code><dd><a name="index-m5407-1833"></a>Generate output for a ColdFire 5407 CPU. The option is now deprecated
|
|
in favor of the equivalent <samp><span class="option">-mcpu=5407</span></samp>.
|
|
|
|
<br><dt><code>-mcfv4e</code><dd><a name="index-mcfv4e-1834"></a>Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).
|
|
This includes use of hardware floating-point instructions.
|
|
The option is equivalent to <samp><span class="option">-mcpu=547x</span></samp>, and is now
|
|
deprecated in favor of that option.
|
|
|
|
<br><dt><code>-m68020-40</code><dd><a name="index-m68020_002d40-1835"></a>Generate output for a 68040, 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 68040.
|
|
|
|
<p>The option is equivalent to <samp><span class="option">-march=68020</span></samp> <samp><span class="option">-mtune=68020-40</span></samp>.
|
|
|
|
<br><dt><code>-m68020-60</code><dd><a name="index-m68020_002d60-1836"></a>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>The option is equivalent to <samp><span class="option">-march=68020</span></samp> <samp><span class="option">-mtune=68020-60</span></samp>.
|
|
|
|
<br><dt><code>-mhard-float</code><dt><code>-m68881</code><dd><a name="index-mhard_002dfloat-1837"></a><a name="index-m68881-1838"></a>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.
|
|
|
|
<br><dt><code>-msoft-float</code><dd><a name="index-msoft_002dfloat-1839"></a>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.
|
|
|
|
<br><dt><code>-mdiv</code><dt><code>-mno-div</code><dd><a name="index-mdiv-1840"></a><a name="index-mno_002ddiv-1841"></a>Generate (do not generate) ColdFire hardware divide and remainder
|
|
instructions. If <samp><span class="option">-march</span></samp> is used without <samp><span class="option">-mcpu</span></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><span class="option">-mcpu</span></samp>). For
|
|
example, the default is “off” for <samp><span class="option">-mcpu=5206</span></samp> and “on” for
|
|
<samp><span class="option">-mcpu=5206e</span></samp>.
|
|
|
|
<p>GCC defines the macro <code>__mcfhwdiv__</code> when this option is enabled.
|
|
|
|
<br><dt><code>-mshort</code><dd><a name="index-mshort-1842"></a>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.
|
|
|
|
<br><dt><code>-mno-short</code><dd><a name="index-mno_002dshort-1843"></a>Do not consider type <code>int</code> to be 16 bits wide. This is the default.
|
|
|
|
<br><dt><code>-mnobitfield</code><dt><code>-mno-bitfield</code><dd><a name="index-mnobitfield-1844"></a><a name="index-mno_002dbitfield-1845"></a>Do not use the bit-field instructions. The <samp><span class="option">-m68000</span></samp>, <samp><span class="option">-mcpu32</span></samp>
|
|
and <samp><span class="option">-m5200</span></samp> options imply <samp><span class="option">-mnobitfield</span></samp><!-- /@w -->.
|
|
|
|
<br><dt><code>-mbitfield</code><dd><a name="index-mbitfield-1846"></a>Do use the bit-field instructions. The <samp><span class="option">-m68020</span></samp> option implies
|
|
<samp><span class="option">-mbitfield</span></samp>. This is the default if you use a configuration
|
|
designed for a 68020.
|
|
|
|
<br><dt><code>-mrtd</code><dd><a name="index-mrtd-1847"></a>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>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>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>In addition, seriously incorrect code results if you call a
|
|
function with too many arguments. (Normally, extra arguments are
|
|
harmlessly ignored.)
|
|
|
|
<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.
|
|
|
|
<br><dt><code>-mno-rtd</code><dd><a name="index-mno_002drtd-1848"></a>Do not use the calling conventions selected by <samp><span class="option">-mrtd</span></samp>.
|
|
This is the default.
|
|
|
|
<br><dt><code>-malign-int</code><dt><code>-mno-align-int</code><dd><a name="index-malign_002dint-1849"></a><a name="index-mno_002dalign_002dint-1850"></a>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><span class="option">-malign-int</span></samp>) or a 16-bit boundary (<samp><span class="option">-mno-align-int</span></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><strong>Warning:</strong> if you use the <samp><span class="option">-malign-int</span></samp> switch, GCC
|
|
aligns structures containing the above types differently than
|
|
most published application binary interface specifications for the m68k.
|
|
|
|
<br><dt><code>-mpcrel</code><dd><a name="index-mpcrel-1851"></a>Use the pc-relative addressing mode of the 68000 directly, instead of
|
|
using a global offset table. At present, this option implies <samp><span class="option">-fpic</span></samp>,
|
|
allowing at most a 16-bit offset for pc-relative addressing. <samp><span class="option">-fPIC</span></samp> is
|
|
not presently supported with <samp><span class="option">-mpcrel</span></samp>, though this could be supported for
|
|
68020 and higher processors.
|
|
|
|
<br><dt><code>-mno-strict-align</code><dt><code>-mstrict-align</code><dd><a name="index-mno_002dstrict_002dalign-1852"></a><a name="index-mstrict_002dalign-1853"></a>Do not (do) assume that unaligned memory references are handled by
|
|
the system.
|
|
|
|
<br><dt><code>-msep-data</code><dd>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><span class="option">-fPIC</span></samp>.
|
|
|
|
<br><dt><code>-mno-sep-data</code><dd>Generate code that assumes that the data segment follows the text segment.
|
|
This is the default.
|
|
|
|
<br><dt><code>-mid-shared-library</code><dd>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><span class="option">-fPIC</span></samp>.
|
|
|
|
<br><dt><code>-mno-id-shared-library</code><dd>Generate code that doesn't assume ID-based shared libraries are being used.
|
|
This is the default.
|
|
|
|
<br><dt><code>-mshared-library-id=n</code><dd>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.
|
|
|
|
<br><dt><code>-mxgot</code><dt><code>-mno-xgot</code><dd><a name="index-mxgot-1854"></a><a name="index-mno_002dxgot-1855"></a>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><span class="option">-fPIC</span></samp> suffices.
|
|
|
|
<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_0029-1856"></a>
|
|
<pre class="smallexample"> relocation truncated to fit: R_68K_GOT16O foobar
|
|
</pre>
|
|
<p>If this happens, you should recompile your code with <samp><span class="option">-mxgot</span></samp>.
|
|
It should then work with very large GOTs. However, code generated with
|
|
<samp><span class="option">-mxgot</span></samp> is less efficient, since it takes 4 instructions to fetch
|
|
the value of a global symbol.
|
|
|
|
<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><span class="option">-mxgot</span></samp> when compiling a single
|
|
object file that accesses more than 8192 GOT entries. Very few do.
|
|
|
|
<p>These options have no effect unless GCC is generating
|
|
position-independent code.
|
|
|
|
</dl>
|
|
|
|
</body></html>
|
|
|