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| <h4 class="subsection">3.17.21 M680x0 Options</h4> |
| |
| <p><a name="index-M680x0-options-1454"></a> |
| These are the ‘<samp><span class="samp">-m</span></samp>’ options defined for M680x0 and ColdFire processors. |
| The default settings depend on which architecture was selected when |
| the compiler was configured; the defaults for the most common choices |
| are given below. |
| |
| <dl> |
| <dt><code>-march=</code><var>arch</var><dd><a name="index-march-1455"></a>Generate code for a specific M680x0 or ColdFire instruction set |
| architecture. Permissible values of <var>arch</var> for M680x0 |
| architectures are: ‘<samp><span class="samp">68000</span></samp>’, ‘<samp><span class="samp">68010</span></samp>’, ‘<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>’ and ‘<samp><span class="samp">cpu32</span></samp>’. ColdFire |
| architectures are selected according to Freescale's ISA classification |
| and the permissible values are: ‘<samp><span class="samp">isaa</span></samp>’, ‘<samp><span class="samp">isaaplus</span></samp>’, |
| ‘<samp><span class="samp">isab</span></samp>’ and ‘<samp><span class="samp">isac</span></samp>’. |
| |
| <p>gcc defines a macro ‘<samp><span class="samp">__mcf</span><var>arch</var><span class="samp">__</span></samp>’ whenever it is generating |
| code for a ColdFire target. The <var>arch</var> in this macro is one of the |
| <samp><span class="option">-march</span></samp> arguments given above. |
| |
| <p>When used together, <samp><span class="option">-march</span></samp> and <samp><span class="option">-mtune</span></samp> select code |
| that runs on a family of similar processors but that is optimized |
| for a particular microarchitecture. |
| |
| <br><dt><code>-mcpu=</code><var>cpu</var><dd><a name="index-mcpu-1456"></a>Generate code for a specific M680x0 or ColdFire processor. |
| 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>’, |
| ‘<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>’ |
| and ‘<samp><span class="samp">cpu32</span></samp>’. The ColdFire <var>cpu</var>s are given by the table |
| below, which also classifies the CPUs into families: |
| |
| <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> |
| <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">51cn</span></samp>’ ‘<samp><span class="samp">51em</span></samp>’ ‘<samp><span class="samp">51qe</span></samp>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <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>’ |
| <br></td></tr></table> |
| |
| <p><samp><span class="option">-mcpu=</span><var>cpu</var></samp> overrides <samp><span class="option">-march=</span><var>arch</var></samp> if |
| <var>arch</var> is compatible with <var>cpu</var>. Other combinations of |
| <samp><span class="option">-mcpu</span></samp> and <samp><span class="option">-march</span></samp> are rejected. |
| |
| <p>gcc defines the macro ‘<samp><span class="samp">__mcf_cpu_</span><var>cpu</var></samp>’ when ColdFire target |
| <var>cpu</var> is selected. It also defines ‘<samp><span class="samp">__mcf_family_</span><var>family</var></samp>’, |
| where the value of <var>family</var> is given by the table above. |
| |
| <br><dt><code>-mtune=</code><var>tune</var><dd><a name="index-mtune-1457"></a>Tune the code for a particular microarchitecture, within the |
| constraints set by <samp><span class="option">-march</span></samp> and <samp><span class="option">-mcpu</span></samp>. |
| The M680x0 microarchitectures are: ‘<samp><span class="samp">68000</span></samp>’, ‘<samp><span class="samp">68010</span></samp>’, |
| ‘<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>’ |
| and ‘<samp><span class="samp">cpu32</span></samp>’. The ColdFire microarchitectures |
| 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>’. |
| |
| <p>You can also use <samp><span class="option">-mtune=68020-40</span></samp> for code that needs |
| to run relatively well on 68020, 68030 and 68040 targets. |
| <samp><span class="option">-mtune=68020-60</span></samp> is similar but includes 68060 targets |
| as well. These two options select the same tuning decisions as |
| <samp><span class="option">-m68020-40</span></samp> and <samp><span class="option">-m68020-60</span></samp> respectively. |
| |
| <p>gcc defines the macros ‘<samp><span class="samp">__mc</span><var>arch</var></samp>’ and ‘<samp><span class="samp">__mc</span><var>arch</var><span class="samp">__</span></samp>’ |
| when tuning for 680x0 architecture <var>arch</var>. It also defines |
| ‘<samp><span class="samp">mc</span><var>arch</var></samp>’ unless either <samp><span class="option">-ansi</span></samp> or a non-GNU <samp><span class="option">-std</span></samp> |
| option is used. If gcc is tuning for a range of architectures, |
| as selected by <samp><span class="option">-mtune=68020-40</span></samp> or <samp><span class="option">-mtune=68020-60</span></samp>, |
| it defines the macros for every architecture in the range. |
| |
| <p>gcc also defines the macro ‘<samp><span class="samp">__m</span><var>uarch</var><span class="samp">__</span></samp>’ when tuning for |
| ColdFire microarchitecture <var>uarch</var>, where <var>uarch</var> is one |
| of the arguments given above. |
| |
| <br><dt><code>-m68000</code><dt><code>-mc68000</code><dd><a name="index-m68000-1458"></a><a name="index-mc68000-1459"></a>Generate output for a 68000. This is the default |
| when the compiler is configured for 68000-based systems. |
| It is equivalent to <samp><span class="option">-march=68000</span></samp>. |
| |
| <p>Use this option for microcontrollers with a 68000 or EC000 core, |
| including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. |
| |
| <br><dt><code>-m68010</code><dd><a name="index-m68010-1460"></a>Generate output for a 68010. This is the default |
| when the compiler is configured for 68010-based systems. |
| It is equivalent to <samp><span class="option">-march=68010</span></samp>. |
| |
| <br><dt><code>-m68020</code><dt><code>-mc68020</code><dd><a name="index-m68020-1461"></a><a name="index-mc68020-1462"></a>Generate output for a 68020. This is the default |
| when the compiler is configured for 68020-based systems. |
| It is equivalent to <samp><span class="option">-march=68020</span></samp>. |
| |
| <br><dt><code>-m68030</code><dd><a name="index-m68030-1463"></a>Generate output for a 68030. This is the default when the compiler is |
| configured for 68030-based systems. It is equivalent to |
| <samp><span class="option">-march=68030</span></samp>. |
| |
| <br><dt><code>-m68040</code><dd><a name="index-m68040-1464"></a>Generate output for a 68040. This is the default when the compiler is |
| configured for 68040-based systems. It is equivalent to |
| <samp><span class="option">-march=68040</span></samp>. |
| |
| <p>This option inhibits the use of 68881/68882 instructions that have to be |
| emulated by software on the 68040. Use this option if your 68040 does not |
| have code to emulate those instructions. |
| |
| <br><dt><code>-m68060</code><dd><a name="index-m68060-1465"></a>Generate output for a 68060. This is the default when the compiler is |
| configured for 68060-based systems. It is equivalent to |
| <samp><span class="option">-march=68060</span></samp>. |
| |
| <p>This option inhibits the use of 68020 and 68881/68882 instructions that |
| have to be emulated by software on the 68060. Use this option if your 68060 |
| does not have code to emulate those instructions. |
| |
| <br><dt><code>-mcpu32</code><dd><a name="index-mcpu32-1466"></a>Generate output for a CPU32. This is the default |
| when the compiler is configured for CPU32-based systems. |
| It is equivalent to <samp><span class="option">-march=cpu32</span></samp>. |
| |
| <p>Use this option for microcontrollers with a |
| CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, |
| 68336, 68340, 68341, 68349 and 68360. |
| |
| <br><dt><code>-m5200</code><dd><a name="index-m5200-1467"></a>Generate output for a 520X ColdFire CPU. This is the default |
| when the compiler is configured for 520X-based systems. |
| It is equivalent to <samp><span class="option">-mcpu=5206</span></samp>, and is now deprecated |
| in favor of that option. |
| |
| <p>Use this option for microcontroller with a 5200 core, including |
| the MCF5202, MCF5203, MCF5204 and MCF5206. |
| |
| <br><dt><code>-m5206e</code><dd><a name="index-m5206e-1468"></a>Generate output for a 5206e ColdFire CPU. The option is now |
| deprecated in favor of the equivalent <samp><span class="option">-mcpu=5206e</span></samp>. |
| |
| <br><dt><code>-m528x</code><dd><a name="index-m528x-1469"></a>Generate output for a member of the ColdFire 528X family. |
| The option is now deprecated in favor of the equivalent |
| <samp><span class="option">-mcpu=528x</span></samp>. |
| |
| <br><dt><code>-m5307</code><dd><a name="index-m5307-1470"></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-m5407-1471"></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-1472"></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_002d40-1473"></a>Generate output for a 68040, without using any of the new instructions. |
| This results in code which 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_002d60-1474"></a>Generate output for a 68060, without using any of the new instructions. |
| This results in code which 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-1475"></a><a name="index-m68881-1476"></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 ‘<samp><span class="samp">__HAVE_68881__</span></samp>’ on M680x0 targets and ‘<samp><span class="samp">__mcffpu__</span></samp>’ |
| on ColdFire targets. |
| |
| <br><dt><code>-msoft-float</code><dd><a name="index-msoft_002dfloat-1477"></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-1478"></a><a name="index-mno_002ddiv-1479"></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 ‘<samp><span class="samp">__mcfhwdiv__</span></samp>’ when this option is enabled. |
| |
| <br><dt><code>-mshort</code><dd><a name="index-mshort-1480"></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-1481"></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-1482"></a><a name="index-mno_002dbitfield-1483"></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-1484"></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-1485"></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 will be generated for calls to those |
| functions. |
| |
| <p>In addition, seriously incorrect code will result 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-1486"></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-1487"></a><a name="index-mno_002dalign_002dint-1488"></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 will |
| align 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-1489"></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-1490"></a><a name="index-mstrict_002dalign-1491"></a>Do not (do) assume that unaligned memory references will be 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>Specified the identification number of the ID based shared library being |
| compiled. Specifying a value of 0 will generate more compact code, specifying |
| other values will force 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-1492"></a><a name="index-mno_002dxgot-1493"></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_0029-1494"></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> |
| |
