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<html lang="en"><head><title>Using the GNU Compiler Collection (GCC)</title><meta http-equiv="Content-Type" content="text/html"><meta name="description" content="Using the GNU Compiler Collection (GCC)"><meta name="generator" content="makeinfo 4.6"><!--Copyright &copy; 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998,1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc.   <p>Permission is granted to copy, distribute and/or modify this documentunder the terms of the GNU Free Documentation License, Version 1.2 orany later version published by the Free Software Foundation; with theInvariant Sections being "GNU General Public License" and "FundingFree Software", the Front-Cover texts being (a) (see below), and withthe Back-Cover Texts being (b) (see below).  A copy of the license isincluded in the section entitled "GNU Free Documentation License".   <p>(a) The FSF's Front-Cover Text is:   <p>A GNU Manual   <p>(b) The FSF's Back-Cover Text is:   <p>You have freedom to copy and modify this GNU Manual, like GNU     software.  Copies published by the Free Software Foundation raise     funds for GNU development.--><meta http-equiv="Content-Style-Type" content="text/css"><style type="text/css"><!--  pre.display { font-family:inherit }  pre.format  { font-family:inherit }  pre.smalldisplay { font-family:inherit; font-size:smaller }  pre.smallformat  { font-family:inherit; font-size:smaller }  pre.smallexample { font-size:smaller }  pre.smalllisp    { font-size:smaller }--></style></head><body><div class="node"><p>Node:&nbsp;<a name="M680x0%20Options">M680x0 Options</a>,Next:&nbsp;<a rel="next" accesskey="n" href="M68hc1x-Options.html#M68hc1x%20Options">M68hc1x Options</a>,Up:&nbsp;<a rel="up" accesskey="u" href="Submodel-Options.html#Submodel%20Options">Submodel Options</a><hr><br></div><h3 class="subsection">M680x0 Options</h4><p>These are the <code>-m</code> options defined for the 68000 series.  The defaultvalues for these options depends on which style of 68000 was selected whenthe compiler was configured; the defaults for the most common choices aregiven below.     <dl><dt><code>-m68000</code>     <dd><dt><code>-mc68000</code>     <dd>Generate output for a 68000.  This is the defaultwhen the compiler is configured for 68000-based systems.     <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>-m68020</code>     <dd><dt><code>-mc68020</code>     <dd>Generate output for a 68020.  This is the defaultwhen the compiler is configured for 68020-based systems.     <br><dt><code>-m68881</code>     <dd>Generate output containing 68881 instructions for floating point. This is the default for most 68020 systems unless <code>--nfp</code> wasspecified when the compiler was configured.     <br><dt><code>-m68030</code>     <dd>Generate output for a 68030.  This is the default when the compiler isconfigured for 68030-based systems.     <br><dt><code>-m68040</code>     <dd>Generate output for a 68040.  This is the default when the compiler isconfigured for 68040-based systems.     <p>This option inhibits the use of 68881/68882 instructions that have to beemulated by software on the 68040.  Use this option if your 68040 does nothave code to emulate those instructions.     <br><dt><code>-m68060</code>     <dd>Generate output for a 68060.  This is the default when the compiler isconfigured for 68060-based systems.     <p>This option inhibits the use of 68020 and 68881/68882 instructions thathave to be emulated by software on the 68060.  Use this option if your 68060does not have code to emulate those instructions.     <br><dt><code>-mcpu32</code>     <dd>Generate output for a CPU32.  This is the defaultwhen the compiler is configured for CPU32-based systems.     <p>Use this option for microcontrollers with aCPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334,68336, 68340, 68341, 68349 and 68360.     <br><dt><code>-m5200</code>     <dd>Generate output for a 520X "coldfire" family cpu.  This is the defaultwhen the compiler is configured for 520X-based systems.     <p>Use this option for microcontroller with a 5200 core, includingthe MCF5202, MCF5203, MCF5204 and MCF5202.     <br><dt><code>-m68020-40</code>     <dd>Generate output for a 68040, without using any of the new instructions. This results in code which can run relatively efficiently on either a68020/68881 or a 68030 or a 68040.  The generated code does use the68881 instructions that are emulated on the 68040.     <br><dt><code>-m68020-60</code>     <dd>Generate output for a 68060, without using any of the new instructions. This results in code which can run relatively efficiently on either a68020/68881 or a 68030 or a 68040.  The generated code does use the68881 instructions that are emulated on the 68060.     <br><dt><code>-msoft-float</code>     <dd>Generate output containing library calls for floating point. <strong>Warning:</strong> the requisite libraries are not available for all m68ktargets.  Normally the facilities of the machine's usual C compiler areused, but this can't be done directly in cross-compilation.  You mustmake your own arrangements to provide suitable library functions forcross-compilation.  The embedded targets <code>m68k-*-aout</code> and<code>m68k-*-coff</code> do provide software floating point support.     <br><dt><code>-mshort</code>     <dd>Consider type <code>int</code> to be 16 bits wide, like <code>short int</code>.     <br><dt><code>-mnobitfield</code>     <dd>Do not use the bit-field instructions.  The <code>-m68000</code>, <code>-mcpu32</code>and <code>-m5200</code> options imply <code>-mnobitfield</code>.     <br><dt><code>-mbitfield</code>     <dd>Do use the bit-field instructions.  The <code>-m68020</code> option implies<code>-mbitfield</code>.  This is the default if you use a configurationdesigned for a 68020.     <br><dt><code>-mrtd</code>     <dd>Use a different function-calling convention, in which functionsthat take a fixed number of arguments return with the <code>rtd</code>instruction, which pops their arguments while returning.  Thissaves one instruction in the caller since there is no need to popthe arguments there.     <p>This calling convention is incompatible with the one normallyused on Unix, so you cannot use it if you need to call librariescompiled with the Unix compiler.     <p>Also, you must provide function prototypes for all functions thattake variable numbers of arguments (including <code>printf</code>);otherwise incorrect code will be generated for calls to thosefunctions.     <p>In addition, seriously incorrect code will result if you call afunction with too many arguments.  (Normally, extra arguments areharmlessly 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>-malign-int</code>     <dd><dt><code>-mno-align-int</code>     <dd>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-bitboundary (<code>-malign-int</code>) or a 16-bit boundary (<code>-mno-align-int</code>). Aligning variables on 32-bit boundaries produces code that runs somewhatfaster on processors with 32-bit busses at the expense of more memory.     <p><strong>Warning:</strong> if you use the <code>-malign-int</code> switch, GCC willalign structures containing the above types  differently thanmost published application binary interface specifications for the m68k.     <br><dt><code>-mpcrel</code>     <dd>Use the pc-relative addressing mode of the 68000 directly, instead ofusing a global offset table.  At present, this option implies <code>-fpic</code>,allowing at most a 16-bit offset for pc-relative addressing.  <code>-fPIC</code> isnot presently supported with <code>-mpcrel</code>, though this could be supported for68020 and higher processors.     <br><dt><code>-mno-strict-align</code>     <dd><dt><code>-mstrict-align</code>     <dd>Do not (do) assume that unaligned memory references will be handled bythe system.     <br><dt><code>-msep-data</code>     <dd>Generate code that allows the data segment to be located in a differentarea of memory from the text segment.  This allows for execute in place inan environment without virtual memory management.  This option implies -fPIC.     <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 environmentwithout virtual memory management.  This option implies -fPIC.     <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 beingcompiled.  Specifying a value of 0 will generate more compact code, specifyingother values will force the allocation of that number to the currentlibrary but is no more space or time efficient than omitting this option.   </dl>   </body></html>
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