-m68000-mc68000- Generate output for a 68000. This is the default
when the compiler is configured for 68000-based systems.
Use this option for microcontrollers with a 68000 or EC000 core,
including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.
-m68020-mc68020- Generate output for a 68020. This is the default
when the compiler is configured for 68020-based systems.
-m68881- Generate output containing 68881 instructions for floating point.
This is the default for most 68020 systems unless --nfp was
specified when the compiler was configured.
-m68030- Generate output for a 68030. This is the default when the compiler is
configured for 68030-based systems.
-m68040- Generate output for a 68040. This is the default when the compiler is
configured for 68040-based systems.
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.
-m68060- Generate output for a 68060. This is the default when the compiler is
configured for 68060-based systems.
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.
-mcpu32- Generate output for a CPU32. This is the default
when the compiler is configured for CPU32-based systems.
Use this option for microcontrollers with a
CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334,
68336, 68340, 68341, 68349 and 68360.
-m5200- Generate output for a 520X “coldfire” family cpu. This is the default
when the compiler is configured for 520X-based systems.
Use this option for microcontroller with a 5200 core, including
the MCF5202, MCF5203, MCF5204 and MCF5202.
-m68020-40- 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.
-m68020-60- 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.
-msoft-float- Generate output containing library calls for floating point.
Warning: the requisite libraries are not available for all m68k
targets. Normally the facilities of the machine's usual C compiler are
used, but this can't be done directly in cross-compilation. You must
make your own arrangements to provide suitable library functions for
cross-compilation. The embedded targets `m68k-*-aout' and
`m68k-*-coff' do provide software floating point support.
-mshort- Consider type
int to be 16 bits wide, like short int.
-mnobitfield- Do not use the bit-field instructions. The -m68000, -mcpu32
and -m5200 options imply -mnobitfield.
-mbitfield- Do use the bit-field instructions. The -m68020 option implies
-mbitfield. This is the default if you use a configuration
designed for a 68020.
-mrtd- Use a different function-calling convention, in which functions
that take a fixed number of arguments return with the
rtd
instruction, which pops their arguments while returning. This
saves one instruction in the caller since there is no need to pop
the arguments there.
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.
Also, you must provide function prototypes for all functions that
take variable numbers of arguments (including printf);
otherwise incorrect code will be generated for calls to those
functions.
In addition, seriously incorrect code will result if you call a
function with too many arguments. (Normally, extra arguments are
harmlessly ignored.)
The rtd instruction is supported by the 68010, 68020, 68030,
68040, 68060 and CPU32 processors, but not by the 68000 or 5200.
-malign-int-mno-align-int- Control whether GCC aligns
int, long, long long,
float, double, and long double variables on a 32-bit
boundary (-malign-int) or a 16-bit boundary (-mno-align-int).
Aligning variables on 32-bit boundaries produces code that runs somewhat
faster on processors with 32-bit busses at the expense of more memory.
Warning: if you use the -malign-int switch, GCC will
align structures containing the above types differently than
most published application binary interface specifications for the m68k.
-mpcrel- Use the pc-relative addressing mode of the 68000 directly, instead of
using a global offset table. At present, this option implies -fpic,
allowing at most a 16-bit offset for pc-relative addressing. -fPIC is
not presently supported with -mpcrel, though this could be supported for
68020 and higher processors.
-mno-strict-align-mstrict-align- Do not (do) assume that unaligned memory references will be handled by
the system.
-msep-data- 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 -fPIC.
-mno-sep-data- Generate code that assumes that the data segment follows the text segment.
This is the default.
-mid-shared-library- 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 -fPIC.
-mno-id-shared-library- Generate code that doesn't assume ID based shared libraries are being used.
This is the default.
-mshared-library-id=n- 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.