Using and Porting GNU CC
These are the `
-m' options defined for the 68000 series. The default
values for these options depends on which style of 68000 was selected when
the compiler was configured; the defaults for the most common choices are
-nfp' was specified when the compiler was configured.
This option inhibits the use of 68881/68882 instructions that have to be
emulated by software on the 68040. If your 68040 does not have code to
emulate those instructions, use `
intto be 16 bits wide, like
-m68000' option implies `
-m68020' option implies `
-mbitfield'. This is the default if you use a configuration designed for a 68020.
rtdinstruction, 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
otherwise incorrect code will be generated for calls to those
In addition, seriously incorrect code will result if you call a function with too many arguments. (Normally, extra arguments are harmlessly ignored.)
rtd instruction is supported by the 68010 and 68020
processors, but not by the 68000.