GNU Info
(gcc-295.info)M88K Options
M88K Options
------------
These `-m' options are defined for Motorola 88k architectures:
`-m88000'
Generate code that works well on both the m88100 and the m88110.
`-m88100'
Generate code that works best for the m88100, but that also runs
on the m88110.
`-m88110'
Generate code that works best for the m88110, and may not run on
the m88100.
`-mbig-pic'
Obsolete option to be removed from the next revision. Use `-fPIC'.
`-midentify-revision'
Include an `ident' directive in the assembler output recording the
source file name, compiler name and version, timestamp, and
compilation flags used.
`-mno-underscores'
In assembler output, emit symbol names without adding an underscore
character at the beginning of each name. The default is to use an
underscore as prefix on each name.
`-mocs-debug-info'
`-mno-ocs-debug-info'
Include (or omit) additional debugging information (about
registers used in each stack frame) as specified in the 88open
Object Compatibility Standard, "OCS". This extra information
allows debugging of code that has had the frame pointer
eliminated. The default for DG/UX, SVr4, and Delta 88 SVr3.2 is
to include this information; other 88k configurations omit this
information by default.
`-mocs-frame-position'
When emitting COFF debugging information for automatic variables
and parameters stored on the stack, use the offset from the
canonical frame address, which is the stack pointer (register 31)
on entry to the function. The DG/UX, SVr4, Delta88 SVr3.2, and
BCS configurations use `-mocs-frame-position'; other 88k
configurations have the default `-mno-ocs-frame-position'.
`-mno-ocs-frame-position'
When emitting COFF debugging information for automatic variables
and parameters stored on the stack, use the offset from the frame
pointer register (register 30). When this option is in effect,
the frame pointer is not eliminated when debugging information is
selected by the -g switch.
`-moptimize-arg-area'
`-mno-optimize-arg-area'
Control how function arguments are stored in stack frames.
`-moptimize-arg-area' saves space by optimizing them, but this
conflicts with the 88open specifications. The opposite
alternative, `-mno-optimize-arg-area', agrees with 88open
standards. By default GCC does not optimize the argument area.
`-mshort-data-NUM'
Generate smaller data references by making them relative to `r0',
which allows loading a value using a single instruction (rather
than the usual two). You control which data references are
affected by specifying NUM with this option. For example, if you
specify `-mshort-data-512', then the data references affected are
those involving displacements of less than 512 bytes.
`-mshort-data-NUM' is not effective for NUM greater than 64k.
`-mserialize-volatile'
`-mno-serialize-volatile'
Do, or don't, generate code to guarantee sequential consistency of
volatile memory references. By default, consistency is guaranteed.
The order of memory references made by the MC88110 processor does
not always match the order of the instructions requesting those
references. In particular, a load instruction may execute before
a preceding store instruction. Such reordering violates
sequential consistency of volatile memory references, when there
are multiple processors. When consistency must be guaranteed,
GNU C generates special instructions, as needed, to force
execution in the proper order.
The MC88100 processor does not reorder memory references and so
always provides sequential consistency. However, by default, GNU
C generates the special instructions to guarantee consistency even
when you use `-m88100', so that the code may be run on an MC88110
processor. If you intend to run your code only on the MC88100
processor, you may use `-mno-serialize-volatile'.
The extra code generated to guarantee consistency may affect the
performance of your application. If you know that you can safely
forgo this guarantee, you may use `-mno-serialize-volatile'.
`-msvr4'
`-msvr3'
Turn on (`-msvr4') or off (`-msvr3') compiler extensions related
to System V release 4 (SVr4). This controls the following:
1. Which variant of the assembler syntax to emit.
2. `-msvr4' makes the C preprocessor recognize `#pragma weak'
that is used on System V release 4.
3. `-msvr4' makes GCC issue additional declaration directives
used in SVr4.
`-msvr4' is the default for the m88k-motorola-sysv4 and
m88k-dg-dgux m88k configurations. `-msvr3' is the default for all
other m88k configurations.
`-mversion-03.00'
This option is obsolete, and is ignored.
`-mno-check-zero-division'
`-mcheck-zero-division'
Do, or don't, generate code to guarantee that integer division by
zero will be detected. By default, detection is guaranteed.
Some models of the MC88100 processor fail to trap upon integer
division by zero under certain conditions. By default, when
compiling code that might be run on such a processor, GNU C
generates code that explicitly checks for zero-valued divisors and
traps with exception number 503 when one is detected. Use of
mno-check-zero-division suppresses such checking for code
generated to run on an MC88100 processor.
GNU C assumes that the MC88110 processor correctly detects all
instances of integer division by zero. When `-m88110' is
specified, both `-mcheck-zero-division' and
`-mno-check-zero-division' are ignored, and no explicit checks for
zero-valued divisors are generated.
`-muse-div-instruction'
Use the div instruction for signed integer division on the MC88100
processor. By default, the div instruction is not used.
On the MC88100 processor the signed integer division instruction
div) traps to the operating system on a negative operand. The
operating system transparently completes the operation, but at a
large cost in execution time. By default, when compiling code
that might be run on an MC88100 processor, GNU C emulates signed
integer division using the unsigned integer division instruction
divu), thereby avoiding the large penalty of a trap to the
operating system. Such emulation has its own, smaller, execution
cost in both time and space. To the extent that your code's
important signed integer division operations are performed on two
nonnegative operands, it may be desirable to use the div
instruction directly.
On the MC88110 processor the div instruction (also known as the
divs instruction) processes negative operands without trapping to
the operating system. When `-m88110' is specified,
`-muse-div-instruction' is ignored, and the div instruction is used
for signed integer division.
Note that the result of dividing INT_MIN by -1 is undefined. In
particular, the behavior of such a division with and without
`-muse-div-instruction' may differ.
`-mtrap-large-shift'
`-mhandle-large-shift'
Include code to detect bit-shifts of more than 31 bits;
respectively, trap such shifts or emit code to handle them
properly. By default GCC makes no special provision for large bit
shifts.
`-mwarn-passed-structs'
Warn when a function passes a struct as an argument or result.
Structure-passing conventions have changed during the evolution of
the C language, and are often the source of portability problems.
By default, GCC issues no such warning.
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