GNU Info

(as.info)MMIX-Opts

---

Next: MMIX-Expand Up: MMIX-Dependent

---

Enter node , (file) or (file)node

Command-line Options
--------------------

   The MMIX version of `as' has some machine-dependent options.

   When `--fixed-special-register-names' is specified, only the register
names specified in Note: MMIX-Regs are recognized in the instructions
`PUT' and `GET'.

   You can use the `--globalize-symbols' to make all symbols global.
This option is useful when splitting up a `mmixal' program into several
files.

   The `--gnu-syntax' turns off most syntax compatibility with
`mmixal'.  Its usability is currently doubtful.

   The `--relax' option is not fully supported, but will eventually make
the object file prepared for linker relaxation.

   If you want to avoid inadvertently calling a predefined symbol and
would rather get an error, for example when using `as' with a compiler
or other machine-generated code, specify `--no-predefined-syms'.  This
turns off built-in predefined definitions of all such symbols,
including rounding-mode symbols, segment symbols, `BIT' symbols, and
`TRAP' symbols used in `mmix' "system calls".  It also turns off
predefined special-register names, except when used in `PUT' and `GET'
instructions.

   By default, some instructions are expanded to fit the size of the
operand or an external symbol (Note: MMIX-Expand).  By passing
`--no-expand', no such expansion will be done, instead causing errors
at link time if the operand does not fit.

   The `mmixal' documentation (Note: mmixsite) specifies that global
registers allocated with the `GREG' directive (Note: MMIX-greg) and
initialized to the same non-zero value, will refer to the same global
register.  This isn't strictly enforcable in `as' since the final
addresses aren't known until link-time, but it will do an effort unless
the `--no-merge-gregs' option is specified.  (Register merging isn't
yet implemented in `ld'.)

   `as' will warn every time it expands an instruction to fit an
operand unless the option `-x' is specified.  It is believed that this
behaviour is more useful than just mimicking `mmixal''s behaviour, in
which instructions are only expanded if the `-x' option is specified,
and assembly fails otherwise, when an instruction needs to be expanded.
It needs to be kept in mind that `mmixal' is both an assembler and
linker, while `as' will expand instructions that at link stage can be
contracted.  (Though linker relaxation isn't yet implemented in `ld'.)
The option `-x' also imples `--linker-allocated-gregs'.

   Usually a two-operand-expression (Note: GREG-base) without a
matching `GREG' directive is treated as an error by `as'.  When the
option `--linker-allocated-gregs' is in effect, they are instead passed
through to the linker, which will allocate as many global registers as
is needed.