#### 9.7.1 Command-line Options

The CRIS version of `as` has these machine-dependent command-line options.

The format of the generated object files can be either ELF or a.out, specified by the command-line options `--emulation=crisaout` and `--emulation=criself`. The default is ELF (criself), unless `as` has been configured specifically for a.out by using the configuration name `cris-axis-aout`.

There are two different link-incompatible ELF object file variants for CRIS, for use in environments where symbols are expected to be prefixed by a leading ‘`_`’ character and for environments without such a symbol prefix. The variant used for GNU/Linux port has no symbol prefix. Which variant to produce is specified by either of the options `--underscore` and `--no-underscore`. The default is `--underscore`. Since symbols in CRIS a.out objects are expected to have a ‘`_`’ prefix, specifying `--no-underscore` when generating a.out objects is an error. Besides the object format difference, the effect of this option is to parse register names differently (see crisnous). The `--no-underscore` option makes a ‘`$`’ register prefix mandatory.

The option `--pic` must be passed to `as` in order to recognize the symbol syntax used for ELF (SVR4 PIC) position-independent-code (see crispic). This will also affect expansion of instructions. The expansion with `--pic` will use PC-relative rather than (slightly faster) absolute addresses in those expansions.

The option `--march=architecture` specifies the recognized instruction set and recognized register names. It also controls the architecture type of the object file. Valid values for architecture are:

`v0_v10`
  All instructions and register names for any architecture variant in the set v0...v10 are recognized. This is the default if the target is configured as cris-*.
`v10`
  Only instructions and register names for CRIS v10 (as found in ETRAX 100 LX) are recognized. This is the default if the target is configured as crisv10-*.
`v32`
  Only instructions and register names for CRIS v32 (code name Guinness) are recognized. This is the default if the target is configured as crisv32-*. This value implies `--no-mul-bug-abort`. (A subsequent `--mul-bug-abort` will turn it back on.)
`common_v10_v32`
  Only instructions with register names and addressing modes with opcodes common to the v10 and v32 are recognized.

When `-N` is specified, `as` will emit a warning when a 16-bit branch instruction is expanded into a 32-bit multiple-instruction construct (see CRIS-Expand).

Some versions of the CRIS v10, for example in the Etrax 100 LX, contain a bug that causes destabilizing memory accesses when a multiply instruction is executed with certain values in the first operand just before a cache-miss. When the `--mul-bug-abort` command line option is active (the default value), `as` will refuse to assemble a file containing a multiply instruction at a dangerous offset, one that could be the last on a cache-line, or is in a section with insufficient alignment. This placement checking does not catch any case where the multiply instruction is dangerously placed because it is located in a delay-slot. The `--mul-bug-abort` command line option turns off the checking.