Need advice on bounds checking approaches

[Joern Rennecke]

> Question: with the above plan, is there a way to provide a default
> expansion of the "check_bounds" pattern into primitive RTL
> (comparisons, conditional branches and call to abort) for those
> targets that don't define an insn for "check_bounds"?

You can use HAVE_check_bounds to test if a "check_bounds" pattern has been
defined in the md file.  If it is defined, you can use gen_check_bounds
to generate this pattern.  The expander might fail (e.g. because the
target can implement the bounds checking insn only for a particular
cpu_, in which case you get a zero return value from gen_check_bounds.