PATCH RFA: Change MIPS ffs<mode>2 from define_insn to define_expand

[Eric Christopher]

> If we simply remove the ffs<mode>2 insn, then calls to __builtin_ffs
> will be expanded into calls to the library function ffs.  Eric felt,
> in an offline discussion, that this would not be the best approach.
> 

This is because I know of users that depend on the set of things that we
emit library calls for to basically not change from release to release
and don't want to introduce any I can avoid :)

> 
> 2005-07-08  Ian Lance Taylor  <ian@airs.com>
> 
> 	* config/mips/mips.md (ffs<mode>2): Rewrite as define_expand.
> 

OK.

Might want to give Richard a chance to object before committing though.

-eric