need for instruction attributes (ia64)

[Jan Beulich]

Looking through ia64.md I find what would seem to be quite inconsistent
application of attributes to insns. Namely I wonder

- whether define_insn and define_insn_and_split should generally have
an itanium_class attribute, and if not, under what conditions this
can/should be omitted

- whether define_split (and define_insn_and_split if all of its
alternatives split) should generally have a predicable attribute with
value no, and if not under what conditions not having this attribute
would make sense (it appears to result in a cond_exec output pattern of
the form "(%Cn) #", but the split code does not appear to ever get
conditionalized, so the patterns seems simply useless, making the
compiler bigger and perhaps slower) 

Thanks, Jan