How can I write an empty conversion instruction

[Richard Henderson]

On Fri, May 06, 2005 at 01:59:06PM -0700, Steve Ellcey wrote:
> I was wondering if anyone could tell me how to write an (empty)
> instruction pattern that does a truncate/extend conversion on a register
> 'in place'.
> 
> All the conversions I see are like this one in ia64/ia64.md:
> 
> (define_insn "extendsfdf2"
>   [(set (match_operand:DF 0 "fr_register_operand" "=f")
>         (float_extend:DF (match_operand:SF 1 "fr_register_operand" "f")))]
>   ""
>   "fnorm.d %0 = %1"
>   [(set_attr "itanium_class" "fmac")])
> 
> Where the source and the destination may or may not be the same
> register.

The best way is to have a post-reload splitter that splits the insn
into nothing at all.


r~