RFC: Simplify rules for ctz/clz patterns and RTL

[Segher Boessenkool]

>>> I think the cost would be something like:
>>> +    case POPCOUNT:
>>> +      *total = COSTS_N_INSNS (3);
>>> +      return false;
>
> Segher> Is that the cost when using popcountb?  It is a lot more
> Segher> expensive when that instruction isn't available (like on
> Segher> most current machines).
>
> 	Yes, but do we even create POPCOUNT rtx if the insn isn't
> supported?  Wouldn't we expand or create libcall early?

I don't know, there's only one way to find out... :-)


Segher