RFC: Simplify rules for ctz/clz patterns and RTL

[Zack Weinberg]

Andrew Pinski wrote:
> On 8/15/07, Zack Weinberg <zack@codesourcery.com> wrote:
>> Is popcount really slow on PowerPC?  (Compared to clz?)
> popcount is really popcount in bytes and then you do a multiple to get
> the real popcount.  This is why it is slower than count leading zeros.
>  Also popcount does not exist in most powerpc's while count leading
> zeros exist in all.

Makes sense.  I don't suppose I could persuade you to teach rs6000 
RTX_COSTS about clz and popcount...?

zw