[dataflow]: patch committed to do incremental scanning of rtl.

[Kenneth Zadeck]

Paolo Bonzini wrote:
>
>> 4) Many of the passes use defered scanning.  In this mode, a bitmap is
>> kept of the insns that have been changed and at the end of the pass
>> all of the marked insns are rescanned.  This is particularly efficient
>> for passes like combine which modify insns many times but do not
>> directly make use of the scanning information.  FWprop also uses this
>> technique and has been re-enabled by this patch.  
>
> Thank you.  I was about to write some thoughts about deferring the
> scan until the end of the pass, but you beat me by a wide margin.
>
> Paolo
Paolo,
 
Any chance of getting you to look at changing regrename to use df
def-use chains?

Kenny