Speeding up GC

[David S. Miller]

   From: law@redhat.com
   Date: Tue, 04 Jun 2002 09:42:28 -0600

   It seems to me we have to classes of short term needs for RTL.
   
     1. We're going to generate various hunks of RTL, none of which will be
        live after the "short term" mode is complete.  Clearly we want these
        to use different pages in the GC allocator and not pollute the GC
        pages that are interesting long-term.
   
Right.

     2. We're going to generate various hunks of RTL, but one or more of those
        hunks may be live after we're done with the "short term" mode.  This
        is the more interesting (and I suspect more important) long term problem
        to solve.
   
Use for_each_rtx() on the RTL you made to mark the pieces such that
RTL unsharing will copy it, move back to long-term mode before you
do the unshare.

I have most of this in my head already. :-)