DECL_RTL vs. explicit make_decl_rtl calls

[law@redhat.com]

In message <20020613192205.GB17782@daikokuya.demon.co.uk>, Neil Booth writes:
 > law@redhat.com wrote:-
 > 
 > > The #2 abuser of garbage collected memory is make_node, also with 15%
 > > of the calls to allocate garbage collected memory.  I haven't investigated
 > > this call chain at all.
 > 
 > Note that IDENTIFIER_NODE is never garbage collected, and should be
 > allocated separately from GC.  They should not really be trees, either,
 > but that would take some fixing, but save a bunch of memory, as almost
 > all of struct tree_common is unused for them.
Yea.  I'm not sure how you're going to get that separation though without
making IDENTIFIER_NODEs something other than trees.

jeff