[tree-ssa] Lazily allocate varrays

[law@redhat.com]

In message <Pine.LNX.4.58.0311261225150.13062@D209.suse.de>, Gerald Pfeifer wri
tes:
 >BTW, how exactly do you measure *overall* memory consumption? 
What do you mean by "overall"? 

Typically what I'm measuring is the amount of data we're requesting from
the GC system.  That does not necessarily translate one to one with the
amount of memory the GC system requests from the OS.

I also watch the amount of GC'd memory that is still live at the end of
compilation, though this number is a lot more difficult to interpret.  In
general it's going down, but that's mostly an artifact of less fragmentation
of pages since none of the memory reduction changes I've been making should
directly change the amount of persistent memory.


Jeff