SSA annotations memory use.

[Jan Hubicka <jh at suse dot cz>]

Hi,
I've been looking into memory usage of tree-profiling branch and after
parsing combine.c roughly 25% is consumed by CFG related datastructurs.
3% are adges, 2.7% tsi linked lists, 6.6% blocks, 7% labels, 13%
statement annotations.

Overall the scenario is not _that_ bad as we cleanup code early so
memory peak is actually 20% smaller for Gerald's testcase and 12% bigger
for GCC binarry compared to mainline, but still this looks like quite
bloated stuff.

I think I can get the CFG usage down by splitting up the info used by
RTL only to be allocated on local basis and prune out some unneded stuff
from edges and blocks, but the major part are the labels and
annotations.  Are there any current plans on getting these smaller?
(one obvious idea is to kill the annotations once function is analyzed
and recompute them when it is being compiled, but this is side step from
plan to build and preserve SSA), but perhaps we can think of breaking it
up to part that survive from analysis to compilatio and part that will
get recomputed cheaply?

Honza