Re: Save 6% of GGC memory (consumed in tree-ssa-pre)

[Jan Hubicka <jh at suse dot cz>]

> Jan Hubicka wrote:
> > Hi,
> > memory statistics for combine.c at -O2 shows 13% of memory to be taken
> > by create_tree_ann function:
> > tree-phinodes.c:156 (allocate_phi_node)             3813160: 4.6% 0: 0.0%          0: 0.0%      22568: 0.3%      12114
> > genrtl.c:17 (gen_rtx_fmt_ee)                        7518920: 9.1% 0: 0.0%       3080: 0.0%    1504400:17.1%     188050
> > tree-dfa.c:209 (create_tree_ann)                   10927080:13.3% 0: 0.0%       7440: 0.1%     728968: 8.3%      91121
> > Total                                              82223861 12694004          6318427          8805836          1369076
> > 
> > This is the same for my now favorite testcase and other common sources.
> > I always accounted it to annotations being bloated, but I unstrumented
> > create_tree_ann for statistics and found out that this all memory is in
> > fact allocated all by tree-vn and it is all there just to hold one
> > pointer value_handle.  I would say that a hashtable would do a lot
> > better job here (or direct use of the annotation pointer on
> > expressions), but I am leaving it for Danny 
> 
> If you use a hashtable, your PRE times will jump about 4 or 5x (my
> recollection but feel free to try it yourself :) )
> It makes *very* heavy use of getting the value handle, and it can't
> really be avoided.

Hmm, can't we somehow figure out what nodes are those allocated in
allocpool and instead of producing annotations for them using the
annotation pointer as value_handle pointer?  That would save one
indirection too.

Honza
> 
> 
>