Re: [Committed] Reduce memory usage of DOM

[Jeffrey Law <law at redhat dot com>]

On Thu, 2006-06-08 at 10:32 -0600, Roger Sayle wrote:

>  678831 ordered_expr(ssa_name,integer_cst)
Definitely weird.

> The patch below avoids the creation of these unnecessary tree
> nodes in DOM, but only adding the FP ordered/unordered annotations
> to floating point comparison edges.  The change is relatively small
> (and obvious once explained), but as shown above saves a significant
> number of memory allocations and may even have an observable effect
> on compile-times.
> 
> 
> The following patch has been tested on x86_64-unknown-linux-gnu
> with a full "make bootstrap", all default languages, and regression
> tested with a top-level "make -k check" with no new failures.
> 
> Committed to mainline as revision 114489.  If someone can measure
> an observable improvement, we may consider this for 4.1.  For 4.3,
> I've a strategy for avoiding the creation of any these trees in
> record_conditions, but thats what I said about 4.2 when 4.1 entered
> stage3: http://gcc.gnu.org/ml/gcc-patches/2004-09/msg00542.html
> Hehe :-}
> 
> 
> 2006-06-08  Roger Sayle  <roger@eyesopen.com>
> 
> 	* tree-ssa-dom.c (record_conditions): Only record "unordered"
> 	conditions from floating point comparisons.
Excellent catch.

I've never been a big fan of that code, but haven't come across a better
way to accomplish the same thing yet.

jeff