[Bug c++/13776] [tree-ssa] Many C++ compile-time regression in 3.5-tree-ssa 040120

[dberlin at dberlin dot org]

------- Additional Comments From dberlin at dberlin dot org  2004-03-13 15:57 -------
Subject: Re:  [tree-ssa] Many C++ compile-time regression in 3.5-tree-ssa 040120


On Mar 13, 2004, at 6:46 AM, rguenth at tat dot physik dot 
uni-tuebingen dot de wrote:
>>>
>>
>> Could we add thresholds to back away from overly complicated 
>> functions?
>
> Or just "split" them up using sort of windowing?  It looks clearly 
> wrong
> to not limit a O(n^2) or O(n^3) algorithm.
>

It's only collecting expressions that is O(n^2). The other parts of the 
algorithm just has a large constant.

Also, it *is* splitting up the function. It performs PRE one expression 
at a time.

We can't perform it one basic block at a time or anything with the 
current algorithm (and it wouldn't make sense to, because you can't 
find the optimal insertion points).



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13776