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

["dberlin at dberlin dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From dberlin at dberlin dot org  2004-03-13 17:07 -------
Subject: Re:  [tree-ssa] Many C++ compile-time regression in 3.5-tree-ssa 040120

> So appearantly PRE got a factor of 10 slower!?
>

Note that the other functions got a factor of 3-5 slower too. As I 
said, PRE just has a larger constant, so it's more noticeable.
This tells me something else important changed, probably in cgraph or 
something.
There is little i can do, a lot of the portions wasting time are 
already O(n) (compute_down_safety for example).
The only thing to do is reduce the number of expressions we PRE, give 
up PRE entirely on such functions, or change PRE algorithms.

I'm actually working on 3 and 2, rather than 1.
1 is tricky, we already give up on expressions that occur once, which 
makes us lose some load motion.
Number 2 requires figuring out what properties of this function make it 
such a pain in the ass, which is what i'm doing.
and #3 is being worked on in the background, i'm waiting for Steven to 
get back to get more work done.




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