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[Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled
- From: "dnovillo at google dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 27 Sep 2007 14:12:30 -0000
- Subject: [Bug tree-optimization/33562] [4.3 Regression] aggregate DSE disabled
- References: <firstname.lastname@example.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #9 from dnovillo at google dot com 2007-09-27 14:12 -------
Subject: Re: [4.3 Regression] aggregate DSE disabled
On 27 Sep 2007 14:01:18 -0000, rguenther at suse dot de
> I sort-of agree. Still DCE was able to handle tree-ssa/complex-4.c
> before we removed V_MUST_DEF. Which is what I'm trying to get back.
Yeah, it is somewhat tempting to make the infrastructure more powerful
because you suddenly get more out of seemingly innocent passes.
However, a more powerful infrastructure creates problems of its own,
it needs to be maintained and it causes slowdowns even in passes that
do not need all the expressive power.
> As "good enough" UD web it would be nice to have only single VDEFs on
> stores (I don't care for clobbers at call sites). Though finding the
> optimal static partitioning to ensure this is probably hard?
Yeah, that is the whole motivation behind the dynamic aspects of
mem-ssa, but getting it right has proven tricky. Unfortunately, I
have not had time to come back to that idea in some time.