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[Bug tree-optimization/34683] SSA rewriting in the loop unroller causes quadratic behavior
- From: "rakdver at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 12 Jan 2008 03:59:29 -0000
- Subject: [Bug tree-optimization/34683] SSA rewriting in the loop unroller causes quadratic behavior
- References: <bug-34683-14773@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #48 from rakdver at gcc dot gnu dot org 2008-01-12 03:59 -------
(In reply to comment #47)
> Most of the PRE/FRE memory is spent in copied VOPs VECs. Unfortunately we
> cannot move them to heap memory easily as the get shared in the PRE tables...
> I tried to be explicit in managing the memory, but it gets really hard (which
> is probably the reason we stick it in GC memory in the first place).
in fact, it copies the VOPS list of each store statement 50 times on average
(once for PRE and once for FRE, i.e., about 100x total). Cannot sccvn be
throttled down somehow so that it does not spend so much memory this way?
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34683