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[Bug tree-optimization/34683] SSA rewriting in the loop unroller causes quadratic behavior
- From: "rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 11 Jan 2008 13:29:17 -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 #47 from rguenth at gcc dot gnu dot org 2008-01-11 13:29 -------
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).
So we could use two variants of all routines, one using GC allocated VECs and
one using heap allocated VECs and use the GC allocated one only for the final
SCC iteration and the PRE tables.
Smells like a task for C++ templates or a really ugly hack in C.
Obviously this is not going to happen for 4.3 :/
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34683