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[Bug tree-optimization/19686] [4.0 Regression] loop performance decrease, not comparing against 0
- From: "andrewhutchinson at cox dot net" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 8 Feb 2005 01:48:24 -0000
- Subject: [Bug tree-optimization/19686] [4.0 Regression] loop performance decrease, not comparing against 0
- References: <20050129065037.19686.dmixm@marine.febras.ru>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From andrewhutchinson at cox dot net 2005-02-08 01:48 -------
I ran testcase with proposed avr_costs patch applied. The result is unchanged.
The initially generated RTL is unfortunately beyond that which can be fixed by
backend. I dont think this problem is avr specific, it should appear on other
targets.
I have attached initially generated RTL. It is alarmingly complex given starting
point. (This is not so apparent in the assembler as the backend has done a
rather good job of tidying up what it can.)
Perhaps somebody could glance at this to see what exactly went off the rails. It
might just be a manifestation of a known problem.
Wish I could help more - but trees are beyond me at the moment.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19686