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From: "rakdver at kam dot mff dot cuni dot cz" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/34244] [4.3 Regression] VRP/SCEV miscompiles Firefox
Date: Wed, 28 Nov 2007 16:05:00 -0000 [thread overview]
Message-ID: <20071128160504.1584.qmail@sourceware.org> (raw)
In-Reply-To: <bug-34244-10053@http.gcc.gnu.org/bugzilla/>
------- Comment #7 from rakdver at kam dot mff dot cuni dot cz 2007-11-28 16:05 -------
Subject: Re: [4.3 Regression] VRP/SCEV miscompiles Firefox
> ------- Comment #6 from rguenth at gcc dot gnu dot org 2007-11-28 15:47 -------
> We could clear the SCEV cache for an SSA_NAME we set a new value range
> (in set_value_range and set_value_range_to_varying), but I
> see that SCEV also caches loop->nb_iterations which we probably would need to
> clear unconditionally (for all loops).
yes, the simplest solution is to call scev_reset somewhere (either in
set_value_range, or in adjust_range_with_scev). However, I fear the
compile time impact would be too large (# of iterations analysis is
fairly time consuming, and not caching the results used to cause
us to spend 10% or more in it).
More feasible solution seems to be to determine the number of iterations
for all loops before the start of VRP, and to remember the values.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34244
next prev parent reply other threads:[~2007-11-28 16:05 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-27 11:12 [Bug tree-optimization/34244] New: " rguenth at gcc dot gnu dot org
2007-11-27 11:30 ` [Bug tree-optimization/34244] " rguenth at gcc dot gnu dot org
2007-11-27 12:04 ` pinskia at gcc dot gnu dot org
2007-11-27 13:57 ` rakdver at gcc dot gnu dot org
2007-11-27 14:04 ` rguenther at suse dot de
2007-11-27 16:48 ` rakdver at gcc dot gnu dot org
2007-11-27 17:00 ` rakdver at gcc dot gnu dot org
2007-11-27 22:21 ` mmitchel at gcc dot gnu dot org
2007-11-28 15:47 ` rguenth at gcc dot gnu dot org
2007-11-28 16:05 ` rakdver at kam dot mff dot cuni dot cz [this message]
2007-11-28 16:13 ` rguenther at suse dot de
2007-11-29 4:29 ` rakdver at gcc dot gnu dot org
2007-11-30 0:32 ` rakdver at gcc dot gnu dot org
2007-11-30 7:20 ` jakub at gcc dot gnu dot org
2007-11-30 8:56 ` hjl at lucon dot org
2007-11-30 13:24 ` jakub at gcc dot gnu dot org
2008-05-31 13:02 ` rguenth at gcc dot gnu dot org
2008-06-06 20:08 ` rguenth at gcc dot gnu dot org
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