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From: "steven at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/39326] Segmentation fault with -O1, out of memory with -O2 Date: Mon, 11 Mar 2013 09:40:00 -0000 [thread overview] Message-ID: <bug-39326-4-lIyBQYKbSc@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-39326-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39326 --- Comment #45 from Steven Bosscher <steven at gcc dot gnu.org> 2013-03-11 09:40:18 UTC --- Patches posted: * Restrict GIMPLE loop invariant code motion of loop-invariant loads and stores to loops with fewer memory references than a certain maximum that is controlled with --param loops-max-datarefs-for-datadeps" from the command line. http://gcc.gnu.org/ml/gcc-patches/2013-03/msg00380.html * Do not create new pseudo-registers for load-after-store transformations in RTL dead store elimination. This reduces the memory foot print after DSE by ~2 percent, and avoids the compile time and memory usage explosion in combine because it gets presented fewer single-def/single-use register moves that are really just register copies. http://gcc.gnu.org/ml/gcc-patches/2013-03/msg00379.html * Make gcse.c respect -fno-gcse-lm. For the RTL PRE problem, this means compile time is reasonable with -fno-gcse-lm. A follow-up patch will implement some mechanism to disable load motion automatically on extreme test cases like the one from this PR. http://gcc.gnu.org/ml/gcc-patches/2013-03/msg00386.html The remaining compile time bottlenecks are: - RTL dead store limination in its analysis phase. This is mostly time spent in dependence tests in alias analysis for instructions in a single basic block, so it's only a problem for test cases where there is a huge number of loads and stores in each basic block. I don't think it is worth speeding up DSE for such extreme cases. - Post-reload CSE because it is in the worst-case quadratic in the number of instructions in a basic block. In most practical cases, post-reload CSE scales linearly with the number of instructions in a basic block, but with a large constant bound. It looks up and down through the instruction chain to see if a reg is not clobbered between a use and a def. Because it only has to do so with hard registers the typical bound is closer to "number of insns in basic block" * "number of hard registers". This is fine, I am not going to try and improve this.
next prev parent reply other threads:[~2013-03-11 9:40 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-39326-4@http.gcc.gnu.org/bugzilla/> 2013-03-06 11:08 ` steven at gcc dot gnu.org 2013-03-06 11:38 ` rguenth at gcc dot gnu.org 2013-03-06 16:50 ` sergstesh at yahoo dot com 2013-03-06 23:39 ` steven at gcc dot gnu.org 2013-03-07 0:08 ` steven at gcc dot gnu.org 2013-03-07 0:27 ` steven at gcc dot gnu.org 2013-03-07 8:10 ` steven at gcc dot gnu.org 2013-03-07 8:45 ` rguenther at suse dot de 2013-03-07 8:48 ` rguenther at suse dot de 2013-03-07 8:53 ` rguenther at suse dot de 2013-03-07 9:58 ` steven at gcc dot gnu.org 2013-03-07 10:14 ` sergstesh at yahoo dot com 2013-03-07 10:15 ` rguenther at suse dot de 2013-03-07 17:14 ` sergstesh at yahoo dot com 2013-03-07 17:31 ` steven at gcc dot gnu.org 2013-03-07 17:34 ` steven at gcc dot gnu.org 2013-03-07 21:48 ` sergstesh at yahoo dot com 2013-03-07 22:16 ` steven at gcc dot gnu.org 2013-03-07 23:19 ` steven at gcc dot gnu.org 2013-03-08 9:14 ` rguenth at gcc dot gnu.org 2013-03-08 9:14 ` rguenth at gcc dot gnu.org 2013-03-08 9:23 ` rguenther at suse dot de 2013-03-09 14:58 ` steven at gcc dot gnu.org 2013-03-09 17:26 ` steven at gcc dot gnu.org 2013-03-11 9:40 ` steven at gcc dot gnu.org [this message] 2013-03-12 10:47 ` rguenth at gcc dot gnu.org 2013-03-12 14:05 ` rguenth at gcc dot gnu.org 2013-03-15 16:07 ` rguenth at gcc dot gnu.org 2013-03-18 8:44 ` rguenth at gcc dot gnu.org 2013-03-21 20:04 ` jakub at gcc dot gnu.org 2013-03-22 14:01 ` rguenth at gcc dot gnu.org 2013-03-26 10:10 ` rguenth at gcc dot gnu.org 2014-01-15 15:14 ` rguenth at gcc dot gnu.org 2014-01-17 13:53 ` rguenth at gcc dot gnu.org 2022-03-10 15:05 ` rguenth at gcc dot gnu.org 2024-02-20 13:14 ` rguenth at gcc dot gnu.org 2009-02-28 15:23 [Bug c/39326] New: " sergstesh at yahoo dot com 2009-03-02 17:16 ` [Bug middle-end/39326] " pinskia at gcc dot gnu dot org 2009-03-03 13:36 ` sergstesh at yahoo dot com 2009-03-03 13:49 ` rguenther at suse dot de 2009-03-03 14:15 ` sergstesh at yahoo dot com 2009-03-17 11:05 ` rguenth at gcc dot gnu dot org 2009-03-17 12:42 ` rguenth at gcc dot gnu dot org 2009-03-17 12:59 ` rguenth at gcc dot gnu dot org 2009-03-17 13:10 ` rguenth at gcc dot gnu dot org
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