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From: "jamborm at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/44423] [4.5/4.6 Regression] Massive performance regression in SSE code due to SRA
Date: Mon, 14 Jun 2010 12:40:00 -0000 [thread overview]
Message-ID: <20100614123953.5528.qmail@sourceware.org> (raw)
In-Reply-To: <bug-44423-2736@http.gcc.gnu.org/bugzilla/>
------- Comment #15 from jamborm at gcc dot gnu dot org 2010-06-14 12:39 -------
(In reply to comment #14)
> SSE performance is fine again, thanks a lot!
>
> One more question, if that's OK...
> Depending on ARRSZ the testcase uses wildly varying amounts of CPU time; it's
> about half a second for ARRSZ=1024, but almost 10 seconds for ARRSZ=20 on my
> machine, which is extremely strange because the operation count is the same in
> both cases. I suspect that something weird is happening with respect to the
> cache and prefetching. Should I open another PR for this?
>
The generated assembly is not different for the two cases, except that
there are much smaller offsets, of course. This means that the lpic
and pre1 arrays are much closer to each other which may be something
the processor does not like. I find this surprising but unless you
can think of a specific missed optimization opportunity (I can't), I
don't think it is a PR material.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44423
next prev parent reply other threads:[~2010-06-14 12:40 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-05 10:17 [Bug regression/44423] New: [4.5/4.6] Massive performance regression in SSE code martin at mpa-garching dot mpg dot de
2010-06-05 10:18 ` [Bug regression/44423] " martin at mpa-garching dot mpg dot de
2010-06-05 10:47 ` rguenth at gcc dot gnu dot org
2010-06-05 10:56 ` [Bug tree-optimization/44423] [4.5/4.6 Regression] Massive performance regression in SSE code due to SRA rguenth at gcc dot gnu dot org
2010-06-08 13:16 ` jamborm at gcc dot gnu dot org
2010-06-08 13:54 ` martin at mpa-garching dot mpg dot de
2010-06-08 14:03 ` rguenth at gcc dot gnu dot org
2010-06-08 14:29 ` jamborm at gcc dot gnu dot org
2010-06-08 14:51 ` rguenth at gcc dot gnu dot org
2010-06-08 15:00 ` jamborm at gcc dot gnu dot org
2010-06-08 15:11 ` rguenth at gcc dot gnu dot org
2010-06-09 9:03 ` jamborm at gcc dot gnu dot org
2010-06-09 9:06 ` jamborm at gcc dot gnu dot org
2010-06-09 11:21 ` jamborm at gcc dot gnu dot org
2010-06-09 12:06 ` martin at mpa-garching dot mpg dot de
2010-06-14 12:40 ` jamborm at gcc dot gnu dot org [this message]
2010-06-14 12:46 ` martin at mpa-garching dot mpg dot de
2010-06-14 12:50 ` jamborm at gcc dot gnu dot org
2010-06-15 9:49 ` jamborm at gcc dot gnu dot org
2010-06-15 10:04 ` jamborm at gcc dot gnu dot org
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