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* [Bug c/33426] New: Support of #pragma ivdep
@ 2007-09-13 21:03 gjunk at sapience dot com
2007-09-13 21:13 ` [Bug c/33426] " rguenth at gcc dot gnu dot org
` (8 more replies)
0 siblings, 9 replies; 10+ messages in thread
From: gjunk at sapience dot com @ 2007-09-13 21:03 UTC (permalink / raw)
To: gcc-bugs
When comparing run time on some (floating point) CPU intensive code, we find
that Intel's ICC (9.1) compiler runs significantly faster (30 - 50%) for some
programs - this seems to stem (large) part from ICC's ability to take advantage
of #pragma ivdep. There may be some other differences of course. Tests were run
using gcc 3.3.3 - re-compiling relevant key code with gcc 4.1.2 did not make
any real change.
Wondering if there are any plans to support this ?
thanks
gene/
--
Summary: Support of #pragma ivdep
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: gjunk at sapience dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug c/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
@ 2007-09-13 21:13 ` rguenth at gcc dot gnu dot org
2007-09-13 21:14 ` pinskia at gcc dot gnu dot org
` (7 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2007-09-13 21:13 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from rguenth at gcc dot gnu dot org 2007-09-13 21:12 -------
Confirmed. Zdenek, we should now be able to attach this to loop information
and preserve it until data dependence analysis, right?
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu dot
| |org, rakdver at gcc dot gnu
| |dot org
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2007-09-13 21:12:49
date| |
Summary|Support of #pragma ivdep |Support of #pragma ivdep
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug c/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
2007-09-13 21:13 ` [Bug c/33426] " rguenth at gcc dot gnu dot org
@ 2007-09-13 21:14 ` pinskia at gcc dot gnu dot org
2007-09-13 21:21 ` rguenth at gcc dot gnu dot org
` (6 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2007-09-13 21:14 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gcc dot gnu dot org 2007-09-13 21:14 -------
What are the exact semantics of ivdep?
Please provide them before asking if we support it.
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |WAITING
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug c/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
2007-09-13 21:13 ` [Bug c/33426] " rguenth at gcc dot gnu dot org
2007-09-13 21:14 ` pinskia at gcc dot gnu dot org
@ 2007-09-13 21:21 ` rguenth at gcc dot gnu dot org
2007-09-13 21:23 ` pinskia at gcc dot gnu dot org
` (5 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2007-09-13 21:21 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2007-09-13 21:21 -------
#pragma ivdep
Says the compiler may assume the following loop nest does not have loop carried
data dependenices.
Supported at least by SGI CC and the Intel compiler.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
Last reconfirmed|2007-09-13 21:12:49 |2007-09-13 21:21:05
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug c/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
` (2 preceding siblings ...)
2007-09-13 21:21 ` rguenth at gcc dot gnu dot org
@ 2007-09-13 21:23 ` pinskia at gcc dot gnu dot org
2007-09-13 21:25 ` rguenth at gcc dot gnu dot org
` (4 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2007-09-13 21:23 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from pinskia at gcc dot gnu dot org 2007-09-13 21:23 -------
http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi/0650/bks/SGI_Developer/books/Pragmas/sgi_html/ch08.html
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug c/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
` (3 preceding siblings ...)
2007-09-13 21:23 ` pinskia at gcc dot gnu dot org
@ 2007-09-13 21:25 ` rguenth at gcc dot gnu dot org
2007-09-13 21:26 ` rguenth at gcc dot gnu dot org
` (3 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2007-09-13 21:25 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from rguenth at gcc dot gnu dot org 2007-09-13 21:25 -------
The SGI compiler restricts the pragma to innermost loops. The Intel compiler
restricts the pragma to affect assumed data-dependencies only, that is, if
data dependence analysis statically can prove a data-dependency this
dependency is _not_ ignored.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|other |c
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug c/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
` (4 preceding siblings ...)
2007-09-13 21:25 ` rguenth at gcc dot gnu dot org
@ 2007-09-13 21:26 ` rguenth at gcc dot gnu dot org
2007-09-13 21:27 ` [Bug other/33426] " pinskia at gcc dot gnu dot org
` (2 subsequent siblings)
8 siblings, 0 replies; 10+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2007-09-13 21:26 UTC (permalink / raw)
To: gcc-bugs
------- Comment #6 from rguenth at gcc dot gnu dot org 2007-09-13 21:26 -------
http://www.intel.com/cd/ids/developer/asmo-na/eng/65774.htm?page=4
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug other/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
` (5 preceding siblings ...)
2007-09-13 21:26 ` rguenth at gcc dot gnu dot org
@ 2007-09-13 21:27 ` pinskia at gcc dot gnu dot org
2007-09-13 22:21 ` gjunk at sapience dot com
2007-09-19 21:34 ` gjunk at sapience dot com
8 siblings, 0 replies; 10+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2007-09-13 21:27 UTC (permalink / raw)
To: gcc-bugs
------- Comment #7 from pinskia at gcc dot gnu dot org 2007-09-13 21:27 -------
http://gcc.gnu.org/ml/gcc-patches/2005-03/msg00166.html
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |other
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug other/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
` (6 preceding siblings ...)
2007-09-13 21:27 ` [Bug other/33426] " pinskia at gcc dot gnu dot org
@ 2007-09-13 22:21 ` gjunk at sapience dot com
2007-09-19 21:34 ` gjunk at sapience dot com
8 siblings, 0 replies; 10+ messages in thread
From: gjunk at sapience dot com @ 2007-09-13 22:21 UTC (permalink / raw)
To: gcc-bugs
------- Comment #8 from gjunk at sapience dot com 2007-09-13 22:21 -------
*** Bug 33427 has been marked as a duplicate of this bug. ***
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
^ permalink raw reply [flat|nested] 10+ messages in thread
* [Bug other/33426] Support of #pragma ivdep
2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
` (7 preceding siblings ...)
2007-09-13 22:21 ` gjunk at sapience dot com
@ 2007-09-19 21:34 ` gjunk at sapience dot com
8 siblings, 0 replies; 10+ messages in thread
From: gjunk at sapience dot com @ 2007-09-19 21:34 UTC (permalink / raw)
To: gcc-bugs
------- Comment #9 from gjunk at sapience dot com 2007-09-19 21:34 -------
Thanks for feedback - not exactly sure where this leaves things - but if gcc
can deliver the same kind of floating point performance as icc it would be a
really good thing.
The 2005 article - wasn't clear to me what that meant other than this was
considered some time back - I assume this is a 2 step process.
(1) making the info available (perhaps that is already done - is that what
that means?)
(2) consuming the info so the optimization engine can do a better job -
which I suspect is work still remaining.
Thank you for all your help.
g/
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33426
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2007-09-13 21:03 [Bug c/33426] New: Support of #pragma ivdep gjunk at sapience dot com
2007-09-13 21:13 ` [Bug c/33426] " rguenth at gcc dot gnu dot org
2007-09-13 21:14 ` pinskia at gcc dot gnu dot org
2007-09-13 21:21 ` rguenth at gcc dot gnu dot org
2007-09-13 21:23 ` pinskia at gcc dot gnu dot org
2007-09-13 21:25 ` rguenth at gcc dot gnu dot org
2007-09-13 21:26 ` rguenth at gcc dot gnu dot org
2007-09-13 21:27 ` [Bug other/33426] " pinskia at gcc dot gnu dot org
2007-09-13 22:21 ` gjunk at sapience dot com
2007-09-19 21:34 ` gjunk at sapience dot com
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