public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte
@ 2013-12-27 16:55 gcc-bugzilla at contacts dot eelis.net
2013-12-27 16:57 ` [Bug libstdc++/59611] " gcc-bugzilla at contacts dot eelis.net
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: gcc-bugzilla at contacts dot eelis.net @ 2013-12-27 16:55 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59611
Bug ID: 59611
Summary: std::copy performs worse than naive implementation
when copying a single known byte
Product: gcc
Version: 4.9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc-bugzilla at contacts dot eelis.net
Created attachment 31524
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31524&action=edit
Testcase
The attached testcase shows how using a naive implementation (mycopy) causes
gcc to generate better code than using std::copy.
(Clang /does/ generate optimal code when using std::copy in this case.)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug libstdc++/59611] std::copy performs worse than naive implementation when copying a single known byte
2013-12-27 16:55 [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte gcc-bugzilla at contacts dot eelis.net
@ 2013-12-27 16:57 ` gcc-bugzilla at contacts dot eelis.net
2013-12-27 22:29 ` [Bug tree-optimization/59611] " glisse at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: gcc-bugzilla at contacts dot eelis.net @ 2013-12-27 16:57 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59611
--- Comment #1 from Eelis <gcc-bugzilla at contacts dot eelis.net> ---
(With -O3)
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/59611] std::copy performs worse than naive implementation when copying a single known byte
2013-12-27 16:55 [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte gcc-bugzilla at contacts dot eelis.net
2013-12-27 16:57 ` [Bug libstdc++/59611] " gcc-bugzilla at contacts dot eelis.net
@ 2013-12-27 22:29 ` glisse at gcc dot gnu.org
2014-06-26 14:49 ` rguenth at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: glisse at gcc dot gnu.org @ 2013-12-27 22:29 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59611
Marc Glisse <glisse at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-12-27
Component|libstdc++ |tree-optimization
Ever confirmed|0 |1
--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> ---
The call to memcpy is folded rather early to:
MEM[(char * {ref-all})p_2(D)] = MEM[(char * {ref-all})&a];
and then we don't touch it anymore, maybe because we don't go through an
SSA_NAME. We thus miss that the RHS is a constant.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/59611] std::copy performs worse than naive implementation when copying a single known byte
2013-12-27 16:55 [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte gcc-bugzilla at contacts dot eelis.net
2013-12-27 16:57 ` [Bug libstdc++/59611] " gcc-bugzilla at contacts dot eelis.net
2013-12-27 22:29 ` [Bug tree-optimization/59611] " glisse at gcc dot gnu.org
@ 2014-06-26 14:49 ` rguenth at gcc dot gnu.org
2014-06-27 10:40 ` rguenth at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-06-26 14:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59611
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot gnu.org
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Mine.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/59611] std::copy performs worse than naive implementation when copying a single known byte
2013-12-27 16:55 [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte gcc-bugzilla at contacts dot eelis.net
` (2 preceding siblings ...)
2014-06-26 14:49 ` rguenth at gcc dot gnu.org
@ 2014-06-27 10:40 ` rguenth at gcc dot gnu.org
2014-07-11 13:44 ` rguenth at gcc dot gnu.org
2014-07-14 11:50 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-06-27 10:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59611
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Depends on| |61473
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
Fixed by the patch for PR61473.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/59611] std::copy performs worse than naive implementation when copying a single known byte
2013-12-27 16:55 [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte gcc-bugzilla at contacts dot eelis.net
` (3 preceding siblings ...)
2014-06-27 10:40 ` rguenth at gcc dot gnu.org
@ 2014-07-11 13:44 ` rguenth at gcc dot gnu.org
2014-07-14 11:50 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-07-11 13:44 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59611
Bug 59611 depends on bug 61473, which changed state.
Bug 61473 Summary: register sized memmove not inlined
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61473
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/59611] std::copy performs worse than naive implementation when copying a single known byte
2013-12-27 16:55 [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte gcc-bugzilla at contacts dot eelis.net
` (4 preceding siblings ...)
2014-07-11 13:44 ` rguenth at gcc dot gnu.org
@ 2014-07-14 11:50 ` rguenth at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: rguenth at gcc dot gnu.org @ 2014-07-14 11:50 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59611
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Verified that the 61473 fix fixed this as well.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-07-14 11:50 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2013-12-27 16:55 [Bug libstdc++/59611] New: std::copy performs worse than naive implementation when copying a single known byte gcc-bugzilla at contacts dot eelis.net
2013-12-27 16:57 ` [Bug libstdc++/59611] " gcc-bugzilla at contacts dot eelis.net
2013-12-27 22:29 ` [Bug tree-optimization/59611] " glisse at gcc dot gnu.org
2014-06-26 14:49 ` rguenth at gcc dot gnu.org
2014-06-27 10:40 ` rguenth at gcc dot gnu.org
2014-07-11 13:44 ` rguenth at gcc dot gnu.org
2014-07-14 11:50 ` rguenth at gcc dot gnu.org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).