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* [Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q;
@ 2014-12-30 20:58 gcc-bugzilla at contacts dot eelis.net
2014-12-30 20:59 ` [Bug c++/64450] " ville.voutilainen at gmail dot com
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: gcc-bugzilla at contacts dot eelis.net @ 2014-12-30 20:58 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64450
Bug ID: 64450
Summary: Optimize 0>=p-q to q>=p for char*p,*q;
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gcc-bugzilla at contacts dot eelis.net
Created attachment 34365
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34365&action=edit
Testcase
It was noticed that Boost's iterator_facade incurred a performance penalty
(while it should ideally be zero-overhead), which results from the fact that
GCC does not optimize 0>=p-q to q>=p for char*p,*q;. See attachment.
This probably applies to > and < and <= as well.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug c++/64450] Optimize 0>=p-q to q>=p for char*p,*q;
2014-12-30 20:58 [Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q; gcc-bugzilla at contacts dot eelis.net
@ 2014-12-30 20:59 ` ville.voutilainen at gmail dot com
2014-12-30 21:36 ` [Bug tree-optimization/64450] " glisse at gcc dot gnu.org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: ville.voutilainen at gmail dot com @ 2014-12-30 20:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64450
Ville Voutilainen <ville.voutilainen at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Status|UNCONFIRMED |NEW
Last reconfirmed| |2014-12-30
CC| |ville.voutilainen at gmail dot com
Ever confirmed|0 |1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/64450] Optimize 0>=p-q to q>=p for char*p,*q;
2014-12-30 20:58 [Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q; gcc-bugzilla at contacts dot eelis.net
2014-12-30 20:59 ` [Bug c++/64450] " ville.voutilainen at gmail dot com
@ 2014-12-30 21:36 ` glisse at gcc dot gnu.org
2014-12-30 21:38 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: glisse at gcc dot gnu.org @ 2014-12-30 21:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64450
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
See also PR61734, Eric already tried in May.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/64450] Optimize 0>=p-q to q>=p for char*p,*q;
2014-12-30 20:58 [Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q; gcc-bugzilla at contacts dot eelis.net
2014-12-30 20:59 ` [Bug c++/64450] " ville.voutilainen at gmail dot com
2014-12-30 21:36 ` [Bug tree-optimization/64450] " glisse at gcc dot gnu.org
@ 2014-12-30 21:38 ` pinskia at gcc dot gnu.org
2023-05-14 23:20 ` pinskia at gcc dot gnu.org
2023-10-23 15:20 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2014-12-30 21:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64450
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #1)
> See also PR61734, Eric already tried in May.
Maybe it is easier to handle now with simplify-and-match.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/64450] Optimize 0>=p-q to q>=p for char*p,*q;
2014-12-30 20:58 [Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q; gcc-bugzilla at contacts dot eelis.net
` (2 preceding siblings ...)
2014-12-30 21:38 ` pinskia at gcc dot gnu.org
@ 2023-05-14 23:20 ` pinskia at gcc dot gnu.org
2023-10-23 15:20 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-05-14 23:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64450
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(for cmp (tcc_comparison)
(simplify
(cmp (pointer_diff @0 @1) integer_zero_p)
(cmp @0 @1)))
Maybe ....
But we might also need handle the match patterns for too:
A CMP B ? A - B : -(A - B)
A CMP B ? A - B : B - A
(which is also on my todo list anyways).
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug tree-optimization/64450] Optimize 0>=p-q to q>=p for char*p,*q;
2014-12-30 20:58 [Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q; gcc-bugzilla at contacts dot eelis.net
` (3 preceding siblings ...)
2023-05-14 23:20 ` pinskia at gcc dot gnu.org
@ 2023-10-23 15:20 ` pinskia at gcc dot gnu.org
4 siblings, 0 replies; 6+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-10-23 15:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64450
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Mine ...
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-10-23 15:20 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2014-12-30 20:58 [Bug c++/64450] New: Optimize 0>=p-q to q>=p for char*p,*q; gcc-bugzilla at contacts dot eelis.net
2014-12-30 20:59 ` [Bug c++/64450] " ville.voutilainen at gmail dot com
2014-12-30 21:36 ` [Bug tree-optimization/64450] " glisse at gcc dot gnu.org
2014-12-30 21:38 ` pinskia at gcc dot gnu.org
2023-05-14 23:20 ` pinskia at gcc dot gnu.org
2023-10-23 15:20 ` pinskia at gcc dot gnu.org
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