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* [Bug tree-optimization/103509] New: ((-1u >> t) & b) != 0 is not optimized to b != 0
@ 2021-11-30 23:35 pinskia at gcc dot gnu.org
2021-11-30 23:43 ` [Bug tree-optimization/103509] " navidrahimi at microsoft dot com
0 siblings, 1 reply; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-11-30 23:35 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103509
Bug ID: 103509
Summary: ((-1u >> t) & b) != 0 is not optimized to b != 0
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take:
bool f1(bool a, int t)
{
unsigned tt = -1;
tt >>= t;
return (a&tt) != 0;
}
bool f2(bool a, int t)
{
unsigned tt = -1;
tt >>= t;
return (tt) != 0;
}
As shown by the above, we know that (-1u>>t)!=0 is always true Therefore we
should be able to optimize f1 to just a!=0
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/103509] ((-1u >> t) & b) != 0 is not optimized to b != 0
2021-11-30 23:35 [Bug tree-optimization/103509] New: ((-1u >> t) & b) != 0 is not optimized to b != 0 pinskia at gcc dot gnu.org
@ 2021-11-30 23:43 ` navidrahimi at microsoft dot com
0 siblings, 0 replies; 2+ messages in thread
From: navidrahimi at microsoft dot com @ 2021-11-30 23:43 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103509
Navid Rahimi <navidrahimi at microsoft dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |navidrahimi at microsoft dot com
--- Comment #1 from Navid Rahimi <navidrahimi at microsoft dot com> ---
Thanks Andrew. How about we close [1] in favor of this, to make sure we have
only single place to track this issue. Previous discussion about this was here
[2].
1) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98956
2) https://gcc.gnu.org/pipermail/gcc-patches/2021-November/585783.html
^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-11-30 23:35 [Bug tree-optimization/103509] New: ((-1u >> t) & b) != 0 is not optimized to b != 0 pinskia at gcc dot gnu.org
2021-11-30 23:43 ` [Bug tree-optimization/103509] " navidrahimi at microsoft dot com
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