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* [Bug tree-optimization/99887] New: Failure to optimize log2 pattern to clz
@ 2021-04-03 0:04 gabravier at gmail dot com
2021-04-06 7:52 ` [Bug tree-optimization/99887] " rguenth at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: gabravier at gmail dot com @ 2021-04-03 0:04 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99887
Bug ID: 99887
Summary: Failure to optimize log2 pattern to clz
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: gabravier at gmail dot com
Target Milestone: ---
static inline unsigned int_log2_rec(unsigned x)
{
return x == 0 ? 0 : int_log2_rec(x >> 1) + 1;
}
unsigned int_log2(unsigned x)
{
return x == 0 ? 0 : int_log2_rec(x) - 1;
}
This can be optimized to `return x == 0 ? x : 31 - __builtin_clz(x);`. This
transformation is done by LLVM, but not by GCC.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/99887] Failure to optimize log2 pattern to clz
2021-04-03 0:04 [Bug tree-optimization/99887] New: Failure to optimize log2 pattern to clz gabravier at gmail dot com
@ 2021-04-06 7:52 ` rguenth at gcc dot gnu.org
2021-04-06 7:59 ` jakub at gcc dot gnu.org
2021-08-03 23:20 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: rguenth at gcc dot gnu.org @ 2021-04-06 7:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99887
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2021-04-06
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed. We're not having CLZ pattern detection (niter analysis can do
popcount only)
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/99887] Failure to optimize log2 pattern to clz
2021-04-03 0:04 [Bug tree-optimization/99887] New: Failure to optimize log2 pattern to clz gabravier at gmail dot com
2021-04-06 7:52 ` [Bug tree-optimization/99887] " rguenth at gcc dot gnu.org
@ 2021-04-06 7:59 ` jakub at gcc dot gnu.org
2021-08-03 23:20 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: jakub at gcc dot gnu.org @ 2021-04-06 7:59 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99887
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Related to PR94793
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug tree-optimization/99887] Failure to optimize log2 pattern to clz
2021-04-03 0:04 [Bug tree-optimization/99887] New: Failure to optimize log2 pattern to clz gabravier at gmail dot com
2021-04-06 7:52 ` [Bug tree-optimization/99887] " rguenth at gcc dot gnu.org
2021-04-06 7:59 ` jakub at gcc dot gnu.org
@ 2021-08-03 23:20 ` pinskia at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-08-03 23:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99887
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This is the same as PR 94793 really.
*** This bug has been marked as a duplicate of bug 94793 ***
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-08-03 23:20 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-04-03 0:04 [Bug tree-optimization/99887] New: Failure to optimize log2 pattern to clz gabravier at gmail dot com
2021-04-06 7:52 ` [Bug tree-optimization/99887] " rguenth at gcc dot gnu.org
2021-04-06 7:59 ` jakub at gcc dot gnu.org
2021-08-03 23:20 ` pinskia at gcc dot gnu.org
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