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* [Bug tree-optimization/96603] New: Failure to optimize memcmp out for more than one byte
@ 2020-08-13 15:20 gabravier at gmail dot com
2020-08-13 19:18 ` [Bug tree-optimization/96603] " msebor at gcc dot gnu.org
2020-08-13 19:36 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: gabravier at gmail dot com @ 2020-08-13 15:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96603
Bug ID: 96603
Summary: Failure to optimize memcmp out for more than one byte
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: ---
int f(const void *s1, const void *s2)
{
return memcmp(s1, s2, 2);
}
This can be optimized to `loadbe16(s1) - loadbe16(s2)` (where loadbe16 is a
function that read a 16-bit big endian number). This transformation is done by
LLVM, but not by GCC.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/96603] Failure to optimize memcmp out for more than one byte
2020-08-13 15:20 [Bug tree-optimization/96603] New: Failure to optimize memcmp out for more than one byte gabravier at gmail dot com
@ 2020-08-13 19:18 ` msebor at gcc dot gnu.org
2020-08-13 19:36 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: msebor at gcc dot gnu.org @ 2020-08-13 19:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96603
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2020-08-13
CC| |msebor at gcc dot gnu.org
Keywords| |missed-optimization
Status|UNCONFIRMED |NEW
Severity|normal |enhancement
Ever confirmed|0 |1
--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
I've been thinking about this transformation, not just for sizes of 2 but for
larger objects as well. Looks like Clang 5 and later implements it for powers
2 up to 16 and does something slightly more involved for other small sizes of
10 bytes and less.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug tree-optimization/96603] Failure to optimize memcmp out for more than one byte
2020-08-13 15:20 [Bug tree-optimization/96603] New: Failure to optimize memcmp out for more than one byte gabravier at gmail dot com
2020-08-13 19:18 ` [Bug tree-optimization/96603] " msebor at gcc dot gnu.org
@ 2020-08-13 19:36 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-08-13 19:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96603
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |DUPLICATE
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 12086.
*** This bug has been marked as a duplicate of bug 12086 ***
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-08-13 19:36 UTC | newest]
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2020-08-13 15:20 [Bug tree-optimization/96603] New: Failure to optimize memcmp out for more than one byte gabravier at gmail dot com
2020-08-13 19:18 ` [Bug tree-optimization/96603] " msebor at gcc dot gnu.org
2020-08-13 19:36 ` pinskia at gcc dot gnu.org
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