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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] Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 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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