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* [Bug tree-optimization/96237] New: Failure to recognize and pattern composed of and+or after shift
@ 2020-07-17 21:16 gabravier at gmail dot com
2020-07-19 20:46 ` [Bug tree-optimization/96237] " pinskia at gcc dot gnu.org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: gabravier at gmail dot com @ 2020-07-17 21:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96237
Bug ID: 96237
Summary: Failure to recognize and pattern composed of and+or
after shift
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: ---
unsigned char f(unsigned char x)
{
auto a = (x >> 3) & 1;
if (x & 16)
a |= 2;
if (x & 32)
a |= 4;
return a;
}
This can be optimized to `return (x >> 3) & 7;`. This transformation is done by
LLVM, but not by GCC.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/96237] Failure to recognize and pattern composed of and+or after shift
2020-07-17 21:16 [Bug tree-optimization/96237] New: Failure to recognize and pattern composed of and+or after shift gabravier at gmail dot com
@ 2020-07-19 20:46 ` pinskia at gcc dot gnu.org
2020-07-19 22:53 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-07-19 20:46 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96237
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/96237] Failure to recognize and pattern composed of and+or after shift
2020-07-17 21:16 [Bug tree-optimization/96237] New: Failure to recognize and pattern composed of and+or after shift gabravier at gmail dot com
2020-07-19 20:46 ` [Bug tree-optimization/96237] " pinskia at gcc dot gnu.org
@ 2020-07-19 22:53 ` pinskia at gcc dot gnu.org
2021-07-17 2:38 ` pinskia at gcc dot gnu.org
2023-06-11 19:30 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2020-07-19 22:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96237
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2020-07-19
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
if (x & 16)
a |= 2;
Maybe should be transformed into:
a |= ((x >> 4) & 0x1) << 1;
Which in turn should be transformed into:
a |= ((x & 0x10) >> 3);
if (x & 32)
a |= 4;
gets transformed into:
a |= ((x & 0x20) >> 3);
And:
a |= ((x & 0x40) >> 3);
a |= ((x & 0x20) >> 3);
Into:
a |= ((x & 0x60) >> 3);
Or:
a |= ((x >> 3) & 0x6);
Combine that with:
a = (x >> 3) & 1;
gets us:
a |= ((x >> 3) & 0x7);
Hopefully I did that correctly.
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/96237] Failure to recognize and pattern composed of and+or after shift
2020-07-17 21:16 [Bug tree-optimization/96237] New: Failure to recognize and pattern composed of and+or after shift gabravier at gmail dot com
2020-07-19 20:46 ` [Bug tree-optimization/96237] " pinskia at gcc dot gnu.org
2020-07-19 22:53 ` pinskia at gcc dot gnu.org
@ 2021-07-17 2:38 ` pinskia at gcc dot gnu.org
2023-06-11 19:30 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-07-17 2:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96237
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org
Status|NEW |ASSIGNED
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I am going to implement the match patterns needed.
Something like:
(for bitop (bit_and bit_ior)
(simplify
(cond @0 (bitop @1 integer_power2@2) @1)
(bitop @1 (lshift @0 ({ log2(@2); }) ))))
Note log2 here is just psedu-code :).
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug tree-optimization/96237] Failure to recognize and pattern composed of and+or after shift
2020-07-17 21:16 [Bug tree-optimization/96237] New: Failure to recognize and pattern composed of and+or after shift gabravier at gmail dot com
` (2 preceding siblings ...)
2021-07-17 2:38 ` pinskia at gcc dot gnu.org
@ 2023-06-11 19:30 ` pinskia at gcc dot gnu.org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-06-11 19:30 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96237
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> I am going to implement the match patterns needed.
This is just expanding:
/* (zero_one != 0) ? z <op> y : y -> ((typeof(y))zero_one * z) <op> y */
Patterns not to just zero_one but rather integer_power2 which I am going to do
the week after next.
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-06-11 19:30 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2020-07-17 21:16 [Bug tree-optimization/96237] New: Failure to recognize and pattern composed of and+or after shift gabravier at gmail dot com
2020-07-19 20:46 ` [Bug tree-optimization/96237] " pinskia at gcc dot gnu.org
2020-07-19 22:53 ` pinskia at gcc dot gnu.org
2021-07-17 2:38 ` pinskia at gcc dot gnu.org
2023-06-11 19:30 ` pinskia at gcc dot gnu.org
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