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* [Bug tree-optimization/112395] New: `CST1| (x & CST0)` -> `0x1e | x` iff `x&CST0` known zero bits outside of CST1 is known to be 0
@ 2023-11-05 19:53 pinskia at gcc dot gnu.org
2023-11-05 19:54 ` [Bug tree-optimization/112395] " pinskia at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-11-05 19:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112395
Bug ID: 112395
Summary: `CST1| (x & CST0)` -> `0x1e | x` iff `x&CST0` known
zero bits outside of CST1 is known to be 0
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
As reported at :
https://gcc.gnu.org/pipermail/gcc-patches/2023-November/635206.html
An exmaple is:
```
unsigned f(unsigned x){
if(x>=32)__builtin_unreachable();
return 30|(x&1); // --> 30|x
}
```
30 is 0x1e and x has a range of [0, 31] (which has a nonzero bits of 0x1f).
The &1 part can be removed from 30|(x&1) as 30 will set every bit except for
the first bit.
I think the following will work.
```
(simplify
(bit_ior (bit_and:s @0 INTEGER_CST@1) INTEGER_CST@2)
(if (wi::bit_and_not (wi::bit_and_not (tree_nonzero_bits (@0), wi::to_wide
(@1)), wi::to_wide (@0)) == 0)
(bit_ior @0 @2))
```
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug tree-optimization/112395] `CST1| (x & CST0)` -> `0x1e | x` iff `x&CST0` known zero bits outside of CST1 is known to be 0
2023-11-05 19:53 [Bug tree-optimization/112395] New: `CST1| (x & CST0)` -> `0x1e | x` iff `x&CST0` known zero bits outside of CST1 is known to be 0 pinskia at gcc dot gnu.org
@ 2023-11-05 19:54 ` pinskia at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-11-05 19:54 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112395
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
Ever confirmed|0 |1
Last reconfirmed| |2023-11-05
Status|UNCONFIRMED |ASSIGNED
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Mine.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2023-11-05 19:53 [Bug tree-optimization/112395] New: `CST1| (x & CST0)` -> `0x1e | x` iff `x&CST0` known zero bits outside of CST1 is known to be 0 pinskia at gcc dot gnu.org
2023-11-05 19:54 ` [Bug tree-optimization/112395] " pinskia at gcc dot gnu.org
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