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* [Bug tree-optimization/113072] New: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level
@ 2023-12-18 18:53 pinskia at gcc dot gnu.org
2023-12-18 19:03 ` [Bug tree-optimization/113072] " pinskia at gcc dot gnu.org
` (5 more replies)
0 siblings, 6 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-18 18:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113072
Bug ID: 113072
Summary: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at
the gimple level
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: TREE
Severity: enhancement
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take:
```
int foo(int a, int b) { return (a ^ 4) & (~a ^ 4); }
```
This should be optimized to 0 but is missed at the gimple level.
RTL Combine catches it:
```
Trying 8, 7 -> 9:
8: {r105:SI=r101:SI^0xfffffffffffffffb;clobber flags:CC;}
REG_DEAD r101:SI
REG_UNUSED flags:CC
7: {r104:SI=r101:SI^0x4;clobber flags:CC;}
REG_UNUSED flags:CC
9: {r103:SI=r104:SI&r105:SI;clobber flags:CC;}
REG_DEAD r105:SI
REG_DEAD r104:SI
REG_UNUSED flags:CC
Failed to match this instruction:
(parallel [
(set (reg:SI 103)
(const_int 0 [0]))
(clobber (reg:CC 17 flags))
])
Successfully matched this instruction:
(set (reg:SI 103)
(const_int 0 [0]))
allowing combination of insns 7, 8 and 9
original costs 4 + 4 + 4 = 12
replacement cost 4
```
via apply_distributive_law (I think) which does basically `(a ^ 4) & (a ^
(~4))` -> `(4 ^ (~4)) & (a ^ a)` which is 0 as `a ^ a` is 0.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/113072] `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level
2023-12-18 18:53 [Bug tree-optimization/113072] New: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level pinskia at gcc dot gnu.org
@ 2023-12-18 19:03 ` pinskia at gcc dot gnu.org
2023-12-18 19:03 ` pinskia at gcc dot gnu.org
` (4 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-18 19:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113072
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Wait this part is wrong `which does basically `(a ^ 4) & (a ^ (~4))` -> `(4 ^
(~4)) & (a ^ a)` which is 0 as `a ^ a` is 0.`
Anyways a pattern like:
```
(simplify
(bit_and (bit_xor @0 @1) (bit_xor @0 @2))
(with { bool wascmp; }
(if (bitwise_inverted_equal_p (@1, @2, &wascmp))
{ wascmp ? constant_boolean_node (false, type) : build_zero_cst (type); })))
```
Is needed for bool.
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/113072] `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level
2023-12-18 18:53 [Bug tree-optimization/113072] New: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level pinskia at gcc dot gnu.org
2023-12-18 19:03 ` [Bug tree-optimization/113072] " pinskia at gcc dot gnu.org
@ 2023-12-18 19:03 ` pinskia at gcc dot gnu.org
2023-12-18 19:09 ` pinskia at gcc dot gnu.org
` (3 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-18 19:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113072
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Ever confirmed|0 |1
Last reconfirmed| |2023-12-18
Assignee|unassigned at gcc dot gnu.org |pinskia at gcc dot gnu.org
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/113072] `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level
2023-12-18 18:53 [Bug tree-optimization/113072] New: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level pinskia at gcc dot gnu.org
2023-12-18 19:03 ` [Bug tree-optimization/113072] " pinskia at gcc dot gnu.org
2023-12-18 19:03 ` pinskia at gcc dot gnu.org
@ 2023-12-18 19:09 ` pinskia at gcc dot gnu.org
2023-12-18 19:10 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-18 19:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113072
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
See Also| |https://gcc.gnu.org/bugzill
| |a/show_bug.cgi?id=111149
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Looks like bool sometimes produces != or ^ :)
```
bool foo(bool a, int b)
{
bool b1 = b == 1;
bool b2 = !b1;
bool c = (a ^ b1);
return c & (a ^ b2);
}
```
Though that is PR 111149 .
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/113072] `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level
2023-12-18 18:53 [Bug tree-optimization/113072] New: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level pinskia at gcc dot gnu.org
` (2 preceding siblings ...)
2023-12-18 19:09 ` pinskia at gcc dot gnu.org
@ 2023-12-18 19:10 ` pinskia at gcc dot gnu.org
2023-12-18 19:40 ` pinskia at gcc dot gnu.org
2024-01-01 0:33 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-18 19:10 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113072
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
here is the bool testcase which just allows the use of ^:
```
bool foo1(bool a, int b)
{
bool b1 = b == 1;
bool b2 = !b1;
return (a ^ b1) & (a ^ b2);
}
```
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/113072] `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level
2023-12-18 18:53 [Bug tree-optimization/113072] New: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level pinskia at gcc dot gnu.org
` (3 preceding siblings ...)
2023-12-18 19:10 ` pinskia at gcc dot gnu.org
@ 2023-12-18 19:40 ` pinskia at gcc dot gnu.org
2024-01-01 0:33 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-18 19:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113072
--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note this applies to `|` instead of `&` too:
```
int foo1(int a, int b)
{
return (a ^ 4) | (~a ^ 4);
}
```
This should be optimized to `-1`. Though this does NOT get optimized to `-1` on
the RTL level ...
^ permalink raw reply [flat|nested] 7+ messages in thread
* [Bug tree-optimization/113072] `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level
2023-12-18 18:53 [Bug tree-optimization/113072] New: `(a ^ CST0) & (~a ^ CST0)` is not optimized to 0 at the gimple level pinskia at gcc dot gnu.org
` (4 preceding siblings ...)
2023-12-18 19:40 ` pinskia at gcc dot gnu.org
@ 2024-01-01 0:33 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 7+ messages in thread
From: pinskia at gcc dot gnu.org @ 2024-01-01 0:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113072
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #2)
> Looks like bool sometimes produces != or ^ :)
> ```
> bool foo(bool a, int b)
> {
> bool b1 = b == 1;
> bool b2 = !b1;
> bool c = (a ^ b1);
> return c & (a ^ b2);
> }
> ```
> Though that is PR 111149 .
I filed a related testcase to the above as PR 113186 but it does not handle the
above I think.
^ permalink raw reply [flat|nested] 7+ messages in thread
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2023-12-18 19:03 ` [Bug tree-optimization/113072] " pinskia at gcc dot gnu.org
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