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* [Bug middle-end/113130] New: `abs(a) == b` could be expanded as `(a == b || a == -b)`
@ 2023-12-24 22:38 pinskia at gcc dot gnu.org
2023-12-29 1:06 ` [Bug middle-end/113130] " jsm28 at gcc dot gnu.org
2023-12-29 1:16 ` pinskia at gcc dot gnu.org
0 siblings, 2 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-24 22:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113130
Bug ID: 113130
Summary: `abs(a) == b` could be expanded as `(a == b || a ==
-b)`
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: pinskia at gcc dot gnu.org
Target Milestone: ---
Take:
```
int f(int a, int c)
{
// c = 1;
int b = a > 0 ? a : -a;
return b == c;
}
int f1(int a, int c)
{
// c = 1;
return a == -c || a == c;
}
```
These 2 functions should produce the same assembly code.
This is especially true for when c is a 1 or 2.
Note for gimple, it might make sense to `ABS_EXPR <a> == c` as the conconal
form as it is only 2 gimple statements rather than 3.
Note `<`, `>`, `>=`, `<=`, and `!=` should be handled too.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug middle-end/113130] `abs(a) == b` could be expanded as `(a == b || a == -b)`
2023-12-24 22:38 [Bug middle-end/113130] New: `abs(a) == b` could be expanded as `(a == b || a == -b)` pinskia at gcc dot gnu.org
@ 2023-12-29 1:06 ` jsm28 at gcc dot gnu.org
2023-12-29 1:16 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: jsm28 at gcc dot gnu.org @ 2023-12-29 1:06 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113130
--- Comment #1 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
Note that the first example (and the suggested one with ABS_EXPR) has undefined
behavior for a == INT_MIN, while the second has undefined behavior for c ==
INT_MIN (and is also not equivalent to the first for negative c).
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug middle-end/113130] `abs(a) == b` could be expanded as `(a == b || a == -b)`
2023-12-24 22:38 [Bug middle-end/113130] New: `abs(a) == b` could be expanded as `(a == b || a == -b)` pinskia at gcc dot gnu.org
2023-12-29 1:06 ` [Bug middle-end/113130] " jsm28 at gcc dot gnu.org
@ 2023-12-29 1:16 ` pinskia at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: pinskia at gcc dot gnu.org @ 2023-12-29 1:16 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113130
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Oh right but the following testcase it should be valid to do and not worry
about INT_MIN either:
```
int f(int a, unsigned short c)
{
// c = 1;
int b = a > 0 ? a : -a;
return b == c;
}
int f1(int a, unsigned short c)
{
// c = 1;
return a == -c || a == c;
}
```
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2023-12-29 1:16 UTC | newest]
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2023-12-24 22:38 [Bug middle-end/113130] New: `abs(a) == b` could be expanded as `(a == b || a == -b)` pinskia at gcc dot gnu.org
2023-12-29 1:06 ` [Bug middle-end/113130] " jsm28 at gcc dot gnu.org
2023-12-29 1:16 ` pinskia at gcc dot gnu.org
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