[Bug tree-optimization/113189] New: `(-X * Y) * -X` can be optimized to `(X * Y) * X`

[Bug tree-optimization/113189] New: `(-X * Y) * -X` can be optimized to `(X * Y) * X`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113189

            Bug ID: 113189
           Summary: `(-X * Y) * -X` can be optimized to `(X * Y) * X`
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, 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 f(int X, int Y)
{
        return (-X * Y) * -X;
}
double fd(double X, double Y)
{
        return (-X * Y) * -X;
}

int g(int X, int Y)
{
        return ((-X) << Y) * -X;
}
```

The negative should be optimized away but currently is only optimized at the
RTL level.

[Bug tree-optimization/113189] `(-X * Y) * -X` can be optimized to `(X * Y) * X`

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113189

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Other examples where the negative can be removed:
```
int foo(int a) {
    return -a * (-a * a);
}

int bar(int a) {
    return (-a * -a) * a;
}
int foo1(int a, int b, int c) {
    return -a * (-b * c);
}
```

bar is handled at the gimple level but foo and foo1 are not.

[Bug tree-optimization/113189] `(-X * Y) * -X` can be optimized to `(X * Y) * X`

[jsm28 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113189

--- Comment #2 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
If Y is INT_MIN and X is -1, removing the negations introduces undefined
behavior in the first example (-(-1) * INT_MIN * -(-1) is valid, -1 * INT_MIN *
-1 has undefined behavior).

For floating types, removing the negations isn't valid if flag_rounding_math.