[Bug target/111078] New: csneg is not used for (cset) * 2 - 1

[Bug target/111078] New: csneg is not used for (cset) * 2 - 1

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111078

            Bug ID: 111078
           Summary: csneg is not used for (cset) * 2 - 1
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64

Take:
```
int f(int a, int b)
{
        return a == b ? 1 : -1;
}


int f0(int a, int b)
{
        int t = a == b;
        return t * 2 - 1;
}
```

These 2 should produce the same code on aarch64 but currently only the first
one produces:
```
        cmp     w0, w1
        mov     w0, 1
        csneg   w0, w0, w0, eq
        ret
```

[Bug target/111078] csneg is not used for (cset) * 2 - 1

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111078

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Another form:
```
int f1(int a, int b)
{
  int t = a != b;
  return (-t)|1;
}
```

[Bug target/111078] csneg is not used for (cset) * 2 - 1

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111078

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|UNCONFIRMED                 |ASSIGNED
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-11-18

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
MIne
For f0 we should be able to match:
(set (reg:SI 98)
    (plus:SI (ashift:SI (eq:SI (reg:CC 66 cc)
                (const_int 0 [0]))
            (const_int 1 [0x1]))
        (const_int -1 [0xffffffffffffffff])))

here. Note -1 is important.

for f1 we should be able to match:
(set (reg:SI 98)
    (ior:SI (neg:SI (ne:SI (reg:CC 66 cc)
                (const_int 0 [0])))
        (const_int 1 [0x1])))

Though I wonder for gimple if we should conconalization to one form or another
...