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

[pinskia at gcc dot gnu.org via Gcc-bugs]

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
```