[Bug target/112304] New: cinc is not being used for (small) constant

["pinskia at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112304

            Bug ID: 112304
           Summary: cinc is not being used for (small) constant
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: pinskia at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64-linux-gnu

Take:
```
int f(int a)
{
        return (a!=0)+42;
}
int f1(int a, int b)
{
        return (a!=0)+b;
}
```
Currently we get:
```
f:
        cmp     w0, 0
        cset    w0, ne
        add     w0, w0, 42
        ret
f1:
        cmp     w0, 0
        cinc    w0, w1, ne
        ret
```

But f should really be:
```
        mov     w1, #42
        cmp     w0, #0
        cinc    w0, w1, ne
        ret
```

Because for many newer aarch64 cores the `mov` in this case is "free" and does
not take up an issue slot or even the for a dual issue, the mov and cmp could
be issued together.  Even though it is the same # of instruction, the second
case is going to be faster due to latencies.