[Bug middle-end/112403] New: `s+ (a?-1:1)` and `a?s-1:s+1` produce two different code generation

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112403

            Bug ID: 112403
           Summary: `s+ (a?-1:1)` and `a?s-1:s+1` produce two different
                    code generation
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
            Blocks: 94274
  Target Milestone: ---
            Target: aarch64

Take:
```
int
foo(int t1, int s)
{
  int t;
  if (t1 >= 0)
    t=1;
  else
    t=-1;
  s+=t;
  return s;
}

int
foo1(int t1, int s)
{
  if (t1 >= 0)
    s++;
  else
    s--;
  return s;
}
```

This current produces:
```
foo:
        cmp     w0, 0
        mov     w2, 1
        csneg   w2, w2, w2, ge
        add     w0, w2, w1
        ret
foo1:
        cmp     w0, 0
        sub     w0, w1, #1
        csinc   w0, w0, w1, lt
        ret
```

But we should be able to even just produce:
```
        asr     w8, w0, #31 // a >= 0 ? -1 : 0
        orr     w8, w8, #0x1 // |1 (or a >= ? -1 : 1)
        add     w0, w8, w1 // s+=that
```

Note on x86, the foo is optimal even:
```
        sarl    $31, %edi
        orl     $1, %edi
        leal    (%rdi,%rsi), %eax
```

I should note this blocks PR 94274 work.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94274
[Bug 94274] fold phi whose incoming args are defined from binary operations