[Bug tree-optimization/113138] New: `x < ~x` can be simplified to `((signed)x) < 0`

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113138

            Bug ID: 113138
           Summary: `x < ~x` can be simplified to `((signed)x) < 0`
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---

Take:
```
#include <stdint.h>
bool srcu(uint32_t x) { return x < ~x; }
bool srcs(int32_t x) { return x < ~x; }
```

But of these can be optimized to:

```
#include <stdint.h>
bool tgt(int32_t x) { return x < 0; }
```

`x >= ~x` can be optimzed to `x >=s 0` (boolean opposites).
While `x > ~x` can be optimized to `(~x) <s 0` or rather `x >s -1` or rather `x
>=s 0`.
While `x <= ~x` can be optimized to `x <s 0`.

So the resulting for loop is:
cmp   lt le gt ge
rcmp  lt lt ge ge