[Bug middle-end/123286] New: SAT_ADD is not constant folded at the gimple level

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123286

            Bug ID: 123286
           Summary: SAT_ADD is not constant folded at the gimple level
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64

I noticed that SAT_ADD was not folded at the gimple level:
Take the following aarch64 function:
```
#include <arm_neon.h>

unsigned long f(void)
{
  return vqadd_u64((uint64x1_t){}, (uint64x1_t){})[0];
}
```

In .optimized we get:
```
long unsigned int f ()
{
  long unsigned int _2;

  <bb 2> [local count: 1073741824]:
  _2 = .SAT_ADD (0, 0); [tail call]
  return _2;

}
```