[Bug tree-optimization/126705] New: `ctz(a*3)` should be simplified into `ctz(a)`

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126705

            Bug ID: 126705
           Summary: `ctz(a*3)` should be simplified into `ctz(a)`
           Product: gcc
           Version: 17.0
            Status: UNCONFIRMED
          Keywords: easyhack, 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: ---

The number of trailing zeros does not change if multiplying by an odd number.

For an example 3*a will have the same # of trailing zeros as a has.

Example:
```
unsigned f(unsigned t)
{
    return __builtin_ctz(t*3);
}
```