[Bug ipa/111430] New: IPA read only variable analysis should handle the case where the storing was the same as the initialization

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111430

            Bug ID: 111430
           Summary: IPA read only variable analysis should handle the case
                    where the storing was the same as the initialization
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

Take:
```
#define CST 1025
static int b = CST;

void f(int a)
{
        if (a)
          b = CST;
}

int g(void)
{
        return b;
}
```

We should be able to optimize out the store to b in f and even the load in g.

This is another way of solving the original testcase in PR 110992.