[Bug tree-optimization/127645] [16/17 Regression] wrong code at -O2 since r16-4708

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127645

--- Comment #8 from Drea Pinski <pinskia at gcc dot gnu.org> ---
Created attachment 65717
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65717&action=edit
Fixes the _limited version

This fixes this version of the testcase (-O2 -fno-tree-sra):
```
union u0 {
    unsigned char f1;
    _Bool f2;
};
__attribute__((noipa))
void f(int c)
{
  union u0 g18;
  g18.f1 = 45;
  if (c) g18.f2 = 1;
  if (g18.f1 != 45)
    __builtin_abort ();
}
int main()
{
  f(0);
}
```

I will finish this up after the cauldron.