[Bug middle-end/119033] New: Unsafe FRE of pointer assignment

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119033

            Bug ID: 119033
           Summary: Unsafe FRE of pointer assignment
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hubicka at gcc dot gnu.org
  Target Milestone: ---

The following (artificial) testcase (pointed to me by Filip Hejsek) is
miscompiled at -O2, since we miss the fact that test3(3) overwrites b[0].

#include <stddef.h>
struct foo 
{
         int a[3];
         int b[3];
};

void test2 (int *a);

__attribute__ ((noipa))
int test3 (int i)
{
        struct foo test;
        test.b[0]=1;
        int *a = &test.a[i];
        int *b = &test.b[0];
        int *ptr = ((size_t)a == (size_t)b) ? b : a;
        *ptr=2;
        //test2 (ptr);
        return test.b[0];
}
int main()
{
        __builtin_printf ("%i %i\n",test3(0), test3(3));
        return 0;
}