gcc/testsuite/gcc.dg/tree-ssa/assign-2.c

/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */

volatile int count;
int arr[4];
void foo()
{
 arr[count++] = 0;
}

/* { dg-final { scan-tree-dump-times "count =" 1 "optimized"} } */