Alias Optimization (by address)
Two pointers that point to members of different arrays can not be aliases, even if the offsets within arrays are not known.
Example:
In the code fragment below, the specific objects pointed to by p and q are not known, but they are members of different arrays, and therefore can not be aliased.
int a[], b[];
void f (int i, int j)
{
int *p, *q;
int x, y;
p = &a[i];
q = &b[j];
x = *(q + 3);
*p = 5;
y = *(q + 3);
g (x, y);
}
Since p and q are not aliased, the second reference to *(q + 3) can be eliminated, as shown below.
int a[], b[];
void f(int i, int j)
{
int *p, *q;
int x, y;
p = &a[i];
q = &b[j];
x = *(q + 3);
*p = 5;
g (x, x);
}