Can a smart pointer be optimized away?

Mind the code

...
{
    int* p = new int(0);
    std::unique_ptr<int> q(p);
    ...
    // make use of 'p'
}
...

In the code above, the unique pointer q is used solely to free p, when time comes. Q is not used by itself.
Since q is never used below the line where it is declared, it can seemingly be released immediately after being declared, thus making use of p "use after free".
The question is q guaranteed to live on until going out of the current scope, or the compiler's optimizer is free to free it before ?