Do mainstream compilers convert passed-by-reference basic types into pass-by-copy?
int foo(const int & i)
{
   cout << i; // Do whatever read-only with i.
}

int foo(const int i)
{
   cout << i;
}

int foo(const int i, int * ptr_i)
{
   cout << i;    // no dereferencement, therefore faster (?)
   // many more read-only operations with i.
   *ptr_i = 123;
}

int foo(const int & i)

int foo(const int i)

int foo(const int &i, int *p)
{
   *p = 42;
   cout << i; // prints 42
   return 0;
}

int main()
{
   int x = 5;
   foo(x, &x);
   return 0;
}

int foo(const int i, int *p)
{
   *p = 42;
   cout << i; // prints 5
   return 0;
}

int main()
{
   int x = 5;
   foo(x, &x);
   return 0;
}

int vars[] = {1,2,3,12,3,23,1,213,231,1,21,12,213,21321,213,123213,213123};

int ok1(const int i){
    return sqrtl(vars[i]);
}

int ok2(const int & i){
    return sqrtl(vars[i]);
}

void main() {
    int i;
    std::cin >> i;
    //i = ok1(i);
    i = ok2(i);
    std::cout << i;
}

i = ok1(i);
000D1014  mov         ecx,dword ptr [i]
000D1017  fild        dword ptr vars (0D3018h)[ecx*4]
000D101E  call        _CIsqrt (0D1830h)
000D1023  call        _ftol2_sse (0D1840h)

i = ok2(i);
013A1014  mov         ecx,dword ptr [i]
013A1017  fild        dword ptr vars (13A3018h)[ecx*4]
013A101E  call        _CIsqrt (13A1830h)
013A1023  call        _ftol2_sse (13A1840h)

int vars[] = {1,2,3,12,3,23,1,213,231,1,21,12,213,21321,213,123213,213123};

int ok1(const int i, int * pi) {
    *pi = 2;
    return sqrtl(vars[i]);
}

int ok2(const int & i, int * pi) {
    *pi = 2;
    return sqrtl(vars[i]);
}

void main() {
    int i;
    int * pi = &i;
    std::cin >> i;
    i = ok1(i, pi);
    //i = ok2(i, pi);
    std::cout << i;
}

i = ok1(i, pi);
00891014  mov         ecx,dword ptr [i]
00891017  fild        dword ptr vars (893018h)[ecx*4] // access vars[i]
0089101E  call        _CIsqrt (891830h)
00891023  call        _ftol2_sse (891840h)

i = ok2(i, pi);
011B1014  fild        dword ptr [vars+8 (11B3020h)]   // access vars[2]
011B101A  call        _CIsqrt (11B1830h)
011B101F  call        _ftol2_sse (11B1840h)