why int& as function parameter uses QWORD(8 byte) memory but int parameter uses DWORD

In the code below,

int firstFunction(int& refParam)
{
    std::cout << "Type of refParam is: " << typeid(refParam).name() << '\n';
    return refParam;
}

int secondFunction(int param)
{
    std::cout << "Type of param is: " << typeid(param).name() << '\n';
    return param;
}

int main()
{
    int firstVar{ 1 };
    int secondVar{ firstFunction(firstVar) };
    int thirdVar{ secondFunction(firstVar) };
}

Console output is

int
int

When i check the assembly code in Godbolt link.

firstFunction(int&):
        push    rbp
        mov     rbp, rsp
        mov     QWORD PTR [rbp-8], rdi
        mov     rax, QWORD PTR [rbp-8]
        mov     eax, DWORD PTR [rax]
        pop     rbp
        ret
secondFunction(int):
        push    rbp
        mov     rbp, rsp
        mov     DWORD PTR [rbp-4], edi
        mov     eax, DWORD PTR [rbp-4]
        pop     rbp
        ret

reference parameter creates a space of 8 bytes QWORD PTR [rbp-8], rdi
instead of 4 bytes in second function DWORD PTR [rbp-4], edi

After seeing eax, DWORD PTR [rax] in line 6 in firstFunction(int&): I thought it might be because the first half(eax) stores the value adress but when i create a third function have char& as parameter it also creates 8 byte space. Godbolt Link

Is there any reason for that?

>Solution :

references are usually implemented as pointers under the hood if it can’t be optimized away, and pointers are 8 bytes in 64-bit mode