Multiple If statements versus single statement with conditions evaluated using logical operators

Question

I am writing a function that checks several conditions before actually executing its task. This is done by a number of if statements. Like so:

bool foo()
{
    if(invalid())
        return false;
    if(dont_execute())
        return false;
    // .. etc
    // Actual execution here
    return true;
}

In this function is there any benefits by changing the multiple conditions to :

bool foo()
{
    if(invalid() || dont_execute() /* || .. etc */)
        return false;
    // Actual execution here
    return true;
}

I feel that the first style is more readable. What I want to know is, if there is any performance impact in using multiple if statements rather than combining using logical operators.

Answer 1

No there is no performance impact. If we compare the assembly of both functions we can see that it is identical for both functions.

Example:

bool f1();
bool f2();

bool combined()
{
    if (f1() || f2())
        return false;

    return true;
}

bool separate()
{
    if (f1())
        return false;

    if (f2())
        return false;

    return true;
}

And here the assembly:

combined():
        sub     rsp, 8
        call    f1()
        mov     r8d, eax
        xor     eax, eax
        test    r8b, r8b
        jne     .L1
        call    f2()
        xor     eax, 1
.L1:
        add     rsp, 8
        ret

separate():
        sub     rsp, 8
        call    f1()
        mov     r8d, eax
        xor     eax, eax
        test    r8b, r8b
        jne     .L7
        call    f2()
        xor     eax, 1
.L7:
        add     rsp, 8
        ret