Why is this ASM slower than C++?

[wossname]

int inline MulAdd__asm(int val, int m, int a)
{
    __asm
    {
        mov eax, val
        imul eax, m
        add eax, a
    }
}

int MulAdd__cpp(int val, int m, int a)
{
    return (val * m) + a;
} 

Why is the inline ASM function about 3 times slower than the C++ version as shown above?