How to determine if memory is aligned?

Question

I am new to optimizing code with SSE/SSE2 instructions and until now I have not gotten very far. To my knowledge a common SSE-optimized function would look like this:

<

Answer 1

This is basically what I'm using. By making the integer a template, I ensure it's expanded compile time, so I won't end up with a slow modulo operation whatever I do.

I always like checking my input, so hence the compile time assertion. If your alignment value is wrong, well then it won't compile...

template 
struct IsAligned
{
    static_assert((alignment & (alignment - 1)) == 0, "Alignment must be a power of 2");

    static inline bool Value(const void * ptr)
    {
        return (((uintptr_t)ptr) & (alignment - 1)) == 0;
    }
};

To see what's going on, you can use this:

// 1 of them is aligned...
int* ptr = new int[8];
for (int i = 0; i < 8; ++i)
    std::cout << IsAligned<32>::Value(ptr + i) << std::endl;

// Should give '1'
int* ptr2 = (int*)_aligned_malloc(32, 32);
std::cout << IsAligned<32>::Value(ptr2) << std::endl;