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

Leave that to the professionals,

https://www.boost.org/doc/libs/1_65_1/doc/html/align/reference.html#align.reference.functions.is_aligned

bool is_aligned(const void* ptr, std::size_t alignment) noexcept; 

example:

        char D[1];
        assert( boost::alignment::is_aligned(&D[0], alignof(double)) ); //  might fail, sometimes

Answer 2

With a function template like

#include <type_traits>

template< typename T >
bool is_aligned(T* p){
    return !(reinterpret_cast<uintptr_t>(p) % std::alignment_of<T>::value);
}

you could check alignment at runtime by invoking something like

struct foo_type{ int bar; }foo;
assert(is_aligned(&foo)); // passes

To check that bad alignments fail, you could do

// would almost certainly fail
assert(is_aligned((foo_type*)(1 + (uintptr_t)(&foo)));