Why use _mm_malloc? (as opposed to _aligned_malloc, alligned_alloc, or posix_memalign)

Question

There are a few options for acquiring an aligned block of memory but they\'re very similar and the issue mostly boils down to what language standard and platforms you\'re ta

Answer 1

_mm_malloc seems to have been created before there was a standard aligned_alloc function, and the need to use _mm_free is a quirk of the implementation.

My guess is that unlike when using posix_memalign, it doesn't need to over-allocate in order to guarantee alignment, instead it uses a separate alignment-aware allocator. This will save memory when allocating types with alignment different to the default alignment (typically 8 or 16 bytes).