Use aligned loads in get_partial_safe

[bill-myers]

In get_partial_safe, it's possible to use aligned loads by declaring the buffer as MaybeUninit<State> and then casting the pointer for std::ptr::copy and zeroing the rest of the buffer, instead of declaring the buffer as an u8 array.

gxhash/src/gxhash/platform/x86_128.rs

Lines 35 to 39 in b2b9d24

	let mut buffer = [0i8; VECTOR_SIZE];
	// Copy data into the buffer
	std::ptr::copy(data as *const i8, buffer.as_mut_ptr(), len);
	// Load the buffer into a __m256i vector
	let partial_vector = _mm_loadu_epi8(buffer.as_ptr());

[ogxd]

From what I can see there is a compiler optimization that stack allocates [0i8; VECTOR_SIZE] instead of heap allocating (probably because VECTOR_SIZE is a constant), so MaybeUninit<State> may not be faster.

[ogxd]

About to close this one unless someone has some snippet to propose?

[notsatvrn]

I tried using a struct which contains only the byte array and is marked as #[repr(align(16))]. I have not tested the performance yet, but this should still allocate on the stack and force 16-byte alignment.