Question

There are 2 pointers to 2 unaligned 8 byte chunks to be loaded into an xmm register. If possible, using intrinsics. And if possible, without using an auxiliary register. Without pinsrd. (SSSE Core 2)

Answer 1

From the msvc specs, it looks like you can do the following:

__m128d xx;                   // an uninitialised xmm register 
xx = _mm_loadh_pd(xx, ptra);  // load the higher 64 bits from (unaligned) ptra
xx = _mm_loadl_pd(xx, ptrb);  // load the lower 64 bits from (unaligned) ptrb

Loading from unaligned storage (in my experience) is very much slower than loading from aligned pointers, so you properly wouldn’t want to be doing this type of operation too often – if you really want higher performance.

Hope this helps.