Function shuffle_epi8

engine/dlib/src/basis/encoder/cppspmd_sse.h:235–267

#if CPPSPMD_SSE2
inline __m128i shuffle_epi8(const __m128i& a, const __m128i& b)
{
	// Just emulate _mm_shuffle_epi8. This is very slow, but what else can we do?
	CPPSPMD_ALIGN(16) uint8_t av[16];
	_mm_store_si128((__m128i*)av, a);
		
	CPPSPMD_ALIGN(16) uint8_t bvi[16];
	_mm_store_ps((float*)bvi, _mm_and_ps(_mm_castsi128_ps(b), _mm_castsi128_ps(_mm_set1_epi32(0x0F0F0F0F))));

	CPPSPMD_ALIGN(16) uint8_t result[16];

	result[0] = av[bvi[0]];
	result[1] = av[bvi[1]];
	result[2] = av[bvi[2]];
	result[3] = av[bvi[3]];
	
	result[4] = av[bvi[4]];
	result[5] = av[bvi[5]];
	result[6] = av[bvi[6]];
	result[7] = av[bvi[7]];

	result[8] = av[bvi[8]];
	result[9] = av[bvi[9]];
	result[10] = av[bvi[10]];
	result[11] = av[bvi[11]];

	result[12] = av[bvi[12]];
	result[13] = av[bvi[13]];
	result[14] = av[bvi[14]];
	result[15] = av[bvi[15]];

	return _mm_andnot_si128(_mm_cmplt_epi8(b, _mm_setzero_si128()), _mm_load_si128((__m128i*)result));
}
#else
CPPSPMD_FORCE_INLINE __m128i shuffle_epi8(const __m128i& a, const __m128i& b) 
{