Reorder_with_lut_again

    static const __m128i SHUFFLE_TABLE[16] = {
         _mm_setr_epi8(12,13,14,15, 8, 9,10,11, 4, 5, 6, 7, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3,12,13,14,15, 8, 9,10,11, 4, 5, 6, 7),
         _mm_setr_epi8( 4, 5, 6, 7,12,13,14,15, 8, 9,10,11, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3, 4, 5, 6, 7,12,13,14,15, 8, 9,10,11),
         _mm_setr_epi8( 8, 9,10,11,12,13,14,15, 4, 5, 6, 7, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3, 8, 9,10,11,12,13,14,15, 4, 5, 6, 7),
         _mm_setr_epi8( 4, 5, 6, 7, 8, 9,10,11,12,13,14,15, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15),

         _mm_setr_epi8(12,13,14,15, 8, 9,10,11, 4, 5, 6, 7, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3,12,13,14,15, 8, 9,10,11, 4, 5, 6, 7),
         _mm_setr_epi8( 4, 5, 6, 7,12,13,14,15, 8, 9,10,11, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3, 4, 5, 6, 7,12,13,14,15, 8, 9,10,11),
         _mm_setr_epi8( 8, 9,10,11,12,13,14,15, 4, 5, 6, 7, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3, 8, 9,10,11,12,13,14,15, 4, 5, 6, 7),
         _mm_setr_epi8( 4, 5, 6, 7, 8, 9,10,11,12,13,14,15, 0, 1, 2, 3),
         _mm_setr_epi8( 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15),
    };
    static void __fastcall ReorderRays( StackFrame& frame, size_t nGroups )
    {        
        RayPacket** pPackets = frame.pActivePackets;
   
        uint32 pReorderIDs[MAX_TRACER_SIZE];
   
        size_t nHits   = 0;
        size_t nFirstMiss = 8*nGroups;

        const char* pRays = (const char*) frame.pRays;
        for( size_t i=0; i<nGroups; i++ )
        {
            uint32* __restrict pPacketRayIDs = pPackets[i]->RayOffsets;
   
            uint64 hits    = frame.pMasks[i];
            uint64 hit_lo  = (hits & 0x0f);
            uint64 hit_hi  = (hits & 0xf0)>>4;
            uint64 pop_lo  = _mm_popcnt_u64(hit_lo);
            uint64 pop_hi  = _mm_popcnt_u64(hit_hi);

            // load lo/hi ID pairs
            __m128i id_lo = _mm_load_si128( (__m128i*) pPacketRayIDs );
            __m128i id_hi = _mm_load_si128( (__m128i*) (pPacketRayIDs+4) );
            
            // store hit/miss iDs
            __m128i shuf_lo   = _mm_shuffle_epi8( id_lo, SHUFFLE_TABLE[hit_lo] );
            __m128i shuf_hi   = _mm_shuffle_epi8( id_hi, SHUFFLE_TABLE[hit_hi] );
            _mm_storeu_si128( (__m128i*)&pReorderIDs[nHits], shuf_lo );
            nHits      +=  pop_lo;
            _mm_storeu_si128( (__m128i*)&pReorderIDs[nHits], shuf_hi );
            nHits      +=  pop_hi;

            // NOTE: Hits MUST be written before misses, or a full-hit packet can corrupt the miss area
            _mm_storeu_si128( (__m128i*)&pReorderIDs[nFirstMiss-4], shuf_lo );
            nFirstMiss -= 4-pop_lo;
            _mm_storeu_si128( (__m128i*)&pReorderIDs[nFirstMiss-4], shuf_hi );
            nFirstMiss -= 4-pop_hi;
        }

       

        // full hit packets
        ReadRaysLoopArgs args;
        args.pPackets = pPackets;
        args.pRayIDs = pReorderIDs;
        args.pRays = (const byte*)pRays;
        ReadRaysLoop(args,nGroups);
    }