fsst_avx512_unroll1.inc

// this software is distributed under the MIT License (http://www.opensource.org/licenses/MIT):
//
// Copyright 2018-2020, CWI, TU Munich, FSU Jena
//
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// You can contact the authors via the FSST source repository : https://github.com/cwida/fsst
//
                        // load new jobs in the empty lanes (initially, all lanes are empty, so loadmask1=11111111, delta1=8).
            job1      = _mm512_mask_expandloadu_epi64(job1, loadmask1, input); input += delta1; 
                        // load the next 8 input string bytes (uncompressed data, aka 'symbols').
   __m512i  word1     = _mm512_i64gather_epi64(_mm512_srli_epi64(job1, 46), symbolBase, 1); 
                        // load 16-bits codes from the 2-byte-prefix keyed lookup table. It also store 1-byte codes in all free slots.
                        // code1: Lowest 8 bits contain the code. Eleventh bit is whether it is an escaped code. Next 4 bits is length (2 or 1).
   __m512i  code1     = _mm512_i64gather_epi64(_mm512_and_epi64(word1, all_FFFF), symbolTable.shortCodes, sizeof(u16));
                        // get the first three bytes of the string. 
   __m512i  pos1      = _mm512_mullo_epi64(_mm512_and_epi64(word1, all_FFFFFF), all_PRIME);
                        // hash them into a random number: pos1 = pos1*PRIME; pos1 ^= pos1>>SHIFT
            pos1      = _mm512_slli_epi64(_mm512_and_epi64(_mm512_xor_epi64(pos1,_mm512_srli_epi64(pos1,FSST_SHIFT)), all_HASH), 4);
                        // lookup in the 3-byte-prefix keyed hash table
   __m512i  icl1      = _mm512_i64gather_epi64(pos1, (((char*) symbolTable.hashTab) + 8), 1);
                        // speculatively store the first input byte into the second position of the write1 register (in case it turns out to be an escaped byte).
   __m512i  write1    = _mm512_slli_epi64(_mm512_and_epi64(word1, all_FF), 8);
                        // lookup just like the icl1 above, but loads the next 8 bytes. This fetches the actual string bytes in the hash table.
   __m512i  symb1     = _mm512_i64gather_epi64(pos1, (((char*) symbolTable.hashTab) + 0), 1);
                        // generate the FF..FF mask with an FF for each byte of the symbol (we need to AND the input with this to correctly check equality).
            pos1      = _mm512_srlv_epi64(all_MASK, _mm512_and_epi64(icl1, all_FF));
                        // check symbol < |str| as well as whether it is an occupied slot (cmplt checks both conditions at once) and check string equality (cmpeq).
   __mmask8 match1    = _mm512_cmpeq_epi64_mask(symb1, _mm512_and_epi64(word1, pos1)) & _mm512_cmplt_epi64_mask(icl1, all_ICL_FREE);
                        // for the hits, overwrite the codes with what comes from the hash table (codes for symbols of length >=3). The rest stays with what shortCodes gave.
            code1     = _mm512_mask_mov_epi64(code1, match1, _mm512_srli_epi64(icl1, 16));
                        // write out the code byte as the first output byte. Notice that this byte may also be the escape code 255 (for escapes) coming from shortCodes.
            write1    = _mm512_or_epi64(write1, _mm512_and_epi64(code1, all_FF));
                        // zip the irrelevant 6 bytes (just stay with the 2 relevant bytes containing the 16-bits code)
            code1     = _mm512_and_epi64(code1, all_FFFF);
                        // write out the compressed data. It writes 8 bytes, but only 1 byte is relevant :-(or 2 bytes are, in case of an escape code)
                        _mm512_i64scatter_epi64(codeBase, _mm512_and_epi64(job1, all_M19), write1, 1);
                        // increase the job1.cur field in the job with the symbol length (for this, shift away 12 bits from the code) 
            job1      = _mm512_add_epi64(job1, _mm512_slli_epi64(_mm512_srli_epi64(code1, FSST_LEN_BITS), 46));
                        // increase the job1.out' field with one, or two in case of an escape code (add 1 plus the escape bit, i.e the 8th)
            job1      = _mm512_add_epi64(job1, _mm512_add_epi64(all_ONE, _mm512_and_epi64(_mm512_srli_epi64(code1, 8), all_ONE)));
                        // test which lanes are done now (job1.cur==job1.end), cur starts at bit 46, end starts at bit 28 (the highest 2x18 bits in the job1 register)
            loadmask1 = _mm512_cmpeq_epi64_mask(_mm512_srli_epi64(job1, 46), _mm512_and_epi64(_mm512_srli_epi64(job1, 28), all_M18));
                        // calculate the amount of lanes in job1 that are done
            delta1    = _mm_popcnt_u32((int) loadmask1); 
                        // write out the job state for the lanes that are done (we need the final 'job1.out' value to compute the compressed string length)
                        _mm512_mask_compressstoreu_epi64(output, loadmask1, job1); output += delta1;