}
+/**
+ * If you squint hard enough (and ignore repcodes), the search operation at any
+ * given position is broken into 4 stages:
+ *
+ * 1. Hash (map position to hash value via input read)
+ * 2. Lookup (map hash val to index via hashtable read)
+ * 3. Load (map index to value at that position via input read)
+ * 4. Compare
+ *
+ * Each of these steps involves a memory read at an address which is computed
+ * from the previous step. This means these steps must be sequenced and their
+ * latencies are cumulative.
+ *
+ * Rather than do 1->2->3->4 sequentially for a single position before moving
+ * onto the next, this implementation interleaves these operations across the
+ * next few positions:
+ *
+ * Pos | Time -->
+ * ----+-------------------
+ * N | ...4
+ * N+1 | ... 3 4
+ * N+2 | ... 2 3 4
+ * N+3 | 1 2 3
+ * N+4 | 1 2
+ * N+5 | 1
+ *
+ * This is very much analogous to the pipelining of execution in a CPU. And just
+ * like a CPU, we have to dump the pipeline when we find a match (i.e., take a
+ * branch).
+ *
+ * When this happens, we throw away our current state, and do the following prep
+ * to re-enter the loop:
+ *
+ * Pos | Time -->
+ * ----+-------------------
+ * N | 1 2 3
+ * N+1 | 1 2
+ * N+2 | 1
+ *
+ * This is also the work we do at the beginning to enter the loop initially.
+ */
+FORCE_INLINE_TEMPLATE size_t
+ZSTD_compressBlock_fast_generic_pipelined(
+ ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
+ void const* src, size_t srcSize,
+ U32 const mls)
+{
+ const ZSTD_compressionParameters* const cParams = &ms->cParams;
+ U32* const hashTable = ms->hashTable;
+ U32 const hlog = cParams->hashLog;
+ /* support stepSize of 0 */
+ size_t const stepSize = cParams->targetLength + !(cParams->targetLength);
+ const BYTE* const base = ms->window.base;
+ const BYTE* const istart = (const BYTE*)src;
+ const U32 endIndex = (U32)((size_t)(istart - base) + srcSize);
+ const U32 prefixStartIndex = ZSTD_getLowestPrefixIndex(ms, endIndex, cParams->windowLog);
+ const BYTE* const prefixStart = base + prefixStartIndex;
+ const BYTE* const iend = istart + srcSize;
+ const BYTE* const ilimit = iend - HASH_READ_SIZE;
+
+ const BYTE* anchor = istart;
+ const BYTE* ip0 = istart;
+ const BYTE* ip1;
+ const BYTE* ip2;
+ const BYTE* ip3;
+ U32 current0;
+
+ U32 rep_offset1 = rep[0];
+ U32 rep_offset2 = rep[1];
+ U32 offsetSaved = 0;
+
+ size_t hash0; /* hash for ip0 */
+ size_t hash1; /* hash for ip1 */
+ size_t hash2; /* hash for ip2 */
+ size_t hash3; /* hash for ip3 */
+ U32 idx0; /* match idx for ip0 */
+ U32 idx1; /* match idx for ip1 */
+ U32 idx2; /* match idx for ip2 */
+ U32 mval; /* src value at match idx */
+ U32 rval; /* src value at ip2 - repcode */
+
+ U32 offcode;
+ const BYTE* match0;
+ size_t mLength;
+
+ DEBUGLOG(5, "ZSTD_compressBlock_fast_generic_pipelined");
+ ip0 += (ip0 == prefixStart);
+ { U32 const curr = (U32)(ip0 - base);
+ U32 const windowLow = ZSTD_getLowestPrefixIndex(ms, curr, cParams->windowLog);
+ U32 const maxRep = curr - windowLow;
+ if (rep_offset2 > maxRep) offsetSaved = rep_offset2, rep_offset2 = 0;
+ if (rep_offset1 > maxRep) offsetSaved = rep_offset1, rep_offset1 = 0;
+ }
+
+ /* start each op */
+_start: /* Requires: ip0 */
+
+ /* calculate positions, ip0 - anchor == 0, so we skip step calc */
+ ip1 = ip0 + stepSize;
+ ip2 = ip1 + stepSize;
+ ip3 = ip2 + stepSize;
+
+ if (ip3 >= ilimit) {
+ goto _cleanup;
+ }
+
+ hash0 = ZSTD_hashPtr(ip0, hlog, mls);
+ hash1 = ZSTD_hashPtr(ip1, hlog, mls);
+ hash2 = ZSTD_hashPtr(ip2, hlog, mls);
+
+ idx0 = hashTable[hash0];
+ idx1 = hashTable[hash1];
+
+ if (idx0 >= prefixStartIndex) {
+ mval = MEM_read32(base + idx0);
+ } else {
+ mval = MEM_read32(ip0) ^ 1;
+ }
+
+ rval = MEM_read32(ip2 - rep_offset1);
+
+ do {
+ current0 = ip0 - base;
+
+ // DEBUGLOG(5, "Searching ip0 = %u", (U32)(ip0 - istart));
+
+ /* write back hash table entry */
+ hashTable[hash0] = current0;
+
+ /* check repcode at ip[2] */
+ if ((MEM_read32(ip2) == rval) & (rep_offset1 > 0)) {
+ ip0 = ip2;
+ match0 = ip0 - rep_offset1;
+ mLength = ip0[-1] == match0[-1];
+ ip0 -= mLength;
+ match0 -= mLength;
+ offcode = 0;
+ mLength += 4;
+ goto _match;
+ }
+
+ /* check match at ip[0] */
+ if (MEM_read32(ip0) == mval) {
+ /* found a match! */
+ goto _offset;
+ }
+
+ /* load next rval */
+ rval = MEM_read32(ip3 - rep_offset1);
+
+ /* load match for ip[1] */
+ if (idx1 >= prefixStartIndex) {
+ mval = MEM_read32(base + idx1);
+ } else {
+ mval = MEM_read32(ip1) ^ 1; /* guaranteed to not match. */
+ }
+
+ /* lookup ip[2] */
+ idx2 = hashTable[hash2];
+
+ /* hash ip[3] */
+ hash3 = ZSTD_hashPtr(ip3, hlog, mls);
+
+ /* advance to next positions */
+ {
+ size_t const step = ((size_t)(ip2 - anchor) >> (kSearchStrength - 1)) + stepSize;
+ assert(step >= 1);
+
+ idx0 = idx1;
+ idx1 = idx2;
+
+ hash0 = hash1;
+ hash1 = hash2;
+ hash2 = hash3;
+
+ ip0 = ip1;
+ ip1 = ip2;
+ ip2 = ip3;
+ ip3 = ip3 + step;
+ }
+ } while (ip3 < ilimit);
+
+_cleanup:
+
+ /* Find matches at end of block. */
+
+ /* TODO */
+
+ /* save reps for next block */
+ rep[0] = rep_offset1 ? rep_offset1 : offsetSaved;
+ rep[1] = rep_offset2 ? rep_offset2 : offsetSaved;
+
+ /* Return the last literals size */
+ return (size_t)(iend - anchor);
+
+_offset: /* Requires: ip0, idx0 */
+
+ /* Compute the offset code. */
+ match0 = base + idx0;
+ rep_offset2 = rep_offset1;
+ rep_offset1 = (U32)(ip0-match0);
+ offcode = rep_offset1 + ZSTD_REP_MOVE;
+ mLength = 4;
+
+ /* Count the backwards match length. */
+ while (((ip0>anchor) & (match0>prefixStart)) && (ip0[-1] == match0[-1])) {
+ ip0--;
+ match0--;
+ mLength++;
+ }
+
+_match: /* Requires: ip0, match0, offcode */
+
+ /* Count the forward length. */
+ mLength += ZSTD_count(ip0 + mLength, match0 + mLength, iend);
+
+ ZSTD_storeSeq(seqStore, (size_t)(ip0 - anchor), anchor, iend, offcode, mLength - MINMATCH);
+
+ ip0 += mLength;
+ anchor = ip0;
+
+ /* write next hash table entry */
+ if (ip1 < ip0) {
+ hashTable[hash1] = ip1 - base;
+ }
+
+ /* Fill table and check for immediate repcode. */
+ if (ip0 <= ilimit) {
+ /* Fill Table */
+ assert(base+current0+2 > istart); /* check base overflow */
+ hashTable[ZSTD_hashPtr(base+current0+2, hlog, mls)] = current0+2; /* here because current+2 could be > iend-8 */
+ hashTable[ZSTD_hashPtr(ip0-2, hlog, mls)] = (U32)(ip0-2-base);
+
+ if (rep_offset2 > 0) { /* rep_offset2==0 means rep_offset2 is invalidated */
+ while ( (ip0 <= ilimit) && (MEM_read32(ip0) == MEM_read32(ip0 - rep_offset2)) ) {
+ /* store sequence */
+ size_t const rLength = ZSTD_count(ip0+4, ip0+4-rep_offset2, iend) + 4;
+ { U32 const tmpOff = rep_offset2; rep_offset2 = rep_offset1; rep_offset1 = tmpOff; } /* swap rep_offset2 <=> rep_offset1 */
+ hashTable[ZSTD_hashPtr(ip0, hlog, mls)] = (U32)(ip0-base);
+ ip0 += rLength;
+ ZSTD_storeSeq(seqStore, 0 /*litLen*/, anchor, iend, 0 /*offCode*/, rLength-MINMATCH);
+ anchor = ip0;
+ continue; /* faster when present (confirmed on gcc-8) ... (?) */
+ } } }
+
+ goto _start;
+}
+
+
size_t ZSTD_compressBlock_fast(
ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
void const* src, size_t srcSize)
{
default: /* includes case 3 */
case 4 :
- return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 4);
+ return ZSTD_compressBlock_fast_generic_pipelined(ms, seqStore, rep, src, srcSize, 4);
case 5 :
- return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 5);
+ return ZSTD_compressBlock_fast_generic_pipelined(ms, seqStore, rep, src, srcSize, 5);
case 6 :
- return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 6);
+ return ZSTD_compressBlock_fast_generic_pipelined(ms, seqStore, rep, src, srcSize, 6);
case 7 :
- return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, 7);
+ return ZSTD_compressBlock_fast_generic_pipelined(ms, seqStore, rep, src, srcSize, 7);
}
}
/* switch to "regular" variant if extDict is invalidated due to maxDistance */
if (prefixStartIndex == dictStartIndex)
- return ZSTD_compressBlock_fast_generic(ms, seqStore, rep, src, srcSize, mls);
+ return ZSTD_compressBlock_fast_generic_pipelined(ms, seqStore, rep, src, srcSize, mls);
/* Search Loop */
while (ip < ilimit) { /* < instead of <=, because (ip+1) */
projects / thirdparty / zstd.git / commitdiff
