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introduce macros STORE_OFFSET() and STORE_REPCODE()

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this meant to abstract the sumtype representation required
to transfert `offcode` to `ZSTD_storeSeq()`.

Unfortunately, the sumtype numeric representation is currently a leaky abstraction
that has permeated many other parts of the code,
especially within `zstd_lazy.c` and also within `zstd_opt.c` and `zstd_compress.c`.

While this PR makes a good job a transfering a large nb of call sites
to using the new macros, there are still a few sites where this transformation is more complex,
or where the numeric representation itself it used "as is".

One of the problematics area is the decision to use the numeric format of the sumtype
within the match finders of `zstd_lazy`.

This commit doesn't change the behavior, it only introduces and employes the macros,
but eventually the resulting code remains identical.

At target, if the numeric representation of the sumtype can be completely abstracted
and no other part of the code depends on it,
it will be possible to move it towards something slightly more efficient.
This commit is contained in:
Yann Collet
2021-12-23 22:03:30 -08:00
parent bec7bbb5a4
commit 1aed962216
8 changed files with 158 additions and 137 deletions
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lib/compress/zstd_opt.c
+22 -19
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@@ -280,15 +280,17 @@ static U32 ZSTD_litLengthPrice(U32 const litLength, const optState_t* const optP
/* ZSTD_getMatchPrice() :
* Provides the cost of the match part (offset + matchLength) of a sequence
* Must be combined with ZSTD_fullLiteralsCost() to get the full cost of a sequence.
* optLevel: when <2, favors small offset for decompression speed (improved cache efficiency) */
* @offcode : expects a scale where 0,1,2 are repcodes 1-3, and 3+ are real_offsets+2
* @optLevel: when <2, favors small offset for decompression speed (improved cache efficiency)
*/
FORCE_INLINE_TEMPLATE U32
ZSTD_getMatchPrice(U32 const offset,
ZSTD_getMatchPrice(U32 const offcode,
U32 const matchLength,
const optState_t* const optPtr,
int const optLevel)
{
U32 price;
U32 const offCode = ZSTD_highbit32(offset+1);
U32 const offCode = ZSTD_highbit32(offcode+1);
U32 const mlBase = matchLength - MINMATCH;
assert(matchLength >= MINMATCH);
@@ -631,7 +633,7 @@ U32 ZSTD_insertBtAndGetAllMatches (
DEBUGLOG(8, "found repCode %u (ll0:%u, offset:%u) of length %u",
repCode, ll0, repOffset, repLen);
bestLength = repLen;
matches[mnum].off = repCode - ll0;
matches[mnum].off = STORE_REPCODE(repCode - ll0 + 1); /* expect value between 1 and 3 */
matches[mnum].len = (U32)repLen;
mnum++;
if ( (repLen > sufficient_len)
@@ -660,7 +662,7 @@ U32 ZSTD_insertBtAndGetAllMatches (
bestLength = mlen;
assert(curr > matchIndex3);
assert(mnum==0); /* no prior solution */
matches[0].off = (curr - matchIndex3) + ZSTD_REP_MOVE;
matches[0].off = STORE_OFFSET(curr - matchIndex3);
matches[0].len = (U32)mlen;
mnum = 1;
if ( (mlen > sufficient_len) |
@@ -694,12 +696,12 @@ U32 ZSTD_insertBtAndGetAllMatches (
if (matchLength > bestLength) {
DEBUGLOG(8, "found match of length %u at distance %u (offCode=%u)",
(U32)matchLength, curr - matchIndex, curr - matchIndex + ZSTD_REP_MOVE);
(U32)matchLength, curr - matchIndex, STORE_OFFSET(curr - matchIndex));
assert(matchEndIdx > matchIndex);
if (matchLength > matchEndIdx - matchIndex)
matchEndIdx = matchIndex + (U32)matchLength;
bestLength = matchLength;
matches[mnum].off = (curr - matchIndex) + ZSTD_REP_MOVE;
matches[mnum].off = STORE_OFFSET(curr - matchIndex);
matches[mnum].len = (U32)matchLength;
mnum++;
if ( (matchLength > ZSTD_OPT_NUM)
@@ -742,11 +744,11 @@ U32 ZSTD_insertBtAndGetAllMatches (
if (matchLength > bestLength) {
matchIndex = dictMatchIndex + dmsIndexDelta;
DEBUGLOG(8, "found dms match of length %u at distance %u (offCode=%u)",
(U32)matchLength, curr - matchIndex, curr - matchIndex + ZSTD_REP_MOVE);
(U32)matchLength, curr - matchIndex, STORE_OFFSET(curr - matchIndex));
if (matchLength > matchEndIdx - matchIndex)
matchEndIdx = matchIndex + (U32)matchLength;
bestLength = matchLength;
matches[mnum].off = (curr - matchIndex) + ZSTD_REP_MOVE;
matches[mnum].off = STORE_OFFSET(curr - matchIndex);
matches[mnum].len = (U32)matchLength;
mnum++;
if ( (matchLength > ZSTD_OPT_NUM)
@@ -938,11 +940,12 @@ static void ZSTD_opt_getNextMatchAndUpdateSeqStore(ZSTD_optLdm_t* optLdm, U32 cu
* and 'matchEndPosInBlock', into 'matches'. Maintains the correct ordering of 'matches'
*/
static void ZSTD_optLdm_maybeAddMatch(ZSTD_match_t* matches, U32* nbMatches,
ZSTD_optLdm_t* optLdm, U32 currPosInBlock) {
U32 posDiff = currPosInBlock - optLdm->startPosInBlock;
ZSTD_optLdm_t* optLdm, U32 currPosInBlock)
{
U32 const posDiff = currPosInBlock - optLdm->startPosInBlock;
/* Note: ZSTD_match_t actually contains offCode and matchLength (before subtracting MINMATCH) */
U32 candidateMatchLength = optLdm->endPosInBlock - optLdm->startPosInBlock - posDiff;
U32 candidateOffCode = optLdm->offset + ZSTD_REP_MOVE;
U32 const candidateMatchLength = optLdm->endPosInBlock - optLdm->startPosInBlock - posDiff;
U32 const candidateOffCode = STORE_OFFSET(optLdm->offset);
/* Ensure that current block position is not outside of the match */
if (currPosInBlock < optLdm->startPosInBlock
@@ -1075,14 +1078,14 @@ ZSTD_compressBlock_opt_generic(ZSTD_matchState_t* ms,
/* large match -> immediate encoding */
{ U32 const maxML = matches[nbMatches-1].len;
U32 const maxOffset = matches[nbMatches-1].off;
U32 const maxOffcode = matches[nbMatches-1].off;
DEBUGLOG(6, "found %u matches of maxLength=%u and maxOffCode=%u at cPos=%u => start new series",
nbMatches, maxML, maxOffset, (U32)(ip-prefixStart));
nbMatches, maxML, maxOffcode, (U32)(ip-prefixStart));
if (maxML > sufficient_len) {
lastSequence.litlen = litlen;
lastSequence.mlen = maxML;
lastSequence.off = maxOffset;
lastSequence.off = maxOffcode;
DEBUGLOG(6, "large match (%u>%u), immediate encoding",
maxML, sufficient_len);
cur = 0;
@@ -1099,15 +1102,15 @@ ZSTD_compressBlock_opt_generic(ZSTD_matchState_t* ms,
opt[pos].price = ZSTD_MAX_PRICE; /* mlen, litlen and price will be fixed during forward scanning */
}
for (matchNb = 0; matchNb < nbMatches; matchNb++) {
U32 const offset = matches[matchNb].off;
U32 const offcode = matches[matchNb].off;
U32 const end = matches[matchNb].len;
for ( ; pos <= end ; pos++ ) {
U32 const matchPrice = ZSTD_getMatchPrice(offset, pos, optStatePtr, optLevel);
U32 const matchPrice = ZSTD_getMatchPrice(offcode, pos, optStatePtr, optLevel);
U32 const sequencePrice = literalsPrice + matchPrice;
DEBUGLOG(7, "rPos:%u => set initial price : %.2f",
pos, ZSTD_fCost(sequencePrice));
opt[pos].mlen = pos;
opt[pos].off = offset;
opt[pos].off = offcode;
opt[pos].litlen = litlen;
opt[pos].price = (int)sequencePrice;
} }