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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_lazy.c
+14 -12
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@@ -197,8 +197,8 @@ ZSTD_DUBT_findBetterDictMatch (
U32 matchIndex = dictMatchIndex + dictIndexDelta;
if ( (4*(int)(matchLength-bestLength)) > (int)(ZSTD_highbit32(curr-matchIndex+1) - ZSTD_highbit32((U32)offsetPtr[0]+1)) ) {
DEBUGLOG(9, "ZSTD_DUBT_findBetterDictMatch(%u) : found better match length %u -> %u and offsetCode %u -> %u (dictMatchIndex %u, matchIndex %u)",
curr, (U32)bestLength, (U32)matchLength, (U32)*offsetPtr, ZSTD_REP_MOVE + curr - matchIndex, dictMatchIndex, matchIndex);
bestLength = matchLength, *offsetPtr = ZSTD_REP_MOVE + curr - matchIndex;
curr, (U32)bestLength, (U32)matchLength, (U32)*offsetPtr, STORE_OFFSET(curr - matchIndex), dictMatchIndex, matchIndex);
bestLength = matchLength, *offsetPtr = STORE_OFFSET(curr - matchIndex);
}
if (ip+matchLength == iend) { /* reached end of input : ip[matchLength] is not valid, no way to know if it's larger or smaller than match */
break; /* drop, to guarantee consistency (miss a little bit of compression) */
@@ -328,7 +328,7 @@ ZSTD_DUBT_findBestMatch(ZSTD_matchState_t* ms,
if (matchLength > matchEndIdx - matchIndex)
matchEndIdx = matchIndex + (U32)matchLength;
if ( (4*(int)(matchLength-bestLength)) > (int)(ZSTD_highbit32(curr-matchIndex+1) - ZSTD_highbit32((U32)offsetPtr[0]+1)) )
bestLength = matchLength, *offsetPtr = ZSTD_REP_MOVE + curr - matchIndex;
bestLength = matchLength, *offsetPtr = STORE_OFFSET(curr - matchIndex);
if (ip+matchLength == iend) { /* equal : no way to know if inf or sup */
if (dictMode == ZSTD_dictMatchState) {
nbCompares = 0; /* in addition to avoiding checking any
@@ -561,7 +561,7 @@ size_t ZSTD_dedicatedDictSearch_lazy_search(size_t* offsetPtr, size_t ml, U32 nb
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = curr - (matchIndex + ddsIndexDelta) + ZSTD_REP_MOVE;
*offsetPtr = STORE_OFFSET(curr - (matchIndex + ddsIndexDelta));
if (ip+currentMl == iLimit) {
/* best possible, avoids read overflow on next attempt */
return ml;
@@ -598,7 +598,7 @@ size_t ZSTD_dedicatedDictSearch_lazy_search(size_t* offsetPtr, size_t ml, U32 nb
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = curr - (matchIndex + ddsIndexDelta) + ZSTD_REP_MOVE;
*offsetPtr = STORE_OFFSET(curr - (matchIndex + ddsIndexDelta));
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
}
@@ -703,7 +703,7 @@ size_t ZSTD_HcFindBestMatch(
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = curr - matchIndex + ZSTD_REP_MOVE;
*offsetPtr = STORE_OFFSET(curr - matchIndex);
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
@@ -738,7 +738,8 @@ size_t ZSTD_HcFindBestMatch(
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = curr - (matchIndex + dmsIndexDelta) + ZSTD_REP_MOVE;
assert(curr > matchIndex + dmsIndexDelta);
*offsetPtr = STORE_OFFSET(curr - (matchIndex + dmsIndexDelta));
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
@@ -1244,7 +1245,7 @@ size_t ZSTD_RowFindBestMatch(
/* Save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = curr - matchIndex + ZSTD_REP_MOVE;
*offsetPtr = STORE_OFFSET(curr - matchIndex);
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
}
@@ -1292,7 +1293,8 @@ size_t ZSTD_RowFindBestMatch(
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = curr - (matchIndex + dmsIndexDelta) + ZSTD_REP_MOVE;
assert(curr > matchIndex + dmsIndexDelta);
*offsetPtr = STORE_OFFSET(curr - (matchIndex + dmsIndexDelta));
if (ip+currentMl == iLimit) break;
}
}
@@ -1685,7 +1687,7 @@ _storeSequence:
const BYTE* const repEnd2 = repIndex < prefixLowestIndex ? dictEnd : iend;
matchLength = ZSTD_count_2segments(ip+4, repMatch+4, iend, repEnd2, prefixLowest) + 4;
offset = offset_2; offset_2 = offset_1; offset_1 = (U32)offset; /* swap offset_2 <=> offset_1 */
ZSTD_storeSeq(seqStore, 0, anchor, iend, 0, matchLength);
ZSTD_storeSeq(seqStore, 0, anchor, iend, STORE_REPCODE_1, matchLength);
ip += matchLength;
anchor = ip;
continue;
@@ -1700,7 +1702,7 @@ _storeSequence:
/* store sequence */
matchLength = ZSTD_count(ip+4, ip+4-offset_2, iend) + 4;
offset = offset_2; offset_2 = offset_1; offset_1 = (U32)offset; /* swap repcodes */
ZSTD_storeSeq(seqStore, 0, anchor, iend, 0, matchLength);
ZSTD_storeSeq(seqStore, 0, anchor, iend, STORE_REPCODE_1, matchLength);
ip += matchLength;
anchor = ip;
continue; /* faster when present ... (?) */
@@ -2028,7 +2030,7 @@ _storeSequence:
const BYTE* const repEnd = repIndex < dictLimit ? dictEnd : iend;
matchLength = ZSTD_count_2segments(ip+4, repMatch+4, iend, repEnd, prefixStart) + 4;
offset = offset_2; offset_2 = offset_1; offset_1 = (U32)offset; /* swap offset history */
ZSTD_storeSeq(seqStore, 0, anchor, iend, 0, matchLength);
ZSTD_storeSeq(seqStore, 0, anchor, iend, STORE_REPCODE_1, matchLength);
ip += matchLength;
anchor = ip;
continue; /* faster when present ... (?) */