From: W. Felix Handte <w@felixhandte.com>
Date: Wed, 16 May 2018 18:55:20 +0000 (-0400)
Subject: Refactor ZSTD_dfast to Use `goto`s
X-Git-Tag: v1.3.5~3^2~37^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1850025156a2169bc0f1b022a9f3d5a6a18c9b05;p=thirdparty%2Fzstd.git

Refactor ZSTD_dfast to Use `goto`s
---

diff --git a/lib/compress/zstd_double_fast.c b/lib/compress/zstd_double_fast.c
index 3e1a1d3c6..de1529006 100644
--- a/lib/compress/zstd_double_fast.c
+++ b/lib/compress/zstd_double_fast.c
@@ -106,6 +106,7 @@ size_t ZSTD_compressBlock_doubleFast_generic(
     /* Main Search Loop */
     while (ip < ilimit) {   /* < instead of <=, because repcode check at (ip+1) */
         size_t mLength;
+        U32 offset;
         size_t const h2 = ZSTD_hashPtr(ip, hBitsL, 8);
         size_t const h = ZSTD_hashPtr(ip, hBitsS, mls);
         U32 const current = (U32)(ip-base);
@@ -120,6 +121,7 @@ size_t ZSTD_compressBlock_doubleFast_generic(
                                base + repIndex;
         hashLong[h2] = hashSmall[h] = current;   /* update hash tables */
 
+        /* check dictMatchState repcode */
         if (dictMode == ZSTD_dictMatchState
             && ((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
             && (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {
@@ -127,73 +129,93 @@ size_t ZSTD_compressBlock_doubleFast_generic(
             mLength = ZSTD_count_2segments(ip+1+4, repMatch+4, iend, repMatchEnd, istart) + 4;
             ip++;
             ZSTD_storeSeq(seqStore, ip-anchor, anchor, 0, mLength-MINMATCH);
-        } else if ( dictMode == ZSTD_noDict
-                 && ((offset_1 > 0) & (MEM_read32(ip+1-offset_1) == MEM_read32(ip+1)))) {
+            goto _match_stored;
+        }
+
+        /* check noDict repcode */
+        if ( dictMode == ZSTD_noDict
+          && ((offset_1 > 0) & (MEM_read32(ip+1-offset_1) == MEM_read32(ip+1)))) {
             mLength = ZSTD_count(ip+1+4, ip+1+4-offset_1, iend) + 4;
             ip++;
             ZSTD_storeSeq(seqStore, ip-anchor, anchor, 0, mLength-MINMATCH);
-        } else {
-            U32 offset;
-            if ( (matchIndexL > prefixLowestIndex) && (MEM_read64(matchLong) == MEM_read64(ip)) ) {
-                mLength = ZSTD_count(ip+8, matchLong+8, iend) + 8;
-                offset = (U32)(ip-matchLong);
-                while (((ip>anchor) & (matchLong>prefixLowest)) && (ip[-1] == matchLong[-1])) { ip--; matchLong--; mLength++; } /* catch up */
-            } else if ( (matchIndexS > prefixLowestIndex) && (MEM_read32(match) == MEM_read32(ip)) ) {
+            goto _match_stored;
+        }
+
+        /* check prefix long match */
+        if ( (matchIndexL > prefixLowestIndex) && (MEM_read64(matchLong) == MEM_read64(ip)) ) {
+            mLength = ZSTD_count(ip+8, matchLong+8, iend) + 8;
+            offset = (U32)(ip-matchLong);
+            while (((ip>anchor) & (matchLong>prefixLowest)) && (ip[-1] == matchLong[-1])) { ip--; matchLong--; mLength++; } /* catch up */
+            goto _match_found;
+        }
+
+        /* check prefix short match */
+        if ( (matchIndexS > prefixLowestIndex) && (MEM_read32(match) == MEM_read32(ip)) ) {
+            size_t const hl3 = ZSTD_hashPtr(ip+1, hBitsL, 8);
+            U32 const matchIndexL3 = hashLong[hl3];
+            const BYTE* matchL3 = base + matchIndexL3;
+            hashLong[hl3] = current + 1;
+
+            /* check prefix + 1 long match */
+            if ( (matchIndexL3 > prefixLowestIndex) && (MEM_read64(matchL3) == MEM_read64(ip+1)) ) {
+                mLength = ZSTD_count(ip+9, matchL3+8, iend) + 8;
+                ip++;
+                offset = (U32)(ip-matchL3);
+                while (((ip>anchor) & (matchL3>prefixLowest)) && (ip[-1] == matchL3[-1])) { ip--; matchL3--; mLength++; } /* catch up */
+            } else {
+                mLength = ZSTD_count(ip+4, match+4, iend) + 4;
+                offset = (U32)(ip-match);
+                while (((ip>anchor) & (match>prefixLowest)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */
+            }
+            goto _match_found;
+        }
+
+        /* check dictMatchState matches */
+        if (dictMode == ZSTD_dictMatchState) {
+            U32 const dictMatchIndexL = dictHashLong[h2];
+            U32 const dictMatchIndexS = dictHashSmall[h];
+            const BYTE* dictMatchL = dictBase + dictMatchIndexL;
+            const BYTE* dictMatchS = dictBase + dictMatchIndexS;
+            assert(dictMatchL < dictEnd);
+            assert(dictMatchS < dictEnd);
+
+            if (dictMatchL > dictLowest && MEM_read64(dictMatchL) == MEM_read64(ip)) {
+                mLength = ZSTD_count_2segments(ip+8, dictMatchL+8, iend, dictEnd, prefixLowest) + 8;
+                offset = (U32)(current - dictMatchIndexL - dictIndexDelta);
+                while (((ip>anchor) & (dictMatchL>dictLowest)) && (ip[-1] == dictMatchL[-1])) { ip--; dictMatchL--; mLength++; } /* catch up */
+                goto _match_found;
+            }
+
+            if (dictMatchS > dictLowest && MEM_read32(dictMatchS) == MEM_read32(ip)) {
                 size_t const hl3 = ZSTD_hashPtr(ip+1, hBitsL, 8);
-                U32 const matchIndexL3 = hashLong[hl3];
-                const BYTE* matchL3 = base + matchIndexL3;
-                hashLong[hl3] = current + 1;
-                if ( (matchIndexL3 > prefixLowestIndex) && (MEM_read64(matchL3) == MEM_read64(ip+1)) ) {
-                    mLength = ZSTD_count(ip+9, matchL3+8, iend) + 8;
+                U32 const dictMatchIndexL3 = dictHashLong[hl3];
+                const BYTE* dictMatchL3 = dictBase + dictMatchIndexL3;
+                assert(dictMatchL3 < dictEnd);
+                if (dictMatchL3 > dictLowest && MEM_read64(dictMatchL3) == MEM_read64(ip)) {
+                    mLength = ZSTD_count_2segments(ip+1+8, dictMatchL3+8, iend, dictEnd, prefixLowest) + 8;
                     ip++;
-                    offset = (U32)(ip-matchL3);
-                    while (((ip>anchor) & (matchL3>prefixLowest)) && (ip[-1] == matchL3[-1])) { ip--; matchL3--; mLength++; } /* catch up */
-                } else {
-                    mLength = ZSTD_count(ip+4, match+4, iend) + 4;
-                    offset = (U32)(ip-match);
-                    while (((ip>anchor) & (match>prefixLowest)) && (ip[-1] == match[-1])) { ip--; match--; mLength++; } /* catch up */
-                }
-            } else if (dictMode == ZSTD_dictMatchState) {
-                U32 const dictMatchIndexL = dictHashLong[h2];
-                U32 const dictMatchIndexS = dictHashSmall[h];
-                const BYTE* dictMatchL = dictBase + dictMatchIndexL;
-                const BYTE* dictMatchS = dictBase + dictMatchIndexS;
-                assert(dictMatchL < dictEnd);
-                assert(dictMatchS < dictEnd);
-                if (dictMatchL > dictLowest && MEM_read64(dictMatchL) == MEM_read64(ip)) {
-                    mLength = ZSTD_count_2segments(ip+8, dictMatchL+8, iend, dictEnd, prefixLowest) + 8;
-                    offset = (U32)(current - dictMatchIndexL - dictIndexDelta);
-                    while (((ip>anchor) & (dictMatchL>dictLowest)) && (ip[-1] == dictMatchL[-1])) { ip--; dictMatchL--; mLength++; } /* catch up */
-                } else if (dictMatchS > dictLowest && MEM_read32(dictMatchS) == MEM_read32(ip)) {
-                    size_t const hl3 = ZSTD_hashPtr(ip+1, hBitsL, 8);
-                    U32 const dictMatchIndexL3 = dictHashLong[hl3];
-                    const BYTE* dictMatchL3 = dictBase + dictMatchIndexL3;
-                    assert(dictMatchL3 < dictEnd);
-                    if (dictMatchL3 > dictLowest && MEM_read64(dictMatchL3) == MEM_read64(ip+1)) {
-                        mLength = ZSTD_count_2segments(ip+1+8, dictMatchL3+8, iend, dictEnd, prefixLowest) + 8;
-                        ip++;
-                        offset = (U32)(current + 1 - dictMatchIndexL3 - dictIndexDelta);
-                        while (((ip>anchor) & (dictMatchL3>dictLowest)) && (ip[-1] == dictMatchL3[-1])) { ip--; dictMatchL3--; mLength++; } /* catch up */
-                    } else {
-                        mLength = ZSTD_count_2segments(ip+4, dictMatchS+4, iend, dictEnd, istart) + 4;
-                        offset = (U32)(current - dictMatchIndexS - dictIndexDelta);
-                        while (((ip>anchor) & (dictMatchS>dictLowest)) && (ip[-1] == dictMatchS[-1])) { ip--; dictMatchS--; mLength++; } /* catch up */
-                    }
+                    offset = (U32)(current + 1 - dictMatchIndexL3 - dictIndexDelta);
+                    while (((ip>anchor) & (dictMatchL3>dictLowest)) && (ip[-1] == dictMatchL3[-1])) { ip--; dictMatchL3--; mLength++; } /* catch up */
                 } else {
-                    ip += ((ip-anchor) >> kSearchStrength) + 1;
-                    continue;
+                    mLength = ZSTD_count_2segments(ip+4, dictMatchS+4, iend, dictEnd, istart) + 4;
+                    offset = (U32)(current - dictMatchIndexS - dictIndexDelta);
+                    while (((ip>anchor) & (dictMatchS>dictLowest)) && (ip[-1] == dictMatchS[-1])) { ip--; dictMatchS--; mLength++; } /* catch up */
                 }
-            } else {
-                ip += ((ip-anchor) >> kSearchStrength) + 1;
-                continue;
+
+                goto _match_found;
             }
+        }
 
-            offset_2 = offset_1;
-            offset_1 = offset;
+        ip += ((ip-anchor) >> kSearchStrength) + 1;
+        continue;
 
-            ZSTD_storeSeq(seqStore, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
-        }
+_match_found:
+        offset_2 = offset_1;
+        offset_1 = offset;
+
+        ZSTD_storeSeq(seqStore, ip-anchor, anchor, offset + ZSTD_REP_MOVE, mLength-MINMATCH);
 
+_match_stored:
         /* match found */
         ip += mLength;
         anchor = ip;