From: Sen Huang <senhuang96@fb.com>
Date: Tue, 28 Sep 2021 14:48:56 +0000 (-0700)
Subject: Pull hot loop into its own function
X-Git-Tag: v1.5.1~1^2~88^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4b7f45cb04d624d5ae2cc5bbaf234fe450ad8c09;p=thirdparty%2Fzstd.git

Pull hot loop into its own function
---

diff --git a/lib/compress/zstd_lazy.c b/lib/compress/zstd_lazy.c
index c94a663be..c76fa840f 100644
--- a/lib/compress/zstd_lazy.c
+++ b/lib/compress/zstd_lazy.c
@@ -1011,61 +1011,65 @@ FORCE_INLINE_TEMPLATE U32 ZSTD_row_nextCachedHash(U32* cache, U32 const* hashTab
     }
 }
 
+/* ZSTD_row_update_internalImpl():
+ * Updates the hash table with positions starting from updateStartIdx until updateEndIdx.
+ */
+FORCE_INLINE_TEMPLATE void ZSTD_row_update_internalImpl(ZSTD_matchState_t* ms,
+                                                        U32 updateStartIdx, U32 const updateEndIdx,
+                                                        U32 const mls, U32 const rowLog,
+                                                        U32 const rowMask, U32 const useCache)
+{
+    U32* const hashTable = ms->hashTable;
+    U16* const tagTable = ms->tagTable;
+    U32 const hashLog = ms->rowHashLog;
+    const BYTE* const base = ms->window.base;
+
+    DEBUGLOG(6, "ZSTD_row_update_internalImpl(): updateStartIdx=%u, updateEndIdx=%u", updateStartIdx, updateEndIdx);
+    for (; updateStartIdx < updateEndIdx; ++updateStartIdx) {
+        U32 const hash = useCache ? ZSTD_row_nextCachedHash(ms->hashCache, hashTable, tagTable, base, updateStartIdx, hashLog, rowLog, mls)
+                                  : (U32)ZSTD_hashPtr(base + updateStartIdx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls);
+        U32 const relRow = (hash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
+        U32* const row = hashTable + relRow;
+        BYTE* tagRow = (BYTE*)(tagTable + relRow);  /* Though tagTable is laid out as a table of U16, each tag is only 1 byte.
+                                                       Explicit cast allows us to get exact desired position within each row */
+        U32 const pos = ZSTD_row_nextIndex(tagRow, rowMask);
+
+        assert(hash == ZSTD_hashPtr(base + updateStartIdx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls));
+        ((BYTE*)tagRow)[pos + ZSTD_ROW_HASH_TAG_OFFSET] = hash & ZSTD_ROW_HASH_TAG_MASK;
+        row[pos] = updateStartIdx;
+    }
+}
+
 /* ZSTD_row_update_internal():
- * Inserts the byte at ip into the appropriate position in the hash table.
- * Determines the relative row, and the position within the {16, 32} entry row to insert at.
+ * Inserts the byte at ip into the appropriate position in the hash table, and updates ms->nextToUpdate.
+ * Skips sections of long matches as is necessary.
  */
 FORCE_INLINE_TEMPLATE void ZSTD_row_update_internal(ZSTD_matchState_t* ms, const BYTE* ip,
                                                     U32 const mls, U32 const rowLog,
                                                     U32 const rowMask, U32 const useCache)
 {
-    U32* const hashTable = ms->hashTable;
-    U16* const tagTable = ms->tagTable;
-    U32 const hashLog = ms->rowHashLog;
     U32 idx = ms->nextToUpdate;
     const BYTE* const base = ms->window.base;
     const U32 target = (U32)(ip - base);
-    const U32 kMaxPositionsToUpdate = 128;
+    const U32 kSkipThreshold = 384;
+    const U32 kMaxMatchStartPositionsToUpdate = 96;
+    const U32 kMaxMatchEndPositionsToUpdate = 32;
 
-    assert(target >= idx);
     if (useCache) {
         /* Only skip positions when using hash cache, i.e. 
          * if we are loading a dict, don't skip anything.
+         * If we decide to skip, then we only update a set number
+         * of positions at the beginning and end of the match.
          */
-        if (UNLIKELY(target - idx > kMaxPositionsToUpdate)) {
-            U32 const bound = idx + 3*kMaxPositionsToUpdate/4;
-            for (; idx < bound; ++idx) {
-                U32 const hash = useCache ? ZSTD_row_nextCachedHash(ms->hashCache, hashTable, tagTable, base, idx, hashLog, rowLog, mls)
-                                        : (U32)ZSTD_hashPtr(base + idx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls);
-                U32 const relRow = (hash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
-                U32* const row = hashTable + relRow;
-                BYTE* tagRow = (BYTE*)(tagTable + relRow);  /* Though tagTable is laid out as a table of U16, each tag is only 1 byte.
-                                                            Explicit cast allows us to get exact desired position within each row */
-                U32 const pos = ZSTD_row_nextIndex(tagRow, rowMask);
-
-                assert(hash == ZSTD_hashPtr(base + idx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls));
-                tagRow[pos + ZSTD_ROW_HASH_TAG_OFFSET] = hash & ZSTD_ROW_HASH_TAG_MASK;
-                row[pos] = idx;
-            }
-            idx = target - kMaxPositionsToUpdate/4;
+        if (UNLIKELY(target - idx > kSkipThreshold)) {
+            U32 const bound = idx + kMaxMatchStartPositionsToUpdate;
+            ZSTD_row_update_internalImpl(ms, idx, bound, mls, rowLog, rowMask, useCache);
+            idx = target - kMaxMatchEndPositionsToUpdate;
             ZSTD_row_fillHashCache(ms, base, rowLog, mls, idx, ip+1);
         }
     }
-
-    DEBUGLOG(6, "ZSTD_row_update_internal(): nextToUpdate=%u, current=%u", idx, target);
-    for (; idx < target; ++idx) {
-        U32 const hash = useCache ? ZSTD_row_nextCachedHash(ms->hashCache, hashTable, tagTable, base, idx, hashLog, rowLog, mls)
-                                  : (U32)ZSTD_hashPtr(base + idx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls);
-        U32 const relRow = (hash >> ZSTD_ROW_HASH_TAG_BITS) << rowLog;
-        U32* const row = hashTable + relRow;
-        BYTE* tagRow = (BYTE*)(tagTable + relRow);  /* Though tagTable is laid out as a table of U16, each tag is only 1 byte.
-                                                       Explicit cast allows us to get exact desired position within each row */
-        U32 const pos = ZSTD_row_nextIndex(tagRow, rowMask);
-
-        assert(hash == ZSTD_hashPtr(base + idx, hashLog + ZSTD_ROW_HASH_TAG_BITS, mls));
-        tagRow[pos + ZSTD_ROW_HASH_TAG_OFFSET] = hash & ZSTD_ROW_HASH_TAG_MASK;
-        row[pos] = idx;
-    }
+    assert(target >= idx);
+    ZSTD_row_update_internalImpl(ms, idx, target, mls, rowLog, rowMask, useCache);
     ms->nextToUpdate = target;
 }