From: Nick Terrell <nickrterrell@gmail.com>
Date: Fri, 20 Sep 2019 07:52:15 +0000 (-0700)
Subject: Widen ZSTD_wildcopy to 32 bytes
X-Git-Tag: v1.4.4~1^2~42^2~7
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cdad7fa512e03557669533ca5143ec138885f1bf;p=thirdparty%2Fzstd.git

Widen ZSTD_wildcopy to 32 bytes
---

diff --git a/lib/common/zstd_internal.h b/lib/common/zstd_internal.h
index 007b03df7..522c1fda2 100644
--- a/lib/common/zstd_internal.h
+++ b/lib/common/zstd_internal.h
@@ -197,7 +197,7 @@ static void ZSTD_copy8(void* dst, const void* src) { memcpy(dst, src, 8); }
 static void ZSTD_copy16(void* dst, const void* src) { memcpy(dst, src, 16); }
 #define COPY16(d,s) { ZSTD_copy16(d,s); d+=16; s+=16; }
 
-#define WILDCOPY_OVERLENGTH 16
+#define WILDCOPY_OVERLENGTH 32
 #define WILDCOPY_VECLEN 16
 
 typedef enum {
@@ -237,11 +237,11 @@ void ZSTD_wildcopy(void* dst, const void* src, ptrdiff_t length, ZSTD_overlap_e
          * On clang-8 unrolling once is +1.4%, twice is +3.3%, thrice is +3%.
          */
         COPY16(op, ip);
-        if (op >= oend) return;
         COPY16(op, ip);
         if (op >= oend) return;
         do {
             COPY16(op, ip);
+            COPY16(op, ip);
         }
         while (op < oend);
     }
@@ -257,7 +257,7 @@ MEM_STATIC void ZSTD_wildcopy8(void* dst, const void* src, ptrdiff_t length)
     BYTE* op = (BYTE*)dst;
     BYTE* const oend = (BYTE*)op + length;
     do {
-        COPY8(op, ip)
+        COPY8(op, ip);
     } while (op < oend);
 }
 
diff --git a/lib/decompress/zstd_decompress_block.c b/lib/decompress/zstd_decompress_block.c
index e799a5c74..27ce137f3 100644
--- a/lib/decompress/zstd_decompress_block.c
+++ b/lib/decompress/zstd_decompress_block.c
@@ -724,12 +724,14 @@ size_t ZSTD_execSequence(BYTE* op,
     assert(oMatchEnd <= oend_w /* Can wildcopy matches */);
 
     /* Copy Literals:
-     * Split out litLength <= 16 since it is nearly always true. +1% on gcc-9.
+     * Split out litLength <= 16 since it is nearly always true. +1.6% on gcc-9.
+     * We likely don't need the full 32-byte wildcopy.
      */
-    if (sequence.litLength <= 16)
-        ZSTD_copy16(op, *litPtr);
-    else
-        ZSTD_wildcopy(op, (*litPtr), sequence.litLength, ZSTD_no_overlap);
+    assert(WILDCOPY_OVERLENGTH >= 16);
+    ZSTD_copy16(op, (*litPtr));
+    if (sequence.litLength > 16) {
+        ZSTD_wildcopy(op+16, (*litPtr)+16, sequence.litLength-16, ZSTD_no_overlap);
+    }
     op = oLitEnd;
     *litPtr = iLitEnd;   /* update for next sequence */
 
@@ -755,18 +757,18 @@ size_t ZSTD_execSequence(BYTE* op,
     assert(match >= prefixStart);
     assert(sequence.matchLength >= 1);
 
-    /* Nearly all offsets are >= 16 bytes, which means we can use wildcopy
+    /* Nearly all offsets are >= WILDCOPY_VECLEN bytes, which means we can use wildcopy
      * without overlap checking.
      */
-    if (sequence.offset >= 16) {
-        /* Split out matchLength <= 16 since it is nearly always true. +1% on gcc-9. */
-        if (sequence.matchLength <= 16)
-            ZSTD_copy16(op, match);
-        else
-            ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength, ZSTD_no_overlap);
+    if (sequence.offset >= WILDCOPY_VECLEN) {
+        /* Split out matchLength <= 32 since it is nearly always true. +1% on gcc-9.
+	 * We copy 32 bytes here since matches are generally longer than literals.
+	 * In silesia, for example ~10% of matches are longer than 16 bytes.
+	 */
+        ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength, ZSTD_no_overlap);
         return sequenceLength;
     }
-    assert(sequence.offset < 16);
+    assert(sequence.offset < WILDCOPY_VECLEN);
 
     /* Copy 8 bytes and spread the offset to be >= 8. */
     ZSTD_overlapCopy8(&op, &match, sequence.offset);